Cytotoxic cytochalasans from cultures of the fungus Metarhizium brunneum TBRC-BCC 79240

Abstract

Fourteen new cytochalasans, brunnesins A–N (1–14), along with eleven known compounds, were isolated from the culture extracts of the insect pathogenic fungus Metarhizium brunneum strain TBRC-BCC 79240. The compound structures were established by spectroscopy, X-ray diffraction analysis, and electronic circular dichroism. Compound 4 exhibited antiproliferative activity against all cell lines tested (mammalian), with 50% inhibition concentration (IC₅₀) values ranging from 2.09 to 16.8 μg mL⁻¹. Compounds 6 and 16 were shown to be bioactive only against non-cancerous Vero cells (IC₅₀ 4.03 and 0.637 μg mL⁻¹, respectively) whereas compounds 9 and 12 were bioactive only against NCI-H187 small-cell lung cancer cells (IC₅₀ 18.59 and 18.54 μg mL⁻¹, respectively). Compounds 7, 13, and 14 showed cytotoxicity against NCI-H187 and Vero cell lines with IC₅₀ values ranging from 3.98–44.81 μg mL⁻¹.