Apple peel fermentation by Lactobacillus plantarum: Phytochemical transformations and enhanced abilities against inhibition of advanced glycation end products

Apple peel, a byproduct of apple processing or consumption, is often discarded, contributing to environmental pollution and a considerable loss of valuable bioresources. This study explored the health-promoting potential of apple peel through fermentation with Lactobacillus plantarum ATCC14917. Our previous study indicated that this strain could increase the in vitro antioxidant activity of apple juice. In this study, we examined the phytochemical changes of apple peel extract (APe) fermented by Lactobacillus plantarum ATCC14917, as well as evaluating its beneficial effects against advanced glycation end products (AGEs)-induced cellular responses. In particular, the primary phytochemicals were identified as chlorogenic acid, rutin, isoquercitrin, quercetin-3-xyloside, and quercitrin in APe. After fermentation by L. plantarum ATCC14917, APe exhibited changes in phytochemical content, as well as induced pronounced anti-inflammatory and antioxidant activities. Notably, fermentation increased the levels of quercitrin and quercetin-3-xyloside, while slightly decreased the levels of chlorogenic acid, rutin, and isoquercitrin. The highest antioxidant activities were observed in APe at a concentration of 2.0 mg/mL after 72 h of fermentation (F-APe). Furthermore, F-APe significantly reduced the ROS level and inflammatory responses in RAW 264.7 cells by modulating RAGE/MAPKs/NF-κB signaling pathway, demonstrating enhanced potentials compared to non-fermented APe (NF-APe). Collectively, our findings provide the first evidence that L. plantarum ATCC14917 fermentation specifically converts apple peel waste into bioactive compounds with enhanced beneficial effects, offering a novel strategy for the prevention and management of diseases linked to AGEs.