Composition and biological properties of soluble post-gastrointestinal digestion fractions of common dry edible beans

Abstract: Dry edible beans are an inexpensive source of quality protein and bioactive compounds including peptides, phenolic acids, flavonols, flavan-3-ols, anthocyanidins, and flavanones. These compounds can impart beneficial health effects by acting as an antioxidant, anti-hypertensive, anti-inflammatory, and anti-atherosclerotic agents in vivo. In this study, we evaluated the antioxidant and anti-inflammatory properties of three common varieties of dry edible beans: Black (BL), Great Northern (GN), and Pinto (PT) beans. Prior to analysis, beans were soaked, cooked, and subjected to simulated in vitro gastrointestinal (GI) digestion. Soluble fractions ( < 3kDa) of in vitro GI digesta were produced and characterized for their phytochemicals, peptides, and free amino acids. The antioxidant and anti-inflammatory properties of these < 3kDa fractions were determined using the human colorectal adenocarcinoma HT-29 cell line. BL bean had significantly higher rates of gastric (42%) and intestinal (8%) digestion compared to GN and PT beans (P < 0.05), respectively, suggesting differences in storage protein structure and proteolysis pattern in BL bean. Amino acids analysis revealed that the < 3kDa fraction of GN bean was low in both essential and non-essential amino acids. However, it had the highest abundance of dipeptides followed by PT and BL beans (P < 0.05). BL and PT beans were richer in flavonols and derivatives of hydroxybenzoic acid compared to GN bean. Each bean fraction (used at 50 µg peptide/mL) ameliorated TNF⍺-induced pro-inflammatory signaling. BL bean was the most effective at lowering AAPH-induced oxidative stress in HT-29 cells, followed by GN bean, while PT bean did not exhibit any antioxidant effect. In conclusion, BL and PT beans were rich in both essential amino acids and polyphenols compared to GN bean. However, BL had higher in vitro GI digestibility and exhibited the highest antioxidant activity.