Silybum Marianum (milk thistle): as Antioxidant, alleviating Pollution-InducedOxidative Stress in the presence of Heavy Metals contamination

Abstract

This study investigates the antioxidant response of Silybum marianum to oxidative stress induced by heavy metals (Cd, Pb, and As), focusing on the role of silymarin and associated defense mechanisms. Plants exposed to metal-contaminated soils showed a marked increase in reactive oxygen species (ROS: up to 6.55 ± 0.68 nmol/g FW) and malondialdehyde (MDA: up to 4.6 ± 0.39 nmol/g FW) levels as compare to control (ROS: 2.3 ± 0.32, MDA: 2 ± 0.71), indicating significant oxidative stress. However, this was met with a robust increase in antioxidant enzyme activities—superoxide dismutase (SOD: 60.5 ± 4.9 U/mg protein), catalase (CAT: 33.36 ± 2.81 U/mg protein)), and glutathione (GSH 6.05 ± 0.58 U/mg protein) in comparison with control (SOD: 34.1 ± 2.71 U/mg protein, CAT: 16.09± 1.25 U/mg protein, GSH: 3.65 ± 0.35µmol/g FW)—demonstrating the plant’s efficient stress mitigation capability. Notably, total silymarin content increased by up to 80% under arsenic exposure, suggesting its active role in neutralizing pollutants. These findings highlight S. marianum’s dual function as a resilient phytoremediator and a bioactive-rich medicinal plant. The plant's ability to maintain physiological stability while enhancing its phytochemical defense under heavy metal stress underscores its environmental and pharmacological significance.