A New Apotirucallane from Walsura trichostemon Leaves and Its Antibacterial and α-Glucosidase Inhibitory Activities

Phytochemical investigation of Walsura trichostemon leaves led to the isolation of a new apotirucallane-type triterpenoid, 11,25-dideacetyl-16-hydroxytrichostemonate ( 1 ), along with two known apotirucallane-type triterpenoids ( 2 and 3 ), two known tirucallane-type triterpenes ( 4 and 5 ), and two known steroids ( 6 and 7 ). Their structures were identified by intensive analysis of 1D and 2D nuclear magnetic resonance, infrared, and mass spectrometry data, which were compared with data reported in the literature. Compounds 2 , 3 , and 5 exhibited moderate antibacterial activity against Pseudomonas aeruginosa (minimum inhibitory concentration (MIC) value: 64 μg/mL), and compound 4 showed weak antibacterial activity against P. aeruginosa (MIC: 128 μg/mL). Furthermore, compound 5 displayed activity against Bacillus cereus (MIC: 64 μg/mL). In addition, compound 4 showed stronger α-glucosidase inhibitory activity than the control, acarbose. The active compound 4 was subjected to molecular docking experiments using AutoDock4 and revealed precise interactions with the active gorge of the enzyme through hydrogen bonding, supporting the in vitro results.