Highly oxidized ergosterols and isariotin analogs from an entomopathogenic fungus,Gibellula formosana,cultivated in the presence of epigenetic modifying agents |
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| Authors: | Teigo Asai Yu-Ming Chung Hiroaki Sakurai Tomoji Ozeki Fang-Rong Chang Yang-Chang Wu Kouwa Yamashita Yoshiteru Oshima |
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| Institution: | 1. Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba-yama, Aoba-ku, Sendai 980-8578, Japan;2. Graduate Institute of Natural Products, College of Pharmacy, Kaohsiung Medical University, Kaohsiung 807, Taiwan;3. Department of Chemistry and Materials Science, Tokyo Institute of Technology, 2-12-1-H-63 O-okayama, Meguro-ku, Tokyo 152-8551, Japan;4. School of Chinese Medicine, College of Chinese Medicine, China Medical University, Taichung 404, Taiwan;5. Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai 981-8558, Japan |
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| Abstract: | The concomitant addition of a histone deacetylase inhibitor, suberoyl bis-hydroxamic acid, and a DNA methyltransferase inhibitor, RG-108, to the culture medium of Gibellula formosana, an entomopathogenic fungus, induced a significant increase in diversity of secondary metabolites. From the culture media were isolated two new highly oxidized ergosterols, formosterols A (1) and B (2), and five new isariotin analogs, 12′-O-acetylisariotin A (4), 1-epi-isariotin A (5), and isariotins K–M (6–8), together with 22,23-epoxy-3,12,14,16-tetrahydroxyergosta-5,7-dien-11-one (named formosterol C) (3), isariotins A (9), C (10), and E (11), TK-57-164A (12), and beauvericin (13). The NMR spectra, X-ray single crystallographic diffraction, and chemical transformations revealed the structures of the two new formosterols and five new isariotins. The stereochemistry of formosterol C (3) was deduced from its spectroscopic data. The side chains of formosterols A–C (1–3) contained cis-22,23-epoxide, which is rarely present in naturally occurring sterols and triterpenes. |
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