Bioactivity of Ribes nigrum L. Juice and Waste Extracts: Chemical Composition, Antioxidant, and Antiproliferative Properties.

This study aimed to assess phytochemical profiles and antioxidant activities of lyophilized black currant fruit juice (BCLJ) and its corresponding waste extract (BCLW) from the Čačanska crna variety, and to evaluate their antiproliferative properties. The main anthocyanins quantified through HPLC-DAD analysis were delphinidin-3-O-rutinoside and cyanidin-3-O-rutinoside, with significantly higher levels in BCLW. Antioxidant activity was examined using the DPPH and β-carotene/linoleic acid methods, with BCLW showing superior effects in both. Antiproliferative potential was evaluated by determining the Ki67 index in renal epithelial cells of rats treated with BCLJ or BCLW. Thirty healthy male rats were randomly assigned to five groups (n = 6) and administered BCLJ or BCLW orally for ten days, receiving 100, 200, and 300 mg/kg b.w. of BCLW (BCLW1, BCLW2, and BCLW3 groups, respectively) or 200 mg of BCLJ. Histopathological and immunohistochemical parameters were assessed in rats' kidneys. Across all epithelial types (cortical proximal tubules, distal medullary proximal tubules, collecting ducts, and urothelial cells of the renal pelvis), the highest Ki67 indices were observed in control animals, particularly in collecting ducts and cortical proximal tubules. The lowest Ki67 values in cortical proximal tubules occurred in the BCLW2 group (p < 0.05 vs. control). These findings suggest that black currant preparations could be valuable functional ingredients.