Development and Assessment of Phytoconstituents-based Nanoemulsion as a Potent Combined Therapy for Neuroprotection in Scopolamine-induced Alzheimer’s Disease Rat Model

Introduction: Nanoemulsions are increasingly recognized as effective carriers for delivering neuroprotective agents in the management of neurodegenerative conditions like Alzheimer’s disease. Alzheimer’s Disease (AD) is a chronic and progressive neurological disorder marked by memory impairment, cognitive dysfunction, oxidative damage, and degeneration of neurons. This study focuses on designing and evaluating a nanoemulsion-based drug delivery system combining Resveratrol and Ginkgo biloba to investigate their potential neuroprotective effects in a scopolamine- induced Alzheimer’s model in Wistar rats. Methods: A total of nine water-in-oil nanoemulsion formulations (F1–F9) were developed using probe sonication and examined for various parameters, including droplet size, zeta potential, polydispersity index (PDI), entrapment efficiency, and in vitro drug release profiles. Results: Among these, Formulation F2, containing 25 mg of Resveratrol and 25 mg of Ginkgo biloba, showed the most favourable characteristics, including a high entrapment efficiency of 90.13%, maximum drug release of 92.33%, a particle size of 92.83 nm, and a zeta potential of 30.75 mV, suggesting good stability of the formulation. For the in vivo evaluation, rats were divided into six groups: normal control, negative control (scopolamine-treated), standard treatment group (Diazepam 2 mg/kg), and three test groups with different formulations. Behavioural studies using the Y-maze demonstrated that the Test Group 1 (treated with F2 formulation) had significantly improved spontaneous alternation behaviour, indicating enhanced cognitive performance. Biochemical analysis showed reduced malondialdehyde (MDA) levels and increased glutathione (GSH) levels, suggesting potent antioxidant activity. Additionally, histopathological examination of brain tissue revealed that the F2-treated group showed reduced neuronal damage and better preservation of hippocampal structure. Discussion: In rats treated with scopolamine, the optimized F2 nanoemulsion showed excellent physicochemical stability and markedly enhanced cognitive function. Strong antioxidant and neuroprotective effects of the combination formulation are indicated by decreased MDA levels, increased GSH levels, and intact hippocampus architecture. Conclusion: The Resveratrol–Ginkgo biloba nanoemulsion (F2) successfully reduced oxidative stress and cognitive impairment, indicating its potential as a treatment for early-stage Alzheimer's disease. Additional research is needed to confirm its therapeutic application.