Fermentation of Chaenomeles sinensis (Thouin) Koehne with lactic acid bacteria: dynamic changes in metabolites and enhancement of antioxidant activity

Lactic acid bacteria (LAB) fermentation is an effective bioprocessing strategy to enhance bioactive components and antioxidant activity of fruit-based products. This study investigated the fermentation of Chaenomeles sinensis (Thouin) Koehne (C. sinensis) using Lactobacillus plantarum and Lactobacillus acidophilus. Fermentation conditions were optimized as follows: ratio of Lactobacillus plantarum and Lactobacillus acidophilus 2:1, inoculation size 0.46% (w/v), fermentation time 6 days and sugar addition 7.6 g, increasing by 80% in proanthocyanidin content (1.84 mg/mL). Furthermore, significant increases in total phenolics, total flavonoids, and superoxide dismutase (SOD) activity were observed under the optimized conditions. Untargeted metabolomics revealed 23 differential metabolites and 5 key metabolic pathways. The fermented product of C. sinensis demonstrated strengthened free radical scavenging ability and effectively attenuated oxidative stress in HepG2 cells by reducing reactive oxygen species (ROS) and malondialdehyde (MDA) levels while enhancing antioxidant enzyme activities, supporting its potential application in functional food ingredients with antioxidant activity.