Understanding the potential health benefits of plant foods proteins beyond their nutritive role

New dietary approaches, ethical and environmental sustainability concerns attract the interest in plant proteins alternative to animal proteins. Beyond the nutritive role, recent research pointed out the potential health benefits of foods proteins and peptides that may exert bioactivities such as antioxidant, antilipidemic, antimicrobial and immunomodulating. There is even now a scarcity of information about the potential effects of pseudocereal proteins and their derived peptides, on chronic inflammation and oxidative stresses, that are considered major causes of age-related diseases and of some forms of cancer. This work aims to help filling these gaps. The immune-modulatory, the antioxidant and the trypsin-inhibitor activities of proteins from quinoa (Chenopodium quinoa Willd.), amaranth (Amaranthus retroflexus L.) and buckwheat (Fagopyrum esculentum Moench) seeds have been assessed in vitro, after purification and separation in different fractions. The three biological effects considered in this work are closely connected to each other for the maintaining of human well-being. Proteins have been tested as such and after simulated gastro-intestinal digestion. The immune-modulation capacity of protein fraction and peptides was evaluated in undifferentiated Caco-2 cells under stimulation with the pro-inflammatory cytokine IL-1β and assessing NF-B pathway activation. All proteins showed a capacity to decrease the inflammatory response, but at different percentages. The antioxidant activity seems to be related to the amino acids composition of the isolated fractions. Our results indicate that the protein fractions with higher trypsin inhibitor (TI) activity also possess radical scavenging and immune modulating properties, supporting the hypothesis of the involvement of TI in protection against oxidation and inflammation. The results showed in most cases a lower activity after proteolysis, but with some exceptions. In addition, the immunomodulation capacity of chenopodin, the major protein of quinoa seeds, was further investigated in order to deep on the molecular mechanisms of action at the basis of the observed effects. The interaction with possible target molecules has been studied in vivo using Caco-2cell models and with in silico structural predictions. Chenopodin mechanism of action involves a competitive inhibition tuning of the inflammatory effect of IL-1β based on its structural features. In conclusion, our findings lay the basis for possible uses as nutraceutical molecules of proteins from pseudocereal seeds.