Isolation, structure elucidation, total synthesis, and biosynthesis of dermazolium A, an antibacterial imidazolium metabolite of a vaginal bacterium Dermabacter vaginalis

Dermabacter vaginalis is a human-derived bacterium isolated from vaginal fluid of a Korean female in 2016. Although several human-related species in Dermabacter genus have been reported there are few studies on their bioactive metabolites. Dermazolium A (1), a rare imidazolium metabolite, was isolated from D. vaginalis along with five known metabolites (2–6) and their chemical structures were determined by NMR, HRMS, and MS/MS data analysis. Feeding experiments using predicted precursors and biomimetic total synthesis of 1 corroborated its structure and led to suggestion of biosynthetic pathway of 1. Antibacterial tests on the isolated compounds showed that 1 is a mild antibacterial agent with MIC values of 41 µg/mL against methicillin-resistant Staphylococcus aureus (MRSA) USA300, Lacticaseibacillus paracasei subsp. paracasei KCTC 3510 and Brevibacterium epidermidis KCTC 3090.