Phytochemical Profiling and Biological Activities of Mitragyna speciosa Leaf Extracts: Antioxidant and α-Glucosidase Inhibitory Activities

Mitragyna speciosa, a medicinal plant native to Southeast Asia, has long been used in traditional medicine and is ethnopharmacologically associated with maintaining physical stamina. This study evaluated the in vitro and in silico biological activities of M. speciosa leaves, focusing on antioxidant potential, α-glucosidase inhibition, and anticancer potential. Phenolic and flavonoid contents, antioxidant capacities (DPPH, FRAP, and ABTS), and α-glucosidase inhibitory activity were assessed. The methanol extract (ME) and methanol fraction (MF) showed comparable total phenolic contents (18.20 ± 1.02 and 18.60 ± 2.31 mg GAE/g, respectively). The ethyl acetate fraction (EF) had the highest flavonoid content (146.16 ± 6.82 mg QE/g), followed by ME (129.90 ± 4.96 mg QE/g) and MF (102.56 ± 5.85 mg QE/g). Strong radical-scavenging activity was observed in ME, MF, and EF, with DPPH IC₅₀ values of 10.62 ± 0.38, 11.06 ± 0.37, and 14.04 ± 1.30 µg/mL, respectively, and ABTS IC₅₀ values of 1.23 ± 0.04, 3.91 ± 0.04, and 5.19 ± 1.92 µg/mL, respectively. These results indicate substantial antioxidant activity associated with phenolic and flavonoid content. The hexane fraction exhibited the strongest α-glucosidase inhibitory activity (IC₅₀ = 55.64 ± 1.14 µg/mL), although it was less potent than quercetin (IC₅₀ = 1.25 ± 0.17 µg/mL). LC-HRMS profiling identified 12 metabolites, including alkaloids, phenolic compounds, and flavonoids. Molecular docking suggested moderate binding affinity of yohimbine to the estrogen receptor (3ERT), warranting further mechanistic investigation in cancer cell models.