Background The growing interest in food waste valorisation has highlighted the potential of citrus by-products, rich in bioactive compounds. In particular, flavonoids contained in Citrus species from Southern Italy could represent a useful resource in the prevention and management of metabolic diseases such as obesity and type 2 diabetes. Methods Eco-friendly extraction methods (maceration, ultrasound, supercritical CO₂) were compared to isolate bioactive compounds from 11 species belonging to the genus Citrus . All extracts were analysed by UV–Vis spectrophotometric assays and HPLC. Subsequently, the antioxidant and α-amylase inhibitory activities, as well as the ability to modulate glucose metabolism and triglycerides accumulation in 3T3-L1 cells differentiated into adipocytes, were evaluated in the most effective extractions. Results Ultrasound-assisted extraction maximized the flavonoids extraction, specially naringin and hesperidin. The extracts showed an antioxidant activity up to 56.18 ± 0.87 %I, reduced the α-amylase activity up to 22.14 ± 0.98 %, as well as approximately doubling glucose uptake (late ripening orange), finally almost completely inhibiting the adipocytes differentiation process. Conclusions Citrus wastes appear to be promising sources of flavonoids with potential benefits against metabolic disorders. Flavonoids derived from Citrus by-products, particularly those with higher antioxidant potency, could be used to develop nutraceuticals and supplements with potential adjuvant effects in the prevention and treatment of metabolic-nutritional diseases such as obesity and diabetes. © 2025 The Author(s).

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