# Dipeptidyl Peptidase-4 Inhibitory Activity of Buckwheat Flour-Derived Peptides and Oral Glucose Tolerance Test of Buckwheat Flour Hydrolysates in Rats

## TL;DR

This study identifies two peptides from buckwheat flour that inhibit DPP-4, a target for managing type 2 diabetes, and tests their effect on blood glucose in rats.

## Contribution

The study is the first to identify Ile-Pro-Trp and Ile-Pro-Ile as DPP-4 inhibitory peptides from a plant source.

## Key findings

- Ile-Pro-Trp and Ile-Pro-Leu were identified as DPP-4 inhibitory peptides from buckwheat flour hydrolysates.
- A fraction of buckwheat flour hydrolysate showed a non-significant trend toward reducing blood glucose in a rat OGTT.

## Abstract

Dipeptidyl peptidase-4 (DPP-4) is a protease that degrades incretin and inhibits the secretion of insulin. Consequently, DPP-4 inhibition promotes insulin secretion and prevents the onset of type 2 diabetes. Given the growing interest in food-derived DPP-4 inhibitory peptides as potential functional ingredients, buckwheat (Fagopyrum esculentum) represents a promising source; however, few studies have investigated the bioactivity of peptides derived from buckwheat flour hydrolysates. In this study, two DPP-4 inhibitory peptides, Ile-Pro-Trp and Ile-Pro-Leu, were identified through purification of buckwheat flour hydrolysate and liquid chromatography–tandem mass spectrometry analysis. In a rat oral glucose tolerance test (OGTT), a fraction of buckwheat flour hydrolysate, crudely purified by reverse-phase column chromatography, showed a non-significant trend toward reducing increases in blood glucose. To our knowledge, this study is the first to show that Ile-Pro-Trp isolated from food protein hydrolysates exhibits considerable DPP-4 inhibitory activity. Moreover, this is the first study identifying Ile-Pro-Ile as a DPP-4 inhibitor from a plant source.