Comparative in Vitro α-amylase and α-glucosidase Inhibitory Activities of the Root Extracts of Selected Medicinal Plants: Implications in Diabetes Phytotherapy

Abstract

The present study comparatively evaluated the in vitro α-amylase and α-glucosidase inhibitory activities of methanolic root extracts of selected medicinal plants and their implications for diabetes phytotherapy. Methanolic root extracts of C. citratus, C. afer, and V. amygdalina were compared with acarbose, a standard synthetic inhibitor. Roots were collected from Ebukuma, Andoni Local Government Area, Rivers State, Nigeria, air-dried, pulverised, extracted with methanol, concentrated, and stored at −4°C before enzyme inhibition assays. Percentage inhibition was determined at concentrations of 20–100 mg/mL, and IC₅₀ values were calculated. All extracts exhibited concentration-dependent inhibition of both α-amylase and α-glucosidase. Among the plant extracts, C. citratus showed the strongest inhibitory activity, with IC₅₀ values of 35.8 ± 1.7 mg/mL for α-amylase and 32.4 ± 1.5 mg/mL for α-glucosidase. Costus afer recorded IC₅₀ values of 47.6 ± 2.0 mg/mL and 45.1 ± 1.3 mg/mL, while V. amygdalina exhibited IC₅₀ values of 58.9 ± 2.2 mg/mL and 48.7 ± 1.4 mg/mL for α-amylase and α-glucosidase, respectively. Acarbose showed the greatest inhibitory potency, with IC₅₀ values of 21.0 ± 1.2 mg/mL for α-amylase and 20.5 ± 1.1 mg/mL for α-glucosidase. These findings demonstrate that C. citratus possesses the highest enzyme-inhibitory potential among the investigated plants and support its further investigation as a potential source of antidiabetic agents. Further studies should isolate the bioactive constituents and elucidate their mechanisms of action.