Phytochemical investigation of <i>Calophyllum sundaicum</i> P.F.Stevens: isolation, structure elucidation, and biological potential

Despite the abundance of xanthones in the <i>Calophyllum</i> genus, the stem bark of <i>C. sundaicum</i> remains understudied. Hence, this study focused on the extraction, isolation, and characterisation of secondary metabolites from <i>C. sundaicum</i> stem bark and the determination of their biological properties. A newly isolated xanthone, sundaixanthone A <b>(1)</b>, along with six known xanthones <b>(2-7)</b>, were structurally elucidated based on 1D/2D NMR, FTIR, and MS analyses. The methanolic extract exhibited the highest TPC (283.8 ± 8.65 mg GAE/g) and strongest antioxidant activity (IC₅₀ 6.39 ± 0.47 μg/mL), while the chloroform extract demonstrated the highest TFC (116.0 ± 0.66 mg QE/g). Moreover, ethyl acetate and methanolic extracts displayed the lowest MIC values (0.056 mg/mL) against Ab10. Molecular docking revealed a strong binding of sundaixanthone A to PBP (-7.5 kJ/mol), exceeding imipenem (-6.0 kJ/mol). These results highlight that <i>C. sundaicum</i> is a promising source of antioxidant and antibacterial agents.