Development and characterization of plant oil-based potent anticholinesterase microemulsion containing withania somnifera extract with enhanced transdermal delivery of phytoconstituents for the treatment of cognitive disorders

Objective: This work was carried out to develop Cymbopogan Citratus (lemon grass)oil based microemulsion formulation loaded with the extract of Withania somnifera which possess enhanced transdermal delivery of phytoconstituents with anticholinesterase activity useful in treating Alzheimer’s disease. Methods: Methanolic extract of Withania somnifera roots were prepared and it was investigated for the inhibition of acetylcholinesterase (AChE) activity by Ellman’s assay. Based on the acetylcholinesterase activity, the specific amount of extract was loaded on to the microemulsion formulation. The Cymbopogan Citratus oil, tween 20, ethanol was used as oil phase, surfactant, and cosurfactant, respectively, for the preparation of microemulsion. Pseudo ternary phase diagram was constructed using a water titration method. The microemulsion formulations were characterized for droplet size, PDI, zeta potential and drug content. The optimized formulation was subjected to in vitro drug release and permeation studies and compared with the extract. Results: IC50 value of ashwagandha extract for anticholinesterase activity was found to be 68.73 µg/ml. The optimized microemulsion formulation had droplet size of 199.9±0.3 nm with PDI 0.029±0.2, zeta potential of-19.49±0.7mv and drug content was found to be 97.5±1.3%. The optimized microemulsion formulation showed 85±1.02% release of withaferin A after 24 h of in vitro drug release study. The prepared microemulsion loaded with ashwagandha extract showed excellent permeation of withaferin A(1.4µg/cm2/min) than the flux obtained from extract solution (0.7µg/cm2/min). Conclusion: Optimised microemulsion formulation is suitable for transdermal delivery of anticholinesterase phytoconstituents from ashwagandha extract hence useful in the treatment of Alzheimer’s disease