Abstract
Villosiclava virens (anamorph: Ustilaginoidea virens), the causal fungal pathogen of rice false smut, has been found to produce various secondary metabolites. The albino strain LN02 is a natural albino phenotype mutant of V. virens due to its inability to produce ustilaginoidins. The fermentation of V. virens LN02 was performed in solid rice medium to obtain fungal cultures, which were chemically investigated. After removing the known metabolites, two new dimeric sorbicillinoids, namely ustisorbicillinols G (1) and H (2), were isolated from the ethyl acetate extract. Their structures were elucidated using spectroscopic data analyses and quantum chemical calculations. Compounds 1 and 2 displayed antibacterial activity towards Ralstonia solanacearum, Agrobacterium tumefaciens and Bacillus subtilis, with median inhibitory concentration (IC(50)) values of 19.76-25.43 μg/mL for 1 and 25.35-45.48 μg/mL for 2. The discovery of new sorbicillinoids will increase the diversity of the secondary metabolites of V. virens and provide candidates for the creation of new antimicrobials as well.