A xanthone from Garcinia lateriflora Blume leaves extract: Isolation, α-glucosidase inhibitory activity, and antioxidant capacity

Context: The leaf extracts of Garcinia lateriflora have activity as α-glucosidase inhibitor and antioxidant. α-glucosidase inhibitor is one of the mechanisms that can treat type 2 diabetic mellitus (T2DM). Aims: To isolate and identify the molecule responsible for the antioxidant activities and α-glucosidase enzyme inhibition of G. lateriflora leaf extract. Methods: The leaves of G. lateriflora were progressively extracted using the maceration method with n-hexane (He), ethyl acetate (EA), and methanol (Me). The isolation procedure used column chromatography, employing the stationary phase of silica gel 60 and Sephadex LH20. The in vitro activity of alpha-glucosidase inhibition was examined using p-nitrophenyl-α-D-glucopyranoside as the substrate. The antioxidant activity was assessed using the DPPH radical scavenging and FRAP assay. Results: Fraction EA12 has greater efficacy in inhibiting the α-glucosidase enzyme and acts as a more potent antioxidant. Compounded EA12a was obtained by further purification and isolation at Fraction EA12. The IC50 value for inhibiting α-glucosidase was determined to be 3.63 ± 0.01 μg/mL. The antioxidant activity, as measured by the FRAP assay, had an IC50 value of 27.08 ± 0.26 μg/mL, while the DPPH radical scavenging assay yielded an IC50 value of 21.31 ± 0.22 μg/mL. The compound EA12a was structurally elucidated using 1H-NMR and LC-MS/MS, revealing its probable structure as 1,3,6,7-tetrahydroxyxanthone. Conclusions: In this study, 1,3,6,7-tetrahydroxyxanthone was identified in G. lateriflora leaves extract with α-glucosidase inhibitory and antioxidant activity.