Quantitative determination of the antifungal compound 6-pentyl-α-pyrone (6PAP) using a simple plate bioassay

An assay relating bioactivity to levels of the antifungal compound 6-pentyl-α-pyrone (6PAP) has been developed. Using Cladosporium strain NZ660US as indicator at a spore concentration of 5×10⁶ spores overlay⁻¹ on malt (adjusted to pH 3·5) agar plates, this assay allows quantitative determination of 6PAP down to a detection limit of 0·5% v/v. This will allow rapid screening of Trichoderma culture extracts to compare the bioactivity of isolates grown under different culture conditions, and can be used in combination with analytical chemical analysis to identify the presence of other bioactive metabolites.