Protective effects of Morus alba L. leaf polyphenols against paraquat-induced apoptosis in macrophages

Context: Paraquat (PQ) induces cytotoxicity primarily through the generation of intracellular reactive oxygen species (ROS), leading to apoptosis. Morus alba L. leaves are rich in polyphenols and known for their potent antioxidant properties. Aims: To quantify the total phenolic content, antioxidant capacity, and antioxidant activity of polyphenol extracts from Morus alba L. leaves (PEFML) and evaluate their protective effect against PQ-induced cytotoxicity in RAW264.7 macrophages. Methods: Total phenolic content, total antioxidant capacity, and antioxidant activity of PEFML were assessed using standard in vitro assays. RAW264.7 macrophages were pretreated with PEFML for 24 hours prior to exposure to PQ (0.8 mM) for an additional 24 hours. Subsequently, cell viability, apoptosis, intracellular ROS generation, and the Bax/Bcl-2 mRNA expression ratio were analyzed. Results: PEFML demonstrated significant antioxidant activity, as indicated by high phenolic content and strong antioxidant capacity. PEFML at concentrations ranging from 1.2 to 9.6 µg/mL exhibited no cytotoxicity in RAW264.7 cells. Notably, PEFML significantly suppressed intracellular ROS generation, particularly at 2.4 and 4.8 µg/mL concentrations. Pre-treatment with PEFML effectively reduced PQ-induced apoptosis in RAW264.7 macrophages by modulating the Bax/Bcl-2 ratio. Conclusions: These findings suggest that PEFML exerts a cytoprotective effect against PQ-induced apoptosis in RAW264.7 macrophages, likely through the attenuation of oxidative stress and regulation of apoptotic signaling pathways.