Identification of a xanthine oxidase inhibitor in barley tea (Mugi-Cha) and its contribution to the inhibitory activity of barley tea

As part of our studies on the prevention of lifestyle-related diseases by processed foods, we evaluated the xanthine oxidase (XO) inhibitory activity of barley tea. The XO inhibitory activity of the tea (a hotwater extract of roasted barley) was not as potent as that of another roasted beverage, coffee. However, the activity of an ethyl acetate-soluble substance in the extract was significantly stronger than that in coffee. Purification of the substance revealed that pyrogallol was the most potent compound. After establishing a quantification method for pyrogallol in barley tea, we analyzed correlations between pyrogallol content, roasted grain color, and XO inhibitory capacity of barley tea. The findings suggest that the XO inhibitory activity of barley tea is related to the roasting degree and chroma b* of barley grains through the content of pyrogallol, although other active compounds may be present in barley tea.