Okugbo Osarhieme Tinuade and Omoregie Ehimwenma Sheena

The search for affordable antidiabetic agents from medicinal plants is urgent, particularly in low- and middle-income countries with limited access to conventional therapy. Detarium microcarpum (D. microcarpum), a West African tree widely used in folk medicine, has not been systematically assessed for inhibiting carbohydrate-digestive enzymes. This study investigated the in vitro α-amylase and α-glucosidase inhibitory activities of petroleum ether (PE), dichloromethane (DCM), and hydro-methanol (HMF) fractions of D. microcarpum stem bark and identified putative bioactive constituents through HPLC and molecular docking. HPLC analyses revealed the presence of triterpenoids (lupeol, betulinic acid), phytosterols (β-sitosterol, stigmasterol), flavonoids (quercetin, kaempferol), and glycosides (specioside, melilotoside) variably across the fractions. All fractions inhibited the test enzymes in a dose-dependent manner. For α-amylase, IC₅₀ values were 0.60±0.02 mg/mL (DCM), 0.90±0.04 mg/mL (PE), and 2.26±0.06 mg/mL (HMF), compared to 0.36±0.01 mg/mL for acarbose. Against α-glucosidase, PE was the most potent (0.10±0.01 mg/mL), followed by DCM (0.19±0.02 mg/mL) and HMF (0.51±0.05 mg/mL); acarbose showed IC₅₀ = 0.54±0.03 mg/ml. Docking studies highlighted β-sitosterol, lupeol, specioside, and verminoside (binding energies ≤ −6.3 kcal/mol) as plausible active principles forming stabilizing interactions within enzyme catalytic subsites. These findings underscore the potential of D. microcarpum stem bark, particularly its PE and DCM fractions, as promising sources of antidiabetic lead compounds.

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