Advances in phytochemistry, pharmacology, and sustainable utilization of orange peels

The genus Citrus (Rutaceae) has long been used in traditional medicine systems, with orange peels recognized as medicinal materials in both Chinese and Western practices. Accordingly, this review focuses on Citrus sinensis (L.) Osbeck and Citrus aurantium, systematically summarizing their phytochemical composition, biological activities, ethnobotanical background, processing characteristics, and sustainable utilization. Orange peels are rich in phenolics, flavonoids, and essential oils, and in vitro and animal studies have reported a range of pharmacological effects, including antioxidant, anti-inflammatory, antitumor, and antidiabetic effects. Advanced analytical platforms such as LC – MS, GC – MS, and metabolomics have enabled comprehensive characterization of citrus peel phytochemicals. This has facilitated correlations with pharmacological activities and strengthened scientific validation. Processing methods, including drying, fermentation, microwave-assisted extraction, and freeze-drying, can significantly influence chemical composition and biological activity. As a major byproduct of the citrus processing industry, orange peel has increasingly been explored for applications in biofuels, biochemicals, and biodegradable materials, aligning with circular economy practices. However, further research is required to clarify molecular mechanisms, the roles of minor bioactive constituents, standardized processing technologies, clinical evidence, and industrial feasibility.