Two New Tremulane-Type Sesquiterpenes From Irpex lacteus Cultured Under Optimized cAMP and Light Conditions

In this study, light exposure and cyclic adenosine monophosphate (cAMP) supplementation were applied as cultivation-based elicitation strategies to two algicolous Irpex species associated with the marine green alga Ulva pertusa, with the aim of facilitating the isolation of new secondary metabolites with antifungal activity. The confrontation assay demonstrated that both I. lacteus YICB-0055 and I. laceratus YICB-0007 exhibit inhibitory effects against Fusarium oxysporum YICB-0025 under light exposure with cAMP supplementation. HPLC analysis revealed a rich metabolite fingerprint under continuous light exposure in the presence of 5 mM cAMP. Chemical investigation of the optimized fermentation afforded two new tremulane-type sesquiterpenes, ceriponols N-O (1 and 2), together with eight known compounds (3-10), all of which were structurally characterized by extensive spectroscopic analyses. These compounds exhibited antifungal activity against plant-pathogenic fungi such as F. oxysporum. The results suggest that cAMP supplementation combined with light exposure may enhance secondary metabolite production in Irpex fungi, indicating their potential as sources of antimicrobial compounds.