Physical and Neurobehavioural Effects of Mentha piperita Ethanolic Leaf Extract on Mercury Intoxicated Wistar Rats

Abstract

Mercury is a persistent environmental toxicant with significant neurotoxic effects, posing serious health risks due to its bioaccumulation and toxicity in various forms—elemental, inorganic, and organic. This study reviews mercury’s toxicological profiles, exposure pathways, and mechanisms of action. Major sources of exposure include contaminated seafood and occupational hazards like dental amalgams. Methylmercury, the most hazardous form, crosses both the blood-brain and placental barriers, severely impacting fetal neural development. Clinical symptoms range from paraesthesia and ataxia to seizures and coma, while inorganic mercury primarily targets renal function via immune-mediated damage. Mercury toxicity mechanisms include oxidative stress, thiol-protein disruption, mitochondrial dysfunction, and calcium imbalance. The review also evaluates the controversial use of ethylmercury (thimerosal) in vaccines, advocating for caution in sensitive populations. In addition, this study examines the protective and therapeutic potential of ethanolic leaf extract of Mentha piperita (ELEMP) against mercury chloride (HgCl₂)-induced neurotoxicity in Wistar rats. Eight groups were analyzed, including control, HgCl₂-only, and various ELEMP-treated groups (400, 800, 1600 mg/kg). ELEMP-treated rats showed significant body weight gains and partial recovery of cerebral and cerebellar weights compared to HgCl₂-only rats. Notably, the 400 mg/kg ELEMP + HgCl₂ group showed significant improvement in cerebellar weight (p=0.048). Neurobehavioral tests indicated HgCl₂ impaired motor coordination and spatial learning, while ELEMP, particularly at 800 mg/kg, significantly improved performance in both motor (p=0.026) and cognitive (p=0.027) tasks. These findings suggest Mentha piperita extract may offer neuroprotection against mercury-induced toxicity.