Phenolic composition, antioxidant capacity and inhibitory effects on α-glucosidase and lipase of immature faba bean seeds

Immature faba bean seeds of five varieties were investigated for changes in phenolic composition, antioxidant capacity and inhibitory effects on α-glucosidase and lipase at three edible stages (S1, S2 and S3). Phenolics and antioxidant capacity in seed coats were significantly higher than those in cotyledons, and the highest was found of FD18 at stage S3. While phenolic content in cotyledons decreased steadily with the harvest time delayed. Eight phenolic compounds were confirmed with epicatechin and catechin prominent and their levels showed a great variability depending on varieties, maturation stages and plant parts of faba bean seeds. Unexpectedly, the inhibitory effects of purified phenolics on α-glucosidase were even stronger than that of the positive control acarbose, and the inhibitory effects on lipase in the cotyledons declined gradually from stage S1 to S3. Significant positive correlations between phenolics from seed coats and antioxidant capacity, and phenolics from cotyledons and the enzyme inhibitory effects were observed. Overall, the immature faba bean seed, especially its seed coat, has great potential as a functional food.