Inhibitory activity of the flavonoids and phenolic acids from Jinyinhua on the xanthine oxidase

The inhibitory effect on of xanthine oxidase was assayed by high-throughput microplate spectrophotometer in ultraviolet region and the developed method was used to screen the compounds separated from Jinyinhua.The in vitro high-throughput screening method for xanthine oxidase inhibitors was developed and optimized with four flavonoids and eight phenolic acids in Jinyinhua being discovered to have xanthine oxidase inhibitory activity.It was found that quercetin,luteolin and 3,4-di-caffeoylquinic acid methyl had excellent activity and their IC₅₀ values were 8.36,6.46 and 2.08 μmol/L respectively.In the crude drug of Jinyinhua,the activity of flavonoid aglycones was better than that of flavonoid glycosides,and the activity of double caffeoyl quinic acids was better than that of single caffeoyl quinic acids.Moreover,the activity of phenolic conjugates of methylated quinic acid was significantly better than that of quinic acid,and the 5-caffeoyl moiety contributed most to the activity of double caffeoyl quinic acids.