Identification of novel derivative of helvolic acid from Metarhizium anisopliae grown in medium with insect component.

Entomopathogenic fungi are unique owing to their versatile ability to produce many bioactive compounds and from the dependence of their morphological differentiation on the presence of insect-derived materials. An entomopathogenic fungus, Metarhizium anisopliae HF293, was found to show insect-material-dependent production of antibacterial compounds, which were purified to homogeneity from 10-d culture broth when the production reached maximum. Two compounds were isolated: the major compound was determined to be helvolic acid and the minor one was a novel derivative of helvolic acid (1,2-dihydrohelvolic acid). Discovery of a novel bioactive compound indicated that insect-derived material would be a useful factor for enhancing the diversity of compounds produced by entomopathogenic fungi.