Valorization of Citrus Waste for Recovery of Nutritional and Bioactive Compounds: A Comprehensive Review

ABSTRACT The Citrus genus, part of the Rutaceae family, includes commercially significant fruit species, namely lemons ( Citrus limon ), oranges ( Citrus sinensis ), mandarins ( Citrus reticulata ), and grapefruits ( Citrus paradisi ), known for their rich nutrient profiles and global consumption. Notably, about 50% of these fruits remain unconsumed, appearing as peel, pulp, seeds, and segment residues after consumption or processing. To address this substantial waste, researchers use various extraction methods, from traditional solvent extraction and steam distillation to advanced techniques such as supercritical fluid extraction, microwave extraction, ultrasound extraction, and pulse electric field extraction, to obtain citrus extracts. Direct disposal of citrus waste poses environmental hazards, including damage to soil flora and water pollution. However, secondary metabolites from citrus waste, such as flavonoids (hesperidin, naringin), phenolic compounds, essential oils, and vitamins, demonstrate significant bioactivities, including anti‐inflammatory, antioxidant, antimicrobial, anticancer, antidiabetic, and cardiovascular protective effects. This review underscores the need for ongoing research to refine extraction methods, discover novel compounds, and elucidate the mechanisms underlying the bioactivities of citrus extracts to support their application in functional foods.