Citrus wastewater as a source of value-added products: Quali-quantitative analysis and in vitro screening on breast cancer cell lines.

Citrus wastewater from industries is a source of bioactive compounds whose recovery could be a useful approach to convert processing waste into potential resources to be exploited in food, pharmaceutical, and chemical companies. Citrus wastewater, obtained from the industrial processing of Citrus sinensis, was freeze-dried and qualitative/quantitative evaluated using HPLC/MS Q-TOF analysis. Antiproliferative activity was investigated on MDA-MB-231 (triple-negative breast cancer cell line), MCF-7 (breast cancer cell line), and its multidrug-resistant variant MCF-7R. Fraction 8 emerged for its cytotoxicity toward MCF-7R cells. Its main component, the polymethoxylated flavone nobiletin (80%), is likely involved in increasing the number of G1-phase MCF-7R cells without inducing cell death. Notably, fraction 8 sensitizes MCF7-R cells to the antiproliferative effects of doxorubicin, thus contributing to overcoming MCF7-R multidrug resistance. Our studies highlighted the possibility of applying a sustainable strategy for citrus wastewater recycling to recover functional compounds as useful adjuvants for the prevention and treatment of malignancies.