Gradient high-performance liquid chromatography using alkylphenone retention indices of insecticidal extracts of...

Purified extracts of four Penicillium strains which were active against the insect pest Spodoptera littoralis were analysed by gradient high-performance liquid chromatography (HPLC) for secondary metabolites using alkylphenone retention indices. HPLC of pure secondary metabolite standards detected previously in the extracts by thin-layer chromatography (TLC) was undertaken in order to obtain bracketed retention indices. More metabolites were detected by HPLC than by TLC, although some compounds detected by TLC in some strains were not detected by this HPLC method. A minority of metabolites were exclusive to each strain, and most were produced by more than one strain. The profiles were more characteristic of each strain when only the larger peaks were considered. This emphasizes the importance of detection limits in secondary metabolite analysis. Some of the implications of these analyses to fungus toxicity and systematic mycology are discussed.