Kombucha Ferments from White and Red Cabbage By-Products as a Sustainable Source of Metabolites with Antioxidant and Anti-Inflammatory Activity

var. capitata) is a widely cultivated vegetable rich in bioactive compounds, but its industrial processing generates significant underutilized by-products, especially cabbage cores. This often-discarded fraction represents a promising and sustainable source of valuable functional components with potential applications in food systems. The study evaluated the biological activity of extracts and kombucha ferments obtained from the leaves and cores of white and red cabbage. Antioxidant capacity was assessed using ABTS, DPPH, and FRAP assays, while intracellular reactive oxygen species (ROS) levels were evaluated in a cell-based model. Cytotoxicity was determined using fibroblast and keratinocyte cell lines with Alamar Blue and Neutral Red assays. Anti-inflammatory activity was assessed by measuring the levels of the cytokines (IL-1β and IL-6) using ELISA, and antimicrobial effects were tested against bacteria associated with skin inflammation. The results showed that fermented white and red cabbage extracts have stronger antioxidant, anti-inflammatory, and antimicrobial effects than unfermented extracts, with the best results observed after 20 days of fermentation. Low concentrations have a beneficial effect on skin cell viability, while higher concentrations result in reduced viability. These results highlight the potential of kombucha-fermented cabbage leaves and cores as a versatile and sustainable source of bioactive compounds for health-promoting applications.