Isolation and Cytotoxicity of Isocoumarins from the Entomogenous Fungus Setosphaeria sp.
- PDF / 168,646 Bytes
- 4 Pages / 594 x 792 pts Page_size
- 85 Downloads / 173 Views
ISOLATION AND CYTOTOXICITY OF ISOCOUMARINS FROM THE ENTOMOGENOUS FUNGUS Setosphaeria sp.
Sha-Sha Liu,1 Wen-Bin Gao,1 Jie Kang,1 Xiao-Hui Yang,1 Fei Cao,1 Fan-Dong Kong,2 You-Xing Zhao,2* and Du-Qiang Luo1*
A new isocoumarin compound named setosphacohol A (1), together with six known ones, alternariol (2), isoaltenuene (3), phomasatin (4), alternariol 5-O-methyl ether (5), 1-deoxyrubralactone (6), and rubralactone (7), was isolated from the entomogenous fungus Setosphaeria sp. The structure of the new compound was elucidated by analysis of the 1D and 2D spectroscopic data as well as MS. Compounds 2, 5, 6 showed moderate cytotoxicity against six human tumor cell lines MCF-7, MGC-803, H1975, Huh-7, A549, and HeLa with IC50 values ranging from 23.04 to 96.91 μg·mL–1. Keywords: Setosphaeria sp., isocoumarins, cytotoxicity. Isocoumarins comprise a six-membered oxygen heterocycle (α-pyranone) [1], along with one benzene ring, and exhibit a wide range of biological activities including anticancer, anti-HIV, antibacterial, antifungal, anti-inflamatory, antileukemic, antimalarial, antitubercular, and hepatoprotective activity [2]. Recently, an entomogenous fungus Setosphaeria sp. (strain LGWB-2) was isolated from Harmonia axyridis, obtained from Baoding (Hebei Province), People′s Republic of China. A new isocoumarin, setosphacohol A (1), together with six known ones (Fig. 1), was isolated from the methanol extract of the rice medium of Setosphaeria sp. Herein, we report the isolation, structural elucidation, and cytotoxicity of compounds 1–7 as shown in Fig. 1. Compound 1 was obtained as a white solid. The molecular formula of 1 was determined as C16H22O7 by HR-ESI-MS at m/z 349.1241 [M + Na]+ (calcd 349.1263). The 1H NMR spectrum (Table 1) suggested the presence of one OH [δ 10.88 (1H, s, 8-OH)], one methyl [δ 0.97 (3H, t, J = 7.2 Hz, CH3-13)], three oxygenated methines [δ 4.46 (1H, m, H-3), 4.87 (1H, d, J = 10.2 Hz, H-4), and 4.15 (1H, m, H-10)], one aromatic proton [δ 6.77 (1H, s, H-5)], and two methoxy groups [δ 3.96 (3H, s, CH3O-6) and 3.89 (3H, s, CH3O-7)]. The 13C NMR spectrum (Table 1) of 1 showed 16 carbon resonances, including one methyl [δ 13.9 (q, C-13)], three methylenes, three oxygenated methine groups, two methoxy groups [56.3 (q, CH3O-6), and 60.8 (q, CH3O-7)], one olefinic carbon [δC 99.5 (d, C-5)], and six quaternary carbons (including one carbonyl δ 169.1). The NMR data of 1 showed close similarity to those in the literature [3], suggesting compound 1 possessed the same planar structure as that reported in the literature. This was further confirmed by interpretation of the HMBC long-range correlations from H-5 to C-4, C-6, C-7, C-8a and C-4a, H-4 to C-3, C-5, C-6, and C-4a, and H-9 to C-3 and C-4, and 1 H–1 H COSY H-3/H-4/H-9/H-10/H-11/H-12/H-13, as shown in Fig. 1. The absolute configurations of compound 1 at C-3 and C-4 were determined from the NOESY and ECD spectra. The NOESY correlation of H-9/H-4 indicated the cis-configuration of H-3 and 4-OH. The simulated ECD spectrum for (3R,4R)-1 via Boltzmann
Data Loading...
