Comparative In Vitro Antioxidant and Antidiabetic Activities of Piliostigma reticulatum Stem Bark Extract: Implications for the Management of Oxidative Stress and Diabetes Mellitus

Medicinal plants rich in natural antioxidants have attracted considerable interest because of their ability to neutralize free radicals and protect biological systems against oxidative damage. Piliostigma reticulatum is widely used in African traditional medicine for managing diabetes and inflammatory disorders; however, comparative information on the antioxidant and antidiabetic activities of its solvent fractions remains limited. This study evaluated the antioxidant and antidiabetic potential of P. reticulatum stem bark solvent fractions using in vitro antioxidant and carbohydrate-hydrolyzing enzyme inhibition assays. Antioxidant activity was assessed using DPPH and ABTS radical-scavenging assays, while ferric reducing antioxidant power (FRAP) evaluated reducing capacity. α-Amylase and α-glucosidase inhibitory activities were also determined. The methanol fraction exhibited the strongest DPPH scavenging activity (IC₅₀ = 1.353 ± 1.239 µg/mL), followed by ethyl acetate (1.717 ± 1.382 µg/mL) and n-hexane (14.023 ± 5.716 µg/mL). Similarly, methanol showed superior ABTS activity (47.420 ± 8.594 µg/mL) and FRAP capacity (1166.0 ± 2.646 trelox equivalent), compared with ethyl acetate and n-hexane fractions. Ethyl acetate demonstrated the strongest α-amylase (IC₅₀ = 9.007 ± 2.431 µg/mL) and α-glucosidase (IC₅₀ = 0.0010 ± 0.0000 µg/mL) inhibitory activities. Overall, P. reticulatum stem bark exhibited solvent-dependent antioxidant and enzyme inhibitory activities, with methanol showing superior antioxidant activity and ethyl acetate demonstrating stronger enzyme inhibition. These findings highlight P. reticulatum as a promising source of bioactive compounds with potential applications in diabetes management.