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.

中文翻译：

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烤大麦提取物影响大鼠尾巴中的血流量，并增加人类的皮肤血流量和皮肤温度

烤大麦提取物（RBE，“ Mugicha”）是一种传统的日本饮料，据报道可改善血液粘度并影响食物功能。建议RBE包含2,5-二酮哌嗪，这是通过焙烤在食品中产生的具有神经保护和免疫刺激作用的功能性成分。在这项研究中，我们研究了RBE对临床和大鼠血液循环的影响。首先，我们通过LC-MS分析确定了RBE中的5种2，5-二酮哌嗪衍生物。其次，我们揭示了RBE影响大鼠尾巴中的血流，并比较了RBE中五种2,5-二酮哌嗪之间对大鼠尾巴血流的功效。特别是，环（d -Phe- l-Pro）在增加大鼠尾巴中的血流方面最有效。我们还通过大鼠主动脉研究了环（d -Phe- 1- Pro）的机制。结果，我们证实了环（d- Phe- 1- Pro）通过在血管内皮中释放一氧化氮而对血管舒张有影响。最后，我们还证实了RBE影响皮肤的血液流动并增加了人类的皮肤温度。