Antifungal Secondary Metabolites Isolated from Mangrove Rhizosphere Soil-Derived Penicillium Fungi

Fungi isolated from mangrove rhizosphere soil of the South China Sea were investigated for the production of potential antifungal metabolites. With 28 fungal isolates, the strains Penicillium javanicum HK1-23 and P. janthinellum HK1-6 showed significant antifungal activities. A bioassay-guided investigation of the two fungal strains led to the isolation of two secondary metabolites, brefeldin A and penicillic acid, with high yields of 143 and 423 mg L^-1, respectively. Penicillic acid showed potent antifungal activities toward Rhizoctonia solani and R. cerealis, with 67.5% and 76% growth inhibition, respectively, at 50 μg mL^-1. Brefeldin A showed strong activity toward R. cerealis, with 56.4% growth inhibition at 50 μg mL^-1. The research highlights the importance of exploring microbes from mangrove rhizosphere soil for the identification of bioactive metabolites for future fungicide development.