Phytochemical analysis, cellular antioxidant and α-glucosidase inhibitory activities of various herb plant organs

Industrial Crops & Products 141 (2019) 111771

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Phytochemical analysis, cellular antioxidant and α-glucosidase inhibitory activities of various herb plant organs

T

Yongsheng Chena,1, Erpei Wangb,1, Zihao Weic, Yanfang Zhengd, Rian Yana, , Xiang Maa,e, ⁎

⁎

a

Department of Food Science and Engineering, Jinan University, Guangzhou, Guangdong, 510632, China Plant Breeding Institute, Sydney Institute of Agriculture, The University of Sydney, Sydney, New South Wales, 2006, Australia c Department of Food Science, Rutgers University, New Brunswick, NJ, 08901, United States d Department of Pharmacology, Medical College, Jinan University, Guangzhou, Guangdong, 510632, China e Department of Biochemistry, The University of Texas Southwestern Medical Centre, Dallas, TX, 75390, United States b

ARTICLE INFO

ABSTRACT

Keywords: Herb plant organs Phytochemicals Antioxidant activity α-Glucosidase inhibitory activity Glucose consumption

Herb plant organs are aboundant in phytochemicals and possess multiple bioactivities. Investigation in the phytochemicals of herb plants organs and associated functionalities essential to explore the potential and deepened the understanding of herb plants. In this study, phytochemicals, antioxidant activity, and α-glucosidase inhibitory activity of leaf, flower, peel, root and seed herb plant organ extracts were investigated. A combination of colorimetric assays and high performance liquid chromatography were applied, and the cellular antioxidant activity was evaluated in the HepG2 model. Results show that leaf and flower organs had the highest total phenolics, flavonoids, flavonols and proanthocyanidins contents. Flower organ possessed the highest 2,2-diphenyl-1-picrylhydrazyl, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging activity, cellular antioxidant activity and α-glucosidase inhibitory activity. Leaf organ had the strongest oxygen radical absorbance capacity and glucose consumption. Ferulic acid, salicylic acid, chlorogenic acid and epigallocatechin gallate were the common phytochemical compounds in plant organs. Phytochemical contents showed significant positive correlations (p < 0.05) with antioxidant and hypoglycemic effects. Results revealed that compared with other plant organs in this study, flower organ possessed excellent antioxidant and glucose regulating activities and could provide basis for the development of related health food and products for the diabetes patients.

1. Introduction Diabetes is described as the metabolic disorder of multiple aetiology, and characterized with elevated blood glucose levels and ratio of mortality for patients (Balkan et al., 2018; WHO, W, 2016). Diabetes induces damage, dysfunction and failure of living organs, for example blindness, renal failure, peripheral vascular, foot ulcers and autonomic dysfunction (Alberti, 1998; Malchoff, 2010). The increase in insulinmediated muscle or adipose tissue glucose uptake causes extracellular hyperglycemia, which stimulates reactive oxygen species (ROS) formation, and overproduced oxidative stress has been regarded as one of the major inducements of diabetic complications (Valko et al., 2007). From the latest epidemiological data by the International Diabetes Federation, estimates of the worldwide diabetic patients for 2017 were about 4,250,000 (age 20–79 years old) and may increase to about 6,290,000 by 2045, which indicates that the prevalence of diabetes was 8.4% in 2017 and is estimated up to 9.9% in 2045 (Cho et al., 2018).

Though there is a growing number of drugs available for diabetes, plant foods abounding in secondary metabolites are of growing interests as alternatives and natural therapies. Compared with diabetes drugs which are associated with some side-effects and high cost, secondary metabolites like phenolics and flavonoids have cheap sources, and plant food rich in those natural antioxidants are more accessible for a wider range of diabetic patients. Plant secondary metabolites, which possess a series of pharmacological and biological effects, have been subjected to the research on their antidiabetic property. Phenolics are regarded as potent natural antioxidants with a series of bioactivities, such as free radical scavenging ability (Helal et al., 2015). Free radicals could be generated by some factors including ultraviolet rays, pollution, and metal ions (copper) (Kehrer and Smith, 1994; Purohit et al., 2018), and the excess of free radicals has poisonous properties and could cause human chronic diseases like diabetes, cancer, cardiovascular and hyperlipemia in different mechanisms (Gerschman et al., 1954). Recent studies reported the potential role of phenolics acting as inhibitors of

Corresponding authors at: Department of Food Science and Engineering, Jinan University, Guangzhou, Guangdong, 510632, China. E-mail address: [email protected] (X. Ma). 1 These authors contributed equally to this work. ⁎

https://doi.org/10.1016/j.indcrop.2019.111771 Received 14 July 2019; Received in revised form 5 September 2019; Accepted 5 September 2019 Available online 17 September 2019 0926-6690/ © 2019 Elsevier B.V. All rights reserved.

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digestive enzymes in blood glucose control, particularly α-glucosidase and α-amylase (Geng et al., 2016; Konczak et al., 2013; Ranilla et al., 2010). These reports suggested the potential antidiabetic effects of plant foods rich in phenolics because of the free radical scavenging and the inhibition of α-glucosidase in the human body. Herb plants are vital beverages world widely and regarded as healthy and functional foods. In the last few decades, many studies also covered the components and bioactivities of herb plant organs, indicating its potent antioxidant activity (Chen et al., 2015; Herrera et al., 2018; Liu et al., 2016a). Different herb plant organs, such as buckwheat (Fagopyrum esculentum) (plant seed organ) (Inglett et al., 2011), honeysuckle (Lonicera japonica) (plant flower organ) (Sun and Tang, 2011), and leaves of Adinandra nitida (plant leaf organ) (Gao et al., 2010), were all reported to possess a series of health benefits and have a long history in Asia. In addition, because of the taste, flavor and health function, the consumption of herb plant organs has increased in China, USA, Canada and Europe in recent years (Chen et al., 2018; Kamara et al., 2004; Piccinelli et al., 2004; Riehle et al., 2013). Component analysis revealed the abundance of phytochemicals in herb plant organs, including phenolics, carotenoids, phytosterols and alkaloids, which are beneficially important to human health, and are receiving more and more attention. It is reported that phenolic compounds are important components in herb plants and exhibit beneficial bioactivities such as reducing the risk of cardiovascular and neurodegenerative, body weight control, anti-hypertensive effect, and antidiabetes (Khan and Mukhtar, 2007). Though previous research also demonstrated that herb plant organs could be applied for inhibiting or preventing chronic diseases caused by oxidative stress (Li et al., 2013), while the hypoglycemic activity of herb plant organs remains infrequent. Also, as a result of differing cultivation conditions, the phytochemical profile and antioxidant activity of herb plant organs vary accordingly, while relevant comparison research is limited. Therefore, the present study focused on the following objectives: (1) determination of the phytochemicals profiles, including phenolics, flavonoids, flavonols, proanthocyanidins of twenty-three herb plant organs samples; (2) comparison of the differences of chemical and cellular antioxidant activities, the inhibitory activity against α-glucosidase, and the glucose consumption in HepG2 model; (3) analysis of the correlation among herb plant organs’ phenolics, flavonoids, flavonol, proanthocyanidins, antioxidant activity, and inhibitory activity against α-glucosidase. The phytochemicals, antioxidant activities, inhibitory activities against αglucosidase and glucose consumption would be of significance for expanding the insight into the antidiabetic properties of herb plant organs and providing basis for the development of novel antidiabetic health food and/or medicinal industry materials.

extracted twice. All filtrates were combined together and dried by vacuum evaporation. After that, the extracts were dissolved in 10 mL water and stored in a fridge at −25 °C before use. 2.3. Measurement of total phenolics content The total phenolics content was analysed by using the FolinCiocalteu colorimetric method (Chen et al., 2014). Sample diluents or standard solution (100 μL) were firstly mixed with distilled water (400 μL), then blended with Folin-Ciocalteu reagent (100 μL) and standed for 6 min at room temperature. After neutralization by 7% sodium carbonate solution (1 mL), and distilled water (800 μL) was added and let it stand for 90 min at room temperature, the absorbance of mixture was read at 760 nm using a microplate reader (Tecan M200 PRO, Switzerland). Gallic acid was used as a standard and the result was expressed as milligram of gallic acid equivalent per gram of dry weight (DW) sample (mg GAE/g DW). 2.4. Measurement of total flavonoids content The total flavonoids content was determined by a colorimetric assay (Chen et al., 2017a). Briefly, extract and/or standard solution (1 mL) were mixed with deionized water (4 mL) and 5% (w/v) NaNO2 (300 μL), respectively. After standing for 5 min at room temperature, 10% (w/v) AlCl3 working solution (300 μL) was added to each tube. After another 6 min, 2 mL of 1 M NaOH working solution and 2.4 mL of distilled water were added to each tube, respectively. The mixture was vortexed and read at 510 nm. Catechin was used as the standard. Result was expressed as milligram of catechin equivalents per gram of DW sample (mg CE/g DW). 2.5. Measurement of total flavonols content The total flavonols content was determined according to a colorimetric assay (Grubešić et al., 2005). One mL of diluent of extract and/or rutin working solution (standard) was mixed with 1 mL of 20 mg/mL AlCl3 and 3 mL of 50 mg/mL NaOAc working solution, respectively. After standing for 2.5 h at room temperature, the absorbance of the mixture was measured at 440 nm. The value of total flavonols content was expressed as milligram of rutin equivalents per gram of DW sample (mg RE/g DW). 2.6. Measurement of total proanthocyanidins content The total proanthocyanidins contents of the herb plant organs were determined by a colorimetric assay (Oki et al., 2002). Diluents of extracts were mixed with 2.5 mL of vanillin working solution (30 mg/mL) and 2.5 mL of sulfuric acid-methanol working solution (30%), respectively. Then the mixtures were incubated at 30 °C for 20 min. The absorbance of mixtures was measured at 500 nm. The value of proanthocyanidins content was displayed as milligram epicatechin equivalents per 100 g of DW sample (mg ECE/100 g DW).

2. Materials and methods 2.1. Materials Fluorescein sodium salt, gallic acid, catechin hydrate, rutin, 2,2′azino-bis (three-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 1,1-dipheny-2-picrylhydrazyl (DPPH), α-glucosidase, p-nitrophenyl-α-D-glucopyranoside (pNP-G) and 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH) were purchased from Sigma-Aldrich LLC. (Shanghai, China). Ascorbic acid, metformin (Met) and Trolox were purchased from Aladdin (Shanghai, China). Twenty-three herb plant organs samples used in this study were bought from a local market in Guangzhou and described in Table 1.

2.7. Measurement of antioxidant activity by the oxygen radical absorbance capacity (ORAC) assay The oxygen radical absorbance capacity assay was performed as previous report (Chen et al., 2017b). Briefly, diluents of extract and/or Trolox (20 μL) were added to wells of 96-well plate and incubated at 37 °C for 10 min. Fluorescein working solution (200 μL) was injected to each well and incubated at 37 °C for 20 min. After that, AAPH working solution (20 μL) was immediately added to well before the start of the measurement. The result of ORAC was displayed as micromoles of Trolox equivalent per gram of DW sample (μM TE/g DW).

2.2. Extraction of phytochemicals Phytochemicals in herb plant organs samples were extracted by following a reported method with minor modification (Chen et al., 2014). Samples (2 g) were mixed with 80% chilled acetone (w/v, 1:50) and homogenized for 3 min before vacuum filtration. The residues were 2

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Table 1 Description of the herb plants organs employed in this study. Variety

Description

Picking parts

Perilla leaves (Perilla frutescens) Ampelopsis grossedentata Chinese wolfberry (herba lycii) bud Forsythia suspensa leaves Apocynum venetum Hawk tea (Litsea coreana Levl. var. lanuginose) Chinese holly leaves (Ilex cornuta, large-leaved) Cyclocarya paliurus Lotus leaves Adinandra nitida merr.ex Ku-Ding-Cha (Ilex kaushue, small-leaved) Partridge tea (Mallotus furetianus) Sweet tea (Strigose hydrangea leaves) Mulberry (Morus nigra) leaves Rose (Rosa rugosa) Jasmine (Jasminum officinale) flower Osmanthus Wild Chrysanthemum Honeysuckle (Lonicera japonica) Tangerine peel Black buckwheat sprout (Fagopyrum tataricum) Roasted barley (Hordeum vulgare) Astragalus

Tender leaf, dark purple Black and white, white crystal Tender leaf, two leaves Little yellow leaves Leaf blade ovoid Leaves alternate, leaves thick Leaves thickly, 8-25 cm long Leaflets papery, elliptic ovoid Quasi-circular object, coarser Thick fleshy, ovoid Bud leaves green, tight fine uniform Round, large lobes Oval, rim serrations Leaf thin, soft Pinnately compound leaf, pour ovoid Tender and soft Golden yellow, spend small capitulum Tight and straight Orange-red or reddish brown Golden yellow, emitting natural luster Skin brown Thickening, woodiness, grey white

leaf leaf leaf leaf leaf leaf leaf leaf leaf leaf leaf leaf leaf leaf flower flower flower flower flower peel seed seed root

2.8. Measurement of DPPH radical scavenging capacity

Quercetin was used as the standard and the results were displayed as milligram quercetin equivalent per gram of DW sample (mg QE/g DW).

After Incubating for 24 h, the upper medium was replaced with 100 μL of medium including herb plant organs samples. The cells were incubated for more 1 h and were washed with PBS buffer. AAPH working solution (600 μM) was added to the wells. Fluorescence intensity changes of intracellular were detected using a Fluoroskan Ascent fluorescent spectrophotometer (Tecan M200 PRO, Switzerland) at 485 nm excitation and 535 nm emission every 5 min for 65 min at 37 °C. The results were calculated as following, CAA (units) = 1 - (∫ SA/∫ CA), ∫ SA represents the integrated area of the tested sample and ∫ SA represents the integrated area of control gotten from the fluorescence versus time curve. The median effective dose (EC50) of tested samples were calculated using the median effect plot of lg (fa/fu) versus lg (dose), fa is related with the treatment (CAA unit) and fu is related with (1- CAA unit). The EC50 values were shown as the mean ± SD and converted to CAA, which were displayed as micromoles of quercetin equivalent (QE)/100 g of samples.

2.9. Measurement of ABTS radical scavenging capacity

2.11. High-performance liquid chromatography analysis

The ABTS radical scavenging capacity of sample extracts was carried out by following a previous reported method with minor modification (Chen et al., 2019a). The ABTS working solution was prepared with ABTS powder (7 mM) and potassium persulphate (2.45 mM) solution mix at 625:11 (w/v). ABTS solution (2.85 mL) and sample diluents or standard solution (150 μL) were mixed and stood for 10 min. The mixtures were detected at 734 nm. The control was prepared with solvent take the place of sample diluents. The values of ABTS radical scavenging capacity of testing samples were calculated by using the following formula:

The phenolics compounds in each sample were analysed using a Waters C18 column (5 μm, 250 × 4.6 mm) on a Thermo Scientific Ultimate 3000 HPLC system (Thermo Fisher Scientific, Germany). The binary mobile phase consisted of CH3CN (A) and 0.4% AcOH in H2O (B). The mobile phase gradient was 0–40 min, solvent A 5–25%; 40–45 min, solvent A 25–35%; 45–50 min, solvent A 35–50%; 50–55 min, solvent A 5%, 55–60 min, solvent A 5%. All sample solutions were filtered through a 0.22 μm PTFE membrane syringe filter and the injection volume was 20 μL for each sample and standard, and the flow rate was 1 mL/min. The absorbance was monitored at 280 nm and the column oven was set at 30 °C. The specific phenolic compounds were identified based on the retention time of pure standards. The results were shown as milligram per gram of DW sample (mg/g DW).

The DPPH radical scavenging capacity was measured according to a reported method with minor modification (Chen et al., 2016b). DPPH working solution (0.2 mM) and different concentrations of sample diluents and/or standard were mixed (1:1, v/v) in tube. The whole body of tube was packed up with aluminium foil and stood statically for 30 min at room temperature. The absorbance of mixtures was detected at 517 nm. The values of DPPH radical scavenging of testing samples were calculated according to the following equation:

DPPH radical scavenging capacity =

ABTS radical scavenging capacity =

Abscontrol

Abssample

Abscontrol

Abscontrol

Abssample

Abscontrol

× 100%

× 100%

Ascorbic acid was employed as the standard and the results were displayed as milligram vitamin C equivalent per gram of DW sample (mg VCE/g DW).

2.12. Measurement of α-glucosidase inhibition The effects of herb plant organs extracts on α-glucosidase activity were analyzed as previously described (Geng et al., 2016). The stored solution of α-glucosidase and pNP-G were preparedin 0.1 M PBS (pH 6.9). α-Glucosidase solution (0.1 U/mL, 1.0 mL) and diluents of the sample (1.0 mL) were blended and incubated in 37 °C water bath for 10 min. After that, pNP-G solution (1.0 mM, 1.0 mL) was added and

2.10. Measurement of cellular antioxidant activity (CAA) The measurement of CAA was carried out in HepG2 model with minor modifications (Chen et al., 2019b). Briefly, HepG2 cells were grown in black 96-well microplates at a density of 6 × 104 cells/well. 3

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tubes were further incubated at 37 °C for more 20 min. Then absolute methanol was employed to denature the enzyme. The absorbance of mixture was read at 405 nm. The PBS solution was adopted as a negative control. α-Glucosidase inhibition activity was calculated using the following equation:

Glucodidase inhibition =

Abscontrol

Abssample

Abscontrol

3.2. Total flavonoids content Flavonoids are one major type of polyphenols, and most of them have been recognized for their antioxidant, anti-inflammatory and antidiabetic activities (O et al., 2005). As shown in Fig. 1(B), the total flavonoid contents of twenty-three tested herb plant organ samples ranged from 1.87 ± 0.14 (roasted barley) to 119.07 ± 6.03 (Osmanthus) mg of CE/g DW. Compared with other, significantly higher average flavonoid contents of herb plant leaf organ and herb plant flower organ were recorded as 49.21 ± 26.91 and 54.93 ± 39.10 mg of CE/g DW (p < 0.05), respectively. In the herb plant leaf organ samples, the flavonoids contents of tested samples ranged from 9.93 ± 1.56 (Chinese wolfberry (herba lycii) bud) to 98.79 ± 10.13 (hawk tea) mg of CE/g DW. In the herb plant flower organ, the flavonoids contents of tested samples ranged from 22.59 ± 0.38 (rose (Rosa rugosa)) to 119.07 ± 6.03 (Osmanthus) mg of CE/g DW. In the herb plant root organ, the flavonoids content of Astragalus was 5.43 ± 0.27 mg of CE/g DW, which is higher than that of herb plant peel organ (tangerine peel, 4.51 ± 0.24 mg of CE/g DW) and herb plant seed organ (black buckwheat sprout, 4.65 ± 0.81 mg of CE/g DW; roasted barley, 1.87 ± 0.14 mg of CE/g DW). Above, the flavonoids contents of tested herb plant organs were higher than that of grains (Adom and Liu, 2002) and wine grapes (Yang et al., 2009) using the same colorization method.

× 100%

The results were shown as IC50 values, μg DW/mL. 2.13. Measurement of glucose consumption in HepG2 cells The glucose consumption testing was performed in HepG2 model following Chen et al. (Chen et al., 2016a) and with minor modification, log phases HepG2 cells were planted in 96-well plates with a density of 2.0 × 104 cells/well, and cultured at 37 °C overnight. Then, the cells were washed once with free FBS DMEM high glucose medium and incubated again with DMEM high glucose medium supplemented with insulin (0.5 μM) for 24 h. Sequentially, the cells were washed once with free FBS DMEM high glucose medium and provided with samples of serial concentrations. Metformin and the DMEM high glucose medium were employed as the positive and blank groups, respectively. The glucose consumption in treated cells were analyzed from the cell culture supernatant by adopting a glucose kit (Jiancheng, Nanjing, China).

3.3. Total flavonols content Flavonols are one of major flavonoids subclasses and ubiquitous in plants, such as edible flowers, vegetables, and fruits. Flavonols exhibit substantial biological activities such as antioxidant, anticancer, antiinflammatory and inhibition to α-glucosidase (D et al., 2018; Hichri et al., 2018). As shown in Fig. 1(C), the total flavonols contents of twenty-three tested herb plant samples ranged from 8.22 ± 0.35 (tangerine peel) to 55.59 ± 2.20 (lotus leaves) mg RE/g DW. In the herb plant leaf organ samples, the flavonols contents of tested samples ranged from 12.22 ± 0.90 (Ku-Ding-Cha (Ilex kaushue, small-leaved)) to 55.59 ± 2.20 (lotus leaves) mg RE/g DW. In the herb plant flower organ samples, the flavonols contents of tested samples were between 13.54 ± 0.47 (rose) and 25.40 ± 1.78 (wild Chrysanthemum) mg RE/ g DW. In the herb plant root organ samples, the flavonols content of Astragalus was 40.88 ± 0.42 mg RE/g DW, which is higher than that of herb plant peel organ (tangerine peel, 8.22 ± 0.35 mg RE/g DW) and herb plant seed organ (black buckwheat sprout, 22.20 ± 2.75 mg RE/g DW; roasted barley, 8.29 ± 0.09 mg RE/g DW).

2.14. Statistical analysis All measurements were carried out in three times. The results were shown as mean ± SD. Statistical comparisons were made by using the Student’s test. P < 0.05 was set as statistical significance. 3. Results and discussion 3.1. Total phenolics content The total phenolics contents (TPC) of herb plant organs samples are shown in Fig. 1(A). Generally, the TPC values varied among different samples, ranging from 2.80 ± 0.15 (black buckwheat (Fagopyrum tataricum) sprout) to 264.59 ± 3.59 (Ampelopsis grossedentata) mg of GAE/g DW. The herb plant leaf organ and herb plant flower organ possessed average phenolics contents of 101.07 ± 67.40 and 100.73 ± 85.19 mg of GAE/g DW, which were significantly higher than other herb plant organs. In the herb plant leaf organ samples, the phenolics contents of tested samples ranged from 3.02 ± 0.50 (mulberry (Morus nigra) leaves) to 264.59 ± 3.59 (Ampelopsis grossedentata) mg of GAE/g DW. In the herb plant flower organ samples, the phenolics contents of tested samples ranged from 17.44 ± 0.68 (wild Chrysanthemum) to 210.73 ± 3.94 (jasmine (Jasminum officinale) flower) mg of GAE/g DW. In the herb plant root organ, the phenolics content of Astragalus flower was 46.98 ± 2.15 mg of GAE/g DW, which is higher than herb plant peel organ (tangerine peel, 3.18 ± 0.51 mg of GAE/g DW) and herb plant seed organ (black buckwheat sprout, 2.80 ± 0.15 mg of GAE/g DW; roasted barley (Hordeum vulgare), 5.48 ± 0.03 mg of GAE/g DW). Consumption of herb plant organs and/or their products have been related to reduced risk of chronic diseases, such as diabetics, obesity, and cardiovascular diseases and these health benefits have been associated with phenolics (Crozier et al., 2009; Del Rio et al., 2013; McDougall et al., 2005). Hypoglycemic effects of many polyphenols were observed, catechin could improve glucose tolerance caused by ingestion of starch and sucrose in rats (Matsumoto et al., 1993); it was reported that application of bio-herb plant source to model mice showed significant decreases in blood sugar level (Shenoy, 2000).

3.4. Total proanthocyanidins content Proanthocyanidins are effective antioxidants and extensively exist in plant (Liu et al., 2016b). Various reports proved diabetes vascular complications are accompanied with oxidative stress in cells, and the oxygen radical accumulation may cause oxidative stress injury (Kizub et al., 2014). Thus, the content of proanthocyanidins is one of the key parameters to evaluate the beneficial properties of herb plant organ. The total proanthocyanidins contents of twenty-three tested herb plant organ samples were exhibited in Fig. 1(D). The total proanthocyanidins contents ranged from 155.26 ± 13.10 (Osmanthus) to 12389.6 ± 515.58 (Adinandra nitida merr.ex) mg ECE/100 g DW. Herb plant leaf organ and flower organ had significantly higher average total proanthocyanidin contents (2498.5 and 2497.6 mg ECE/100 g DW, respectively) than that of other herb plant organs (p < 0.05). In the herb plant leaf organ samples, Adinandra nitida merr.ex had the highest total proanthocyanidins content (12389.6 ± 515.58 mg ECE/100 g DW), while partridge tea (Mallotus furetianus) had the lowest proanthocyanidins content (259.41 ± 38.06 mg ECE/100 g DW). In the herb plant flower organs, jasmine flower had the highest proanthocyanidins content (10660.6 ± 226.06 mg ECE/100 g DW), followed by rose, 4

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Fig. 1. Total phenolics (A), total flavonoids (B), total flavonols (C), and total proanthocyanidins (D) contents of the twenty-three herb plant organ samples. Bars with different letters differ significantly at p < 0.05.

honeysuckle (Lonicera japonica), wild Chrysanthemum, while Osmanthus had the lowest proanthocyanidins content (155.26 ± 13.10 mg ECE/ 100 g DW). In herb plant seed organs, the proanthocyanidins content of black buckwheat sprout (461.55 ± 252.45 mg ECE/100 g DW) is higher than that of roast barley (260.15 ± 13.83 mg ECE/100 g DW). The proanthocyanidins content of tangerine peel (herb plant peel organ, 348.76 ± 44.25 mg ECE/100 g DW) is higher than that of Astragalus (herb plant root organ, 325.05 ± 72.46 mg ECE/100 g DW).

(the lowest, 0.11 ± 0.002 mg/g DW), which indicated that herb plant organ is not the source of caffeic acid. Syringic acid was detected in three samples, with the highest content in rose tea (2.83 ± 0.20 mg/g DW), followed by honeysuckle and hawk tea. Similarly, EC was only detected in three samples, with the highest content in Chinese wolfberry bud (10.26 ± 0.28 mg/g DW), followed by Adinandra nitida merr.ex and jasmine flower. Ferulic acid was found in eleven samples, with the highest in Ampelopsis grossedentata (17.31 ± 0.06 mg/g DW), followed by Forsythia suspensa leaves, Chinese wolfberry bud, Astragalus, Ku-Ding-Cha (small-leaved), rose, black buckwheat sprout, partridge tea, Apocynum venetum, lotus leaves, and tangerine peel. ECG was detected in nine samples, with the highest in Forsythia suspensa leaves (3.15 ± 0.15 mg/g DW), followed by jasmine flower, rose, wild Chrysanthemum, hawk tea, roasted barley, perilla leaves (Perilla frutescens), Apocynum venetum and Cyclocarya paliurus (the lowest, 0.003 ± 0.0002 mg/g DW). Salicylic acid was detected in ten samples, the highest in hawk tea (33.62 ± 1.18 mg/g DW), followed by honeysuckle, wild Chrysanthemum, Chinese holly leaves (Ilex cornuta, largeleaved), Ku-Ding-Cha (small leaved), lotus leaves, roasted barley, Apocynum venetum, Cyclocarya paliurus, and perilla leaves (the lowest, 0.63 ± 0.01 mg/g DW). Chlorogenic acid, an ester with quinic acid of caffeic acid, is an effective antioxidant in vivo (Kasai et al., 2000) and is absorbed in the blood circulation (Riceevans et al., 1996). Chlorogenic

3.5. High performance liquid chromatography analysis As shown in Table 3, the free phenolics compounds in twenty-three herb plant organs covers caffeic acid, syringic acid, epicatechin (EC), ferulic acid, epicatechin gallate (ECG), salicylic acid, chlorogenic acid, epigallocatechin gallate (EGCG), quercetin, cinnamic acid, and kaempferol, which are known effective compositions in herb plants and regarded as safe to human (structures could be seen in the supporting information). The respective amounts of these phenolics compounds in twenty-three herb plant organ samples are showed as mg/g DW. Caffeic acid is a representative of hydroxyl cinnamic acids in plant (Olthof et al., 2001), however, it was only detected in five tested samples, with highest content (1.96 ± 0.08 mg/g DW) in rose, followed by Chinese wolfberry bud, hawk tea, partridge tea and Adinandra nitida merr.ex 5

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acid was detected in thirteen tested samples, the highest in honeysuckle (13.15 ± 0.44 mg/g DW), followed by Chinese wolfberry bud, hawk tea, rose, lotus leaves, Apocynum venetum, wild Chrysanthemum, Chinese holly leaves (large-leaved), roasted barley, mulberry leaves, jasmine flower, Adinandran nitida merr.ex, and Cyclocarya paliurus (the lowest, 0.72 ± 0.01 mg/g DW), indicating that most of herb plant organs are chlorogenic acid sources in diet. EGCG was detected in all herb plant organ samples with the highest content in Ampelopsis grossedentata (3.65 ± 0.12 mg/g DW), followed by jasmine flower, rose, hawk tea, partridge tea, Ku-Ding-Cha (small leaved), lotus leaves, sweet tea (Strigose hydrangea leaves), roasted barley, and Apocynum venetum (the lowest, 0.04 ± 0.001 mg/g). Quercetin was detected in four samples, with the highest content in Adinandra nitida merr.ex (2.09 ± 0.09 mg/ g), followed by wild Chrysanthemum, hawk tea and black buckwheat sprout (the lowest, 0.37 ± 0.03 mg/g DW). Cinnamic acid was detected in five samples, with the highest content in Astragalus (4.72 ± 0.11 mg/g DW), followed by rose, hawk tea, Ku-Ding-Cha (small leaved), and Chinese wolfberry bud (the lowest, 0.03 ± 0.003 mg/g DW). Kaempferol was detected in nine herb plant organs, with the highest content in Astragalus (1.57 ± 0.03 mg/g DW), followed by tangerine peel, wild Chrysanthemum, Adinandra nitida merr.ex, Ku-Ding-Cha (small leaved), Chinese wolfberry bud, Chinese holly leaves (large-leaved), roasted barley, and rose (the lowest, 0.03 ± 0.0005 mg/g DW). 3.6. In vitro antioxidant activity by ORAC, DPPH and ABTS The in vitro antioxidant activities were measured by ORAC, DPPH radical scavenging and ABTS radical scavenging assays. The ORAC values of herb plant organs samples are presented in Fig. 2(A). In all tested samples, the ORAC values ranged from 346.12 ± 50.72 (black buckwheat sprout) to 20056.3 ± 1701.5 (Adinandra nitida merr.ex) μmol TE/g DW. In the herb plant leaf organ samples, Adinandra nitida merr.ex had the highest total ORAC value (20056.3 ± 1701.5 μmol TE/ g DW), followed by Ku-Ding-Cha (small leaved), hawk tea, Forsythia suspensa leaves, Ampelopsis grossedentata, sweet tea, leaf of Chinese holly (large-leaved), lotus leaves, Cyclocarya paliurus, Chinese wolfberry bud, partridge tea, perilla leaves and Apocynum venetum, while mulberry leaf had the lowest ORAC value (447.97 ± 64.73 μmol TE/g DW). In the herb plant flower organ samples, jasmine flower had the highest ORAC value (4766.1 ± 185.67 μmol TE/g DW), followed by Osmanthus, wild Chrysanthemum and rose, while honeysuckle had the lowest ORAC value (1255.6 ± 140.56 μmol TE/g DW). In the herb plant seed organ samples, the ORAC value of roasted barley (1476.1 ± 24.38 μmol TE/g DW) was higher than that of black buckwheat sprout (346.12 ± 50.72 μmol TE/g DW). The ORAC value of tangerine peel (1440.4 ± 118.58 μmol TE/g DW) is higher than that of Astragalus (1172.3 ± 125.51 μmol TE/g DW). The DPPH values of herb plant organ samples are shown in Fig. 2(B). In all tested samples, the DPPH values ranged from 2.47 ± 0.15 (mulberry leaves) to 188.52 ± 4.02 (Ampelopsis grossedentata) mg QE/g DW. In the herb plant leaf organ samples, Ampelopsis grossedentata had the highest DPPH value (188.52 ± 4.02 mg QE/g DW), followed by sweet tea, partridge tea, hawk tea, Apocynum venetum, Adinandra nitida merr.ex, perilla leaves, lotus leaves, Cyclocary apaliurus, Forsythia suspensa leaves, Chinese holly leaves (large-leaved), Ku-Ding-Cha (small leaved) and Chinese wolfberry bud, mulberry leaves had the lowest DPPH value (2.47 ± 0.15 mg QE/g DW). In the herb plant flower organ samples, jasmine flower had the significantly highest DPPH value (165.58 ± 6.76 mg QE/g DW, p < 0.01), followed by rose tea, Osmanthus, and honeysuckle, while wild Chrysanthemum had the lowest DPPH value (4.40 ± 0.08 mg QE/g DW). In the herb plant seed organ samples, black buckwheat sprout (4.08 ± 0.03 mg QE/g DW) and roasted barley (3.97 ± 0.17 mg QE/g DW) had the similar DPPH values. However, the DPPH value of Astragalus (12.40 ± 0.93 mg QE/g DW) was higher than that of tangerine peel

Fig. 2. ORAC (A), DPPH (B), ABTS (C) values of the twenty-three herb plant organ samples. Bars with different letters differ significantly at p < 0.05.

(3.80 ± 0.02 mg QE/g DW). The ABTS values of herb plant organs tested samples are shown in Fig. 2(C). In all tested samples, the ABTS values ranged from 4.94 ± 0.16 (roasted barely) to 573.07 ± 14.90 (jasmine flower) mg VCE/g DW. In the herb plant leaf organ samples, Ampelopsis grossedentata had the highest ABTS value (518.10 ± 12.50 mg VCE/g DW), followed by Adinandra nitida merr.ex, sweet tea, hawk tea, partridge tea, 6

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(573.07 ± 14.90 mg VCE/g DW, p < 0.01), followed by rose, Osmanthus, and honeysuckle, while wild Chrysanthemum had the lowest ABTS value (51.15 ± 1.26 mg VCE/g DW). In the herb plant seed organ samples, the ABTS value of black buckwheat sprout was higher than that of roasted barley (Fig. 2(C)). The ABTS value of Astragalus was higher than that of tangerine peel. Similarly, Herrera reported that nineteen highly consumed herbal infusions could be selected as potential sources of phytochemicals and antioxidants (Herrera et al., 2018). 3.7. Cellular antioxidant activity The cellular antioxidant activity (CAA) values of tested herb plant organ samples are displayed in Fig. 3. In all tested samples, the CAA values ranged from 0 (Apocynum venetum, hawk tea, Cyclocarya paliurus, black buckwheat sprout) to 327.89 ± 89.28 μmol of QE/100 g (rose tea). In the herb plant leaf organ samples, perilla leaves had the highest CAA value (119.10 ± 4.53 μmol of QE/100 g), followed by Ampelopsis grossedentata, lotus leaves, partridge tea, Adinandra nitida merr.ex, sweet tea, Chinese wolfberry bud, Chinese holly leaves (large-leaved), Forsythia Suspensa leaves, mulberry leaves, and Apocynum venetum (not detected, ND), hawk tea (ND), Cyclocarya paliurus (ND) and Ku-DingCha (small leaved). In the herb plant flower organ samples, rose had the highest CAA values (327.89 ± 89.28 μmol of QE/100 g), followed by honeysuckle, jasmine flower, wild Chrysanthemum and Osmanthus. In the herb plant seed organ samples, the CAA value of roasted barley was higher than that of black buckwheat sprout (Fig. 2(C)). The CAA value of Astragalus was higher than that of tangerine peel. As displayed in

Fig. 3. Cellular antioxidant activity values of the twenty-three herb plant organ samples. Bars with different letters differ significantly at p < 0.05.

lotus leaves, Apocynum venetum, Forsythia suspensa leaf, Cyclocarya paliurus, leaf of Chinese holly (large-leaved), perilla leaves, and Ku-DingCha (small leaved), mulberry leaves had the lowest ABTS value (14.42 ± 0.22 mg VCE/g DW). In the herb plant flower organ, particularly jasmine flower had the highest ABTS value

Table 2 Average phytochemical contents, antioxidant activity, α-glucosidase inhibitory activity, and glucose consumption of herb plants organs. Herb plant leaves organs

Mean

SD

CV(%)

Herb plant flowering organs

Mean

SD

CV(%)

Total phenolics (mg of gallic acid equiv./g DW) Total flavonoids (mg of catechin equiv./g DW) Total flavonols (mg of rutin equiv.g DW) Total proanthocyanidins (mg of epicatechin equiv./100 g DW) DPPH (mg of quercetin equiv./g DW) ABTS (mg of vitamin c equiv./g DW) ORAC (μM Trolox equiv./g DW) CAA (μmol of QE/100 g) α-Glucosidase inhibitory activity (IC50 values, μg DW/mL)

101.07 49.21 29.33 2498.52

67.40 26.91 12.89 3511.52

66.69 54.68 43.94 140.54

100.73 54.93 17.70 2497.63

85.19 39.10 4.95 4567.97

84.57 71.18 27.99 182.89

35.34 184.04 3865.98 32.72 10.63

52.03 130.51 5047.45 36.97 19.98

147.26 70.91 130.56 112.98 188.03

50.56 230.33 2437.72 115.84 0.61

68.45 212.80 1495.92 138.95 0.90

135.39 92.39 61.37 119.95 147.31

Glucose consumption (mmol/L) Herb plant peel organs Total phenolics (mg of gallic acid equiv./g DW) Total flavonoids (mg of catechin equiv./g DW) Total flavonols (mg of rutin equiv.g DW) Total proanthocyanidins (mg of epicatechin equiv./100 g DW) DPPH (mg of quercetin equiv./g DW) ABTS (mg of vitamin c equiv./g DW) ORAC (μM Trolox equiv./g DW) CAA (μmol of QE/100 g) α-Glucosidase inhibitory activity (IC50 values, μg DW/mL)

0.58 Mean 3.18 4.51 8.22 348.76

0.97 SD 0.51 0.24 0.35 44.25

167.00 CV(%) 16.09 5.30 4.24 12.69

0.43 Mean 46.98 5.43 40.88 325.05

0.61 SD 2.15 0.27 0.42 72.46

142.84 CV(%) 4.57 5.04 1.04 22.29

3.80 14.43 1440.43 16.37 ND

0.02 0.19 118.58 3.00 ND

0.51 1.34 8.23 18.31 ND

12.40 76.27 1172.30 37.80 ND

0.93 4.23 125.51 8.09 ND

7.53 5.55 10.71 21.40 ND

ND Mean 4.14 3.26 15.25 360.85

ND SD 1.90 1.97 9.83 142.41

ND CV(%) 45.80 60.39 64.51 39.47

Total phenolics (mg of gallic acid equiv./g DW) Total flavonoids (mg of catechin equiv./g DW) Total flavonols (mg of rutin equiv.g DW) Total proanthocyanidins (mg of epicatechin equiv./ 100 g DW) DPPH (mg of quercetin equiv./g DW) ABTS (mg of vitamin c equiv./g DW) ORAC (μM Trolox equiv./g DW) CAA (μmol of QE/100 g) α-Glucosidase inhibitory activity (IC50 values, μg DW/ mL) Glucose consumption (mmol/L) Herb plant root organs Total phenolics (mg of gallic acid equiv./g DW) Total flavonoids (mg of catechin equiv./g DW) Total flavonols (mg of rutin equiv.g DW) Total proanthocyanidins (mg of epicatechin equiv./ 100 g DW) DPPH (mg of quercetin equiv./g DW) ABTS (mg of vitamin c equiv./g DW) ORAC (μM Trolox equiv./g DW) CAA (μmol of QE/100 g) α-Glucosidase inhibitory activity (IC50 values, μg DW/ mL) Glucose consumption (mmol/L)

ND

ND

ND

4.03 10.66 911.11 9.34 13.70 ND

0.07 8.09 799.01 13.21 19.37 ND

1.78 75.89 87.70 141.42 141.42 ND

Glucose consumption (mmol/L) Herb plant seed organs Total phenolics (mg of gallic acid equiv./g DW) Total flavonoids (mg of catechin equiv./g DW) Total flavonols (mg of rutinequiv.g DW) Total proanthocyanidins (mg of epicatechin equiv./100 g DW) DPPH (mg of quercetin equiv./g DW) ABTS (mg of vitamin c equiv./g DW) ORAC (μM Trolox equiv./g DW) CAA (μmol of QE/100 g) α-Glucosidase inhibitory activity (IC50 values, μg DW/mL) Glucose consumption (mmol/L)

ND: not detected. 7

8

ND: not detected.

Perilla leaves Ampelopsis grossedentata Rose Chinese wolfberry bud Forsythia Suspensa leaves Osmanthus Tangerine peel Astragalus Apocynum venetum Jasmine flower Hawk tea Wild Chrysanthemum Chinese holly leaves (large-leaved) Honeysuckle Cyclocarya paliurus Lotus leaves Adinandra nitida merr.ex Ku-Ding-Cha (small leaved) Partridge tea Sweet tea Black buckwheat sprout Roasted barley Mulberry leaves

ND ND 1.96 0.86 ND ND ND ND ND ND 0.29 ND ND ND ND ND 0.11 ND 0.13 ND ND ND ND

± 0.02a

± 0.002a

± 0.05b

± 0.08d ± 0.04c

Caffeic acid ND ND 2.83 ± 0.20c ND ND ND ND ND ND ND 0.43 ± 0.01a ND ND 0.75 ± 0.02b ND ND ND ND ND ND ND ND ND

Syringic acid ND ND ND 10.26 ± 0.28c ND ND ND ND ND 1.63 ± 0.07a ND ND ND ND ND ND 7.41 ± 0.11b ND ND ND ND ND ND

EC

Table 3 Phenolics compounds in the twenty-three herb plants organ samples.

ND 17.31 ± 0.06 h 0.94 ± 0.03c 6.50 ± 0.23f 9.71 ± 0.28 g ND 0.35 ± 0.04a 6.24 ± 0.07e 0.36 ± 0.01a ND ND ND ND ND ND 0.35 ± 0.01a ND 2.01 ± 0.05d 0.42 ± 0.01a ND 0.67 ± 0.03b ND ND

Ferulic acid 0.06 ± 0.006abc ND 0.14 ± 0.03c ND 3.15 ± 0.15e ND ND ND 0.02 ± 0.002ab 0.40 ± 0.02d 0.11 ± 0.02bc 0.11 ± 0.01c ND ND 0.003 ± 0.0002a ND ND ND ND ND ND 0.08 ± 0.002abc ND

ECG 0.63 ± 0.01a ND ND ND ND ND ND ND 1.7 ± 0.06b ND 33.62 ± 1.18 h 8.52 ± 0.41f 5.64 ± 0.04e 23.32 ± 1.01 g 0.85 ± 0.01a 2.95 ± 0.10c ND 4.12 ± 0.21d ND ND ND 2.29 ± 0.05bc ND

Salicylic acid ND ND 7.30 ± 0.30c 12.23 ± 0.33e ND ND ND ND 1.83 ± 0.05b 0.81 ± 0.02a 9.29 ± 0.49d 1.83 ± 0.13b 1.82 ± 0.02b 13.15 ± 0.44f 0.72 ± 0.01a 1.96 ± 0.14b 0.80 ± 0.01a ND ND ND ND 1.02 ± 0.01a 0.84 ± 0.03a

Chlorogenic acid ND 3.65 2.84 ND ND ND ND ND 0.04 3.61 2.81 ND ND ND ND 0.41 ND 0.78 0.95 0.16 ND 0.13 ND ± 0.01a

± 0.06c ± 0.02d ± 0.01a

± 0.04b

± 0.001a ± 0.05f ± 0.15e

± 0.12f ± 0.13e

EGCG ND ND ND ND ND ND ND ND ND ND 0.93 1.14 ND ND ND ND 2.09 ND ND ND 0.37 ND ND

± 0.03a

± 0.09d

± 0.02b ± 0.09c

Quercetin

ND ND 0.19 0.03 ND ND ND 4.72 ND ND 0.04 ND ND ND ND ND ND 0.03 ND ND ND ND ND

± 0.002a

± 0.0004a

± 0.11c

± 0.01b ± 0.003a

Cinnamic acid

ND ND 0.03 0.10 ND ND 0.59 1.57 ND ND ND 0.48 0.10 ND ND ND 0.15 0.15 ND ND ND 0.08 ND

± 0.004b

± 0.006d ± 0.008d

± 0.009e ± 0.007c

± 0.004f ± 0.03 g

± 0.000a ± 0.004c

Kaempferol

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Table 2, the average CAA value of herb plant flower organ was the highest in all tested herb plant organs, followed by herb plant leaf organ, root organ, peel organ and the seed organ. The results indicated that the herb plant flower organ could be effective absorbed by HepG2 cells and had the most potent cellular antioxidant activity. 3.8. α-Glucosidase inhibitory activity Suppressing the postprandial blood sugar level may be via inhibiting the activity of α-glucosidase, which plays a major role in dietary starch digestion (Inzucchi, 2002). α-Glucosidase is located in the brush border of the small intestine and breaks down starch and disaccharides by acting upon α(1→4) bonds, releasing α-glucose (Kim et al., 2010). Acarbose, a commercial anti-diabetic drug for treating type 2 diabetes, is a α-glucosidase inhibitor (Bischoff, 1994). In recent decades, uncovering new and natural sources of α-glucosidase inhibitors, such as phenolics, has captivated the attention of food scientists around the world. The α-glucosidase inhibitory activities of all tested samples are exhibited in Fig. 4, expressed as IC50 values (μg DW/mL). Among all the twenty-three tested samples, only twelve samples showed α-glucosidase inhibitory activities with the IC50 values ranging from 1.06 ± 0.02 (rose tea) to 73.46 ± 1.26 (Forsythia suspensa leaves) μg DW/mL. Rose had the lowest IC50 value (1.06 ± 0.02 μg DW/mL), followed by partridge tea, jasmine flower, sweet tea, hawk tea, Cyclocarya paliurus, Ampelopsis grossedentata, lotus leaves, Adinandra nitida merr.ex, black buckwheat sprout, and perilla leaves. Forsthia suspense leaf had the highest IC50 value (73.46 ± 1.26 μg DW/mL). The higher IC50 value, the weaker α-glucosidase inhibitory activity. In other words, rose had the strongest α-glucosidase inhibitory activity, followed by partridge tea, jasmine flower, sweet tea, hawk tea, Cyclocarya paliurus, Ampelopsis grossedentata, lotus leaves, Adinandra nitida merr.ex, black buckwheat sprout, and perilla leaves, and Forsythia suspense leaves. As shown in Table 3, rose flower had various phenolic compounds, indicating that phenolic compounds had great contributions to α-glucosidase inhibitory properties, similar to previous reports (You et al., 2012; Zhang et al., 2015).

Fig. 4. α-Glucosidase inhibitory activity EC50 values of the twenty-three herb plant organ samples. Bars with different letters differ significantly at p < 0.05.

3.9. Glucose consumption activity in HepG2 model in vitro The glucose consumption activity of all tested samples was expressed as mmol/L glucose. As depicted in Fig. 5, only seven samples had glucose consumption activity in HepG2 model in vitro, as well as αglucosidase inhibitory activity. In control group (Met), the value of glucose consumption in HepG2 cell model was 1.44 ± 0.54 mmol/L. Ampelopsis grossedentata (2.72 ± 0.36 mmol/L) and partridge tea (2.44 ± 0.08 mmol/L) had the highest glucose consumption, followed

Fig. 5. Glucose consumption activity values of the twenty-three herb plant organ samples in HepG2 cell model. Bars with different letters differ significantly at p < 0.05.

Table 4 Correlation coefficients among phenolics, flavonoids, flavonols, proanthocyanidins, antioxidant activity, α-glucosidase inhibitory activity, and glucose consumption of herb plants organs.

Phenolics Flavonoids Flavonols Proanthocyanidins ABTS ORAC DPPH α-Glucosidase inhibitory activity CAA Glucose consumption

Phenolics

Flavonoid

Flavonols

Proanthocyanidins

ABTS

ORAC

DPPH

α-Glucosidase inhibitory activity

CAA

Glucose consumption

1.000

0.589** 1.000

0.102 0.267 1.000

0.393 0.365 0.365 1.000

0.929** 0.539** 0.220 0.587** 1.000

0.696** 0.695** 0.062 0.205 0.493* 1.000

0.878** 0.382 0.196 0.515* 0.930** 0.333 1.000

0.409 0.349 0.445* 0.534** 0.478* 0.216 0.448* 1.000

0.282 −0.012 −0.010 0.123 0.362 −0.083 0.380 0.150

0.444* 0.121 −0.074 −0.038 0.457* 0.082 0.426* 0.205

1.000

0.520* 1.000

** Correlation is significant at the 0.01 level (2-tailed). * Correlation is significant at the 0.05 level (2-tailed). 9

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by Adinandra nitida merr.ex, Osmanthus, rose, Chinese wolfberry bud and perilla leaves. Similar with CAA values, the glucose consumption activity of some samples were not detected in HepG2 cell model, which may be caused by the inefficient absorbance of phytochemicals from those samples in HepG2 cells. In all, the results indicate that, compared other herb plant organs, the herb plant leaf organ had the stronger glucose absorption regulation.

4. Conclusions Collectively, results show that herb plant organs abound in phenolics, flavonoids, flavonols and proanthocyanidins, and possess high antioxidant, α-glucosidase inhibitory and glucose consumption activities. Among all the tested herb plant organs, herb plant flower organ (rose and jasmine flower) and herb plant leaf organ (Adinandra nitida merr.ex, hawk tea, lotus leaves, Apocynum venetum and Cyclocarya paliurus) were good sources of natural antioxidants and exhibited hypoglycemic activity. HPLC analysis revealed common plant organ phytochemicals, including ferulic acid, salicylic acid, chlorogenic acid and epigallocatechin gallate. Statistical analysis uncovered the significant positive correlations (p < 0.05) between antioxidants and hypoglycemic effects. Results indicate that plant organs, especially flower and leaf organs, possessed excellent antioxidant and glucose regulating activities and could provide basis for the development of related health food and products for the diabetes patients. Further study will concentrate on the main phytochemicals and related mechanisms of α-glucosidase inhibition and glucose consumption.

3.10. Correlations Phytochemicals devote to the antioxidant, α-glucosidase inhibitory and glucose consumption activities, however, correlation coefficients among phenolics, flavonoids, flavonols, proanthocyanidins, and antioxidant, α-glucosidase inhibitory and glucose consumption activities of herb plant organs are not yet clear. Hence it is worth to investigate which types of phytochemicals contribute to antioxidant, α-glucosidase inhibitory and glucose consumption activities (Geng et al., 2016; Pang et al., 2016). As listed in Table 4, phenolics showed significant coefficients with flavonoids (r = 0.589**, p < 0.01), DPPH (r = 0.878**, p < 0.01), ABTS (r = 0.929**, p < 0.01), ORAC (r = 0.696**, p < 0.01), glucose consumption (r = 0.444*, p < 0.05), respectively; in accordance with previous reports that phenolics were correlated to antioxidant activity (Adom and Liu, 2002). Certainly, phenolics showed weak positive correlation with flavonols (r = 0.102), proanthocyanidins (r = 0.393), α-glucosidase inhibitory activities (r = 0.409), and CAA value (r = 0.282). The results reflected that phenolics compounds clearly devote to antioxidative and glucose consumption activities. Flavonoids displayed significant contribution to ABTS (r = 0.539**, p < 0.01) and ORAC (r = 0.695**, p < 0.01); as well as phenolics, flavonoids showed weak positive correlation with flavonols (r = 0.267), proanthocyanidins (r = 0.365), DPPH (r = 0.382), and glucose consumption (r = 0.121). However, the correlations coefficients between flavonoids and α-glucosidase inhibitory activity, CAA values were positive (r = 0.349) and negative (r = -0.012), which indicated that flavonoids in herb plant organs had weak inhibitory effects on α-glucosidase and CAA. Interestingly, flavonols had weak correlations with chemicals antioxidant activities but had negative correlations with CAA (r = -0.010) and glucose consumption (r = -0.074), and had a significant positive correlation with α-glucosidase inhibitory activity (r = 0.445**, p < 0.01); the results indicated that flavonols from herb plant organs act as cellular antioxidants and could regulate blood glucose level. Proanthocyanidins showed significant correlations with ABTS (r = 0.587**, p < 0.01), DPPH (r = 0.515*, p < 0.05), and αglucosidase inhibitory activity (r = 0.534, p < 0.01), with weak positive correlative with ORAC (r = 0.205) and CAA (r = 0.123), however, proanthocyanidins had a weak negative correlation with glucose consumption (r = -0.038) which means proanthocyanidins from herb plant organs had weak α-glucosidase inhibitory activity. ABTS displayed significant correlation coefficients with ORAC (r = 0.493*, p < 0.05), DPPH (r = 0.930**, p < 0.01), α-glucosidase inhibitory activity (r = 0.478*, p < 0.05) and glucose consumption (r = 0.457*, p < 0.05), with a weak positive correlation with CAA (r = 0.362). ORAC exhibited weak correlations with DPPH (r = 0.333), α-glucosidase inhibitory activity (r = 0.216) and glucose consumption (r = 0.082), especially, with a weak correlation with CAA (r = -0.083). Interestingly, DPPH showed significant correlation coefficients with αglucosidase inhibitory activity (r = 0.448*, p < 0.05) and glucose consumption (r = 0.426*, p < 0.05). Interestingly, the correlation coefficient between antioxidant activity and α-glucosidase inhibitory activity is similar to previous reports (Khan and Mukhtar, 2007; Lorenzo and Munekata, 2016). The results present that both of phenolics contents and antioxidant activity had positive contributions to glucose consumption.

Declaration of Competing Interest There are no conflicts to declare. Acknowledgements We gratefully acknowledge financial support from China Postdoctoral Science Foundation (2017M622910). And the authors are thankful to Dr. Yuyun Lu from National University of Singapore for his assistance in writing. Appendix A. Supplementary data Supplementary material related to this article can be found, in the online version, at doi:https://doi.org/10.1016/j.indcrop.2019.111771. References Adom, K.K., Liu, R.H., 2002. Antioxidant activity of grains. J. Agric. Food Chem. 50, 6182–6187. Alberti, M.G.M.M., 1998. Definition, diagnosis and classification of diabetes mellituss and its complications. Part 1 : diagnosis and classiffication of diabetes mellitus. Provisional report of a WHO consultation. Diabetic Medicine, pp. 15. Balkan, İ.A., Doğan, H.T., Zengin, G., Colak, N., Ayaz, F.A., Gören, A.C., Kırmızıbekmez, H., Yeşilada, E., 2018. Enzyme inhibitory and antioxidant activities of Nerium oleander L. flower extracts and activity guided isolation of the active components. Ind. Crop. Prod. 112, 24–31. Bischoff, H., 1994. Pharmacology of alpha-glucosidase inhibition. Eur J Clin Invest. J. Clin. Invest. 24, 3–10. Chen, C., Zhang, B., Fu, X., Liu, R.H., 2016a. A novel polysaccharide isolated from mulberry fruits (Murus alba L.) and its selenide derivative: structural characterization and biological activities. Food Funct. 7, 2886–2897. Chen, X.-M., Ma, Z., Kitts, D.D., 2018. Effects of processing method and age of leaves on phytochemical profiles and bioactivity of coffee leaves. Food Chem. 249, 143–153. Chen, Y., Chen, G., Fu, X., Liu, R.H., 2015. Phytochemical Profiles and Antioxidant Activity of Different Varieties of Adinandra Tea (Adinandra Jack). J. Agric. Food Chem. 63, 169–176. Chen, Y., Huang, J., Hu, J., Yan, R., Ma, X., 2019a. Comparative study on the phytochemical profiles and cellular antioxidant activity of phenolics extracted from barley malts processed under different roasting temperatures. Food Funct. 10, 2176–2185. Chen, Y., Liu, J., Geng, S., Liu, Y., Ma, H., Zheng, J., Liu, B., Liang, G., 2019b. Lipasecatalyzed synthesis mechanism of tri-acetylated phloridzin and its antiproliferative activity against HepG2 cancer cells. Food Chem. 277, 186–194. Chen, Y., Ma, X., Fu, X., Yan, R., 2017a. Phytochemical content, cellular antioxidant activity and antiproliferative activity of Adinandra nitida tea (Shiyacha) infusion subjected to in vitro gastrointestinal digestion. RSC Adv. 7, 50430–50440. Chen, Y., Shen, Y., Fu, X., Abbasi, A.M., Yan, R., 2017b. Stir-frying treatments affect the phenolics profiles and cellular antioxidant activity of Adinandra nitida tea (Shiyacha) in daily tea model. Int. J. Food Sci. Technol. 52, 1820–1827. Chen, Y., Wang, G., Wang, H., Cheng, C., Zang, G., Guo, X., Liu, R.H., 2014. Phytochemical Profiles and Antioxidant Activities in Six Species of Ramie LeavesPLOprofiles and antioxidant activities in six species of ramie leaves. S One 9, e108140. Chen, Y., Zhang, R., Liu, C., Zheng, X., Liu, B., 2016b. Enhancing antioxidant activity and

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Y. Chen, et al.

289–298. Liu, B., Chen, Y., Mo, H., Ma, H., Zhao, J., 2016a. Catapult steam explosion significantly increases cellular antioxidant and anti-proliferative activities of Adinandra nitida leaves. J. Funct. Foods 23, 423–431. Liu, Y., Liao, W.J., Zhu, Z., Zeng, H., He, H.Q., Sun, X.L., Xu, X.F., Huang, L., Wang, W.M., Zhou, X.Y., 2016b. Effect of procyanidine on VEGFR-2 expression and transduction pathway in rat endothelial progenitor cells under high glucose conditions. Genet. Mol. Res. Gmr. 15. Lorenzo, J.M., Munekata, P.E.S., 2016. Phenolic compounds of green tea:Health benefits and technological application in food. Asian Pac. J. Trop. Biomed. 6, 709–719. Malchoff, C.D., 2010. Diagnosis and classification of diabetes mellitus. Diabetes Care 33, S62–S69. Matsumoto, N., Ishigaki, F., Ishigaki, A., Iwashina, H., Hara, Y., 1993. Reduction of Blood Glucose Levels by Tea CatechinJ. Agric. Chem. Society Japablood glucose levels by tea catechin. n. 57, 525–527. McDougall, G.J., Shpiro, F., Dobson, P., Smith, P., Blake, A., Stewart, D., 2005. Different polyphenolic components of soft fruits inhibit α-amylase and α-glucosidase. J. Agric. Food Chem. 53, 2760–2766. O, C., M, K, A, K, S, O, 2005. Quercetin, a flavonoid antioxidant, prevents and protects streptozotocin-induced oxidative stress and beta-cell damage in rat pancreas. Pharmacol. Res. 51, 117–123. Oki, T., Masuda, M., Kobayashi, M., Nishiba, Y., Furuta, S., Suda, I., Sato, T., 2002. Polymeric procyanidins as radical-scavenging components in red-hulled rice. J. Agric. Food Chem. 50, 7524–7529. Olthof, M.R., Hollman, P.C.H., Katan, M.B., 2001. Chlorogenic Acid and Caffeic Acid Are Absorbed in Humans. J. Nutr. 131, 66–71. Pang, D., You, L., Li, T., Zhou, L., Sun-Waterhouse, D., Liu, R.H., 2016. Phenolic profiles and chemical-or cell-based antioxidant activities of four star fruit (Averrhoa carambola) cultivars. RSC Adv. 6, 90646–90653. Piccinelli, A.L., De Simone, F., Passi, S., Rastrelli, L., 2004. Phenolic constituents and antioxidant activity of Wendita caiysina leaves (Burrito), a folk Paraguayan tea. J. Agric. Food Chem. 52, 5863–5868. Purohit, R., Ross, M.O., Batelu, S., Kusowski, A., Stemmler, T.L., Hoffman, B.M., Rosenzweig, A.C., 2018. Cu+-specific CopB transporter: Revising P1B-type ATPase classification. P. Natl. Acad. Sci. USA. 115, 201721783. Ranilla, L., Kwon, Y., Apostolidis, E., Shetty, K., 2010. Phenolic compounds, antioxidant activity and in vitro inhibitory potential against key enzymes relevant for hyperglycemia and hypertension of commonly used medicinal plants, herbs and spices in Latin America. Bioresource Technol. 101, 4676–4689. Riceevans, C.A., Miller, N.J., Paganga, G., 1996. Structure-antioxidant activity relationships of flavonoids and phenolic acids. Free Radic. Biol. Med. 20, 933–956. Riehle, P., Vollmer, M., Rohn, S., 2013. Phenolic compounds in Cistus incanus herbal infusions-antioxidant capacity and thermal stability during the brewing process. Food Res. Int. 53, 891–899. Shenoy, C., 2000. Hypoglycemic activity of bio-tea in mice. Indian J. Exp. Biol. 38, 278–279. Sun, S.S., Tang, R.C., 2011. Adsorption and UV protection properties of the extract from honeysuckle onto wool. Ind. Eng. Chem. Res. 50, 4217–4224. Valko, M., Leibfritz, D., Moncol, J., Cronin, M.T.D., Mazur, M., Telser, J., 2007. Free radicals and antioxidants in normal physiological functions and human disease. Int. J. Biochem. Cell B 39, 44–84. WHO, W, 2016. Global report on diabetes. World Health Organization. Yang, J., Martinson, T.E., Liu, R.H., 2009. Phytochemical profiles and antioxidant activities of wine grapes. Food Chem. 116, 332–339. You, Q., Chen, F., Wang, X., Jiang, Y., Lin, S., 2012. Anti-diabetic activities of phenolic compounds in muscadine against alpha-glucosidase and pancreatic lipase. LWT-Food Sci. Technol. 46, 164–168. Zhang, B., Deng, Z., Ramdath, D.D., Tang, Y., Chen, P.X., Liu, R., Liu, Q., Tsao, R., 2015. Phenolic profiles of 20 Canadian lentil cultivars and their contribution to antioxidant activity and inhibitory effects on α-glucosidase and pancreatic lipase. Food Chem. 172, 862–872.

antiproliferation of wheat bran through steam flash explosion. J. Food Sci. Tech. Mys. 53, 3028–3034. Cho, N.H., Shaw, J.E., Karuranga, S., Huang, Y., da Rocha Fernandes, J.D., Ohlrogge, A.W., Malanda, B., 2018. IDF Diabetes Atlas: Global estimates of diabetes prevalence for 2017 and projections for 2045. Diabetes research and clinical practice. Crozier, A., Jaganath, I.B., Clifford, M.N., 2009. Dietary phenolics: chemistry, bioavailability and effects on health. Nat. Prod. Rep. 26, 1001–1043. D, Åh., Sari, S., M, o., Barut, B., A, Ãz., Liptaj, T., 2018. Potential of Potentilla inclinata and its polyphenolic compounds in K ± -glucosidase inhibition: kinetics and interaction mechanism merged with docking simulations. Int. J. Biol. Macromol. 108, 81–87. Del Rio, D., Rodriguez-Mateos, A., Spencer, J.P., Tognolini, M., Borges, G., Crozier, A., 2013. Dietary (poly) phenolics in human health: structures, bioavailability, and evidence of protective effects against chronic diseases. Antioxid. Redox. Sign. 18, 1818–1892. Gao, H., Liu, B., Liu, F., Chen, Y., 2010. Anti-proliferative effect of camellianin A in Adinandra nitida leaves and its apoptotic induction in human Hep G2 and MCF-7 cells. Molecules 15, 3878–3886. Geng, S., Chen, Y., Abbasi, A.M., Ma, H., Mo, H., Liu, B., 2016. Tannin fraction from Ampelopsis grossedentata leaves tea (Tengcha) as an antioxidant and alpha-glucosidase inhibitory nutraceutical. Int. J. Food Sci. Tech. 51, 2692–2700. Gerschman, R., Gilbert, D., Nye, S.W., Dwyer, P., Fenn, W.O., 1954. Oxygen poisoning and X-irradiation: a mechanism in common. Glutathione 119, 623–626. Grubešić, R.J., Vuković, J., Kremer, D., Vladimir-Knežević, S., 2005. Spectrophotometric method for polyphenols analysis: Prevalidation and application on Plantago L. species. J. Pharm. Biomed. Anal. 39, 837–842. Helal, A., Desobry, S., Banon, S., Shamsia, S.M., 2015. Antioxidant activity and bioaccessibility of phenols-enriched edible casein/caseinate coatings during in vitro digestion. J. Dairy Res. 82, 56–63. Herrera, T., Aguilera, Y., Rebollo-Hernanz, M., Bravo, E., Benitez, V., Martinez-Saez, N., Arribas, S.M., Dolores del Castillo, M., Martin-Cabrejas, M.A., 2018. Teas and herbal infusions as sources of melatonin and other bioactive non-nutrient components. LWTFood Sci. Technol. 89, 65–73. Hichri, F., Salah, N.B., Omri, A., Hossan, A., Jannet, H.B., 2018. New antioxidant Cglycosyl flavone and flavonol derivatives from the Tunisian Achille acretica L. SAfr. J. Bot. 116, 1–5. Inglett, G.E., Chen, D., Berhow, M., Lee, S., 2011. Antioxidant activity of commercial buckwheat flours and their free and bound phenolic compositions. Food Chem. 125, 923–929. Inzucchi, S.E., 2002. Oral antihyperglycemic therapy for type 2 diabetes: scientific review. JAMA 287, 360–372. Kamara, B.I., Brand, D.J., Brandt, E.V., Joubert, E., 2004. Phenolic metabolites from honeybush tea (Cyclopia subternata). J. Agric. Food Chem. 52, 5391–5395. Kasai, H., Fukada, S., Yamaizumi, Z., Sugie, S., Mori, H., 2000. Action of chlorogenic acid in vegetables and fruits as an inhibitor of 8-hydroxydeoxyguanosine formation in vitro and in a rat carcinogenesis model. Food Chem. Toxicol. 38, 467–471. Kehrer, J.P., Smith, C.V., 1994. 2Free Radicals in Biology: Sources, Reactivities, and Roles in the Etiology of Human DiseasesNatural Antioxidants in Human Health & Disease–free radicals in biology: sources, reactivities, and roles in the etiology of human diseases. . 5, 25–62. Khan, N., Mukhtar, H., 2007. Tea polyphenols for health promotion. Life Sci. 81, 519–533. Kim, K.Y., Kurihara, H., Kim, S.M., 2010. α-glucosidase inhibitory activity of bromophenol purified from the red alga Polyopes lancifolia. J. Food Sci. 75, H145–H150. Kizub, I.V., Klymenko, K.I., Soloviev, A.I., 2014. Protein kinase C in enhanced vascular tone in diabetes mellitus. Int. J. Cardiol. 174, 230–242. Konczak, Izabela, Dalar, 2013. Phenolic contents, antioxidant capacities and inhibitory activities;against key metabolic syndrome relevant enzymes of herbal teas from;Eastern Anatolia. Ind. Crop. Prod. 44, 383–390. Li, S., Li, S.K., Gan, R.Y., Song, F.L., Kuang, L., Li, H.B., 2013. Antioxidant capacities and total phenolic contents of infusions from 223 medicinal plants. Ind. Crop. Prod. 51,

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