Three 9-amino-1,10-anthracenedione derivatives with anti-MRSA/VRE activity from Fusarium sp. - fermented Cassia obtusifolia seeds.

Three undescribed 9-amino-1,10-anthracenedione derivatives, cassiaobtusins A-C (1-3) and seven known compounds (4-10) were isolated from fermented Cassia obtusifolia seeds by the fungus Fusarium sp. YIM F04813. Their structures were elucidated through comprehensive spectroscopic analyses, and the absolute configuration of 1 was confirmed by single-crystal X-ray diffraction. Cassiaobtusins feature a 6/6/6-fused tricyclic scaffold formed by anthraquinone skeleton rearrangement. Compounds (1-3) were evaluated for antimicrobial activity against multidrug-resistant pathogens. 3 exhibited potent activity against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VRE) with MIC values of 4 μg/mL and 8 μg/mL, and the MBC values were 8 μg/mL and 16 μg/mL, respectively. This study highlights the utility of microbial biotransformation for expanding the chemical diversity of plant-derived quinones.