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Vibralactone derivatives containing γ, δ, ε-lactone cores from cultures of the basidiomycete Boreostereum vibrans
Fitoterapia 128 (2018) 7–11
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Vibralactone derivatives containing γ, δ, ε-lactone cores from cultures of the basidiomycete Boreostereum vibrans
T
Kai-Ting Duan, Zheng-Hui Li, Xing Yu, Qing-Xia Yuan, Wen-Xuan Wang, Jing Li, He-Ping Chen, ⁎ ⁎ Tao Feng , Ji-Kai Liu School of Pharmaceutical Sciences, South-Central University for Nationalities, Wuhan 430074, China
A R T I C LE I N FO
A B S T R A C T
Keywords: Boreostereum vibrans Vibralactone derivatives Lactone Cytototxicity
Five vibralactone derivatives containing γ, δ, ε-lactone cores, namely vibralactones X (1), Y (2), and Z1–Z3 (3–5), together with the known vibralactone, have been isolated from cultures of the basidiomycete Boreostereum vibrans. Compounds 3–5 possessed a novel bis-γ-lactone group which was found in vibralactone derivatives for the first time. Compounds 3 and 5 exhibited moderate cytotoxicities to human cancer cell lines referring to that of cisplatin.
1. Introduction
2. Results and discussion
The fungus Boreostereum vibrans is considered as a talent strain by our group due to its high productive ability of multiple natural products including vibralactone derivatives [1–8], terpenoids [9], and benzene ring derivatives [6–8]. Of them, vibralactone and its derivatives are highlighted by its structural novelty and potent bioactivities. In 2006, our group reported the novel structure vibralactone. It possesses a βlactone in conjugation of a cyclopentane, as well as an isopentene substituent. Meanwhile, it is also a good pancreatic lipase inhibitor with an IC50 value of 0.4 μg/mL [1]. The unique structures and potent bioactivities of vibralactone and its derivatives have aroused many follow-up studies including the total syntheses [10,11], biosynthetic pathway investigations [12,13], and other bioactive tests [3,9]. As our ongoing research for new and bioactive compounds from B. vibrans, many small amount of novel compounds have been discovered. For instance, oxime and other N-containing vibralactone derivatives have been isolated from the scale-up fermentation broths [14]. In doing so, our study on natural products from B. vibrans seems endless. Herein, we are about to reported five new isolates, namely vibralactones X (1), Y (2), and Z1–Z3 (3–5), together with the known vibralactone, from a scale-up fermentation broth of B. vibrans (Fig. 1). The compounds are featured by containing a different lactone moiety including γ, δ, ε-lactone cores. Particularly, compounds 3–5 possessed an interesting framework owning a bis-γ-lactone group, which also showed cytotoxicities to human cancer cell lines.
Compound 1 was isolated as a colorless oil. The molecular formula was determined as C12H18O3 by HRESIMS at m/z 233.1149 (calcd for C12H18O3Na, 233.1148). The IR data at 1751 cm−1 indicated the presence of a carbonyl carbon. In the 1H NMR spectrum (Table 1), two singlets for methyl groups at δH 1.66 and 1.71 and two olefinic protons at δH 5.14 and 5.35 are readily identified. In addition, signals at δH 4.68 (1H, dd, J = 12.8, 1.7 Hz, H-5a), 4.32 (1H, ddd, J = 12.8, 4.7, 2.5 Hz, H-5b), and 4.01 (2H, br s, H-12) were ascribable for protons of oxygenated carbons. In the 13C NMR and DEPT spectra, twelve resonances were observed, which displayed as two methyl, four methylene, three methine, and three quaternary carbons. These data were related to those of 1,5-secovibralactone [2]. The main difference was that the double bond between C-4 and C-5 in 1,5-secovibralactone was saturated in 1, as indicated by the 1H–1H COSY correlation of δH 2.51 and 2.34 (each 1H, m, H-4) with δH 4.68 (1H, dt, J = 12.8, 1.7 Hz, H-5a) and 4.32 (1H, ddd, J = 12.8, 4.7, 2.5 Hz, H-5b), as well as the HMBC correlations from H-4 to δC 121.2 (d, C-2) and δC 139.2 (s, C-3). In addition, the ε-lactone group was confirmed by HMBC correlations from H-5 to δC 174.2 (s, C-6). Analyses of other 1D and 2D NMR data suggested that the other parts of 1 were the same to those of 1,5-secovibralactone. Sincere the absolute configuration of C-1 in 1,5-secovibralactone was identified by the optical rotation calculations, the configuration of C-1 in 1 was identified as S by comparison of the optical rotation data ([α]25 D = + 24.7° (c = 0.25, CHCl3)) with that of 1,5secovibralactone ([α]14 D = + 107.5° (c = 0.34, CHCl3)). Compound 1 was, therefore, established as vibralactone X, as depicted.
⁎
Corresponding authors. E-mail addresses: [email protected] (T. Feng), [email protected] (J.-K. Liu).
https://doi.org/10.1016/j.fitote.2018.04.020 Received 14 March 2018; Received in revised form 22 April 2018; Accepted 27 April 2018 Available online 30 April 2018 0367-326X/ © 2018 Elsevier B.V. All rights reserved.
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K.-T. Duan et al.
10
9
O
OH
10
O
6
O O
3
9 8
2
4
5 12
3
O
O
8
O
8
H
O
OH
2
OH 11
6
O O
O
O
5
O
8
O O
O H H
H H
4
3
Fig. 1. Structures of vibralactone and compounds 1–5. 1H-1H
Compound 2 was isolated as a colorless oil. The molecular formula was established as C12H20O3 by the negative HRESIMS data (measured at m/z 211.1138 [M - H]−; calcd for C12H19O3, 211.1340). Preliminary analyses of 1D NMR data suggested that 2 should be a vibralactone derivative, which possessed similar moieties like an isopentene group and a lactone carbon at δC 173.9 (s, C-6). Detailed analysis of NMR data suggested that 2 might have a structure closely related to that of vibralactone Q [7], except for the double bond between C-1 and C-2 was saturated in 2, which was supported by the 1H–1H COSY data as shown in Fig. 2. The δ-lactone moiety was proved by the HMBC correlations from δH 4.38 (1H, ddd, J = 11.1, 4.7, 2.0 Hz, H-12a) and 3.98 (1H, dd, J = 11.1, 4.7 Hz, H-12b) to C-6. The relative configuration was established by the ROESY data (Fig. 2). The cross peak between H-1 and H-3 suggested that H-1 and H-3 were in the same side, which allowed the major substituents of C-13 and the isopentene group were equatorial. Finally, compound 2 was identified as vibralactone Y. Compound 3 was isolated as a colorless oil. The molecular formula was established as C12H16O5 by the HRESIMS (measured at m/z 239.0926 [M - H]−; calcd for C12H15O5, 239.0925), corresponding to five degrees of unsaturation. The 13C NMR spectrum, along with the DEPT data, indicated that 3 had two methyl, three methylene, three methine, and four quaternary carbons (Table 2). Of them, two carbonyl carbons at δC 176.7 (s, C-5) and 179.8 (s, C-6), together with two olefinic carbons at δC 171.1 (s, C-3) and 117.3 (d, C-4), occupied three degrees of unsaturation, indicating that compound 3 should have a bicyclic ring system. The 1H–1H COSY spectrum afforded a number of cross peaks, establishing a fragment as shown in Fig. 2. In the HMBC spectrum (Fig. 2), the correlation from δH 4.33 (1H, dd, J = 10.2,
OH
1 2
12
O
O
OH
10
O
O
3
12
OH
H
O
6
OH
4
2
O
11
1
O
2
O
12
1
8 1
6
4
OH
7
1
12
5
3 5
H Vibralalctone
O OH
11
9
7
2
O
O
O
1
6
10
8
7
O
11
COSY
O
HMBC
ROESY
Fig. 2. Key correlations in 2D NMR spectra of 2 and 3.
Table 2 13 C NMR data of compounds 1–5 (δ in ppm). No.
1a
2a
3b
4b
5b
1 2 3 4 5 6 7 8 9 10 11 12
40.2 (d) 121.2 (d) 139.2 (s) 30.4 (t) 64.4 (t) 174.2 (s) 30.0 (t) 120.9 (d) 134.6 (s) 25.9 (q) 18.0 (q) 67.4 (t)
40.4 (d) 31.5 (t) 30.4 (d) 35.1 (t) 60.0 (t) 173.9 (s) 29.7 (t) 120.6 (d) 134.5 (s) 25.8 (q) 17.9 (q) 73.1 (t)
40.5 (d) 30.2 (t) 171.1 (s) 117.3 (d) 176.7 (s) 179.8 (s) 29.9 (t) 86.1 (d) 71.0 (s) 25.0 (q) 26.6 (q) 75.2 (t)
39.3 (d) 31.2 (t) 170.9 (s) 117.1 (d) 176.5 (s) 180.5 (s) 29.4 (t) 85.9 (d) 72.4 (s) 25.6 (q) 26.0 (q) 74.9 (t)
37.0 (d) 31.7 (t) 169.2 (s) 115.9 (d) 175.1 (s) 178.6 (s) 28.9 (t) 80.4 (d) 142.7 (s) 110.8 (t) 16.6 (q) 73.6 (d)
a b
Measured at 150 MHz in CDCl3. Measured at 150 MHz in methanol-d4.
6.1 Hz, H-8) to C-6 suggested that a γ-lactone ring was built by C-6, C-1, C-7, and C-8. In addition, the HMBC correlations from δH 4.88 (1H, d, J = 17.9 Hz, H-12) to C-5, C-3, and C-4 suggested that another γ-lactone ring was built by C-5, C-4, C-3, and C-12. Furthermore, the HMBC correlations from δH 1.14 (3H, s, H-10) and 1.31 (3H, s, H-11) to δC 71.0 (s, C-9) indicated an oxygenated isopropyl. It was connected to C-8
Table 1 1 H NMR data of 15 (δ in ppm, J in Hz). No.
1a
2a
1 2a 2b 3 4a 4b 5a 5b 7a 7b 8 10 11 12a 12b
3.68 (m) 5.35 (s)
2.50 2.13 1.24 2.19 1.57
a b
2.51 2.34 4.68 4.32 2.58 2.46 5.14 1.71 1.66 4.01
(m) (m) (td, 12.8, 1.7) (ddd, 12.8, 4.7, 2.5) (m) (m) (m) (3H, s) (3H, s) (s)
(m) (m) (m) (m) (m)
3b
4b
5b
3.15 (m) 2.96 (dd, 16.5, 5.1) 2.68 (dd, 16.5, 8.4)
3.11 (ddd, 18.3, 9.3, 5.3) 2.93 (dd, 16.4, 5.3) 2.67 (dd, 16.4, 9.3)
3.05 (ddd, 17.7, 9.1, 5.7) 2.94 (dd, 16.4, 5.7) 2.71 (dd, 16.4, 9.1)
6.02 (br s)
6.01 (br s)
6.01 (br s)
2.44 1.92 4.33 1.14 1.31 4.88
2.55 2.02 4.37 1.20 1.27 4.95
2.40 2.21 5.01 4.98 1.79 4.87
3.72 (m) 2.56 2.28 5.10 1.71 1.62 4.38 3.98
(m) (m) (m) (3H, s) (3H, s) (ddd, 11.1, 4.7, 2.0) (dd, 11.1, 4.7)
Measured at 600 MHz in CDCl3. Measured at 600 MHz in methanol-d4. 8
(m) (m) (dd, 10.2, 6.1) (3H, s) (3H, s) (d, 17.9)
(m) (m) (dd, 8.7, 3.7) (3H, s) (3H, s) (d, 17.8)
(m) (m) (dd, 8.6, 4.1) (s); 4.95 (s) (3H, s) (d, 17.8)
Fitoterapia 128 (2018) 7–11
K.-T. Duan et al.
as deduced from HMBC correlation from H-8 to C-9. Compound 3 was identified as an interesting vibralactone containing a pair of γ-lactone groups. The relative configuration was established by the ROESY data (Fig. 2). H-8 was detected to have a strong correlation with H-7a (δH 2.44) and a weak correlation with H-7b (δH 1.92). H-1 was found to have a key cross peak with H-7a (no cross peak found between H-1 with H-7b). In addition, a weak cross peak of H-8 with H-1 was also detected. These data suggested that H-1 and H-8 were in the same side. Compound 3 was, therefore, identified as vibralactone Z1, as depicted. Compound 4 was detected to have the same molecular formula to that of 3 on the basis of HRESIMS data (measured at m/z 239.0925 [M H]−; calcd for C12H15O5, 239.0925). The 1H and 13C NMR data of 4 were also closely related to that of 3. Two γ-lactone groups and an oxygenated isopropyl could be established readily. Further analyses of 2D NMR data proved that 4 had the same planar structure to that of 3. However, the ROESY spectrum of 4 displayed some differences from that of 3. The cross peak between H-1 and H-8 could not be detected. Analysis of 1H NMR data indicated that the coupling constant of H-1 in 4 was a little bit to that in 3 (Table 1). In addition, the chemical shift of C-1 in 4 displayed the biggest difference to that in 3. These data suggested that H-1 and H-8 should be in the opposite side in 4. Therefore, compound 4 was established as a stereoisomer of 3, namely vibralactone Z2. Compound 5 was detected to have a molecular formula C12H14O4 by the HRESIMS (measured at m/z 223.09656 [M + H]+; calcd for C12H15O4, 223.09703), 18 unit less than that of 4. The 1D NMR data suggested that 5 also have two γ-lactones. However, the signals at δC 142.7 (s, C-9) and 110.8 (t, C-10) indicated the existence of a terminal double bond. The HMBC correlations from δH 1.79 (3H, s, H-11) and 4.95 (1H, dd, J = 6.9, 1.4 Hz, H-8) to C-9 suggested the terminal double bond should be at C-9 and C-10. Detailed analyses of 2D NMR data suggested that the other parts of 5 were the same to that of 4. The ROESY data, as well as the coupling constants, suggested that 5 shared the same relative configuration to that of 4. Compound 5 was, therefore, identified as vibralactone Z3. The known compound was identified as vibralactone by the comparison of NMR data with those reported in the literature [1]. The biosynthetic pathway studies have proved that vibralactone and its derivatives shared the same biosynthetic precursor 3-prenyl-4-hydroxybenzylalcohol [12,13]. The biosynthetic pathway of 1–5 was proposed as shown in Scheme 1. Briefly, 3-prenyl-4-hydroxybenzylalcohol was oxidized to yield the ε-lactone 1, the latter underwent a hydrolysis to give a possible intermediate, which might give rise to the δ-lactone 2 and the novel bis-γ-lactones 3–5 respectively by dehydration reaction in different positions. Our previous studies suggested that vibralactone derivatives possessing a β-lactone core might have significant pancreatic lipase inhibitory effects, while other compounds were low or inactive. In order to find more bioactive properties of vibralactone derivatives, compounds 1–5 were evaluated for their cytotoxicities against five human cancer cell lines (HL-60, SMMC-7721, A-549, MCF-7, and SW480) using the method we reported previously [15]. The results suggested that compounds 3 and 5 exhibited moderate cytotoxicities (Table 3). Compound 4 did not show any cytotoxic activity which might be affected by the different stereoconfiguration of it with 3.
MS and HRESIMS were measured on Bruker HCT/Esquire (Bruker, Karlsruher, Germany). Preparative HPLC was performed on an Agilent 1100 series (Agilent Technologies, Santa Clara, CA, USA) with a Zorbax SB-C18 (5 μm, 9.4 × 150 mm) column. Silica gel (200–300 mesh and 80–100 mesh, Qingdao Marine Chemical Inc., Qingdao, China), RP-18 gel (40–75 μm, Fuji Silysia Chemical Ltd., Kasugai, Japan) and Sephadex LH-20 (Amersham Biosciences, Upssala, Sweden) were used for column chromatography. Fractions were monitored by TLC (Qingdao Marine Chemical Inc., China) and spots visualized by heating silica gel plates immersed in vanillin-H2SO4 in EtOH. 3.2. Fungal material and cultivation conditions Boreostereum vibrans was collected from the Ailao Mountain of Yunnan Province, China in August 2005, and identified by Prof. Mu Zang of Kunming Institute of Botany, CAS. A voucher specimen (NO. BV20150901D.4) has been deposited in School of Pharmaceutical Sciences, South-Central University for Nationalities. The culture medium consisted of glucose 5%; peptone 0.15%; yeast extract 0.5%; KH2PO4 0.05%; and MgSO4 0.05% in liter of deionized water (pH 6.5 before autoclaving). The fungus was grown in Erlenmeyer flasks (500 with 300 mL of medium). Fermentation was carried out in a rotary shaker at 28 °C and 160 rpm for 20 days. 3.3. Extraction and isolation The whole cultural broth (50 L) of B. vibrans was extracted four times with EtOAc (20 L). The organic layer was concentrated under reduced pressure to give a crude extract (41 g). The residue was subjected to column chromatography (CC) over silica gel (200–300 mesh), eluted with a petroleum ether-acetone gradient (25:1, 20:1, 15:1, 10:1, 5:1, 2:1, 1:1, v/v) to afford fractions A-H. Fraction C (9.7 g) was first isolated by silica gel CC eluted with petroleum ether-EtOAc (2:1, v/v) to afford six subfractions C1–C6, then subfraction C6 (280 mg) was separated repeatedly by HPLC (MeCN/H2O from 5/5 to 7/3 in 20 min, v/ v) to give 3 (2 mg, retention time (rt) = 13.8 min), 4 (4 mg, rt. = 14.9 min), and 5 (2 mg, rt. = 15.4 min). Fraction D (4.4 mg) was isolated by silica gel CC eluted with petroleum ether-EtOAc (4:1) to afford five subfractions D1–D5. Fraction D3 (450 mg) was isolated by Sephadex LH-20 CC (CHCl3/MeOH, 1:1) and further purified by HPLC (MeCN/H2O from 4/6 to 7/3 in 20 min) to give 1 (3 mg, rt. = 12.7 min) and 2 (2 mg, rt. = 15.3 min). Fraction D4 (600 mg) was further isolated by silica gel CC eluted with petroleum ether–acetone (8:1) to afford vibralactone (120 mg). 3.3.1. Vibralactone X (1) Colorless oil; [α]25 D + 24.7 (c 0.25, CHCl3); IR (KBr) νmax: 3420, 2947, 2870, 1751, 1636, 1384, 1322, 1234, 1102 cm−1; 1H (CDCl3, 600 MHz) and 13C NMR (CDCl3, 150 MHz) data, see Table 2; HRESIMS (positive): m/z 233.1149 [M + Na]+ (calcd for C12H18O3Na, 233.1148).
3.1. General experimental procedures
3.3.2. Vibralactone Y (2) Colorless oil; [α]25 D – 76.0 (c 0.25, CHCl3); IR (KBr) νmax: 3428, 2955, 2930, 1720, 1634, 1385, 1327, 1203, 1108, 1082 cm−1; 1H (CDCl3, 600 MHz) and 13C NMR (CDCl3, 150 MHz) data, see Table 2; HRESIMS (negative): m/z 211.1138 [M - H]− (calcd for C12H19O3, 211.1340).
Optical rotations were measured on a Jasco-P-1020 polarimeter (Horiba, Kyoto, Japan). UV spectra were measured on a Shimadzu UV2401 PC spectrophotometer (Shimadzu, Kyoto, Japan). IR spectra were obtained by using a Bruker Tensor 27 FT-IR spectrometer (Bruker, Karlsruher, Germany) with KBr pellets. NMR spectra were acquired with instruments of Avance III 600 (Bruker, Karlsruher, Germany). ESI-
3.3.3. Vibralactone Z1 (3) Colorless oil; [α]25 D + 20 (c 0.25, methanol); IR (KBr) νmax: 3441, 2922, 1761, 1751, 1628, 1372, 1316, 1102, 1030 cm−1; 1H (methanol‑d4, 600 MHz) and 13C NMR (methanol‑d4, 150 MHz) data, see Table 2; HRESIMS (negative): m/z 239.0926 [M - H]− (calcd for C12H15O5, 239.0925).
3. Experimental section
9
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K.-T. Duan et al.
HO
[O]
1
6
O
O
(1,5)-cyclization
OH
O
OH
3
1
6
5
5
H vibralalctone
1 hydrolysis
OH
OH
HO HO
1
6
esterification
O
1
6
12
3
OH HO
2
HO
[O] OH
HO
O
HO
esterification
O
O
O O
3 12 5
12
esterification
OH
OH O
O
O
O O
9
6 1
12
O
OH
5
OH
O
O
O
12
3
O
3 12
OH
1
6
3 5
Scheme 1. Plausible biosynthetic pathway of 1–5.
method in 96-well microplates [15]. Briefly, 100 μL of adherent cells were seeded into each well of 96-well cell culture plates and allowed to adhere for 12 h before addition of test compounds, while suspended cells were seeded just before drug addition with initial density of 1 × 105 cells/mL. Each tumor cell line was exposed to the test compound at concentrations of 40 μM in triplicates for 48 h, and all tests were done in twice with cisplatin (Sigma, Los Angeles, USA) as a positive control.
3.3.4. Vibralactone Z2 (4) Colorless oil; [α]25 D + 56 (c 0.25, methanol); IR (KBr) νmax: 3440, 2919, 1759, 1749, 1631, 1382, 1322, 1102, 1035 cm−1; 1H (methanol‑d4, 600 MHz) and 13C NMR (methanol‑d4, 150 MHz) data, see Table 2; HRESIMS (negative): m/z 239.0925 [M - H]− (calcd for C12H15O5, 239.0925). 3.3.5. Vibralactone Z3 (5) Colorless oil; [α]25 D + 37, (c 0.15, methanol); IR (KBr) νmax: 3443, 2930, 2926, 1760, 1751, 1636, 1457, 1381, 1219, 1101, 1065 cm−1; 1 H (methanol‑d4, 600 MHz) and 13C NMR (methanol‑d4, 150 MHz) data, see Table 2; HRESIMS (positive): m/z 223.09656 [M + H]+ (calcd for C12H15O4, 223.09703).
Conflict of interest The authors declare no conflict of interest. We confirm that this manuscript has been submitted exclusively to Fitoterapia, and that no portion of this material has been previously published in any medium including electronic journals or computer databases of a public nature. We guarantee that no related work is under consideration for publication or has been published elsewhere in any medium.
3.4. Cytotoxicity Five human cancer cell lines, breast adenocarcinoma MCF-7, hepatocellular carcinoma SMMC-7721, human myeloid leukemia HL-60, colon carcinoma SW480, and lung cancer A-549 were used. Cells were cultured in RPMI-1640 or in DMEM medium (Hyclone, Logan, UT, USA), supplemented with 10% fetal bovine serum (Hyclone, USA) in 5% CO2 at 37 °C. The cytotoxicity assay was performed according to 3(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT)
Acknowledgments This work was financially supported by the National Natural Science Foundation of China (81561148013, 21502239), the National Key Research and Development Program of China (2017YFC1704007), the
Table 3 Cytotoxicities of compounds 1–5 (IC50, μM). Sample
HL-60
SMMC-7721
A-549
MCF-7
SW480
1 2 3 4 5 Cisplatina
> 40 > 40 13.4 ± 1.12 > 40 17.5 ± 1.46 2.1 ± 1.21
> 40 > 40 23.6 ± 0.45 > 40 14.9 ± 2.44 9.7 ± 1.22
> 40 > 40 26.5 ± 2.75 > 40 16.3 ± 0.77 8.1 ± 0.95
> 40 > 40 17.9 ± 2.91 > 40 > 40 14.5 ± 0.78
> 40 > 40 > 40 > 40 28.3 ± 2.32 15.2 ± 1.17
a
Positive control. 10
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Key Projects of Technological Innovation of Hubei Province (No. 2016ACA138), and the Fundamental Research Funds for the Central University, South-Central University for Nationalities (CZP18005, CZQ17010, CZQ17008, CZT18013, CZT18014). The authors thank Analytical & Measuring Centre, South-Central University for Nationalities for the NMR measurements.
[6]
[7]
[8]
Appendix A. Supplementary data [9]
Supplementary data to this article can be found online at https:// doi.org/10.1016/j.fitote.2018.04.020.
[10] [11]
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[15]
11
compounds from the cultures of basidiomycete Boreostereum vibrans, J. Asian Nat. Prod. Res. 15 (2013) 950–955. G.Q. Wang, K. Wei, L. Zhang, Z.H. Li, Q.A. Wang, J.K. Liu, Three new vibralactonerelated compounds from cultures of basidiomycete Boreostereum vibrans, J. Asian Nat. Prod. Res. 16 (2014) 447–452. H.P. Chen, Z.Z. Zhao, R.H. Yin, X. Yin, T. Feng, Z.H. Li, K. Wei, J.K. Liu, Six new vibralactone derivatives from cultures of the fungus Boreostereum vibrans, Nat. Prod. Bioprospect. 4 (2014) 271–276. H.P. Chen, M.Y. Jiang, Z.Z. Zhao, T. Feng, Z.H. Li, J.K. Liu, Vibralactone biogenesisassociated analogues from submerged cultures of the fungus Boreostereum vibrans, Nat. Prod. Bioprospect. 8 (2018) 37–45. J.H. Ding, T. Feng, Z.H. Li, L. Li, J.K. Liu, Twelve new compounds from the basidiomycete Boreostereum vibrans, Nat. Prod. Bioprospect. 2 (2012) 200–205. Q. Zhou, B.B. Snider, Synthesis of ( ± )-vibralactone, Org. Lett. 10 (2008) 1401–1404. A.J. Leeder, R.J. Heap, L.J. Brown, X. Franck, R.C.D. Brown, A short diastereoselective total synthesis of ( ± )-vibralactone, Org. Lett. 18 (2016) 5971–5973. P.J. Zhao, Y.L. Yang, L. Du, J.K. Liu, Y. Zeng, Elucidating the biosynthetic pathway for vibralactone: a pancreatic lipase inhibitor with a fused bicyclic β-lactone, Angew. Chem. Int. Ed. 52 (2013) 2298–2302. Y.L. Yang, H. Zhou, G. Du, K.N. Feng, T. Feng, X.L. Fu, J.K. Liu, Y. Zeng, A monooxygenase from Boreostereum vibrans catalyzes oxidative decarboxylation in a divergent vibralactone biosynthesis pathway, Angew. Chem. Int. Ed. 55 (2016) 5463–5466. H.P. Chen, Z.Z. Zhao, Z.H. Li, Z.J. Dong, K. Wei, X. Bai, L. Zhang, C.N. Wen, T. Feng, J.K. Liu, Novel natural oximes and oxime esters with a vibralactone backbone from the basidiomycete Boreostereum vibrans, ChemistryOpen 5 (2016) 142–149. Y. Huang, S.B. Zhang, H.P. Chen, Z.Z. Zhao, Z.Y. Zhou, Z.H. Li, J.K. Liu, New acetylenic acids and derivatives from the edible mushroom Craterellus lutescens (Cantharellaceae), J. Agric. Food Chem. 65 (2017) 3835–3841.
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Fitoterapia journal homepage: www.elsevier.com/locate/fitote
Vibralactone derivatives containing γ, δ, ε-lactone cores from cultures of the basidiomycete Boreostereum vibrans
T
Kai-Ting Duan, Zheng-Hui Li, Xing Yu, Qing-Xia Yuan, Wen-Xuan Wang, Jing Li, He-Ping Chen, ⁎ ⁎ Tao Feng , Ji-Kai Liu School of Pharmaceutical Sciences, South-Central University for Nationalities, Wuhan 430074, China
A R T I C LE I N FO
A B S T R A C T
Keywords: Boreostereum vibrans Vibralactone derivatives Lactone Cytototxicity
Five vibralactone derivatives containing γ, δ, ε-lactone cores, namely vibralactones X (1), Y (2), and Z1–Z3 (3–5), together with the known vibralactone, have been isolated from cultures of the basidiomycete Boreostereum vibrans. Compounds 3–5 possessed a novel bis-γ-lactone group which was found in vibralactone derivatives for the first time. Compounds 3 and 5 exhibited moderate cytotoxicities to human cancer cell lines referring to that of cisplatin.
1. Introduction
2. Results and discussion
The fungus Boreostereum vibrans is considered as a talent strain by our group due to its high productive ability of multiple natural products including vibralactone derivatives [1–8], terpenoids [9], and benzene ring derivatives [6–8]. Of them, vibralactone and its derivatives are highlighted by its structural novelty and potent bioactivities. In 2006, our group reported the novel structure vibralactone. It possesses a βlactone in conjugation of a cyclopentane, as well as an isopentene substituent. Meanwhile, it is also a good pancreatic lipase inhibitor with an IC50 value of 0.4 μg/mL [1]. The unique structures and potent bioactivities of vibralactone and its derivatives have aroused many follow-up studies including the total syntheses [10,11], biosynthetic pathway investigations [12,13], and other bioactive tests [3,9]. As our ongoing research for new and bioactive compounds from B. vibrans, many small amount of novel compounds have been discovered. For instance, oxime and other N-containing vibralactone derivatives have been isolated from the scale-up fermentation broths [14]. In doing so, our study on natural products from B. vibrans seems endless. Herein, we are about to reported five new isolates, namely vibralactones X (1), Y (2), and Z1–Z3 (3–5), together with the known vibralactone, from a scale-up fermentation broth of B. vibrans (Fig. 1). The compounds are featured by containing a different lactone moiety including γ, δ, ε-lactone cores. Particularly, compounds 3–5 possessed an interesting framework owning a bis-γ-lactone group, which also showed cytotoxicities to human cancer cell lines.
Compound 1 was isolated as a colorless oil. The molecular formula was determined as C12H18O3 by HRESIMS at m/z 233.1149 (calcd for C12H18O3Na, 233.1148). The IR data at 1751 cm−1 indicated the presence of a carbonyl carbon. In the 1H NMR spectrum (Table 1), two singlets for methyl groups at δH 1.66 and 1.71 and two olefinic protons at δH 5.14 and 5.35 are readily identified. In addition, signals at δH 4.68 (1H, dd, J = 12.8, 1.7 Hz, H-5a), 4.32 (1H, ddd, J = 12.8, 4.7, 2.5 Hz, H-5b), and 4.01 (2H, br s, H-12) were ascribable for protons of oxygenated carbons. In the 13C NMR and DEPT spectra, twelve resonances were observed, which displayed as two methyl, four methylene, three methine, and three quaternary carbons. These data were related to those of 1,5-secovibralactone [2]. The main difference was that the double bond between C-4 and C-5 in 1,5-secovibralactone was saturated in 1, as indicated by the 1H–1H COSY correlation of δH 2.51 and 2.34 (each 1H, m, H-4) with δH 4.68 (1H, dt, J = 12.8, 1.7 Hz, H-5a) and 4.32 (1H, ddd, J = 12.8, 4.7, 2.5 Hz, H-5b), as well as the HMBC correlations from H-4 to δC 121.2 (d, C-2) and δC 139.2 (s, C-3). In addition, the ε-lactone group was confirmed by HMBC correlations from H-5 to δC 174.2 (s, C-6). Analyses of other 1D and 2D NMR data suggested that the other parts of 1 were the same to those of 1,5-secovibralactone. Sincere the absolute configuration of C-1 in 1,5-secovibralactone was identified by the optical rotation calculations, the configuration of C-1 in 1 was identified as S by comparison of the optical rotation data ([α]25 D = + 24.7° (c = 0.25, CHCl3)) with that of 1,5secovibralactone ([α]14 D = + 107.5° (c = 0.34, CHCl3)). Compound 1 was, therefore, established as vibralactone X, as depicted.
⁎
Corresponding authors. E-mail addresses: [email protected] (T. Feng), [email protected] (J.-K. Liu).
https://doi.org/10.1016/j.fitote.2018.04.020 Received 14 March 2018; Received in revised form 22 April 2018; Accepted 27 April 2018 Available online 30 April 2018 0367-326X/ © 2018 Elsevier B.V. All rights reserved.
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10
9
O
OH
10
O
6
O O
3
9 8
2
4
5 12
3
O
O
8
O
8
H
O
OH
2
OH 11
6
O O
O
O
5
O
8
O O
O H H
H H
4
3
Fig. 1. Structures of vibralactone and compounds 1–5. 1H-1H
Compound 2 was isolated as a colorless oil. The molecular formula was established as C12H20O3 by the negative HRESIMS data (measured at m/z 211.1138 [M - H]−; calcd for C12H19O3, 211.1340). Preliminary analyses of 1D NMR data suggested that 2 should be a vibralactone derivative, which possessed similar moieties like an isopentene group and a lactone carbon at δC 173.9 (s, C-6). Detailed analysis of NMR data suggested that 2 might have a structure closely related to that of vibralactone Q [7], except for the double bond between C-1 and C-2 was saturated in 2, which was supported by the 1H–1H COSY data as shown in Fig. 2. The δ-lactone moiety was proved by the HMBC correlations from δH 4.38 (1H, ddd, J = 11.1, 4.7, 2.0 Hz, H-12a) and 3.98 (1H, dd, J = 11.1, 4.7 Hz, H-12b) to C-6. The relative configuration was established by the ROESY data (Fig. 2). The cross peak between H-1 and H-3 suggested that H-1 and H-3 were in the same side, which allowed the major substituents of C-13 and the isopentene group were equatorial. Finally, compound 2 was identified as vibralactone Y. Compound 3 was isolated as a colorless oil. The molecular formula was established as C12H16O5 by the HRESIMS (measured at m/z 239.0926 [M - H]−; calcd for C12H15O5, 239.0925), corresponding to five degrees of unsaturation. The 13C NMR spectrum, along with the DEPT data, indicated that 3 had two methyl, three methylene, three methine, and four quaternary carbons (Table 2). Of them, two carbonyl carbons at δC 176.7 (s, C-5) and 179.8 (s, C-6), together with two olefinic carbons at δC 171.1 (s, C-3) and 117.3 (d, C-4), occupied three degrees of unsaturation, indicating that compound 3 should have a bicyclic ring system. The 1H–1H COSY spectrum afforded a number of cross peaks, establishing a fragment as shown in Fig. 2. In the HMBC spectrum (Fig. 2), the correlation from δH 4.33 (1H, dd, J = 10.2,
OH
1 2
12
O
O
OH
10
O
O
3
12
OH
H
O
6
OH
4
2
O
11
1
O
2
O
12
1
8 1
6
4
OH
7
1
12
5
3 5
H Vibralalctone
O OH
11
9
7
2
O
O
O
1
6
10
8
7
O
11
COSY
O
HMBC
ROESY
Fig. 2. Key correlations in 2D NMR spectra of 2 and 3.
Table 2 13 C NMR data of compounds 1–5 (δ in ppm). No.
1a
2a
3b
4b
5b
1 2 3 4 5 6 7 8 9 10 11 12
40.2 (d) 121.2 (d) 139.2 (s) 30.4 (t) 64.4 (t) 174.2 (s) 30.0 (t) 120.9 (d) 134.6 (s) 25.9 (q) 18.0 (q) 67.4 (t)
40.4 (d) 31.5 (t) 30.4 (d) 35.1 (t) 60.0 (t) 173.9 (s) 29.7 (t) 120.6 (d) 134.5 (s) 25.8 (q) 17.9 (q) 73.1 (t)
40.5 (d) 30.2 (t) 171.1 (s) 117.3 (d) 176.7 (s) 179.8 (s) 29.9 (t) 86.1 (d) 71.0 (s) 25.0 (q) 26.6 (q) 75.2 (t)
39.3 (d) 31.2 (t) 170.9 (s) 117.1 (d) 176.5 (s) 180.5 (s) 29.4 (t) 85.9 (d) 72.4 (s) 25.6 (q) 26.0 (q) 74.9 (t)
37.0 (d) 31.7 (t) 169.2 (s) 115.9 (d) 175.1 (s) 178.6 (s) 28.9 (t) 80.4 (d) 142.7 (s) 110.8 (t) 16.6 (q) 73.6 (d)
a b
Measured at 150 MHz in CDCl3. Measured at 150 MHz in methanol-d4.
6.1 Hz, H-8) to C-6 suggested that a γ-lactone ring was built by C-6, C-1, C-7, and C-8. In addition, the HMBC correlations from δH 4.88 (1H, d, J = 17.9 Hz, H-12) to C-5, C-3, and C-4 suggested that another γ-lactone ring was built by C-5, C-4, C-3, and C-12. Furthermore, the HMBC correlations from δH 1.14 (3H, s, H-10) and 1.31 (3H, s, H-11) to δC 71.0 (s, C-9) indicated an oxygenated isopropyl. It was connected to C-8
Table 1 1 H NMR data of 15 (δ in ppm, J in Hz). No.
1a
2a
1 2a 2b 3 4a 4b 5a 5b 7a 7b 8 10 11 12a 12b
3.68 (m) 5.35 (s)
2.50 2.13 1.24 2.19 1.57
a b
2.51 2.34 4.68 4.32 2.58 2.46 5.14 1.71 1.66 4.01
(m) (m) (td, 12.8, 1.7) (ddd, 12.8, 4.7, 2.5) (m) (m) (m) (3H, s) (3H, s) (s)
(m) (m) (m) (m) (m)
3b
4b
5b
3.15 (m) 2.96 (dd, 16.5, 5.1) 2.68 (dd, 16.5, 8.4)
3.11 (ddd, 18.3, 9.3, 5.3) 2.93 (dd, 16.4, 5.3) 2.67 (dd, 16.4, 9.3)
3.05 (ddd, 17.7, 9.1, 5.7) 2.94 (dd, 16.4, 5.7) 2.71 (dd, 16.4, 9.1)
6.02 (br s)
6.01 (br s)
6.01 (br s)
2.44 1.92 4.33 1.14 1.31 4.88
2.55 2.02 4.37 1.20 1.27 4.95
2.40 2.21 5.01 4.98 1.79 4.87
3.72 (m) 2.56 2.28 5.10 1.71 1.62 4.38 3.98
(m) (m) (m) (3H, s) (3H, s) (ddd, 11.1, 4.7, 2.0) (dd, 11.1, 4.7)
Measured at 600 MHz in CDCl3. Measured at 600 MHz in methanol-d4. 8
(m) (m) (dd, 10.2, 6.1) (3H, s) (3H, s) (d, 17.9)
(m) (m) (dd, 8.7, 3.7) (3H, s) (3H, s) (d, 17.8)
(m) (m) (dd, 8.6, 4.1) (s); 4.95 (s) (3H, s) (d, 17.8)
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as deduced from HMBC correlation from H-8 to C-9. Compound 3 was identified as an interesting vibralactone containing a pair of γ-lactone groups. The relative configuration was established by the ROESY data (Fig. 2). H-8 was detected to have a strong correlation with H-7a (δH 2.44) and a weak correlation with H-7b (δH 1.92). H-1 was found to have a key cross peak with H-7a (no cross peak found between H-1 with H-7b). In addition, a weak cross peak of H-8 with H-1 was also detected. These data suggested that H-1 and H-8 were in the same side. Compound 3 was, therefore, identified as vibralactone Z1, as depicted. Compound 4 was detected to have the same molecular formula to that of 3 on the basis of HRESIMS data (measured at m/z 239.0925 [M H]−; calcd for C12H15O5, 239.0925). The 1H and 13C NMR data of 4 were also closely related to that of 3. Two γ-lactone groups and an oxygenated isopropyl could be established readily. Further analyses of 2D NMR data proved that 4 had the same planar structure to that of 3. However, the ROESY spectrum of 4 displayed some differences from that of 3. The cross peak between H-1 and H-8 could not be detected. Analysis of 1H NMR data indicated that the coupling constant of H-1 in 4 was a little bit to that in 3 (Table 1). In addition, the chemical shift of C-1 in 4 displayed the biggest difference to that in 3. These data suggested that H-1 and H-8 should be in the opposite side in 4. Therefore, compound 4 was established as a stereoisomer of 3, namely vibralactone Z2. Compound 5 was detected to have a molecular formula C12H14O4 by the HRESIMS (measured at m/z 223.09656 [M + H]+; calcd for C12H15O4, 223.09703), 18 unit less than that of 4. The 1D NMR data suggested that 5 also have two γ-lactones. However, the signals at δC 142.7 (s, C-9) and 110.8 (t, C-10) indicated the existence of a terminal double bond. The HMBC correlations from δH 1.79 (3H, s, H-11) and 4.95 (1H, dd, J = 6.9, 1.4 Hz, H-8) to C-9 suggested the terminal double bond should be at C-9 and C-10. Detailed analyses of 2D NMR data suggested that the other parts of 5 were the same to that of 4. The ROESY data, as well as the coupling constants, suggested that 5 shared the same relative configuration to that of 4. Compound 5 was, therefore, identified as vibralactone Z3. The known compound was identified as vibralactone by the comparison of NMR data with those reported in the literature [1]. The biosynthetic pathway studies have proved that vibralactone and its derivatives shared the same biosynthetic precursor 3-prenyl-4-hydroxybenzylalcohol [12,13]. The biosynthetic pathway of 1–5 was proposed as shown in Scheme 1. Briefly, 3-prenyl-4-hydroxybenzylalcohol was oxidized to yield the ε-lactone 1, the latter underwent a hydrolysis to give a possible intermediate, which might give rise to the δ-lactone 2 and the novel bis-γ-lactones 3–5 respectively by dehydration reaction in different positions. Our previous studies suggested that vibralactone derivatives possessing a β-lactone core might have significant pancreatic lipase inhibitory effects, while other compounds were low or inactive. In order to find more bioactive properties of vibralactone derivatives, compounds 1–5 were evaluated for their cytotoxicities against five human cancer cell lines (HL-60, SMMC-7721, A-549, MCF-7, and SW480) using the method we reported previously [15]. The results suggested that compounds 3 and 5 exhibited moderate cytotoxicities (Table 3). Compound 4 did not show any cytotoxic activity which might be affected by the different stereoconfiguration of it with 3.
MS and HRESIMS were measured on Bruker HCT/Esquire (Bruker, Karlsruher, Germany). Preparative HPLC was performed on an Agilent 1100 series (Agilent Technologies, Santa Clara, CA, USA) with a Zorbax SB-C18 (5 μm, 9.4 × 150 mm) column. Silica gel (200–300 mesh and 80–100 mesh, Qingdao Marine Chemical Inc., Qingdao, China), RP-18 gel (40–75 μm, Fuji Silysia Chemical Ltd., Kasugai, Japan) and Sephadex LH-20 (Amersham Biosciences, Upssala, Sweden) were used for column chromatography. Fractions were monitored by TLC (Qingdao Marine Chemical Inc., China) and spots visualized by heating silica gel plates immersed in vanillin-H2SO4 in EtOH. 3.2. Fungal material and cultivation conditions Boreostereum vibrans was collected from the Ailao Mountain of Yunnan Province, China in August 2005, and identified by Prof. Mu Zang of Kunming Institute of Botany, CAS. A voucher specimen (NO. BV20150901D.4) has been deposited in School of Pharmaceutical Sciences, South-Central University for Nationalities. The culture medium consisted of glucose 5%; peptone 0.15%; yeast extract 0.5%; KH2PO4 0.05%; and MgSO4 0.05% in liter of deionized water (pH 6.5 before autoclaving). The fungus was grown in Erlenmeyer flasks (500 with 300 mL of medium). Fermentation was carried out in a rotary shaker at 28 °C and 160 rpm for 20 days. 3.3. Extraction and isolation The whole cultural broth (50 L) of B. vibrans was extracted four times with EtOAc (20 L). The organic layer was concentrated under reduced pressure to give a crude extract (41 g). The residue was subjected to column chromatography (CC) over silica gel (200–300 mesh), eluted with a petroleum ether-acetone gradient (25:1, 20:1, 15:1, 10:1, 5:1, 2:1, 1:1, v/v) to afford fractions A-H. Fraction C (9.7 g) was first isolated by silica gel CC eluted with petroleum ether-EtOAc (2:1, v/v) to afford six subfractions C1–C6, then subfraction C6 (280 mg) was separated repeatedly by HPLC (MeCN/H2O from 5/5 to 7/3 in 20 min, v/ v) to give 3 (2 mg, retention time (rt) = 13.8 min), 4 (4 mg, rt. = 14.9 min), and 5 (2 mg, rt. = 15.4 min). Fraction D (4.4 mg) was isolated by silica gel CC eluted with petroleum ether-EtOAc (4:1) to afford five subfractions D1–D5. Fraction D3 (450 mg) was isolated by Sephadex LH-20 CC (CHCl3/MeOH, 1:1) and further purified by HPLC (MeCN/H2O from 4/6 to 7/3 in 20 min) to give 1 (3 mg, rt. = 12.7 min) and 2 (2 mg, rt. = 15.3 min). Fraction D4 (600 mg) was further isolated by silica gel CC eluted with petroleum ether–acetone (8:1) to afford vibralactone (120 mg). 3.3.1. Vibralactone X (1) Colorless oil; [α]25 D + 24.7 (c 0.25, CHCl3); IR (KBr) νmax: 3420, 2947, 2870, 1751, 1636, 1384, 1322, 1234, 1102 cm−1; 1H (CDCl3, 600 MHz) and 13C NMR (CDCl3, 150 MHz) data, see Table 2; HRESIMS (positive): m/z 233.1149 [M + Na]+ (calcd for C12H18O3Na, 233.1148).
3.1. General experimental procedures
3.3.2. Vibralactone Y (2) Colorless oil; [α]25 D – 76.0 (c 0.25, CHCl3); IR (KBr) νmax: 3428, 2955, 2930, 1720, 1634, 1385, 1327, 1203, 1108, 1082 cm−1; 1H (CDCl3, 600 MHz) and 13C NMR (CDCl3, 150 MHz) data, see Table 2; HRESIMS (negative): m/z 211.1138 [M - H]− (calcd for C12H19O3, 211.1340).
Optical rotations were measured on a Jasco-P-1020 polarimeter (Horiba, Kyoto, Japan). UV spectra were measured on a Shimadzu UV2401 PC spectrophotometer (Shimadzu, Kyoto, Japan). IR spectra were obtained by using a Bruker Tensor 27 FT-IR spectrometer (Bruker, Karlsruher, Germany) with KBr pellets. NMR spectra were acquired with instruments of Avance III 600 (Bruker, Karlsruher, Germany). ESI-
3.3.3. Vibralactone Z1 (3) Colorless oil; [α]25 D + 20 (c 0.25, methanol); IR (KBr) νmax: 3441, 2922, 1761, 1751, 1628, 1372, 1316, 1102, 1030 cm−1; 1H (methanol‑d4, 600 MHz) and 13C NMR (methanol‑d4, 150 MHz) data, see Table 2; HRESIMS (negative): m/z 239.0926 [M - H]− (calcd for C12H15O5, 239.0925).
3. Experimental section
9
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HO
[O]
1
6
O
O
(1,5)-cyclization
OH
O
OH
3
1
6
5
5
H vibralalctone
1 hydrolysis
OH
OH
HO HO
1
6
esterification
O
1
6
12
3
OH HO
2
HO
[O] OH
HO
O
HO
esterification
O
O
O O
3 12 5
12
esterification
OH
OH O
O
O
O O
9
6 1
12
O
OH
5
OH
O
O
O
12
3
O
3 12
OH
1
6
3 5
Scheme 1. Plausible biosynthetic pathway of 1–5.
method in 96-well microplates [15]. Briefly, 100 μL of adherent cells were seeded into each well of 96-well cell culture plates and allowed to adhere for 12 h before addition of test compounds, while suspended cells were seeded just before drug addition with initial density of 1 × 105 cells/mL. Each tumor cell line was exposed to the test compound at concentrations of 40 μM in triplicates for 48 h, and all tests were done in twice with cisplatin (Sigma, Los Angeles, USA) as a positive control.
3.3.4. Vibralactone Z2 (4) Colorless oil; [α]25 D + 56 (c 0.25, methanol); IR (KBr) νmax: 3440, 2919, 1759, 1749, 1631, 1382, 1322, 1102, 1035 cm−1; 1H (methanol‑d4, 600 MHz) and 13C NMR (methanol‑d4, 150 MHz) data, see Table 2; HRESIMS (negative): m/z 239.0925 [M - H]− (calcd for C12H15O5, 239.0925). 3.3.5. Vibralactone Z3 (5) Colorless oil; [α]25 D + 37, (c 0.15, methanol); IR (KBr) νmax: 3443, 2930, 2926, 1760, 1751, 1636, 1457, 1381, 1219, 1101, 1065 cm−1; 1 H (methanol‑d4, 600 MHz) and 13C NMR (methanol‑d4, 150 MHz) data, see Table 2; HRESIMS (positive): m/z 223.09656 [M + H]+ (calcd for C12H15O4, 223.09703).
Conflict of interest The authors declare no conflict of interest. We confirm that this manuscript has been submitted exclusively to Fitoterapia, and that no portion of this material has been previously published in any medium including electronic journals or computer databases of a public nature. We guarantee that no related work is under consideration for publication or has been published elsewhere in any medium.
3.4. Cytotoxicity Five human cancer cell lines, breast adenocarcinoma MCF-7, hepatocellular carcinoma SMMC-7721, human myeloid leukemia HL-60, colon carcinoma SW480, and lung cancer A-549 were used. Cells were cultured in RPMI-1640 or in DMEM medium (Hyclone, Logan, UT, USA), supplemented with 10% fetal bovine serum (Hyclone, USA) in 5% CO2 at 37 °C. The cytotoxicity assay was performed according to 3(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT)
Acknowledgments This work was financially supported by the National Natural Science Foundation of China (81561148013, 21502239), the National Key Research and Development Program of China (2017YFC1704007), the
Table 3 Cytotoxicities of compounds 1–5 (IC50, μM). Sample
HL-60
SMMC-7721
A-549
MCF-7
SW480
1 2 3 4 5 Cisplatina
> 40 > 40 13.4 ± 1.12 > 40 17.5 ± 1.46 2.1 ± 1.21
> 40 > 40 23.6 ± 0.45 > 40 14.9 ± 2.44 9.7 ± 1.22
> 40 > 40 26.5 ± 2.75 > 40 16.3 ± 0.77 8.1 ± 0.95
> 40 > 40 17.9 ± 2.91 > 40 > 40 14.5 ± 0.78
> 40 > 40 > 40 > 40 28.3 ± 2.32 15.2 ± 1.17
a
Positive control. 10
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Key Projects of Technological Innovation of Hubei Province (No. 2016ACA138), and the Fundamental Research Funds for the Central University, South-Central University for Nationalities (CZP18005, CZQ17010, CZQ17008, CZT18013, CZT18014). The authors thank Analytical & Measuring Centre, South-Central University for Nationalities for the NMR measurements.
[6]
[7]
[8]
Appendix A. Supplementary data [9]
Supplementary data to this article can be found online at https:// doi.org/10.1016/j.fitote.2018.04.020.
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