Highly oxidized ergosterols and isariotin analogs from an entomopathogenic fungus, Gibellula formosana, cultivated in the presence of epigenetic modifying agents

Teigo Asai, Yu Ming Chung, Hiroaki Sakurai, Tomoji Ozeki, Fang Rong Chang, Yang Chang Wu, Kouwa Yamashita, Yoshiteru Oshima

Research output: Contribution to journalArticle

16 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)5817-5823
Number of pages7
JournalTetrahedron
Volume68
Issue number29
DOIs
Publication statusPublished - 2012 Jul 22

ASJC Scopus subject areas

  • Biochemistry
  • Drug Discovery
  • Organic Chemistry

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