Abstract:Fruit and vegetable juices，as natural sources of antioxidants，exhibit variable efficacy due to differences in their row materials，varieties，and processing techniques.This study evaluated the antioxidant efficacy of 14 functional fruit and vegetable juices（including sour cherry juice，beetroot juice，and pomegranate juice）using the ferric reducing antioxidant power（FRAP）and oxygen radical absorbance capacity（ORAC）assays，and explored the contribution of polyphenol subclass content and structural characteristics to antioxidant activity.The results showed significant differences in the content of antioxidant compounds and antioxidant efficacy among the juices.Sour cherry juice，enriched in polyphenols and their subclasses，exhibited significantly higher ORAC [（210 710.06±5 636.69）μmol TE/L]and FRAP [（185.34±0.60）mmol Fe2+/L]values than other juices，followed closely by beetroot juice.Correlation analysis indicated that total polyphenol content dominated antioxidant capacity，showing highly significant positive correlations with ORAC（R=0.995，P＜0.001）and FRAP（R=0.966，P＜0.001）.Flavonoids were identified as the key enhancing components within subclasses，with correlation coefficients with ORAC and FRAP all greater than 0.96.Further analysis demonstrated that differences in the proportion and structure of polyphenol subclasses in fruit and vegetable juices also affected antioxidant capacity.ORAC was highly sensitive to the structure of polyphenol subclasses（particularly flavonols）and depended on the adaptability of specific molecular configurations for hydrogen atom transfer，whereas FRAP exhibited a concentration-dependent effect on total polyphenol content.These findings confirm that the antioxidant capacity of fruit and vegetable juices is jointly determined by polyphenol content and structural characteristics dominated by flavonoids.