Controlled carotenoid cleavage and nanoencapsulation for the production of photoprotective retinoids from Daucus carota

This study presents an integrated strategy for the valorization of carrot ( Daucus carota L.) processing waste through the production of photoprotective retinoid-enriched ingredients obtained via controlled carotenoid cleavage and nanoencapsulation. Carrot discards were extracted using different organic solvents, with hexane and dichloromethane yielding the highest contents of β-carotene and α-carotene. Successive extraction cycles showed a saturation-like behavior, supporting the selection of 2–4 cycles for optimal carotenoid recovery. Carotenoids were converted into apocarotenoids and retinoids using several oxidative treatments, including UV irradiation, heating, ultrasound, and air bubbling, with or without Fenton-based radical initiation. Among these, UV irradiation was the only condition that consistently generated retinoids, with yields significantly enhanced in the presence of the Fenton system. A Box–Behnken experimental design identified carotenoid concentration and irradiation time as the main factors governing degradation and retinoid formation, favoring low carotenoid loads and short exposure times to minimize secondary photodegradation. The resulting retinoid-enriched extract (RE) exhibited enhanced photoprotective activity in UVB-irradiated HaCaT keratinocytes, increasing cell viability by approximately 15–20% compared to a carotenoid extract (CE) at the highest tested concentration (5,000 μ g/mL). In contrast, both extracts showed comparable antioxidant and anti-inflammatory effects. To enhance stability and dermal delivery, RE was incorporated into nanostructured lipid carriers (NLCs). Optimized NLCs displayed a mean particle size of ~210 nm, high encapsulation efficiency (>99%), and a stable negative zeta potential (~−40 mV), maintaining physicochemical stability under refrigerated storage. Overall, this work demonstrates a scalable, green-compatible approach that combines controlled carotenoid cleavage with nanotechnology to obtain stable, photoprotective retinoid-enriched ingredients with potential applications in dermocosmetic formulations.