Abstract
Natural products have played an important role in the discovery and development of antibacterial agents. This paper described the isolation of a new ursane-type pentacyclic triterpenoid, (18β,19αH)-3-oxo-urs-12-en-27α-oic acid (2), from the tree bark of Sandoricum koetjape Merr. Along with this, five known compounds-β-caryophyllene oxide (1), bryononic acid (3), 7-deacetylgedunin (4), 7-deacetyl-7-oxogedunin (5), and 12,20-dihydroxydammar-24-en-3-one (6)-were successfully isolated, and one compound, 12β-hydroxydammarenolic acid (7), was reported in our previous report. All compounds (1-7) were tested with their antibacterial properties against two Gram-positive (Enterococcus faecalis and Staphylococcus saprophyticus) and two Gram-negative (Citrobacter freundii and Salmonella enterica) bacteria. The structures of the isolated compounds were elucidated using NMR spectroscopy and mass spectrometry data. A preliminary antibacterial assay showed that only compound 7 inhibited the growth of the tested bacteria, with an inhibition zone diameter of 7.5-9 mm at a concentration of 1 mg/mL. DFT analyses explained electronic profiles with HOMO-LUMO gaps (4.54-6.34 eV) and electrophilicity from 1.73 to 4.39 eV. To elucidate the antibacterial mechanism of compound 7, a molecular docking study was conducted. The findings from both in vitro and in silico analyses suggest that compound 7 is a promising antibacterial candidate for further investigation.