Effects of food phenolics on digestive proteases by in vitro and in silico approaches

The interactions between various food ingredients and digestive enzymes can alter how food nutrients are absorbed and have an impact on an individual's health. Phenols and polyphenols (PPs) are effective in treating certain chronic diseases and play a function in metabolic regulation. The majority of phenolic compounds (PPs) that are consumed remain in the gastrointestinal tract, where they can have a variety of advantageous effects because phenolic compounds are generally poorly absorbed following food intake. Because they have the purported ability to suppress proteolytic digesting enzymes, PPs are commonly referred to be anti-nutritional factors in this context. The fact that reports on this subject frequently contradict one another, mostly as a result of various experimental setups, emphasizes the necessity of using consistent methodologies to assess the impact of PPs. Using albumin, gluten, and hemoglobin as substrates, the effects of several PPs (at physiological concentrations) were evaluated "in vitro" on the activities of pepsin, trypsin, and chymotrypsin. Results show that PPs may affect proteolytic activity in opposite ways, depending on the protein substrate and the enzyme. Therefore, a computational approach based on molecular docking and molecular dynamics simulations has been applied to investigate the interactions polyphenols may have with the enzymes and substrates. The analysis focused on the chymotripsin-ovalbumin system as a proof of concept to provide a mechanistic explanation for PPs opposite behavior in affecting proteolytic activity described in vitro. Results show that all the PPs under investigation can interact both with the enzyme and the substrate. However, it is interesting to note that only the PPs inhibiting the enzyme in vitro could induce structure modification on the substrate which could promote its partial denaturation. According to these results, a substrate-dependent inhibition can be hypothesized to explain opposite ways of PPs to affect protein digestion. The evidence gathered here suggests the possibility of considering some PPs as “digestion-promoting agents” in the formulation of functional foods.