*2.6. Effect of OPs on Hepatic Oxidative Indexes in Cd-Exposed Mice*

An increased MDA level is an important indicator of oxidative stress. The Cd-exposed mice group showed the highest levels of hepatic MDA, while the OPs treatment significantly lowered the level of MDA (*p* < 0.01, Figure 4A). More importantly, the effects of OPs were better than that of EDTA. OPs markedly inhibited lipid peroxidation (MDA as an indicator) and MDA production in Cd-exposed mice. As shown in Figure 4B–D, antioxidant markers such as SOD, CAT, and GSH-Px were significantly reduced in the Cd-exposed mice group compared to the control group. OPs retained higher activity of antioxidant enzymes in Cd-exposed mice. OPs exhibited a strong reductive effect on Cd-induced oxidative stress in the liver.

**Figure 4.** Effects of OPs on MDA level, SOD, CAT, and GSH-Px activities in Cd-induced mice. (**A**) Malondialdehyde (MDA); (**B**) Superoxide dismutase (SOD); (**C**) Catalase (CAT); (**D**) Glutathione peroxidase (GSH-Px). The data were expressed as mean ± SEM, *n* = 6 in each group. Compared with the control group, \*\* *p* < 0.01; compared with the Cd group, # *p* < 0.05, ## *p* < 0.01.
