Fatty Acids, Epicatechin-Dimethylgallate, and Rutin Interact with Buckwheat Starch Inhibiting Its Digestion by Amylase: Implications for the Decrease in Glycemic Index by Buckwheat Flour

Abstract

Glycemic indexes of bread made from mixtures of wheat flour and buckwheat flour are lower than those made from wheat flour. To discuss the mechanism of the buckwheat flour-dependent decrease in glycemic indexes, the formation of a starch-iodine complex and amylase-catalyzed digestion of starch were studied using buckwheat flour itself and buckwheat flour from which fatty acids, rutin, and proanthocyanidins including flavan-3-ols had been extracted. Absorbance due to the formation of a starch-iodine complex was larger in extracted than control flour, and starch in extracted flour was more susceptible to pancreatin-induced digestion than starch in control flour. Fatty acids, which were found in the buckwheat flour extract, bound to amylose in the extracted flour, inhibiting its digestion by pancreatin. Rutin and epicatechin-dimethylgallate, which were also found in the extract, bound to both amylose and amylopectin in the extracted flour, inhibiting their digestion induced by pancreatin. We discussed from these results that the lower glycemic indexes of bread made from mixtures of wheat flour and buckwheat flour were due to binding of fatty acids, rutin, and epicatechin-dimethylgallate, which were contained in buckwheat flour, to wheat flour starch.

Differences in metabolomic profiles of the naturally contaminated grain of barley, oats and rye

“…The fatty acid profile will thus determine the qualitative composition of produced volatile compounds. Significant differences in contents of individual fatty acids depend on the chemical composition of grain, which is connected with the type of cereal, cultivar and soil conditions (Takahama and Hirota, 2010). Volatile compounds produced most frequently via enzymatic decomposition of lipids is a characteristic trait for a given grain, being the main component of the profile of chemical compounds, comprising the taste and aroma of a given grain (Baker et al, 2006).…”

Starch Hydrolase Inhibitors from Edible Plants

“…Fatty acids could bind to amylose to form starch-lipid complex and render the starch more resistant to amylase-catalyzed digestion. Synergistically, rutin and proanthocyanidins are reported to be inhibitors of a-amylase (Takahama & Hirota, 2010).…”

“…Buckwheat (Fagopyrum esculentum) is widely used as a constituent of foods such as noodles and bread blended with flour from other cereals (Takahama & Hirota, 2010). Lin, Liu, Yu, Lin, and Mau (2009) made breads by mixing 15% of buckwheat flour with 85% of wheat flour in the hope to develop functional foods for diabetic patient.…”

Activity‐Guided Fractionation to Identify Blue Wheat (UC66049 Triticum aestivum L.) Constituents Capable of Inhibiting In Vitro Starch Digestion

“…Fraction AH-6-III was found to contain oleic, linoleic, and linolenic acid, as well as minor amounts of palmitic acid. For instance, in a recent study on buckwheat starch, fatty acids were among the compounds that were found to inhibit buckwheat starch digestion by α-amylase (Takahama and Hirota 2010). Although less likely, it is also possible that minor amounts of triglycerides were not fully extracted by using acetone and ethyl acetate before the alkaline hydrolysis of the extraction residue or that they had been released in the starch digestion step and not completely removed before the alkaline hydrolysis.…”