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Hirsutane Sesquiterpenes from the FungusLentinusconnatusBCC 8996

Vatcharin Rukachaisirikul, Chittreeya Tansakul, Saowanit Saithong, Chaveng Pakawatchai, Masahiko Isaka, Rapheephat Suvannakad
2005 Journal of natural products  
Two new hirsutane sesquiterpenes, connatusins A (1) and B (2), were isolated from the fungus Lentinus connatus BCC 8996. The structures, closely related to hypnophilin, were elucidated on the basis of the spectroscopic data. An X-ray analysis was performed to confirm the structure of 1. Six known compounds were also obtained. Panepoxydone (5), panepoxydione (6), and dihydrohypnophilin (8) exhibited significant antimalarial and cytotoxic activities. Many biologically active secondary metabolites
more » ... condary metabolites have been isolated from the genus Lentinus, for example, an antitumor polysaccharide, 1 the antibiotic cortinellin, 2 and antimicrobial hirsutane sesquiterpenes. 3 However, chemical investigation of L. connatus has not been reported. The crude EtOAc extract of the culture broth of L. connatus BCC8996 showed significant cytotoxicity against human oral epidermoid carcinoma cells (KB), human breast cancer cells (BC), human lung cancer cells (NCI-H187), and Vero cells, as well as activity against the malarial parasite Plasmodium falciparum K1, with respective IC 50 values of 3.0, 1.5, 0.18, 0.90, and 3.1 µg/mL. Investigation of the extracts of the fungal culture filtrate and mycelium led to the isolation and structural determination of two new hirsutane sesquiterpenes, connatusins A (1) and B (2), along with six known compounds, 2,2-dimethyl-6-methoxy-4-chromanone (3), 4 2,2-dimethyl-3-hydroxy-6-methoxy-4chromanone (4), 4 panepoxydone (5), 4,5 panepoxydione (6), 5 hypnophilin (7), 3,6 and the dihydro derivative of hypnophilin (8). 3,6 The known compounds were identified by comparison of the NMR data with those previously reported. All compounds were tested for antimalarial and cytotoxic activities. Connatusin A (1) was isolated as colorless needles, from which the molecular formula was established as C 15 H 22 O 4 by HREIMS. The UV maximum at 268 nm and IR absorptions at 1704 and 1648 cm -1 indicated the presence of an R, -unsaturated carbonyl group. 6 The 1 H NMR signals were similar to those of 7, 3,6 except for the replacement of an oxymethine proton signal at δ 3.44 (H-6) and nonequivalent exomethylene signals at δ 5.46 and 6.14 (H 2 -15) with a singlet signal of a vinylic methyl group at δ 1.99. Two additional singlets due to hydroxy protons (δ 5.32 and 5.99) were also observed. The 13 C NMR spectrum showed 15 carbon signals: one ketone carbonyl (δ 202.8); five quaternary (δ 43.2, 55.0, 85.5, 145.5, and 152.2); three methine (δ 34.6, 54.1, and 81.0); two methylene (δ 44.2 and 46.6); and four methyl (δ 10.3, 16.6, 22.6, and 28.5) carbons. The COSY and HMBC spectra (see Supporting Information) indicated that ring C of 1 was identical to that of 7, with nonequivalent methylene protons attached at C-8 (δ 46.6). HMBC correlations between H 2 -8 and the carbonyl carbon (C-6), an oxyquaternary carbon (δ 85.5, C-7), and a meth-
doi:10.1021/np0502286 pmid:16309322 fatcat:ocpkxme35vhqzh27otja6paane