Neuroprotective Effects of Ethanolic Extract of Aloe Vera on Mercury-induced Damage in Rat Amygdala and Hippocampus: Histological and Docking Study

Abstract

Aim: Investigate the neuroprotective effects of ethanolic extract of Aloe vera (EEAV) on mercury chloride-induced damage in the amygdala and hippocampus of adult male Wistar rats, using histological and molecular docking approaches. Study Design: 35 rats were randomly assigned into five groups (n=7): Group A (control), Group B (5 mg/kg HgCl₂), Group C (500 mg/kg EEAV), Group D (5 mg/kg HgCl₂ + 250 mg/kg EEAV), and Group E (5 mg/kg HgCl₂ + 500 mg/kg EEAV). Place and Duration of Study: Department of Human Anatomy, Chukwuemeka Odumegwu Ojukwu University, Anambra State, Nigeria between March and April 2025. Methodology: Sample: 35 male Wistar Rats weighing between 200-230g were used for this         study. Acclimatized for 7 days and were randomly selected into five groups of seven animals each (A to E). Results Data was analyzed using S.P.S.S version 25 and results expressed as mean± S.E.M(P≤ .05). Y-maze results revealed significant impairments in spatial memory and locomotor activity in Group B, indicated by increased % alternation (30.13 ± 1.19, p = .02) and reduced number of entries (8.25 ± 0.75), compared to the control. Treatment with EEAV, particularly at 500 mg/kg, markedly improved cognitive performance (Group E: % alternation = 11.50 ± 1.62). Molecular docking revealed that Aloe vera compounds such as emodin, chrysophanol, aloe-emodin, and pomiferin showed strong binding affinities to key neuroprotective proteins. Emodin (−9.0 kcal/mol) and chrysophanol (−8.8 kcal/mol) bound effectively to the GABA receptor (PDB: 1M2Z) and serotonin transporter (PDB: 5XR8) in the amygdala, surpassing diazepam (−8.1 kcal/mol). Auriculasin (−7.5 kcal/mol) and pomiferin (−7.9 kcal/mol) also interacted strongly with BDNF (PDB: 1BND) and acetylcholinesterase (PDB: 1Q3W). Additional interactions with metallothioneins (MT-1, PDB: 1MHU; MT-2, PDB: 2MHU) suggest antioxidant and metal-chelating activities. Most compounds met Lipinski, Ghose, Veber, and Egan criteria, indicating good oral bioavailability. Histological analysis revealed neuronal degeneration in the hippocampus and amygdala of HgCl₂-exposed rats, while EEAV treatment preserved normal cytoarchitecture. Conclusion: This study reveals that Aloe vera may possess neuroprotective potential against mercury-induced neurotoxicity through bioactive compounds that exhibit strong receptor interactions and favorable drug-likeness properties.