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

Despite the abundance of xanthones in the Calophyllum genus, the stem bark of C. sundaicum remains understudied. Hence, this study focused on the extraction, isolation, and characterisation of secondary metabolites from C. sundaicum stem bark and the determination of their biological properties. A newly isolated xanthone, sundaixanthone A (1), along with six known xanthones (2-7), 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 C. sundaicum is a promising source of antioxidant and antibacterial agents.