Bipodonines A–J, a new class of natural sesquiterpenes with a 2-(tetrahydro-2H-pyran-2-yl)propan-2-ol system from the fungus Bipolaris cynodontis DJWT-01

Abstract

Ten novel sesquiterpenes, bipodonines A–J (1–10) with a 2-(tetrahydro-2H-pyran-2-yl)propan-2-ol system, and two known polyketide–terpenoids (11 and12) were characterized from Bipolaris cynodontis DJWT-01. The structures of new compounds were determined using extensive spectroscopic analyses, derivative reactions, X-ray diffraction analysis, ECD data and DP4+ calculations. Further investigation showed that bipodonines A and B featuring γ- and δ-lactone might be degradative derivatives of polyketide–terpenoid 11. Compounds 5, 7 and 11 promoted the proliferation of LPS-stimulated splenic lymphocytes at 20.0 μM in vitro. Compound 11 showed potent cytotoxic activities against four cell lines and also showed antimicrobial activity against Fusarium solani and F. oxysporum with minimum inhibitory concentrations (MICs) of 4.00 and 2.00 μg mL⁻¹, respectively. The plausible biosynthetic pathways, in vitro cytotoxicity, antimicrobial, and immunomodulatory activities of these compounds are discussed.