Effect of germination on the content of polyphenols and antioxidation activity of kidney beans(Phaseolus vulgarisl L.)

The effect of germination on the content of polyphenols and flavonoids and antioxidant activity of black beans,speckled kidney beans,and purple beans was studied. The correlation between phenolic content,flavonoid content and antioxidant activity was analyzed. It was found that the content of phenolics and flavonoids in all three germinated beans(0~6 d) significantly lower than in raw beans(p<0.05). The loss of phenolics and flavonoids during soaking stage was higher than that during germination stage among all three beans. Interestingly,after germination for 6 days,content of phenolics and flavonoids in black bean began to increase,implying phenolics release caused by endo-enzymes. Generally,the antioxidant activity determined with DPPH· radical scavenging capacity(DPPH),ABTS+· radical scavenging capacity(ABTS),ferric reducing antioxidant power(FRAP) or oxygen radical absorption capacity(ORAC) all showed decreasing trends during germination process,which was highly correlated with content of phenolics and flavonoids in the beans. The most correlated indices with r of 0.955 in this study was content of phenolics and the ABTS values. Research also showed that the antioxidant activity of black beans increased after 4 day germination,and the ORAC value of black beans and speckled kidney beans after 6 day germination were even higher than those of 0 d. In conclusion,better biologically active substance could be obtained for different beans under suitable conditions.