Effect of Hydro-Methanolic Extract of Macadamia Integrifolia Nuts on Oxidative Stress and Inflammatory Markers in Male Wistar Rats

Background: Oxidative stress and inflammation contribute to the pathogenesis of several chronic diseases. Bioactive compounds in tree nuts, including Macadamia integrifolia, may influence redox balance and inflammatory signalling. This study evaluated the effects of hydro-methanolic Macadamia integrifolia nut extract on oxidative stress and inflammatory markers in male Wistar rats.

Methods: Twenty-four male Wistar rats were randomly allocated into four groups (n = 6 per group): control, 250 mg/kg, 500 mg/kg, and 1000 mg/kg extract-treated groups. The extract was administered orally once daily for 28 days. At study completion, serum levels of catalase (CAT), superoxide dismutase (SOD), malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GPx), tumour necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), C-reactive protein (CRP), interleukin-10 (IL-10), and nuclear factor kappa B (NF-κB) were measured using standard spectrophotometric and ELISA methods. Statistical analysis was performed using one-way ANOVA with Tukey’s post hoc test.

Results: CAT and SOD activities showed no significant differences across all groups (p > 0.05). MDA levels were also comparable between control and treated groups, indicating no significant change in lipid peroxidation. In contrast, GSH levels decreased progressively with increasing extract dose, with significant reductions observed in the 500 mg/kg and 1000 mg/kg groups compared with the control (p < 0.05). GPx activity followed a similar dose-dependent decline, with significant reductions in the medium- and high-dose groups (p < 0.05). For inflammatory markers, TNF-α and IL-6 concentrations did not differ significantly among groups (p > 0.05). However, CRP levels were significantly lower in the 500 mg/kg and 1000 mg/kg groups compared with the control (p < 0.05). IL-10 and NF-κB concentrations also decreased significantly in the medium- and high-dose groups (p < 0.05), demonstrating a dose-dependent modulation of inflammatory signalling pathways.

Conclusion: Hydro-methanolic Macadamia integrifolia extract exerted selective, dose-dependent effects on glutathione-related antioxidant systems and inflammatory biomarkers without altering primary enzymatic antioxidants or lipid peroxidation.