Article pubs.acs.org/JAFC
Isolation, Characterization, and Antiproliferative Activities of Eudesmanolide Derivatives from the Flowers of Inula japonica Chunfeng Xie,†,‡ Hao Wang,† Xiaocong Sun,† Linghao Meng,† Meicheng Wang,† Mark Bartlam,§ and Yuanqiang Guo*,† †
State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University, Tianjin 300071, People’s Republic of China ‡ State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, People’s Republic of China § State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, Tianjin 300071, People’s Republic of China S Supporting Information *
ABSTRACT: Inula japonica belongs to the family Asteraceae, and its flowers have been used as dietary supplements and health tea in China. The study aimed to identify the bioactive components with the antiproliferative property. Ten 1,10-secoeudesmanolide derivatives, including four new compounds (1−4), were isolated from the flowers of I. japonica. Their structures were established on the basis of the interpretation of spectroscopic data and electronic circular dichroism (ECD) calculations. All of these isolates were evaluated for their antiproliferative activities against MCF-7 and MDA-MB-231 human breast cancer cells. Compound 4 possessed the most potent effects, with the IC50 values of 0.20 ± 0.04 and 6.22 ± 1.30 μM against MCF-7 and MDA-MB-231 cells, respectively. The present investigation indicated that eudesmanolide derivatives from the flowers of I. japonica, especially compound 4, might be used as potential antitumor chemotherapy agent candidates. KEYWORDS: Inula japonica, 1,10-seco-eudesmanolides, breast cancer cells, antiproliferative activities
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resonance (NMR) spectra were acquired on a Bruker AV 400 spectrometer using tetramethylsilane (TMS) as a reference at room temperature. High-performance liquid chromatography (HPLC) was performed on a CXTH LC3000 system [Beijing Chuangxin Tongheng Instruments Co., Ltd., China; flow rate, 5.5 mL/min; ultraviolet (UV) detection, 210 nm]. The column used for HPLC isolation was a YMCpack ODS-AM column (250 × 20 mm). Silica gel (200−300 mesh) used was from Qingdao Marine Chemical Group Co., Ltd., China. Chemical reagents and biological reagents were from Tianjin Chemical Reagent Company, China, and Sigma Company, respectively. MCF-7 and MDA-MB-231 cells were from the Institute of Basic Medical Sciences, Chinese Academy of Sciences (China). Plant Material. The flowers of I. japonica were purchased at Materia Medica Market of Anguo county, Hebei province, China, in December 2013 and identified by Dr. Chunfeng Xie (College of Pharmacy, Nankai University, China). The deposition of a voucher specimen (20131219IJ) was carried out by the Laboratory of the Research Department of Natural Medicines, College of Pharmacy, Nankai University, China. Extraction and Isolation. The air-dried flowers of I. japonica (4.5 kg) were extracted with methanol (3 × 40 L) under reflux. The methanol solvent was concentrated to obtain a residue (0.6 kg), which was suspended in water (1.5 L) and partitioned with ethyl acetate (3 × 1.5 L). The ethyl acetate-soluble layer (295 g) was chromatographed on a silica gel column (acetone/petroleum ether, from 0:100 to 30:100) to give eight fractions (F1−F8). F2 (17 g) was fractionated by medium-pressure liquid chromatography (MPLC) over octadecylsilica
INTRODUCTION Inula japonica Thunb. (family Asteraceae) grows extensively in northern China, Japan, and Korea.1 Its flowers have been used as dietary supplements and health tea in China.2 In addition, the flowers of I. japonica were historically used to treat microbial infections, bronchitis and inflammation, digestive disorders, and some tumors.3 Sesquiterpenoids,4,5 especially sesquiterpene lactone dimers,6−10 were the main components of I. japonica, which showed anti-inflammatory and cytotoxic activities.3,11 During our continuous research on the chemical composition of medicinal foods,12−14 ten 1,10-seco-eudesmanolide derivatives, including four new compounds (1−4), were isolated and characterized from the flowers of I. japonica. The antiproliferative activities against the human breast cancer cell lines of these sesquiterpene lactones were also evaluated. Herein, structure elucidation and antiproliferative effects of these isolates 1−10 are described in this paper.
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MATERIALS AND METHODS
General. The infrared (IR) spectra (KBr) were acquired on a Nicolet MAGNA-560 instrument. The optical rotations and electronic circular dichroism (ECD) spectra were determined on an Insmark IP120 automatic polarimeter (Shanghai InsMark Instrument Technology Co., Ltd., Shanghai, China) and a Jasco J-715 spectropolarimeter, respectively. High-resolution electrospray ionization mass spectrometry (HR-ESIMS) spectra were obtained by an Agilent 6520 Q-TOF LC/MS system (Agilent, Santa Clara, CA) or IonSpec 7.0 T FTICR MS (IonSpec Co., Ltd., Lake Forest, CA) instrument. ESIMS spectra were determined on a LCQ-Advantage mass spectrometer (Finnigan Co., Ltd., San Jose, CA). Nuclear magnetic © 2015 American Chemical Society
Received: Revised: Accepted: Published: 9006
June 22, 2015 September 30, 2015 October 1, 2015 October 1, 2015 DOI: 10.1021/acs.jafc.5b03075 J. Agric. Food Chem. 2015, 63, 9006−9011
Article
Journal of Agricultural and Food Chemistry
Table 1. 1H (400 MHz) and 13C NMR (100 MHz) Spectroscopic Data for Compounds 1 and 2 (δ ppm in CDCl3 and J in Hz)a 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1′ 2′ 3′ 4′ 5′ 6′ 1″ 2″ 3″ 4″ a
2
δH
position 3.93 1.25 1.01 2.69
m m, 1.43 m m, 1.29 m m
5.19 3.46 4.94 2.47
d (1.8) m ddd (7.8, 3.9, 2.1) m, 2.68 m
δC
δH
2.47 m 1.14 d (6.8) 1.16 d (6.8)
64.0 26.5 31.0 33.0 132.2 69.1 42.9 74.9 34.6 133.6 136.3 169.5 124.9 20.5 18.6 177.0 34.0 18.8 18.9
CH2 CH2 CH2 CH C CH CH CH CH2 C C C CH2 CH3 CH3 C CH CH3 CH3
2.47 m 1.14 d (6.8) 1.16 d (6.8)
177.3 34.2 19.0 19.0
C CH CH3 CH3
5.94 d (2.4), 6.37 d (2.7) 1.81 s 0.86 d (6.9)
3.93 1.25 1.02 2.69
m m, 1.42 m m, 1.26 m m
5.22 3.48 4.94 2.48
d (1.8) m ddd (7.8, 3.8, 2.1) m, 2.72 m
5.95 d (2.3), 6.37 d (2.7) 1.81 s 0.88 d (6.8) 2.09 1.86 1.21 0.89 0.88
m, 2.30 m m m, 1.37 m t (6.8) d (6.8)
2.04 s
δC 64.2 26.5 31.1 33.0 132.0 68.9 42.8 75.0 34.6 133.7 136.3 169.5 124.9 20.5 18.5 173.2 41.6 31.9 29.2 11.2 19.2 171.2 20.9
CH2 CH2 CH2 CH C CH CH CH CH2 C C C CH2 CH3 CH3 C CH2 CH CH2 CH3 CH3 C CH3
The assignments were based on DEPT and 2D NMR experiments. Table 1. ESIMS m/z: 429 [M + Na]+. HR-ESIMS m/z: 429.2245 [M + Na]+, calcd for C23H34NaO6 429.2253. Japonicone U (3). Yellow oil. [α]23 D : +10.6 (c 0.23, CH2Cl2). ECD (CH3CN): 212 (Δε −18.74), 238 (Δε 3.03). IR (KBr) νmax: 3441, 2956, 2924, 2869, 2852, 1770, 1732, 1683, 1462, 1377, 1235, 1164, 1029, 984, 953, 916, 850, 816, 752, 633 cm−1. 1H NMR (400 MHz, CDCl3) and 13C NMR (100 MHz, CDCl3) data: see Table 2. ESIMS m/z: 689 [M + Na]+. HR-ESIMS m/z: 689.3299 [M + Na]+, calcd for C38H50NaO10 689.3302. Japonicone V (4). Yellow oil. [α]23 D : +13.0 (c 0.19, CH2Cl2). ECD (CH3CN): 211 (Δε −20.36), 237 (Δε 3.10). IR (KBr) νmax: 3443, 2956, 2924, 2869, 2852, 1770, 1732, 1670, 1463, 1377, 1236, 1166, 1126, 1085, 1030, 984, 919, 903, 815, 723, 701, 675, 633 cm−1. 1H NMR (400 MHz, CDCl3) and 13C NMR (100 MHz, CDCl3) data: see Table 2. ESIMS m/z: 717 [M + Na]+. HR-ESIMS m/z: 717.3613 [M + Na]+, calcd for C40H54NaO10 717.3615. Computational Methods. The calculated ECD spectra were obtained according to the published methods previously.12,15,16 Antiproliferative Activities. The antiproliferative activities of compounds 1−10 were evaluated by the 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide (MTT) assay. Cells (1 × 104/well) were incubated for 48 h in the absence or presence of the tested compounds. Then, cells were incubated for another 4 h after adding MTT solution [5 mg/mL in phosphate-buffered saline (PBS)], and the formazan crystals were solubilized with dimethyl sulfoxide (DMSO). The absorbance was determined at 490 nm using a microplate reader (Thermo Fisher Scientific, Inc., Waltham, MA). Etoposide was used as a positive control. The experiments were performed in triplicate.
(ODS) (MeOH in H2O, from 81 to 92%) to yield three subfractions (F2‑1−F2‑3). F2‑1 was purified by HPLC (80% MeOH in H2O) to obtain compound 1 (tR = 42 min, 5.9 mg). Fraction F3 afforded seven subfractions F3‑1−F3‑7 through the same MPLC (MeOH in H2O, 78− 94%). The further purification of F3‑2 afforded compounds 2 (tR = 29 min, 69.4 mg) and 5 (tR = 19 min, 7.6 mg) using the above HPLC system (84% MeOH in H2O). Fraction F4 (7 g) was fractioned on the same MPLC (76−92% MeOH in H2O) to afford four subfractions F4‑1−F4‑4, and F4‑1 purified by the HPLC system (65% MeOH in H2O) afforded compound 6 (tR = 53 min, 14.2 mg). Fraction F5 was chromatographed on MPLC (74−93% MeOH in H2O) to give five subfractions F5‑1−F5‑5. The further purification of F5‑3 by HPLC (83% MeOH in H2O) gave compound 7 (tR = 23 min, 13.3 mg), while F5‑4 purified using HPLC (89% MeOH in H2O) yielded compounds 3 (tR = 22 min, 23.9 mg) and 4 (tR = 35 min, 24.1 mg). On the basis of a similar procedure, fraction F6 afforded seven subfractions F6‑1−F6‑7, and compound 8 (tR = 16 min, 12.9 mg) was isolated from F6‑3 (84% MeOH in H2O); fraction F8 afforded eight subfractions F8‑1−F8‑8, and compounds 9 (tR = 14 min, 17.8 mg) and 10 (tR = 25 min, 20.8 mg) were isolated from F8‑4 (75% MeOH in H2O). (4S,6S,7S,8R)-1,6-O,O-Diisobutyrylbritannilactone (1). Yellow oil. [α]23 D : −18.8 (c 0.11, CH2Cl2). ECD (CH3CN): 193 (Δε 1.50), 213 (Δε −5.64). IR (KBr) νmax: 3423, 2957, 2924, 2871, 2851, 1766, 1731, 1662, 1464, 1403, 1378, 1347, 1320, 1274, 1191, 1154, 1038, 975, 946, 892, 853, 817, 760, 722, 638 cm−1. 1H NMR (400 MHz, CDCl3) and 13C NMR (100 MHz, CDCl3) data: see Table 1. ESIMS m/z: 407 [M + H]+. HR-ESIMS m/z: 407.2431 [M + H]+, calcd for C23H35O6 407.2434. (4S,6S,7S,8R)-1-O-Acetyl-6-O-(3-methylvaleryloxy)britannilactone (2). Yellow oil. [α]23 D : −20.2 (c 0.16, CH2Cl2). ECD (CH3CN): 193 (Δε 3.59), 212 (Δε −17.59). IR (KBr) νmax: 3446, 2959, 2925, 2874, 2852, 1766, 1732, 1663, 1463, 1402, 1380, 1366, 1318, 1243, 1179, 1153, 1034, 976, 949, 893, 818, 637, 607 cm−1. 1H NMR (400 MHz, CDCl3) and 13C NMR (100 MHz, CDCl3) data: see
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RESULTS AND DISCUSSION Column chromatography (silica gel, MPLC, and HPLC) separation of the ethyl acetate layer from the methanol extract of the flowers of I. japonica afforded two new 1,10-seco9007
DOI: 10.1021/acs.jafc.5b03075 J. Agric. Food Chem. 2015, 63, 9006−9011
Article
Journal of Agricultural and Food Chemistry
Table 2. 1H (400 MHz) and 13C NMR (100 MHz) Spectroscopic Data for Compounds 3 and 4 (δ ppm in CDCl3 and J in Hz)a 3 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1′ 2′ 3′ 4′ 5′ 6′ 7′ 8′ 9′ 10′ 11′ 12′ 13′ 14′ 15′ 1″ 2″ 1‴ 2‴ 3‴ 4‴ 5‴ 6‴ 1″″ 2″″ a
4
δH
position 3.95 1.38 1.26 2.64
m, 4.05 m m, 1.52 m m m
5.56 2.51 4.98 2.33
s m m m, 2.62 m
δC
δH
2.33 m 1.11 d (6.9) 1.11 d (6.9)
64.1 26.8 31.8 33.8 133.1 65.9 49.4 75.5 34.8 134.0 55.2 177.4 35.1 20.8 18.9 63.1 81.3 57.7 134.2 136.9 26.0 45.0 82.6 36.0 29.7 139.7 170.2 119.2 17.0 14.3 171.1 20.9 175.7 34.1 18.7 18.5
CH2 CH2 CH2 CH C CH CH CH CH2 C C C CH2 CH3 CH3 C CH CH C C CH2 CH CH CH2 CH C C CH2 CH3 CH3 C CH3 C CH CH3 CH3
2.03 s
170.8 21.1
C CH3
2.05 m, 2.40 m 1.80 s 0.86 d (6.9) 4.57 s 2.77 m
2.05 2.85 4.21 2.35 2.23
m, 2.98 m m m m, 2.05 m m
6.21 d (3.3), 5.52 d (3.0) 1.03 d (7.2) 1.63 s 1.97 s
3.95 1.38 1.26 2.65
m, 4.05 m m, 1.52 m m m
5.58 2.51 4.98 2.33
s m m m, 2.63 m
2.05 m, 2.40 m 1.80 s 0.89 d (7.0) 4.56 s 2.78 m
2.05 2.85 4.21 2.35 2.23
m, 2.98 m m m m, 2.05 m m
6.21 d (3.2), 5.52 d (3.0) 1.03 d (7.2) 1.63 s 1.98 s 2.18 1.31 1.23 0.86 0.88
m, 2.22 m m m, 1.31 m t (7.4) d (7.0)
2.03 s
δC 64.1 26.8 31.9 33.9 133.0 65.8 49.5 75.6 34.7 134.0 55.2 177.4 35.1 20.8 19.4 63.1 81.3 57.6 134.1 136.9 26.0 45.0 82.6 36.0 29.7 139.7 170.2 119.2 17.0 14.3 171.1 20.9 172.1 41.6 31.6 29.2 11.2 18.5 170.8 20.9
CH2 CH2 CH2 CH C CH CH CH CH2 C C C CH2 CH3 CH3 C CH CH C C CH2 CH CH CH2 CH C C CH2 CH3 CH3 C CH3 C CH2 CH CH2 CH3 CH3 C CH3
The assignments were based on DEPT and 2D NMR experiments.
oxygenated methylene proton at δH 3.93 (m), and six methyl protons at δH 0.86 (3H, d, 6.9), 1.14 (6H, d, 6.8), 1.16 (6H, d, 6.8), and 1.81 (3H, s). The 13C NMR spectrum (Table 1) of compound 1 showed 23 carbon resonances. On the basis of the one-dimenisonal (1D) NMR spectra, two isobutyryl groups were obvious [δH 2.47 (m, H-2′), 1.14 (d, 6.8, H-3′), 1.16 (d, 6.8, H-4′) and 2.47 (m, H-2″), 1.14 (d, 6.8, H-3″), 1.16 (d, 6.8, H-4″); δC 177.0 (C-1′), 34.0 (C-2′), 18.8 (C-3′), 18.9 (C-4′) and 177.3 (C-1″), 34.2 (C-2″), 19.0 (C-3″), 19.0 (C-4″)]. The additional 15 resonances included two methyls, five methylenes (including an exo-methylene and one oxygenated methylene), four methines (including two oxygenated methines), and four quaternary carbons on the basis of distortionless enhancement by polarization transfer (DEPT) and heteronuclear multiplequantum coherence (HMQC) spectra. According to the aforementioned spectroscopic evidence, the unsaturation degrees, and the Inula sesquiterpenes,4,19,20 compound 1
eudesmanolide derivatives 1 and 2, two new sesquiterpene lactone dimers 3 and 4, and six known analogues 5−10 (Figure 1). The known compounds were identified as 1-O-acetyl-6-Oisobutyrylbritannilactone (5),17 1,6-O,O-diacetylbritannilactone (6),17 6-O-(3-methylvaleryloxy)britannilactone (7),4 6-O-isobutyryl britannilactone (8),4 1-O-acetyl-britannilactone (9),17 and inulanolide A (10).18 Compound 1 was obtained as yellow oil, and its molecular formula was deduced to be C23H34O6 by HR-ESIMS (HRESIMS m/z 407.2431 [M + H] + , calcd for C 23 H 35 O 6 407.2434), suggesting seven unsaturation degrees. The IR spectrum of compound 1 showed strong absorption bands of olefinic (1662 cm−1), carbonyl (1731 cm−1), γ-lactone (1766 cm−1), and hydroxy (3423 cm−1) groups. The 1H NMR spectrum (Table 1) showed the presence of an exo-methylene at δH 5.94 (d 2.4) and 6.37 (d 2.7), two oxygenated methine protons at δH 5.19 (d 1.8) and 4.94 (ddd 7.8, 3.9, and 2.1), an 9008
DOI: 10.1021/acs.jafc.5b03075 J. Agric. Food Chem. 2015, 63, 9006−9011
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Journal of Agricultural and Food Chemistry
Figure 1. Structures of compounds 1−10 from the flowers of I. japonica.
Figure 2. Selected HMBC and 1H−1H COSY correlations of compounds 1−4.
might possess a 1,10-seco-eudesmanolide skeleton, which was confirmed by HMBC and 1H−1H correlation spectroscopy (COSY) experiments (Figure 2). HMBC correlations of H-1 (δH 3.93) with δC 177.3 and of H-6 (δH 5.19) with δC 177.0 placed two isobutyryl groups at C-1 and C-6, respectively. Further analyses of the two-dimensional (2D) NMR spectra led to the assignment of all of the proton and carbon signals, and the planar structure for compound 1 was thus established. The relative configuration of compound 1 was determined on the basis of nuclear Overhauser effect spectroscopy (NOESY) experiment and coupling constants. The small coupling constants of H-6 with H-7 (d, 1.8 Hz) as well as NOESY correlations of H-7/H-8 and H-6/H3-15 (Figure 3) suggested a cis configuration for the bicyclic ring and an α orientation of the 6-isobutyryl group. Through comparing the calculated and experimental ECD spectra, as shown in Figure 4, the absolute configurations of C-4, C-6, C-7, and C-8 in compound 1 were determined as 4S, 6S, 7S, and 8R, respectively. The structure of compound 1 was thus elucidated as (4S,6S,7S,8R)-1,6-O,O-diisobutyrylbritannilactone. The ab-
Figure 3. Selected NOESY correlations of compounds 1−4.
solute configuration of compound 1 was consistent with the 1,10-seco-eudesmanolide derivative 1-O-acetylbritannilactone from Inula britannica, whose absolute configuration was 9009
DOI: 10.1021/acs.jafc.5b03075 J. Agric. Food Chem. 2015, 63, 9006−9011
Article
Journal of Agricultural and Food Chemistry
Figure 4. Calculated and experimental ECD spectra for compounds 1 (left) and 3 (right) in acetonitrile.
10′R in compound 3. The structure of compound 3 was therefore elucidated, and the compound was named japonicone U. The molecular formula of compound 4 was deduced to be C40H54O10 according to HR-ESIMS (m/z 717.3613 [M + Na]+, calcd for C40H54NaO10 717.3615). The 13C and 1H NMR spectroscopic data of compound 4 (Table 2) resembled the sesquiterpene dimer japonicone Q,9 except for an acetoxy group in compound 4 instead of the hydroxy group of C-1 in japonicone Q. Furthermore, the HMBC correlation from H-1 to C-1″ confirmed that the acetoxy group was located at C-1 (Figure 2). According to the above analysis, the structure of compound 4 was elucidated as shown (Figure 1). In the ECD spectrum (Figure S25 of the Supporting Information) of compound 4, a negative Cotton effect appeared at 211 nm, while a positive Cotton effect was observed at 237 nm. The ECD features in compound 4 were identical with those of compound 3, indicating that both compounds possessed the same configuration. The absolute configuration of compound 4 was therefore assigned to be 4R, 6R, 7R, 8S, 11S, 1′R, 2′R, 3′S, 7′S, 8′R, and 10′R, and the compound was named japonicone V. The flowers of I. japonica have been employed for patients suffering from cancers.3 Compounds 1−10 were therefore assayed in vitro for their antiproliferative activities against MCF7 and MDA-MB-231 cells through the MTT method (Table 3). All of the isolated compounds displayed the antiproliferative
determined by single-crystal X-ray crystallography with Cu Kα radiation.17 Compound 2 possessed a molecular formula C23H34O6 according to HR-ESIMS (HR-ESIMS m/z 429.2245 [M + Na]+, calcd for C23H34NaO6 429.2253). The NMR data (Table 1) were comparable to those of compound 9.17 The only difference was that the hydroxy group at C-6 in compound 9 was replaced by the 3-methylvaleryloxy group in compound 2. On the basis of confirmations with 1H−1H COSY, HMBC, and NOESY spectra (Figures 2 and 3), compound 2 was assigned to be 1-O-acetyl-6-O-(3-methylvaleryloxy)britannilactone. The ECD spectrum of compound 2 (Figure S24 of the Supporting Information) resembled that of compound 1 with the Cotton effects at 193 nm (positive) and 212 nm (negative), and the absolute configuration was thus defined as 4S, 6S, 7S, and 8R. Compound 3 gave a molecular formula C38H50O10 deduced from HR-ESIMS (m/z 689.3299 [M + Na]+, calcd for C38H50NaO10 689.3302), indicating 14 unsaturation degrees. The 13C and DEPT NMR spectra of compound 3 revealed 38 carbon signals, including 8 methyls, 8 methylenes, 10 methines, and 12 quarternary carbons, which was confirmed by HMQC (Table 2). It was obvious that two acetyl groups and one isobutyryl group (δC 171.1 and 20.9, δH 1.97; δC 170.8 and 21.1, δH 2.03; δC 175.7, 34.1, 18.7, and 18.5, δH 2.33 and 1.11) were present from the NMR spectra, including 1H−1H COSY and HMBC correlations (Table 2). On the basis of the spectroscopic data and the molecular formula, compound 3 might be a sesquiterpene dimer consisting of eudesmane and guaiane sesquiterpenoids.6−10 A detailed comparison to known sesquiterpene dimer 10 revealed that the 13C and 1H NMR spectroscopic data of compound 3 resembled those of compound 10, except for an isobutyryloxy group in compound 3 instead of the hydroxy group attached to C-6 in compound 10. The locations of two acetoxy groups and one isobutyryloxy group were established by a HMBC experiment, revealing correlations of the proton signals at δH 3.95, 4.57, and 5.56 with δC 171.1 (C-1″), 170.8 (C-1″″), and 175.7 (C-1‴), respectively (Figure 2). The further analysis of 1H−1H COSY and HMBC correlations confirmed it. The NOESY correlations of H-4/H7, H-4/H-8, and H3-15/H-6 were observed (Figure 3). The absolute configuration of compound 3 was also determined through the time-dependent density functional theory (TDDFT) ECD calculations. As shown in Figure 4, the calculated ECD spectrum of compound 3 matched the experimental result well (Figure 4), suggesting an absolute configuration of 4R, 6R, 7R, 8S, 11S, 1′R, 2′R, 3′S, 7′S, 8′R, and
Table 3. Antiproliferative Activities of Compounds 1−10 against Two Human Breast Cancer Cell Lines IC50 (μM)a compound 1 2 3 4 5 6 7 8 9 10 etoposideb
MCF-7 >100 15.56 29.64 0.20 32.30 68.00 26.34 23.64 >100 6.69 21.78
± ± ± ± ± ± ±
MDA-MB-231 1.16 5.05 0.04 6.28 3.70 4.97 3.43
± 1.86 ± 1.86
93.60 15.55 27.46 6.22 70.97 79.46 36.32 76.52 >100 39.96 57.43
± ± ± ± ± ± ± ±
6.10 1.93 3.54 1.30 3.42 8.59 3.91 4.78
± 2.31 ± 0.56
The data were expressed as means ± standard deviation. bEtoposide was used as a positive control.
a
9010
DOI: 10.1021/acs.jafc.5b03075 J. Agric. Food Chem. 2015, 63, 9006−9011
Article
Journal of Agricultural and Food Chemistry
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effects. Compound 4 exhibited the most potent effect, with an IC50 value of 0.20 ± 0.04 μM against MCF-7 cells, followed by compounds 10 (6.69 ± 1.86 μM) and 2 (15.56 ± 1.16 μM). For the MDA-MB-231 cell line, all of the isolates, except compound 9, showed significant cytotoxicity, with the IC50 values ranging from 6.22 ± 1.30 to 93.60 ± 6.10 μM. Compound 4 still displayed the highest antiproliferative activity (IC50 value of 6.22 ± 1.30 μM) against MDA-MB-231 cells, which was much more active than the positive control, etoposide. In summary, ten 1,10-seco-eudesmanolide derivatives, including four new compounds, were isolated from the flowers of I. japonica. The antiproliferative potencies of these compounds were investigated through the MTT assay. The results revealed that some of them, especially the new compound 4, showed strong antiproliferative effects on the human breast cancer cells and might be used as potential antitumor chemotherapy agent candidates.
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ASSOCIATED CONTENT
* Supporting Information S
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jafc.5b03075. 1D and 2D NMR, HR-ESIMS, and ECD spectra of compounds 1−4 (PDF)
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AUTHOR INFORMATION
Corresponding Author
*Telephone/Fax: +86-22-23502595. E-mail: victgyq@nankai. edu.cn. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported by the Ministry of Science and Technology 973 Project (2014CB560709), the Tianjin Science and Technology Program (13JCQNJC13600), the Specialized Research Fund for the Doctoral Program of Higher Education of China (20120031120048), and the Fundamental Research Funds for the Central Universities of China (65011201).
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REFERENCES
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DOI: 10.1021/acs.jafc.5b03075 J. Agric. Food Chem. 2015, 63, 9006−9011
