Anti-diabetic compounds from the seeds of Psoralea corylifolia

Journal Pre-proof Anti-diabetic compounds from the seeds of Psoralea corylifolia

Gaohui Zhu, Yanhong Luo, Xuejiao Xu, Huijiao Zhang, Min Zhu PII:

S0367-326X(19)31855-6

DOI:

https://doi.org/10.1016/j.fitote.2019.104373

Reference:

FITOTE 104373

To appear in:

Fitoterapia

Received date:

16 September 2019

Revised date:

11 October 2019

Accepted date:

12 October 2019

Please cite this article as: G. Zhu, Y. Luo, X. Xu, et al., Anti-diabetic compounds from the seeds of Psoralea corylifolia, Fitoterapia (2018), https://doi.org/10.1016/ j.fitote.2019.104373

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© 2018 Published by Elsevier.

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Anti-diabetic compounds from the seeds of Psoralea corylifolia

Gaohui Zhua, Yanhong Luoa, Xuejiao Xua, Huijiao Zhanga, Min Zhua* a

Department of Endocrinology, Children’s Hospital of Chongqing Medical University,

Corresponding author

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E-mail address: [email protected] (M. Zhu)

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Chongqing 400014, China

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ABSTRACT A

new

aurone

named

(2Z)-2-[(4'-hydroxyphenyl)

methylene]-6-hydroxy-7-prenyl-3(2H)-benzofurane (1), two new flavonoids named (2S)-7-methoxy-6-(2-hydroxy-3-methylbut-3-en-1-yl)-2-(4-hydroxyphenyl)chroman(2),

(2S)-4'-hydroxyl-7-hydroxymethylene-6-(2'',3''-epoxy-3''-methylbutyl)flavanone

(3),

f

4-one

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and a new coumestan named bavacoumestan E (4), together with eleven known

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compounds (5-15), were isolated from the seeds of Psoralea corylifolia. The chemical

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structures were elucidated by spectroscopic and physico-chemical analyses. All

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isolates were evaluated for in vitro inhibitory activity against DGAT, PTP1B and α-glucosidase. Compounds 1, 2 and 3 showed potential inhibitory activities on

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DGAT1 with IC50 values of 35.2 ± 1.3, 51.3 ± 1.1 and 43.4 ± 0.7 μM, respectively.

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Compounds 6 and 8 displayed the significant inhibitory activities on α-glucosidase

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with IC50 value of 28.0 and 23.0 μM, respectively.

Keywords: Psoralea corylifolia; diabetes; PTP1B; DGAT; α-glucosidase

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1. Introduction Diabetes mellitus is the world’s largest endocrine disease and it have caused very high mortality rate. From 2007 to 2010, the number of patients with diabetes in China increased from 92.4 to 113.9 million [1]. Among two type diabetes, there are almost 90% of diabetic patients suffer from type 2 diabetes mellitus (T2DM). Therefore,

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searching for new therapy with lower toxicity to treat diabetes is a serious project. Protein tyrosine phosphatase 1B (PTP1B) is a enzyme that catalyzes protein tyrosine

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dephosphorylate [2]. Overexpression of PTP1B inhibit the insulin receptor (IR)

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signaling cascade and the level of blood glucose could be decreased [3]. And

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diacylglycerol acyltransferase (DGAT) is also a key enzyme in triacylglycerol (TG) synthesis, which catalyzes the final step of the TG synthesis pathway by using

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diacylglycerol and fatty acyl CoA as substrates [4]. However, DGAT1, one of the

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isoform of DGAT, is regard as the true enzyme which responsible for synthesis of TG

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[5]. Published studies have showed that a long-term high fat diet has a obviously detrimental effect on ß-cell function and causes the accurence of type 2 diabetes [1]. Thus, inhibiting the activity of DGAT1 could indirectly decrease the damage of β-cell. Psoralea corylifolia L. (Leguminosae) is an annual herbaceous plant found predominantly in Southeast Asia. In China, the seeds of P. corylifolia are known as "Bu-Gu-Zhi " and it is valuable and important folk medicine which recorded in Chinese pharmacopoeia. The seeds of P. corylifolia are traditionally used to treat asthma [6], spermatorrhea [7], bacterial infections [7], gynecological bleeding [5], and osteoporosis [8]. Previous phytochemical and biological studies showed that P.

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corylifolia have a large range of constituents including flavonoids [9], coumarins [10], and meroterpenoids [11]. And some compounds have displayed potential biological activities such as anti- inflammatory [12], antioxidant [13] as well as antibacterial [14] properties. During the course of our search for anti-diabetic compounds from P. corylifolia,

a

new

aurone

named

(2Z)-2-[(4'-hydroxyphenyl)

f

methylene]-6-hydroxy-7-prenyl-3(2H)-benzofurane (1), two new flavonoids named

oo

(2S)-7-methoxy-6-(2-hydroxy-3-methylbut-3-en-1-yl)-2-(4-hydroxyphenyl)chroman-

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4-one

(3)

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(2S)-4'-hydroxyl-7-hydroxymethylene-6-(2'',3''-epoxy-3''-methylbutyl)flavanone

(2),

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and a new coumestan named bavacoumestan E (4), together with eleven known compounds (5-15), were isolated from the seeds of Psoralea corylifolia. Herein, we

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report the isolation, structural elucidation of new compounds, and the evaluation of

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their inhibitory activities on DGAT and PTP1B. Furthermore, the inhibitory activity

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on α-glucosidase of all isolates were also studied. 2. Results and discussion

Compound 1, obtained as a light yellow amorphous powder, showed the molecular formula as C 20 H18 O4 determined by HREIMS at m/z 322.1198 [M]+. The 1 H NMR spectrum (Table 1) showed a set of AA'XX' spin system at δH 7.72 (2H, d, J = 8.5 Hz, H-2',6') and 6.92 (2H, d, J = 8.5 Hz, H-3',5'), a set of AX spin system at δH 7.37 (1H, d, J = 8.5 Hz, H-4) and 6.75 (1H, d, J = 8.5 Hz, H-5), an olefinic proton at δH 6.56 (1H, s, H-10) and a prenyl group at δH 3.48 (2H, d, J = 7.5 Hz, H-1''), 5.33-5.34 (1H, m, H-2''), 1.80 (3H, s, H-4'') and 1.62 (3H, s, H-5''). Further observation of the

13

C

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NMR spectrum, it was found that compound 1 contained twenty carbons including twelve aromatic carbons, a set of prenyl carbons, a carbonyl carbon and two olefinic carbons. The NMR data of 1 were similar to those of licoagroaurone, revealing the same aurone skeleton [15]. In addition, the position of prenyl group could be deduced by the key HMBC correlations of δC 3.48 (H-1'') with 122.3 (C-2''), 133.0 (C-3'') and 113.2 (C-7) (Figure 2). The Z-stereochemistry of the double bond at C-10 in 1 was

as

(2Z)-2-[(4'-hydroxyphenyl)

methylene]-6-

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elucidated

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deduced by the chemical shift of δC 112.1 (C-10) [15]. Thus, the structure of 1 was

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hydroxy-7-prenyl-3(2H)-benzofurane.

Compound 2 was obtained as a yellow powder. The molecular formula was

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established as C 21 H22O5 based on HREIMS at m/z 354.1460 for the [M]+. Its 1 H NMR

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spectrum (Table 1) revealed the presence of a tetra-substituted aromatic ring at δH

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7.65 (1H, s, H-5), 6.54 (1H, s, H-8), a AA'XX'-type aromatic ring at δH 7.41 (2H, d, J

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= 8.5 Hz, H-2',6'), 6.90 (2H, d, J = 8.5 Hz, H-3',5'), two olefinic protons at δH 4.83 (1H, overlap, H-4''), 4.71 (1H, br s, H-4''), a methyl signal at δH 1.79 (C-5''), and a methoxy group at δH 3.91 (3H, s). The

13

C NMR spectrum of 2 indicated twenty-one

carbons, including twelve aromatic carbons, a carbonyl carbon at δC 190.4 (C-4), two olefinic carbons at δC 148.9 (C-3''), 110.0 (C-4''), a methyl carbon at δC 17.7 (C-5''), and a methoxy group at δC 56.0. Detailed analysis of the NMR spectra data of 2 revealed that they were very similar to those of saniculamin A [16], and the key difference between them was only the exist of methoxy group in 2. Furthermore, the position of side chain could be deduced by the key HMBC correlations of δH 2.88,

Journal Pre-proof 2.67 (H-1'') with δC 122.5 (C-6), 164.7 (C-7), and of δH 7.65 (H-5) with δC 36.6 (C-1'') (Figure 2). In addition, the NMR data and specific rotation ([α]ᴅ25-7.8) were consistent with those of saniculamin A ([α]ᴅ25-8.0), indicating the same absolute configuration between them [16]. On the basis of the above data, the structure of 2 was

elucidated

as

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(2S)-7-methoxy-6-(2-hydroxy-3-methylbut-3-en-1-yl)-2-(4-hydroxyphenyl)chroman-

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4-one.

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Compound 3 was isolated as a yellow amorphous powder that gave a formula of

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C21 H22O5 by HREIMS at m/z 354.1462 for the [M]+. The flavanone nature of this

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compound was supported by a comparison of its NMR data with those of 2, which showed signals of protons and carbons for the flavanone. However, detailed 13

C NMR spectrum data of 3 revealed several

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examination of the 1 H NMR and

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noticeable differences of the side chain which located at C-6 and C-7. The structure of

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side chain which located at C-6 could be deduced by the key HMBC correlations of δH 2.79 (H-1'') to δC 128.5 (C-5), 122.0 (C-6) and 63.6 (C-2''), of δH 2.90 (H-2'') to δC 122.0 (C-6), 29.6 (C-1'') and 57.7 (C-3''), of δH 1.35 (H-4'') to δC 63.6 (C-2'') and 57.7 (C-3''), and of δH 1.26 (H-5'') to δC 63.6 (C-2'') and 58.7 (C-3'') (Figure 2). In addition, the HMBC correlations of δH 4.56 (H-6'') to δ C 122.0 (C-6), 125.2 (C-7) and 100.2 (C-8) indicated that the hydroxymethylene is located at C-7. Furthermore, the rotation ([α]ᴅ25 -7.2) were consistent with those of 2, indicating the same absolute configuration

between

them.

Thus,

the

structure

of

(2S)-4'-hydroxyl-7-hydroxymethylene-6-(2'',3''-epoxy-3''-methylbutyl)flavanone was

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determined. Compound 4 was obtained as a yellow amorphous powder. The molecular formula was established as C 21 H20 O5 based on HREIMS at m/z 352.1307 for the [M]+. The 1 H NMR spectrum (Table 1) indicated two aromatic rings including a a set of ABX spin system at δH 7.70 (1H, d, J = 8.5 Hz, H-5), 6.95 (1H, dd, J = 8.5, 2.0 Hz, H-6), 7.19 (1H, d, J = 2.0 Hz, H-8), and a tetra-substituted aromatic ring at δH 7.63 (1H, s, H-2')

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and 6.93 (1H, s, H-5'), a prenyl group at δH 3.34 (2H, d, J = 2.5 Hz, H-1''), 5.36-5.39

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(1H, m, H-2''), 1.77 (3H, s, H-4'') and 1.73 (3H, s, H-5'') and a methoxy group at δH

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3.81 (3H, s). Twenty-one carbons, including twelve aromatic carbons, a carbonyl

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carbon at δC 156.1 (C-2), a prenyl group at δC 27.7 (C-1''), 121.9 (C-2''), 132.6 (C-3''), 25.7 (C-4''), 17.8 (C-5'') and a methoxy group at δC 56.3 were observed in the

13

C

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NMR spectrum of 4. The NMR data of 4 were similar to those of bavacoumestan D

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[17], revealing the same coumestan feature. By carefully observation of the NMR

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spectrum of 4 and bavacoumestan D, it was found that the methoxy group of 4 replaced the hydroxyl group of bavacoumestan D. The position of prenyl group could be deduced by the key HMBC correlations of δH 3.34 (H-1'') with δC 121.1 (C-2'), 126.7 (C-3'), 159.5 (C-4'), 121.9 (C-2'') and 132.6 (C-3''), and of δH 7.63 (H-2') with δC 27.7 (C-1'') (Figure 2). In addition, the location of the methoxy group was determined at C-4' by the HMBC correlations between δH 3.81 and δC 159.5 (C-4'). On the basis of the above data, the structure of 4 was elucidated as bavacoumestan E. Moreover, eleven known compounds (5-15) were obtained from P. corylifolia, and identified as coryaurone A (5) [7], bavachinone B (6) [7], bavacoumestan C (7) [7],

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bavacoumestan B (8) [7], corylifols E (9) [18], corylifols D (10) [18], Δ3 ,2-hydroxybakuchiol

(11)

[19],

13-methoxyiso-bakuchiol

(12)

[19],

13-ethoxyisobakuchiol (13) [19], 15-demetyl-12,13-dihydro-13-ketobakuchiol (14) [19], Δ1 ,3-hydroxybakuchiol (15) [19] by comparing their NMR data with those in literatures (Figure 1). The anti-diabetic activities of compounds 1-15 were evaluated via inhibiting the

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activities of DGAT, PTP1B and α- glucosidase using in vitro assay (Table 2). In DGAT

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inhibitory assay, kuraridin was used as a positive control. In this assay, compounds 1,

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3-5, 7, 8, 10, 14 showed selective inhibitory activities on DGAT1 with IC 50 values

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ranging from 35.2 ± 1.3 to 145.7 ± 1.0 μM, and all the compounds showed moderate inhibitory activity against DGAT1 except compounds 5 and 14. Among these isolates,

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compound 1 showed the strongest inhibitory activity against DGAT1 with IC50 value

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of 35.2 ± 1.3 μM. It indicated the aurone might have promising DGAT1 inhibitory

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activity. In addition, Compound 7 (IC50 = 59.4 ± 1.3 μM) displayed high inhibitory activity on DGAT1 compared with that of 8 (IC50 = 95.8 ± 0.7 μM), which indicated the hydroxyl group linked with C-1'' might be responsible for the DGAT1 inhibitory activity. As for PTP1B inhibitory assay, RK-682 was used as a positive control (Table 2). Among the isolates, compounds 1-5, 7-13, 15 showed moderate inhibitory activity on PTP1B with IC50 values ranging from 9.4 ± 0.8 to 25.8 ± 0.7 μM, while compounds 6 and 14 showed very weak inhibitory effects. Compound 7 (IC50 = 10.2 ± 0.9 μM), which had a hydroxyl moiety at C-1'', exhibited a significantly higher PTP1B

Journal Pre-proof inhibitory activity than compound 8 (IC50 = 24.1 ± 0.7 μM). it indicated that this hydroxyl moiety might be linked with the PTP1B inhibitory activity. In addition, the inhibitory activity against α-glucosidase of all isolates were also evaluated (Table 3), and acarbose was used to be the positive control. Compounds 1-10 showed the significant inhibitory activity on α-glucosidase with IC50 values ranging from 23.0 to 179.4 μM. Compound 8 (IC50 = 23.0 μM) displayed high

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inhibitory activity on α- glucosidase compared with that of 7 (IC50 = 69.8 μM). It

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indicated that the hydroxyl group which located at C-1'' might has negative effect on

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α-glucosidase inhibitory activity. And meroterpenes showed very weak inhibitory

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activities on α-glucosidase. 3. Experimental section

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3.1 General experimental procedures

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UV spectra were measured with a JASCO V-650 spectrophotometer (JASCO,

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Tokyo, Japan). IR spectra were measured as a solid film on a Bruker Hyperion 2000 FTIR microscope connected to a Vertex 70 spectrometer (Bruker, Billerica, MA, USA). Nuclear magnetic resonance (NMR) spectra were obtained from a Varian Unity Inova 500 MHz spectrometer (Varian Unity Inova, Phoenix, USA) using TMS as the internal standard. Mass spectra were were measured using a Q-TOF micro mass spectrometer (AB, Foster City, CA, USA). Column chromatography was conducted using silica gel 60 (Yantai Xinde Chemical Co., Ltd, Yantai, China ) and RP-18 (Merck, Darmstadt, Germany). TLC was performed with precoated silica gel GF254 glass plates (Zhi Fu HuangWu Pilot Plant of Silica Gel Development, Yantai, China).

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HPLC was performed on Waters series (2487 UV/Visible Detector; Waters, Milford, MA, USA) by using C18 preparative column(10 mm, 20 mm × 250 mm). 3.2 Plant material The seeds of Psoralea corylifolia were collected in Yibin, Sichuan province, China, and authenticated by Professor Ying Wang (College of Pharmacy, Chongqing Medical

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Chongqing Medical University, Chongqing, China.

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University). A voucher specimen of the plant (No. 20170412) was deposited at

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3.3 Extraction and isolation

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The dried powder of the seeds of P. corylifolia (10.0 kg) was were repeatedly

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extracted with 95% EtOH aqueous (80 L × 3) to give 1.3 kg crude extract. This extract was suspended in H2 O, successively partitioned with petroleum ether, CHCl3 ,

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EtOAc and n-BuOH to give PE (159.1 g), CH2 Cl2 (211.9 g), EtOAc (312.4 g) and

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n-BuOH (181.4 g), respectively. Part of the EtOAc-soluble fraction (150.0 g) was

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subjected to column chromatography (CC) on silica gel eluted with a gradient of CH2 Cl2 -MeOH (from 0:1 to 1:0) to yield 10 fractions (Fr.1-Fr.10). Fr.3 (17.1 g) was chromatographed over silica gel, eluted with a gradient of CH2 Cl2 -MeOH (from 0:1 to 1:1), and was separated into 11 fractions (Fr.3.1-Fr.3.11). Fr.3.5 (2.7 g) was subjected to silica gel column eluted with PE-EtOAc (from 1:0 to 0:1) to get 12 fractions (Fr.3.5.1-Fr.3.5.12), after which the Fr.3.5.4 (854.3 mg) was subjected to the ODS column and eluted with MeOH-H2 O (3:7 to 10:0) to afford 9 fractions (Fr.3.5.4.1-Fr.3.5.4.9). Further purification of Fr.3.5.4.4 (177.5 mg) was performed by HPLC, using an gradient solvent system 45%-55% MeOH in H2 O over 70 min

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yielded compounds 1 (14.1 mg, t R = 43.7 min), 2 (17.3 mg, t R = 52.7 min) and 5 (8.2 mg, t R = 65.7 min). In addition, Fr.3.5.4.5 (124.7 mg) via semi-preparative HPLC using a gradient solvent system of 45%-60% MeOH in H2 O over 80 min yielded compounds 7 (11.4 mg, t R = 31.3 min), 4 (8.9 mg, t R = 42.7 min), 9 (7.9 mg, t R = 47.5 min) and 6 (23.1 mg, t R = 61.7 min). Moreover, Fr.3.5.4.8 (94.5 mg) via

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semi-preparative HPLC using a solvent system of 65% MeOH in H2 O over 120 min

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yielded compounds 7 (17.9 mg, t R = 21.5 min), 8 (14.5 mg, t R = 31.1 min), 10 (14.2

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mg, t R = 34.7 min) and 12 (20.4 mg, t R = 55.7 min).The Fr.3.5.4.7 (102.4 mg) was

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separated by HPLC, using an gradient solvent system 55%-70% MeOH in H2 O over

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60 min, yielded compounds 11 (12.2 mg, t R = 48.3 min), 13 (7.7 mg, t R = 53.5 min) and 14 (8.9 mg, t R = 65.1 min). And the Fr.3.4.6 (242.4 mg) was performed by HPLC,

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using an gradient solvent system 45%-60% MeOH in H2 O over 80 min yielded

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compounds 15 (15.9 mg, t R = 41.2 min) and 3 (9.8 mg, t R = 63.5 min).

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3.4. Spectroscopic data

(2Z)-2-[(4'-hydroxyphenyl) methylene]-6-hydroxy-7-prenyl-3(2H)-benzofurane (1): light yellow amorphous powder; IR (KBr) ν max 3407, 3291, 1789, 1620, 1608 cm−1 ; UV (MeOH) λmax (nm) (log ε): 267 (4.58), 384 (4.17); 1 H (500 MHz) and

13

C NMR

(125 MHz) spectral data in acetone-d6 , see Table 1; HREIMS: m/z 322.1198 [M]+ (calcd for C20 H18 O4, 322.1205).

(2S)-7-methoxy-6-(2-hydroxy-3-methylbut-3-en-1-yl)-2-(4-hydroxyphenyl)chroma n-4-one (2): yellow powder; [α]ᴅ25-7.8 (c 0.59, MeOH); IR (KBr) ν max 3350, 1615, 1605, 1525, 1498, 1446, 1350, 1257 cm−1 ; UV (MeOH) λmax (nm) (log ε): 210 (4.02),

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13

C NMR (125 MHz) spectral data in acetone-d6 , see

Table 1; HREIMS: m/z 354.1460 [M]+ (calcd for C21 H22 O5, 354.1467). (2S)-4'-hydroxyl-7-hydroxymethylene-6-(2'',3''-epoxy-3''-methylbutyl)flavanone (3): yellow amorphous powder; [α]ᴅ25-7.2 (c 0.45, MeOH); IR (KBr) ν max 3370, 2930, 1662, 1614, 1428 cm−1 ; UV (MeOH) λmax (nm) (log ε): 239 (3.97), 341 (3.37).; 1 H (500 MHz) and

13

C NMR (125 MHz) spectral data in acetone-d6 , see Table 1;

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HREIMS: m/z 354.1462 [M]+ (calcd for C21 H22 O5, 354.1467).

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Bavacoumestan E (4): yellow amorphous powder; IR (KBr) ν max 3425, 3342, 1705,

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1634, 1601, 1457, 1408, 1317, 1265, 1138, 1117,1064, 1057, 1027 cm−1 ; UV (MeOH) λmax (nm) (log ε): 325 (3.67), 305 (3.87); 1 H (500 MHz) and

13

C NMR (125 MHz)

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spectral data in acetone-d6 , see Table 1; HREIMS: m/z 352.1307 [M]+ (calcd for

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C21 H20 O 5, 352.1311).

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3.5 DGAT1 and DGAT2 assays

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DGAT activity assays were carried out as described previously [5]. Briefly, DGAT activity in total membranes prepared from DGAT2- or DGAT1- overexpressing Sf-9 and HEK293 Tet-on cells was determined by measuring the formation of [14 C]-triacylglycerol from [14 C]-oleoyl CoA. The reaction mixture for the DGAT1 assay contained 175 mM Tris (pH 7.5), 100 mM MgCl2 (5 mM MgCl2 for DGAT2 assay), 200 μM sn-1,2-diacylglycerol, 20 μM [1- 14C]-oleoyl CoA (5.5 μCi), 2 mg/ml BSA, and 32 μg of the membrane protein. The mixture was incubated for 20 min at 37 °C and then the reaction was stopped by addition of 1.5 ml of stop solution [2-propanol- heptane-water (80:20:2, v/v/v)] and vortexed with 1.0 ml of heptane and

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0.5 ml of water. The top heptane phase was collected and washed with 2.0 ml alkaline ethanol solution [ethanol-0.5 N NaOH-water (50:10:40, v/v/v)]. The radioactivity of the top phase was determined by liquid scintillation counting (Tri-Carb 2900TR Liquid Scintillation Analyzer, PerkinElmer, Inc., Massachusetts, Waltham, USA) 3.6 PTP1B assays The enzyme activity was measured using p-nitrophenyl phosphate (pNPP) as

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described previously [20]. Each 96 well (final volume: 100 μl) was added 2 mM

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pNPP and PTP1B (0.05-0.1 μg) in a buffer containing 50 mM citrate (pH 6.0),0.1 M

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NaCl, 1 mM ethylene diamine tetraacetic acid (EDTA), and 1 mM dithiothreitol

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(DTT), with or without test compounds. Following incubation at 37 °C for 30 min, the reaction was terminated with 1 M NaOH. The amount of produced p-nitrophenol was

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3.7 Glucosidase assays

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estimated by measuring the absorbance at 405 nm.

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α-Glucosidase inhibitory activity was measured as described previously with minor modifications [21]. α-Glucosidase activity was determined by adding 3 mM p-nitrophenyl-α-D-glucopyranoside (25 μl) and 0.2 U/ml α- glucosidase (25 μ l) into the sample solution (625 μl). Each reaction was carried out at 37 ℃ for 30 min and stopped by adding 0.1 M Na2 CO 3 (380 μl). Enzymatic activity was quantified by measuring absorbance at 401 nm. One unit of α-glucosidase activity was defined as the amount of enzyme liberating p- nitrophenol (1.0 μM) per min. The inhibitory effects of the tested compounds were expressed as the concentrations that inhibited 50% of the enzyme activity (IC 50 ). Acarbose, a known α-glucosidase inhibitor, was

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used as positive control. Conflict of interest All authors declared no conflflicts of interest. Acknowledgements The authors was are thankful to the workers of Kunming Plant Biotechnology Co.

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LTD.

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[1] T. Mittermayer, E. Caveney, C.D. Oliveira, L. Gourgiotis, M. Puri, L.J. Tai, J.R.

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Turner, Addressing Unmet Medical Needs in Type 2 Diabetes: A Narrative Review of

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Drugs under Development. Curr. Diabetes. Rev. 11 (1) (2015) 17-31. [2] S. Zhang, Z.Y. Zhang, PTP1B as a drug target: recent developments in PTP1B

al

inhibitor discovery. Drug. Discov. Today. 12 (9-10) (2007) 373-381.

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[3] X.Q. Li, Q. Xu,, J. Luo, L.J. Wang, B. Jiang, R.S. Zhang, D.Y. Shi, Design,

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synthesis and biological evaluation of uncharged catechol derivatives as selective inhibitors of PTP1B. Eur. J. Med. Chem. 136 (2017) 348-359. [4] A. Subauste, C.F Burant, DGAT: novel therapeutic target for obesity and type 2 diabetes mellitus. Curr. Drug. Targets. Immune. Endocr. Metabol. Disord. 3 (4) (2003) 263-270. [5] M.O. Kim, S.U. Lee, H.J. Lee, K. Choi, H. Kim, S. Lee, S.J. Oh, S. Kim, J.S. Kang, H.S. Lee, Y.S. Kwak, S. Cho, Identification and validation of a selective small molecule inhibitor targeting the diacylglycerol acyltransferase 2 activity. Biol. Pharm. Bull. 36 (7) (2013) 1167-1173.

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[6] P.L. Wang, F.X. Zhang, Z.C. Qiu, Z.H. Yao, M.S. Wong, X.S. Yao, Y. Dai, Isolation and identification of metabolites of bakuchiol in rats. Fitoterapia. 109 (2016) 31-38. [7] T.H. Won, I.H. Song, K.H. Kim, W.Y. Yang, S.K. Lee, D.C. Oh, W.K. Oh, K.B. Oh, J. Skin, Bioactive metabolites from the fruits of Psoralea corylifolia. J. Nat. Prod.

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78 (4) (2015) 666-673.

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[8] G.D. Xiao, X.K. Li, T. Wu, Z.H. Cheng, Q.J. Tang, T. Zhang, Isolation of a new

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meroterpene and inhibitors of nitric oxide production from Psoralea corylifolia fruits

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guided by TLC bioautography. Fitoterapia. 83 (8) (2012) 1553-1557.

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[9] V.K. Bhalla, U.R. Nayak, S. Dev, Some new flavonoids from Psoralea corylifolia. Tetrahedron Lett. 9 (1968) 2401-2406.

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[10] K.Y. Oh, J.H. Lee, M.J. Curtis-Long, J.K. J.K. Cho, Kim, W.S. Lee, K.H. Park,

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Glycosidase inhibitory phenolic compounds from the seed of Psoralea corylifolia.

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Food. Chem. 121 (4) (2010) 940-945. [11] S. Yin, C.Q. Fan, Y. Wang, L. Dong, J.M. Yue, Antibacterial prenylflavone derivatives from Psoralea corylifolia and their structure-activity relationship study. Bioorgan. Med. Chem. 35 (48) (2004) 4387-4392. [12] K.K. Anand, M.L. Sharma, B. Singh, B.J.R. Ghatak, Anti- inflammatory, antipyretic and analgesic properties of bavachinin-a flavanone isolated from seeds of Psoralea corylifolia Linn (Babchi). Indian. J. Exp. Biol. 16 (11) (1978) 1216-1217. [13] J.M. Guo, X.C. Weng, H. Wu, Q.H. Li, K.S. Bi, Antioxidants from a Chinese medicinal herb-Psoralea corylifolia L. Food. Chem. 91 (2) (2005) 287-292.

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[14] N.A. Khatune, M.E. Islam, M.E. Haque, P. Khondkar, M.M. Rahman, Antibacterial compounds from the seeds of Psoralea corylifolia. Fitoterapia. 75 (2) (2004) 228-230. [15] W. Li, Y. Asada, T. Yoshikawa, Flavonoid constituents from Glycyrrhiza glabra hairy root cultures. Phytochemistry. 55 (5) (2000) 447-456.

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[16] G.M. Xu, Z.M. Wang, B.Q. Zhao, N.Z. Liu, S.H. Yang, Y.H. Liu, J.F. Wang, XJ.

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Zhou, Saniculamins A and B, two new flavonoids from Sanicula lamelligera Hance

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inhibiting LPS-induced nitric oxide release. Phytochemistry. Lett. 18 (2016) 35-38.

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Asian. Nat. Prod. Res. (2019) 1-7.

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[17] M.Y. Chai, A new bioactive coumestan from the seeds of Psoralea corylifolia. J.

[18] P. Song, X.Z. Yang, G.Q. Yuan, Cytotoxic constituents from Psoralea corylifolia.

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J. Asian. Nat. Prod. Res. 15 (6) (2013) 624-630.

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[19] Y.W. Huang, X.Y. Liu, Y.C. Wu, Y.M. Li, F.J. Guo, Meroterpenes from

1298-1303.

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Psoralea corylifolia against pyricularia oryzae. Planta Med. 80 (15) (2014)

[20] T. Hamaguchi, T. Sudo, H. Osada, RK-682, a potent inhibitor of tyrosine phosphatase, arrested the mammalian cell cycle progression at G1 phase. Febs. Lett. 372 (1) (1995) 54-58. [21] K.Y. Kim, K.A. Nam, H. Kurihara, S.M. Kim, Potent α-glucosidase inhibitors purified from the red alga Grateloupia elliptica. Phytochemistry. 69 (16) (2008) 2820-2825.

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Figure 1. Structures of compounds 1-15.

Figure 2. Key HMBC correlations of compounds 1-4.

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C: 125 MHz). δC

2

147.6

3

4

5

183.1

7.37, d (8. 5) 6.75, d (8. 5)

δH 5.45, dd, (13.0, 2. 5) 3.05, dd, (16.5, 13. 0) 2.67, d, (16.5, 3. 0)

125.7

113.0

δC 80.4

44.4

190.4

7.65, s

δH 5.47, dd, (13.0, 2.5) 3.06, dd, (16.5, 1 3.0) 2.69, dd, (16.5, 3. 0)

4 δC

δH

80.8

δC 156.1

102.6 44.7

f

δH

3

129.5

7.68, s

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No.

2

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1

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13

C NMR spectral data of compounds 1-4 in acetone-d6 (1 H: 500

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MHz,

13

159.7

128.5

7.70, d (8.5)

120.9

122.0

6.95, d d, (8.5, 2.0)

114.1

166.9

7

113.2

8

163.9

9

115.1

163.1

163.8

157.1

112.1

114.5

115.2

114.9

127.7

131.0

131.3

103.7

2'

3'

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6.56, s 7.72, d, (8. 5) 6.92, d, (8. 5)

4' 5'

6'

164.7

6.54, s

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1'

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6

10

122.5

190.8

6.58, s

100.2

157.9 7.19, d, (2.0)

98.9

131.0

7.41, d, (9.0)

128.7

7.40, d, (8.5)

129.1

117.1

6.90, d, (9.0)

115.8

6.90, d, (8.5)

116.2

126.7

158.7

159.5

161.0 6.92, d, (8. 5) 7.72, d, (8. 5)

99.4

125.2

158.3

117.1

6.90, d, (9.0)

115.8

6.90, d, (8.5)

116.2

131.0

7.41, d, (9.0)

128.7

7.40, d, (8.5)

129.1

7.63, s

6.93, s

121.1

101.9

153.1

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1''

3.48, d, (7. 5)

22.7

2.88, dd, (13.0, 5. 0) 2.67, dd, (13.0, 8. 0)

2''

5.335.34, m

122.3

4.26, m

29.6

3.34, d, (2.5)

27.7

74.9

2.90, t, (6.0)

63.6

5.36-5.3 9, m

121.9

110.0

1.80, s

18.2

5''

1.62, s

26.0

1.79, s

148.9

1.35, s

17.7

1.26, s

25.1

4.56, d (0.5)

60.0

6''

1.77, s

25.7

1.73, s

17.8

56.0

3.81, s

56.3

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3.91, s

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-OC H3

19.2

132.6

f

4''

4.83, over lap 4.71, br s

57.7

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133.0

2.79, d, (6.0)

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3''

36.6

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Table 2. Inhibitory effects of compounds 1-15 (µM) on DGAT activity (expressed as IC50 values) IC50 a DGAT2

PTP1B

35.2 ± 1.3

> 200

11.3 ± 1.4

51.3 ± 1.1

94.1 ± 1.5

18.5 ± 0.8

43.4 ± 0.7

> 200

9.4 ± 0.8

96.5 ± 1.2

> 200

13.3 ± 1.2

5

137.1 ± 0.9

> 200

21.3 ± 1.1

6

81.0 ± 1.0

127.4 ± 1.2

>60

7

59.4 ± 1.3

> 200

10.2 ± 0.9

8

95.8 ± 0.7

> 200

24.1 ± 0.7

9

78.6 ± 1.1

105.7 ± 0.8

16.3 ± 1.3

10

85.0 ± 0.9

> 200

21.3 ± 0.5

11

91.8 ± 1.1

131.4 ± 1.3

25.8 ± 0.7

1 2 3 4

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DGAT1

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78.5 ± 0.7

120.3 ± 1.1

31.4 ± 0.9

13

95.3 ± 1.3

134.7 ± 0.8

22.1 ± 0.4

14

145.7 ± 1.0

> 200

>60

15

81.1 ± 0.8

127.4 ± 1.0

14.3 ± 1.4

kuraridineb

10.3 ± 1.2

18.1 ± 0.9

RK-682b a

4.4 ± 0.6

IC50 values were determined by regression analyses and expressed as means ± SD

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of three replicates. Positive control.

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Table 3. Inhibitory effects of compounds 1- 15 (µM) on α- glucosidase activity (expressed as IC 50 values)

Inhibition (I%)

Compound

100 (μM)

50 (μM)

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250 (μM)

IC50 (μM) 25 (μM)

10 (μM)

4.7 ± 1.1

-

97.4 ± 2.3 67.5 ± 1.5 39.2 ± 1.2

2

77.6 ± 2.3

3

89.7 ± 2.2 80.1 ± 2.9 73.7 ± 1.8 53.2 ± 2.0 37.4 ± 1.6

32.7

4

81.2 ± 1.3

51.8 ± 1.1 33.5 ± 1.9

89.1

5

95.8 ± 5.2

78.3 ± 1.1 67.2 ± 1.7 49.8 ± 1.5 35.7 ± 1.4

62.1

6

97.2 ± 3.5 89.9 ± 3.2 72.9 ± 1.4 49.0 ± 1.4 31.3 ± 1.4

28.0

7

71.2 ± 1.0

8.9 ± 1.8

69.8

8

84.2 ± 2.4 69.9 ± 3.2 42.9 ± 1.4 21.0 ± 1.4 27.3 ± 1.4

23.0

9

67.2 ± 4.2 37.2 ± 1.5 23.7 ± 1.4

5.7 ± 1.1

-

157.5

10

75.2 ± 3.1 41.2 ± 2.4 24.7 ± 1.7

4.6 ± 1.1

-

179.4

-

-

-

11

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1

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60.4 ± 1.6 48.1 ± 1.9 39.0 ± 1.1 20.0 ± 1.1

-

5.2 ± 1.3

60.1 ± 1.7 44.1 ± 1.5 31.1 ± 1.4

-

-

-

73.8 41.2

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-

-

-

-

-

-

13

-

-

-

-

-

-

14

-

-

-

-

-

-

15

-

-

-

-

-

-

Acarbosea

60.1 ± 0.8

3.4 ± 1.1

–

214.8

21.2 ± 1.5 10.5 ± 1.4

IC50 values represent the means ± SEM of three parallel measurements.

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Positive control.

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Graphical abstract