HPLC method for measurement of human salivary α-amylase inhibition by aqueous plant extracts.

Control of hyperglycemia is an important treatment in metabolic disorders such as type II diabetes and obesity. α-Amylase, as the first enzyme of glucose release from dietary polysaccharides, is a potential target to identify new sources of novel anti-obesity and anti-diabetic drugs. In this work, different herbal extracts as α-amylase inhibitors were studied by measuring the rate of the cleavage of a maltooligomer substrate 2-chloro-4-nitrophenyl-β-D-maltoheptoside. Measurement of chromophore containing products after reversed phase HPLC separation was used for α-amylase activity measurement. Rates of hydrolysis catalysed by human salivary α-amylase were determined in the presence and absence of lyophilised water extracts of eleven herbs. Remarkable bioactivities were found for extracts of Cinnamomum zeylanicum Blume (bark), Camellia sinensis L. (leaf), Ribes nigrum L. (leaf), Laurus nobilis L. (leaf), Vaccinium macrocarpon Aiton (fruit) and Syzygium aromaticum L. (bud). Determined IC₅₀ values were in 0.017-41 μg/ml range for these six selected plant extracts. Our results confirm the applicability of this HPLC-based method for the quick and reliable comparison of plants as α-amylase inhibitors.