Changes in phenolic composition and bioactivity of raw and pickled cowpea (Vigna unguiculata L. Walp.) green pod after in vitro simulated gastrointestinal digestion

摘要

Here, the changes in phenolic composition and antioxidant activities (ABTS, DPPH, and FRAP) of raw and pickled cowpea green pod during in vitro simulated gastrointestinal digestion (GID) were investigated. The inhibitory activities of the undigested and digested samples towards alpha-amylase, alpha-glucosidase and lipase were determined. Results revealed that total phenolic (TP) and flavonoid (TF) contents of both raw and pickled samples were increased after gastric and intestinal digestion, and the pickled sample had lower TP and TF content after each digestion phase. A similar trend was observed for antioxidant activities, which were significantly correlated with TP and TF contents (p 0.05). Seven phenolic compounds were identified and quantified by HPLC-DAD. Their contents were affected by digestion and pickling, and raw cowpea pod had higher contents before and after GID. Inhibitory effects towards alpha-amylase, alpha-glucosidase and lipase were increased for raw cowpea pod after GID. Pickled cowpea pod also showed an increased inhibitory activity towards lipase, while no activity towards alpha-amylase and alpha-glucosidase. Raw cowpea pod had higher inhibitory effects towards alpha-amylase, alpha-glucosidase and lipase than the pickled one at each digestion phase. Our results showed that pickling process reduced the health-promoting properties of cowpea green pod.