In Vivo Assessment of the Photoprotective Potential of Underutilized Carob Fractions by Using Caenorhabditis elegans

The revalorization of agro-industrial by-products is a key strategy for promoting sustainability and the circular economy. This study assessed the photoprotective potential of underutilized carob (Ceratonia siliqua L.) fractions, including unripe and mature pods, leaves, and seed tissues, through chemical characterization, in vitro assays, and in vivo validation. Extracts showed high polyphenol contents (up to 4.8 g GAE/100 g) and strong antioxidant activity (up to 45 g TE/100 g). Photoprotective properties were confirmed by a solar protection factor of up to 17 and erythema transmission values of 3-6, indicating efficient UV absorption and anti-inflammatory potential, which together support overall skin protection. To validate these effects under physiological conditions, Caenorhabditis elegans was used as an in vivo model under three exposure modalities: complete exposure (contact and ingestion), the barrier effect (UV shielding by the medium), and the physiological effect (systemic protection after ingestion). Seed episperm and unripe pods showed the highest efficacy. Notably, complete exposure reduced UV-induced lethality from 98% to below 50%, mainly due to the barrier effect. This is the first report demonstrating the photoprotective activity of carob by-products in C. elegans, supporting their potential as natural ingredients for cosmetic and nutraceutical applications, and contributing to the sustainable revalorization of local agricultural residues.