New α-Glucosidase inhibitors from Croton bonplandianum Croton bonplandianum Baill (Euphorbiaceae)

Purpose: To isolate and evaluate α-glucosidase inhibitors from dichloromethane extract of Croton bonplandianum Baill as probable remedy for management of diabetes.
Methods: Activity-guided isolation of constituents from dichloromethane extract was carried out. Fractionation of dichloromethane extract by column chromatography on silica gel and Sephadex LH 20 using different mobile phase systems led to the isolation of compounds (A-I). The structures of these isolated compounds were established by ultraviolet (UV) and infrared (IR) spectroscopy. Proton nuclear magnetic resonance (¹H NMR), ¹³C NMR and mass spectrophotometry, electron impact mass spectroscopy (EIMS) and high resolution mass spectroscopy (HRMS) were used for structural elucidation. All the isolated compounds were screened for their α-glucosidase inhibitory activity using standard in vitro α-glucosidase inhibition assay. Acarbose was used as positive control.
Results: On the basis of their physical and spectral data from literature, the isolated compounds were identified as n-pentacosanyl-n-nonadeca-7′-en-9′-α-ol-1′-oate (A), n-tridecanyl n-octadec-9,12-dienoate (B), nonacosyl hexadecanoate (C), heptacosanoic acid (D), 1,3,5-trihydroxy-2-hexadecanoylamino- (6e,9e)-heptacosdiene (E),cumarin (F), betulin (G), stigmasterol (H), and 3,5-dimethoxy 4-hydroxy cinnamic acid (I).Compounds F, GandI possessed significant α-glucosidase inhibitory activity in a concentration-dependent manner with 50 % inhibitory concentration (IC₅₀) values ranging from 23.0 to 26.7 μg/mL, relative to that of the positive control, acarbose (IC₅₀, 38.2 μg/mL).
Conclusion: The plant contains bioactive compounds with α-glucosidase inhibitory activity. This lendssome support for the traditional use of this herb in the management of diabetes. Compound F, GandI possessed significant α-glucosidase inhibitory activity in a concentration-dependent manner and may be developed as a new α-glucosidase inhibitor.

Keywords
α-Glucosidase; Inhibition; Diabetes; Acarbose; Cumarin; Betulin; 3,5-Dimethoxy 4-hydroxy cinnamic acid; Croton bonplandianum