Protective Antioxidant Effects of Azadirachta indica Extract in Retina Tissue of a Diabetic Rat Model
Anuoluwapo Ilegomah *
Department of Biochemistry, Lead City University, Ibadan, Nigeria.
Osasenaga Ighodaro
Department of Biochemistry, Lead City University, Ibadan, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Aims: The present study aimed to evaluate the protective antioxidant effects of ethanol leaf extract of Azadirachta indica (A.I) leaves in the retina of streptozotocin (STZ)-induced diabetic rats.
Study Design: This research was an experimental, randomized, controlled in vivo study.
Place and Duration of Study: Department of Biochemistry, Lead City university, Ibadan, Nigeria, between September 2024 and July 2025.
Methodology: Diabetes was induced in male Wistar rats by a single intraperitoneal injection of STZ (55 mg/kg). Diabetic rats were treated daily with A.I leaf extract at doses of 200 and 400 mg/kg for 21 days. Metformin (70 mg/kg) served as a positive control, while untreated diabetic rats served as negative control, and non-diabetic rats served as normal control groups. Retinal homogenates were assayed for malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD) activity, catalase (CAT) activity, and total protein using standard colorimetric/kit methods. Fasting blood glucose (FBG) was monitored. Data were analyzed by one-way ANOVA followed by Tukey's post hoc test (P < 0.05).
Results: Streptozotocin-induced diabetes (n = 5 per group) significantly increased retinal malondialdehyde (MDA) from 2.115 ± 0.03175 to 2.292 ± 0.00354 μM and reduced total protein from 29.30 ± 1.68 to 17.95 ± 1.68 mg/g tissue (P < 0.05). Antioxidant markers also declined, including glutathione (GSH) (1.594 ± 0.4791 to 0.6349 ± 0.1350 mM), superoxide dismutase (SOD) (0.02875 ± 0.00984 to 0.002622 ± 0.00016 U/mg), and catalase (CAT) (6.179 ± 0.505 to 1.615 ± 0.684 U/mg) (P < 0.05). Treatment with A.I extract (200 mg/kg) reduced MDA to 2.069 ± 0.01343 μM and restored SOD (0.02957 ± 0.01220 U/mg) and CAT (4.083 ± 0.812 U/mg) toward control levels (P < 0.05 vs. diabetic), with partial recovery of GSH (0.6979 ± 0.02581 mM) and total protein (25.22 ± 2.21 mg/g tissue). The 400 mg/kg dose showed moderate effects, while metformin produced comparable improvements across all parameters. Although all treatments significantly improved oxidative stress markers compared with the untreated diabetic group (P < 0.05), no statistically significant differences were observed between the extract-treated groups and metformin (P > 0.05), indicating comparable efficacy.
Conclusion: Ethanol extract of A.I leaves exerts significant antioxidant protection in the diabetic retina by attenuating lipid peroxidation, restoring enzymatic and non-enzymatic antioxidant defenses, and preserving retinal protein integrity. These findings support its potential as an affordable natural therapeutic agent for mitigating oxidative stress in early diabetic retinopathy, warranting further mechanistic, dose-optimization, and translational studies.
Keywords: Azadirachta indica, diabetic retinopathy, oxidative stress, streptozotocin, antioxidant enzymes