Zhaohong Ci^{1, 2}, Chengyu Jiang^{1, 2}, Chigen Tsukamoto², Michiyuki Kojima^{2, 3,}

The pods of common beans (Phaseolus vulgaris) are rich in various nutrients, and they could therefore be important parts of the human diet. In the present study, we have analyzed the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and the contents of polyphenols, anthocyanin, vitamin C, and carotenoid in the pods of 3 varieties of common beans. French beans had the highest DPPH radical scavenging activity and polyphenol contents among the three varieties. The anthocyanin content was 3.93 mg/g D.W. in French beans, but not detected in bush beans and Romano beans. The vitamin C and carotenoid contents ranged from 0.45-1.96 and 0.31-0.60 mg/g D.W. in the pods of these common beans, respectively. Moreover, we found French beans contained monomeric (Fra.I), oligomeric (Fra.II), and polymeric (Fra.III) polyphenols (67%, 31%, and 2%, respectively). In contrast, monomeric polyphenols are the main polyphenols (Fra.I > 96%) in bush beans and Romano beans. Oligomeric polyphenols (Fra.II) show higher DPPH radical scavenging activity than monomeric ones (Fra.I) in French beans. Oligomeric polyphenols with both B-type and A-type bonds were present in Fra.II from French beans. We identified malvidin 3,5-diglucoside as the anthocyanin in French beans by HPLC-PDA/MS. In summary, as a vegetable, French beans have the highest antioxidant activity among the three varieties of common bean pods studied here.

DPPH radical scavenging activity, monomeric polyphenols, oligomeric polyphenols, anthocyanin, malvidin 3, 5-diglucoside