**5. Phenolic compounds during gastrointestinal digestion: bioaccessibility and bioavailability**

Bioaccessibility is defined from a nutritional point of view as the fraction of compounds liberated from the food matrix within the human gastrointestinal tract and available for intestinal absorption. The gastrointestinal tract is prone to oxidative stress due to its function as a primary digestive system and exposure to various stimuli [15, 29, 67]. The bioaccessibility and bioavailability of several phenolic compounds have been studied, noting that the aglycones in isoflavones are more bioavailable than their conjugated counterparts [9]. The absorption and bioavailability of phenolic compounds are commonly affected by low solubility, low permeability, and low stability in the gastrointestinal tract [29]. Some researchers have suggested that 5–20% of the total polyphenol content in legumes can be absorbed. The preventive action provided by these compounds depends on bioaccessibility. However, in the case of chronic diseases, such as stomach and colorectal cancer, they do not depend on the polyphenols bioaccessibility; still, gut microbiota can increase the bioavailability of the phenolic content of foods and quadruple their antioxidant activity [9, 12, 15, 29, 67].
