Effects of Hydro-Methanolic Extract of Macadamia Nuts on Haematological Parameters in Male Wistar Rats

Background: To evaluate the effects of the hydro-methanolic extract of Macadamia integrifolia nuts on haematological parameters in male Wistar rats. Methods: The study employed an experimental, controlled laboratory study using a dose–dependent treatment model. The study was conducted in an animal house of the Department of Human Physiology, Rivers State University, Nigeria. Twenty-four male Wistar rats were randomly assigned into four groups (n=6 per group): control, low dose (250 mg/kg), medium dose (500 mg/kg), and high dose (1000 mg/kg) of hydro-methanolic Macadamia integrifolia nuts extract. The extract was administered daily for 28 days. Wistar rats received daily administration of hydro-methanolic extract of Macadamia integrifolia nuts for 28 days. Standard haematological parameters were analysed using established laboratory methods. Data were expressed as mean ± SEM, and statistical significance was set at P < 0.05. Results: Significant dose-dependent alterations were observed in erythrocyte indices. The low-dose group showed marked reductions in packed cell volume (33.0 ± 0.6% vs 45.3 ± 1.5%), haemoglobin (11.0 ± 0.2 g/dL vs 15.1 ± 0.5 g/dL), and red blood cell count (5.0 ± 0.3 ×10⁶/µL vs 6.7 ± 0.1 ×10⁶/µL) compared with control (P < 0.05). The medium dose partially attenuated these reductions. In contrast, the high dose restored packed cell volume (44.3 ± 1.5%), haemoglobin (14.97 ± 0.7 g/dL), and red blood cell count (6.02 ± 0.1 ×10⁶/µL) to values comparable with control. Mean corpuscular haemoglobin increased significantly at low and medium doses, while mean corpuscular haemoglobin concentration remained unchanged across groups. Mean corpuscular volume decreased at low and medium doses but increased at the high dose. White blood cell count was significantly elevated at the high dose (13.57 ± 1.1 ×10³/µL) relative to control (10.8 ± 1.0 ×10³/µL; P < 0.05), whereas platelet count and differential leukocyte percentages showed no significant differences. Conclusion: Hydro-methanolic Macadamia integrifolia nuts extract exerted biphasic, dose-dependent effects on haematological parameters, with low doses associated with erythrocyte suppression and higher doses restoring erythroid indices and increasing total leukocyte count.