Bioactive polyketides from cultures of the entomopathogenic fungus Hypocrella luteola TBRC-BCC 76666

Abstract

Entomopathogenic fungi of the genus Hypocrella are known to produce bioactive compounds, in particular polyketides. Here, a chemical investigation of the entomopathogenic fungus Hypocrella luteola strain TBRC-BCC 76666 was performed to identify possible novel compounds indicated from HPLC and ¹H NMR spectra profiles of culture extracts. Eight novel compounds were isolated, including six new polyketides (1–6) and two other naturally occurring compounds (7–8), along with seven known compounds. The compound structures were established by spectroscopic analysis, the application of modified Mosher's method, and electronic circular dichroism. Compounds 1 and 5 were cytotoxic against both NCI-H187 and Vero cells (IC₅₀ = 9.9 and 58.9 μM, respectively), whereas compound 4 was active only against MCF-7 cells (IC₅₀ = 42.5 μM). Ascherxanthone B (9) exhibited antiproliferative activity against all cell lines tested (Plasmodium falciparum, mammalian, and fungal), with IC₅₀ and MIC values in the range 0.9–30.5 μM.