A new ursane-type triterpene and potent antibacterial alkylbenzoquinones from the aerial parts of M aesa balansae

A new ursane-type triterpene (1) alongside two known alkylbenzoquinones, dihydromaesanin (2) and embeliquinone (3), were isolated from the aerial parts of Maesa balansae. The structure of 1 was elucidated based on 1D-, 2D-NMR, and HRESI-MS data. The two alkylbenzoquinones were tested on 13 phytopathogenic bacterial strains. Compound 2 displayed exceptional antibacterial activity against Acidovorax avenae subsp. cattleyae, Xanthomonas arboricola pv. pruni, X. campestris pv. campestris, and Ralstonia solanacearum with MIC values in a range of 1.6-100 µg/mL. Additionally, compound 3 exhibited antibacterial activity against A. avenae subsp. cattleyae with a MIC value of 50 µg/mL. Notably, the antibacterial activities of compounds 2 and 3 against various phytopathogenic bacteria were evaluated for the first time. Furthermore, the antibacterial mechanisms of compounds 2 and 3 against tested phytobacteria were elucidated via molecular docking studies, demonstrating strong binding with the active site of RpfF and DNA gyrase B (binding energies below -5.6 kcal/mol).