Synergistic Anti-dementia Effects of Symplocos racemosa Nanoemulsion:Isolation, Molecular Docking, and In Vivo Evaluation

Introduction: Dementia, marked by a decline in mental abilities like memory that interferes with daily life, is primarily caused by Alzheimer's Disease (AD). Symplocos racemosa, rich in acetyl oleanolic acid, serves as a neuroprotective agent by lowering amyloid β levels in the brain. This study aims to develop a nanoemulsion for the targeted delivery of S. racemosa phytoconstituents to enhance therapeutic efficacy against dementia. The study also aims to find out the mechanism of the responsible molecules via molecular docking studies. Methods: S. racemosa bark was ultrasonically extracted with methanol and ethyl acetate, yielding six phytoconstituents: ellagic acid, betulinic acid, acetyl oleanolic acid, salireposide (from methanol), oleanolic acid, symlocoside (from ethyl acetate), isolated by column chromatography. Molecular docking against AChE and BACE-1 was conducted using CB Dock-2. A chitosan- based nanoemulsion containing all six compounds was prepared to enhance brain delivery and was physically characterized. All isolated phytoconstituents and nanoemulsions were evaluated for their in vitro enzyme inhibition (AChE and BACE-1) potential. Its anti-dementia efficacy was evaluated in scopolamine-induced rodent models using Hebb-Williams and Elevated Plus Maze tests, complemented by histopathological analysis of the brain cortex to assess therapeutic effects. Results: Docking studies showed acetyl oleanolic acid had stronger binding to BACE-1 and AChE than donepezil. This was further supported by an in vitro enzyme inhibition assay. Nanoemulsion at 200 and 400 mg/kg significantly reduced the time taken by memory-impaired mice to complete the Hebb-Williams Maze and transfer latency in the Elevated Plus Maze. Histopathological analysis showed a significant recovery of cortical damage. This indicates that the nanoemulsion has strong potential for the treatment of Alzheimer ’s-related neurodegeneration. Discussion: The neuroprotective action of S. racemosa nanoemulsion (SRMN) is attributed to the large-scale presence of its phytoconstituents, which reportedly exhibit a better binding affinity and inhibitory action against AChE and BACE-1 than donepezil. Additionally, the nanoemulsion enhanced bioavailability, stability, and blood-brain barrier penetration, which in turn improved therapeutic outcomes. From behavioral and histological studies, we observed that SRMN performed well in terms of memory improvement and cortical protection, suggesting that it is a very good multi-target approach for dementia. Conclusion: The prepared nanoemulsion from S. racemosa’s isolated phytoconstituents is reported to exhibit synergistic action, thereby effectively managing dementia through BACE-1 and AChE inhibition.