The metabolites of Talaromycesflavus: Part 2. Biological activity and biosynthetic studies

The soil fungus Talaromycesflavus (Klöcker) Stolk and Samson is an effective biological control for Verticillium wilt of eggplant (Solanummelongena L.), a disease caused by the fungus Verticilliumdahliae Kleb. The water soluble metabolites isolated from the broth when the fungus is grown in liquid still culture, hydroxymethylmaltol (1), 5,6-dihydro-3,5-dihydroxy-6-hydroxymethyl-2H-pyran-2-one (3), and D-glucono-1,4-lactone (5), do not show antifungal activity against V. dahliae; however, hydrogen peroxide displays this inhibition. This peroxide has been detected in the T. flavus broth and it, together with 5, is the product of the glucose oxidase catalyzed oxidation of D-glucose. The results of the search for this antifungal activity are presented. [1- 13 C] Labelled sodium acetate was utilized as a precursor for studying the biosynthesis of the T. flavus metabolites 4,6-dihydroxy-5-methylphthalide (7), methyl 4-carboxy-5-hydroxyphthalaldehydate (8), and talaroflavone (9). The incorporation of label into these compounds is discussed. Keywords: Talaromycesflavus, fungal metabolites, hydrogen peroxide, biosynthesis, talaroflavone.