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 spice ingredients in Asian dishes, but the peels are usually discarded, producing a large amount of waste despite the presence of phenolic compounds. Phenolic compounds are essential for scavenging reactive oxygen species (ROS) generated naturally during metabolism. This study aimed to investigate the profile of phenolic compounds (total phenolic content, total flavonoid content, and individual phenolic compounds) and antioxidant activities (2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, ferric reducing antioxidant power, and oxygen radical absorbance capacity) of Citrus hystrix peel ethanolic extract (CHPPE). Their functional properties in a biological model (cell viability and 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 phenolic compounds (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 activity, which significantly improving cell viability and reducing the presence of intracellular ROS. The cytoprotective effect of CHPPE was higher than that of ascorbic acid, indicating a strong natural antioxidative capacity. Our research reveals the potential of CHPPE as a functional ingredient in the food and pharmaceutical industries.