From phytochemical complexity to biological function: A comparative study of Capparis spinosa fruit extracts

Capparis spinosa L. is a Mediterranean species traditionally used for the treatment of inflammatory and skin-related disorders and increasingly explored as a source of multifunctional ingredients for dermocosmetic applications. In this study, three commercially available C. spinosa fruit extracts obtained through different extraction strategies (two aqueous extracts, CAP1 and CAP2, and one hydroalcoholic extract, CAP3) were comparatively investigated using an integrated phytochemical and biological approach. Phytochemical profiling by LC-DAD-ESI-MS/MS revealed a complex composition dominated by flavonol glycosides (mainly quercetin- and kaempferol-based derivatives), phenylpropanoid esters, and glucosinolates, which define the core chemical signature of caper fruits. While the extracts shared a largely overlapping qualitative profile, marked differences in relative metabolite abundance were related to the extraction solvent, the drug-to-extract ratio, and formulation parameters. The biological relevance of the extracts was evaluated using skin-related cellular models and antimicrobial assays. All extracts showed good cytocompatibility in human keratinocytes and preserved epithelial barrier integrity. Distinct, concentration-dependent effects were observed on intracellular ROS modulation, UVB-induced cellular senescence, collagen type I production in dermal fibroblasts, and antimicrobial activity. CAP1 exhibited the most pronounced antioxidant and antimicrobial effects, CAP2 showed intermediate and balanced activity, whereas CAP3 displayed a more complex redox behaviour combined with marked anti-senescent activity. Overall, these findings demonstrate that extraction strategy critically influences the biological performance of C. spinosa fruit extracts and support their potential as multifunctional dermocosmetic ingredients targeting skin homeostasis, photoaging, and the balance of the skin microbiome (including bacterial and fungal components).