Roasted Barley Extract Affects Blood Flow in the Rat Tail and Increases Cutaneous Blood Flow and Skin Temperature in Humans

Abstract

Roasted barley extract (RBE, "Mugicha") is a traditional Japanese beverage reported to improve blood viscosity and affect food functionality. RBE is suggested to contain 2,5-diketopiperazines, which are the functional component with neuroprotective and immunostimulatory effects that are produced in food through roasting. In this study, we investigated the effects of RBE on blood circulation, both clinically and in rats. At first, we confirmed five 2,5-diketopiperazine derivatives in RBE by LC-MS analysis. Secondarily, we revealed that RBE affects blood flow in the rat tail and compared the efficacy on rat tail blood flow among five 2,5-diketopiperazines in RBE. Especially, cyclo(d-Phe-l-Pro) was the most effective in increasing blood flow in the rat tail. We also researched the mechanism of cyclo(d-Phe-l-Pro) with rat aorta study. As a result, we confirmed that cyclo(d-Phe-l-Pro) has an effect on vasodilatation through the release of nitric oxide in the vascular endothelium. Finally, we also confirmed that RBE affects cutaneous blood flow and increases skin temperature in humans.

Roasted Barley Extract (Mugicha) Containing Cyclo(D-Phe-L-Pro) Prevents a Decrease in Skin Temperature in Cold Conditions: A Randomized, Double-Blind, Placebo-Controlled, Crossover Study

“…Blood flow has thermal movement, which is important in human homeostasis (14). We also reported that cyclo(d-Phe-l-Pro) has a vasodilatation effect via NO production in the endothelium (13). Thus, we assumed that RBE efficacy for skin temperature in this clinical study was also derived from vasodilatation due to cyclo(d-Phe-l-Pro).…”

“…We reported previously that RBE containing cyclo(d-Phe-l-Pro) affects skin blood flow and skin temperature (13). However, our previous study only included women and used cold-water immersion.…”

“…Then subjects removed their socks and drank the sample beverages. We measured the temperature of the left foot instep at intervals of 5 min for 100 min (4,5,13). The skin temperature was estimated using infrared thermography (H2640; Nippon Avionics Company, Tokyo, Japan).…”

“…We previously reported that RBE containing cyclo(d-Phe-l-Pro) affects blood flow in rat tails (13). We also reported that cyclo(d-Phe-l-Pro) is the important chemical of RBE and affects vasodilatation through the eNOS pathway in the endothelium (13).…”

Roasted Barley Extract (Mugi-cha) Containing Cyclo(d-Phe-l-Pro) Prevents Lowering of the Cutaneous Blood Flow and Skin Temperature under Air Conditioning: A Randomized, Double-Blind, Placebo-Controlled, Crossover Study

“…Roasted barley extract (RBE) or mugi-cha is a popular traditional beverage in Japan. 1 RBE is also well-known as a healthy caffeine-free beverage. Many Japanese people, children, infants, and adults, drink RBE because RBE is uncaffeinated and low-calorie.…”