Abstract:
Different parts of wheat (whole wheat flour, bran, and refined flour) were subjected to simulated gastrointestinal digestion in vitro, to determine changes in the release of active antioxidant substances (polyphenols) and flavonoids, as well as total antioxidant capacity. The results showed that the maximum quantities of polyphenols and flavonoids released from whole wheat, bran, and refined flour during gastric digestion were 2.157-, 1.653-, 3.092-, and 1.825-, 1.574-, 3.179-times the values at 0 h, respectively. Similarly, the maximum oxygen radical absorption capacity (ORAC) values for whole wheat, bran, and refined flour were 2.601-, 1.658-, and 6.197-times the values at 0 h, respectively. On the other hand, the maximum quantities of polyphenols released from whole wheat, bran, and refined flour during in vitro simulated intestinal digestion were 1.541-, 1.042-, and 1.578-times the values at 0 h of intestinal digestion, and 3.429-, 1.697-, and 4.975-times the values at 0 h of gastric digestion, respectively. Additionally, the maximum quantities of flavonoids released from whole wheat, bran, and refined flour were 1.428-, 1.026-, and 1.570-times the values at 0 h of intestinal digestion, and 2.421-, 1.570-, and 4.913-times the values at 0 h of gastric digestion, respectively. Similarly, the maximum ORAC values for whole wheat, bran, and refined flour were 1.464-, 1.039-, and 1.514-times the values at 0 h of intestinal digestion, and 3.694-, 1.690-, 9.017-times the values at 0 h of gastric digestion, respectively. The results show that the polyphenols (such as flavonoids) bound to grains were converted to free polyphenols from the bound form due to gastric acid and enzymatic hydrolysis via gastrointestinal protease during gastrointestinal digestion. Thus, polyphenols bound to grains can be digested and absorbed in the upper gastrointestinal tract.
