Apple Peel Polyphenols and Their Beneficial Actions on Oxidative Stress and Inflammation

Abstract

Since gastrointestinal mucosa is constantly exposed to reactive oxygen species from various sources, the presence of antioxidants may contribute to the body’s natural defenses against inflammatory diseases.HypothesisTo define the polyphenols extracted from dried apple peels (DAPP) and determine their antioxidant and anti-inflammatory potential in the intestine. Caco-2/15 cells were used to study the role of DAPP preventive actions against oxidative stress (OxS) and inflammation induced by iron-ascorbate (Fe/Asc) and lipopolysaccharide (LPS), respectively.ResultsThe combination of HPLC with fluorescence detection, HPLC-ESI-MS TOF and UPLC-ESI-MS/MS QQQ allowed us to characterize the phenolic compounds present in the DAPP (phenolic acids, flavonol glycosides, flavan-3-ols, procyanidins). The addition of Fe/Asc to Caco-2/15 cells induced OxS as demonstrated by the rise in malondialdehyde, depletion of n-3 polyunsaturated fatty acids, and alterations in the activity of endogenous antioxidants (SOD, GPx, G-Red). However, preincubation with DAPP prevented Fe/Asc-mediated lipid peroxidation and counteracted LPS-mediated inflammation as evidenced by the down-regulation of cytokines (TNF-α and IL-6), and prostaglandin E2. The mechanisms of action triggered by DAPP induced also a down-regulation of cyclooxygenase-2 and nuclear factor-κB, respectively. These actions were accompanied by the induction of Nrf2 (orchestrating cellular antioxidant defenses and maintaining redox homeostasis), and PGC-1α (the “master controller” of mitochondrial biogenesis).ConclusionOur findings provide evidence of the capacity of DAPP to reduce OxS and inflammation, two pivotal processes involved in inflammatory bowel diseases.

Apple as a Source of Dietary Phytonutrients: Bioavailability and Evidence of Protective Effects against Human Cardiovascular Disease

“…Chlorogenic acid tends to be higher in the flesh than in the peel. In agreement with the polyphenol composition, apples with the peels are better able to inhibit cancer cell proliferation when compared to apples without the peels [26].…”

Effects of Grape Wine and Apple Cider Vinegar on Oxidative and Antioxidative Status in High Cholesterol-Fed Rats

“…There are few studies in this field. Denis et al [24] provided evidence of the capacity of polyphenols of dried apple peels to reduce oxidative stress and inflammation in gastrointestinal mucosa of intestine. Although the target tissue was different, their results revealed the antioxidant effect of polyphenols in apple was in agreement with our study.…”

The in vitro evaluation of isolated procyanidins as modulators of cytokine-induced eotaxin production in human alveolar epithelial cells

“…Scientists are now working toward defining the bioactive molecules that are eliciting effects and through which mechanisms they modulate change [16][17][18]. There is substantial evidence that procyanidins are capable of modulating key inflammatory pathways in various tissues which has been reviewed elsewhere [7].…”