Antioxidant Activity of Bound Phenolics from Broad Beans at Different Edible Stages

The antioxidant activity of bound phenolic extracts of seed coats and cotyledons at three edible stages S1(138 DAS),S2(156 DAS)and S3(173 DAS)from five broad bean varieties(Fengdou 6,13,15,17 and 18)were studied in this paper(DAS,day after seeding). The contents of total phenol,flavonoid and condensed tannin were measured by Folin-phenol method,sodium nitrite-aluminum chloride method and vanilla methanol method,respectively. The antioxidant activity was evaluated by DPPH radical scavenging activity,trolox equivalent antioxidant activity(TEAC)and iron reduction antioxidant activity(FRAP). Meanwhile,the relationship between the contents of phenolic compound and antioxidant activity was analyzed using correlation analysis. The results showed that the contents of total phenol,flavonoid,condensed tannin and antioxidant activity of seed coats were higher than those of cotyledons. Phenol contents and antioxidant activity of Fengdou 18 harvested from S2 were the highest in seed coats and cotyledons,while those of Fengdou 17 harvested from S1 were the lowest in seed coats and S3 were the lowest in cotyledons. There had differences in phenol content and antioxidant activity among different varieties during the whole harvesting process. In seed coats,(contents of total phenol)TPC and(contents of flavonoid)FC were significantly correlated with DPPH and FRAP(P<0.01),(contents of condensed tannin)CTC was significantly correlated with DPPH,TEAC and FRAP(P<0.01),and in cotyledons,TPC and FC were significantly correlated with DPPH,TEAC and FRAP(P<0.01).