Abstract:A comparative study was conducted to investigate the polyphenol content and biological activity of colorful （blue,white,purple,and black） hulless barley in Yunnan Province. The soluble and insoluble bound polyphenols were extracted from hulless barley,and the contents of polyphenols and flavonoids were determined. The composition of phenolic compounds was analyzed by using high-performance liquid chromatography（HPLC）. In addition,the in vitro antioxidant activity and metabolic syndrome-related enzyme inhibitory activity of polyphenol extracts of hulless barley were measured,and its protective effect on H2O2-induced oxidative damage in HepG2 cells was discussed. The results showed that black hulless barley had significantly higher contents of polyphenols and flavonoids compared to other hulless barley （P<0.05）. There were large differences in the composition of phenolic compounds among the four hulless barley. Black barley had the least types of phenolic compounds in soluble polyphenols （9 types） and the most types of phenolic compounds in insoluble bound polyphenols （18 types）. Furthermore,the soluble and insoluble bound polyphenols in black hulless barley exhibited significantly higher DPPH radical scavenging activity,hydrogen peroxide scavenging activity,and trolox equivalent antioxidant capacity compared to blue,white,and purple hulless barley （P<0.05）.However,there was no significant difference in the ferric reducing antioxidant power （FRAP） between black hulless barley and purple hulless barley （P>0.05）. Among the four types of polyphenol extracts of hulless barley,blue hulless barley showed the best inhibitory effect on α-amylaseand α-glucosidase,while purple hulless barley had the best inhibitory effect on lipase. Additionally,the polyphenol extracts of all four types of hulless barley significantly reduced the production of reactive oxygen species （ROS） and malondialdehyde （MDA） induced by H2O2 in HepG2 cells at high concentrations and increased the content of glutathione （GSH） and catalase （CAT） and superoxide dismutase （SOD） activity （P<0.05）.