A New Ursane-Type Pentacyclic Triterpenoid from the Tree Bark of Sandoricum koetjape: Antibacterial, DFT, and Molecular Docking Study

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 (<b>2</b>), from the tree bark of <i>Sandoricum koetjape</i> Merr. Along with this, five known compounds-β-caryophyllene oxide (<b>1</b>), bryononic acid (<b>3</b>), 7-deacetylgedunin (<b>4</b>), 7-deacetyl-7-oxogedunin (<b>5</b>), and 12,20-dihydroxydammar-24-en-3-one (<b>6</b>)-were successfully isolated, and one compound, 12β-hydroxydammarenolic acid (<b>7</b>), was reported in our previous report. All compounds (<b>1</b>-<b>7</b>) were tested with their antibacterial properties against two Gram-positive (<i>Enterococcus faecalis</i> and <i>Staphylococcus saprophyticus</i>) and two Gram-negative (<i>Citrobacter freundii</i> and <i>Salmonella enterica</i>) bacteria. The structures of the isolated compounds were elucidated using NMR spectroscopy and mass spectrometry data. A preliminary antibacterial assay showed that only compound <b>7</b> 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 <b>7</b>, a molecular docking study was conducted. The findings from both in vitro and in silico analyses suggest that compound <b>7</b> is a promising antibacterial candidate for further investigation.