Inhibitory Properties of Aqueous Ethanol Extracts of Propolis on Alpha-Glucosidase

The objective of the present study was to evaluate the inhibitory properties of various extracts of propolis on alpha-glucosidase from baker's yeast and mammalian intestine. Inhibitory activities of aqueous ethanol extracts of propolis were determined by using 4-nitrophenyl-D-glucopyranoside, sucrose and maltose as substrates, and acarbose as a positive reference. All extracts were significantly effective in inhibiting α-glucosidase from baker's yeast and rat intestinal sucrase in comparison with acarbose (P < 0.05). The 75% ethanol extracts of propolis (75% EEP) showed the highest inhibitory effect on α-glucosidase and sucrase and were a noncompetitive inhibition mode. 50% EEP, 95%, EEP and 100% EEP exhibited a mixed inhibition mode, while water extracts of propolis (WEP) and 25% EEP demonstrated a competitive inhibition mode. Furthermore, WEP presented the highest inhibitory activity against maltase. These results suggest that aqueous ethanol extracts of propolis may be used as nutraceuticals for the regulation of postprandial hyperglycemia.