Fermented Wild Chicory (Cichorium intybus L.) Leaves as a Promising Food Ingredient: Phytochemical Profile and Antioxidant Potential

Wild chicory (Cichorium intybus L.) is a spontaneous, widely distributed Mediterranean plant traditionally used in both food and herbal medicine, owing to its high content of bioactive compounds with antioxidant activity. Lactic acid fermentation is increasingly explored as a mild technological strategy to modulate the phytochemical and functional profile of vegetable matrices, but its effect on wild chicory leaves remains largely uncharacterised. In this study, fresh wild chicory leaves were subjected to controlled fermentation using inoculum suspensions containing 106 cells/mL Lactiplantibacillus plantarum, either alone or in co-culture with Saccharomyces cerevisiae (103 cells/mL), for 24 and 48 h at 37 °C. Fermentation with L. plantarum, alone or in co-culture, rapidly and significantly lowered the pH from approximately 5.5 to 4.3 within 24 h. A significant effect of time was observed for total flavonoid content, DPPH, FRAP, and ORAC, but not for total phenolic content. Averaged across treatments, flavonoid content decreased following fermentation, DPPH showed a transient increase at 24 h, FRAP was significantly lower at 48 h than at baseline, and ORAC increased at both fermented time points. Descriptive UPLC-DAD analysis of wild leaves revealed differences between unfermented and fermented sample for 24 h. Chicoric acid was detected only in the unfermented samples, whereas caffeic and 3,4-O-caffeoylquinic acids were detected in the fermented samples. Among flavonoids, kaempferol-3-O-glucoside, rutin, and luteolin were also detected, whose relative abundance varied following fermentation. These findings highlight distinct changes in the phytochemical profile and in vitro antioxidant capacity of wild chicory leaf extracts following fermentation, and support further investigation of fermented material as a potential food ingredient.