Effect of in vitro gastrointestinal digestion on phenolic compounds and the antioxidant activity of Aloe vera

Abstract The aim of this work is to study the effect of digestion on the total polyphenol content, flavonoids and the antioxidant activity of Aloe vera. Total polyphenol contents and flavonoid spectrophotometric methods: The evaluation of the antioxidant activity was carried out by three methods, DPPH, ABTS and CUPRAC. To confirm the results obtained we carried out an analysis by ATR-FTIR. The total phenol content found in the Aloe vera extract studied was 1.3638 mg EAG/100 g, while the content of flavonoids found in the Aloe vera extract studied was 0.690 mg EQ/100 g. The values of total polyphenols and flavonoids decreased under the effect of gastrointestinal digestion. The spectra obtained during the ATR-FTIR analysis show that Aloe vera is rich in phenolic compounds and flavonoids. Intense bands corresponding to O–H bonds, C=C bond, C–H, CO, CH3 and CH2 confirm the presence of these bioactive compounds. For both the DPPH and CUPRAC methods, Aloe vera extract reveals a strong antioxidant activity, which gradually decreases during the oral and gastric phase and then increases after the intestinal digestion. For the ABTS method, the antioxidant activity decreases during the oral phase, increases during the gastric phase and then decreases again during the intestinal phase.