Effect of in vitro digestion on phenolic compounds and antioxidant capacity of different apple (Malus domestica) varieties harvested in Mexico

Apple has phenolic compounds that provide it antioxidant capacity, but during the digestion process, these compounds can undergo changes that modify their bioaccessibility and subsequently decrease the beneficial effects on human health. The present study aimed to analyze the effect of in vitro gastrointestinal digestion on bioaccessibility (B) of the total content of phenolic compounds (PC), flavonoids (TF), anthocyanins (TA), and antioxidant capacity (ABTS, DPPH) of five different apple varieties. Samples were subjected to static in vitro digestion model following the InfoGest consensus protocol. After the in vitro digestion, the PC, TF, TA, ABTS, and DPPH content were significantly different (p≤ 0.05) in each digestion stage. The intestinal stage released higher content of PC (20.79–81.43 %) and TF (43.08–83.41 %), while the gastric stage released higher content of TA (126.49–204.23 %) (p ≤ 0.05). The Principal Component Analysis (PCA) indicated that Red Delicious variety was mainly correlated with higher content of PC, TF, and TA before and after in vitro digestion. At the gastric stage, TA presented correlation with ABTS (r: 0.83) and DPPH (r: 0.87), while, in the intestinal stage, PC and TF presented the highest correlation with ABTS (r: 0.97–0.98) and DPPH (r: 0.86–0.92). Though in vitro digestion favors the release of PC, TF, and TA, their content was lower than that obtained before in vitro digestion, which suggests that chemical extraction could overestimate the bioavailability of phenolic compounds.