Integrated Pharmacological, Antimicrobial, Neuroprotective, and Behavioral Evaluation of Selected Medicinal Plants for the Management of Alzheimer's Disease

Abstract

Abstract: Background: Alzheimer's disease (AD) is a progressive neurodegenerative disorder and medicinal plants that could be used for inhibiting the enzymes that cause the disease, have antioxidant, neuroprotective, and cognitive supporting properties should be investigated. Objective: This study aimed to comparatively evaluate Bacopa monnieri, Withania somnifera, Curcuma longa, and Ginkgo biloba for pharmacological, antimicrobial, cellular neuroprotective, and behavioral effects relevant to experimental AD research. Methodology: The four medicinal plants were investigated for them in-vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activity, DPPH radical scavenging activity, and antimicrobial activity against Escherichia coli, Staphylococcus aureus and Candida albicans. The neuroprotective effect was evaluated by the MTT, reactive oxygen species (ROS), and malondialdehyde (MDA) assays on the cellular model of SH-SY5Y cell injury induced by hydrogen peroxide (H2O2). Ten rats per group were used to assess behavioral outcomes in a streptozotocin induced AD-like rat model in the Morris water maze, novel object recognition and open-field tests. Results: Ginkgo biloba demonstrated the strongest AChE inhibition (IC₅₀ = 104.0 µg/mL), whereas C. longa exhibited the greatest DPPH radical-scavenging activity (88.3%). C. longa produced inhibition zones of 14.9 mm, 17.5 mm, and 13.8 mm against E. coli, S. aureus, and C. albicans, respectively. In injured SH-SY5Y cells, C. longa increased viability to 79.6%, compared with 55.2% in the injury control, representing a 44.2% relative increase. In behavioral testing involving rats rather than human patients, its novel object recognition index reached 64.5%, compared with 43.5% in AD-model controls, while escape latency decreased to 25.9 seconds from 45.8 seconds. Conclusion: Curcuma longa showed the most promising overall experimental profile, but additional testing is required before it can be applied in clinical settings.