Bioactive compounds of Citrus hystrix peel ethanolic extract and their antioxidant potential under hydrogen peroxide-induced oxidative stress in Caco-2 cells

Citrus hystrix is a fruit native to tropical Southeast Asia and Southern China. The fruits and leaves are well-known as spice ingredients in Asian dishes, but the peels are usually discarded, producing a large amount of waste despite containing phenolic compounds. Phenolic compounds are essential to scavenge reactive oxygen species (ROS) generated naturally during metabolism. This study aimed to investigate the phenolic compounds profile (total phenolic content, total flavonoid content, individual phenolic compounds) and antioxidant activities (2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, ferric reducing antioxidant power, oxygen radical absorbance capacity) of Citrus hystrix peel ethanolic extract (CHPPE). Its functional properties in a biological model (cell viability, intracellular ROS) were also evaluated using Caco-2 cells under H2O2-induced oxidative stress. We identified 37 compounds, including flavonoids (26), phenolic acids (3), stilbenes (2), lignans (1), and other phenolics (5). CHPPE contained (mg/g CHPPE) hesperidin (16.10±0.05), diosmin (1.95±0.08), neohesperidin (23.83±0.06), and naringin (2.39±0.03). CHPPE exhibited remarkable antioxidant activities which significantly improved cell viability and reduced the presence of intracellular ROS. The cytoprotective effect of CHPPE was higher than ascorbic acid, showing strong natural antioxidative capacity. Our research revealed the potential of CHPPE to be applied as a functional ingredient in the food and pharmaceutical industries.