Comparative study of alpha-glucosidase inhibition of four Vietnamese medicinal plants Combretum quadrangulare, Dicranopteris linearis, Psychotria adenophylla, and Garcinia schomburgkiana: In vitro and in vivo studies.

Four medicinal plants C. quadrangulare, D. linearis, P. adenophylla, and G. schomburgkiana growing in the South of Vietnam were investigated for their alpha-glucosidase inhibition. The crude methanol extract of C. quadrangulare was determined to be the most active extract, then was selected for further in vivo assays including antidiabetic study and toxicity. In vitro alpha-glucosidase inhibition of four medicinal plants C. quadrangulare, D. linearis, P. adenophylla, and G. schomburgkiana was screened using standard procedures. In vivo antidiabetic activity, acute toxicity and subchronical toxicity of C. quadrangulare leaves was assessed on Swiss albino mice. Swiss albino mice were induced with diabetes by intraperitoneal injection of alloxan at a dose of 150 mg/kg body weight. High-performance liquid chromatography with evaporative light scattering detector (HPLC-ELSD) were used to detect the bioactive components of C. quadrangulare leaves. All crude extracts from the studied plants showed promising alpha-glucosidase inhibition, with IC₅₀ values ranging from 2.4 to 35.3 μg/mL. The methanol extract of C. quadrangulare leaves was determined to be the most active extract. This extract was then selected for antidiabetic assay using alloxan induced model of type 2 diabetes mellitus mice. The results indicated that the extract at a dose of 400 mg/kg can effectively decrease blood glucose levels that is comparable to that of glibenclamide 2 mg/kg. This compound showed moderate activity toward alpha-glucosidase. Therefore, our study indicated that C. quadrangulare, D. linearis, P. adenophylla, and G. schomburgkiana extract are potential materials for producing α-glucosidase inhibitor drugs.