Ustisorbicillinols G and H, Two New Antibacterial Sorbicillinoids from the Albino Strain LN02 of Rice False Smut Fungus Villosiclava virens

<i>Villosiclava virens</i> (anamorph: <i>Ustilaginoidea virens</i>), 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 <i>V. virens</i> due to its inability to produce ustilaginoidins. The fermentation of <i>V. virens</i> 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 (<b>1</b>) and H (<b>2</b>), were isolated from the ethyl acetate extract. Their structures were elucidated using spectroscopic data analyses and quantum chemical calculations. Compounds <b>1</b> and <b>2</b> displayed antibacterial activity towards <i>Ralstonia solanacearum</i>, <i>Agrobacterium tumefaciens</i> and <i>Bacillus subtilis</i>, with median inhibitory concentration (IC₅₀) values of 19.76-25.43 μg/mL for <b>1</b> and 25.35-45.48 μg/mL for <b>2</b>. The discovery of new sorbicillinoids will increase the diversity of the secondary metabolites of <i>V. virens</i> and provide candidates for the creation of new antimicrobials as well.