Antioxidant and α-amylase/α-glucosidase Inhibitory Activities 0f Leaf, Bark, and Seed Extracts of Moringa oleifera Grown in Buon Ma Thuot, Vietnam

Abstract

Buon Ma Thuot in Vietnam's Central Highlands features basalt-rich soil and a mild highland climate that may favor the accumulation of bioactive phytochemicals. This study assessed the antioxidant and α-amylase/α-glucosidase inhibitory activities of Moringa oleifera leaf, bark, and seed extracts collected from this region to identify the most bioactive plant part and isolate functional fractions. Sequential solvent fractionation (hexane, chloroform, diethyl ether, ethyl acetate, water) was applied to the ethanol-extracted leaf sample, which exhibited the highest initial activity, to enrich bioactive compounds. The Buon Ma Thuot Moringa leaf extract exhibited significantly higher phenolic and flavonoid contents than those reported for M. oleifera from other regions, correlating with enhanced antioxidant and enzyme-inhibitory effects. Among the fractions, the chloroform-soluble layer showed the strongest DPPH radical scavenging activity (IC₅₀ ≈ 117 µg/mL), the diethyl ether fraction had the highest α-amylase inhibition (IC₅₀ ≈ 11.5 mg/mL), and the ethyl acetate fraction provided the most potent α-glucosidase inhibition (IC₅₀ ≈ 2.1 mg/mL). The latter value is notably more potent than most previously reported values (e.g., >5 mg/mL) for Moringa extracts, highlighting the phytochemical richness of leaves grown in this ecological zone. These findings suggest that M. oleifera leaves from Buon Ma Thuot are promising natural sources of antioxidants and mild enzyme inhibitors, with potential applications in functional foods or adjunct therapy for type 2 diabetes.