Neurodegenerative diseases are hereditary or sporadic conditions that result in the progressive loss of the structure and function of neurons as well as neuronal death. Although a range of diseases lie under this umbrella term, Alzheimer's disease (AD) and Parkinson's disease (PD) are the most common neurodegenerative diseases that affect a large population around the globe. Alzheimer's disease is characterized by the abnormal accumulation of extracellular amyloid-β plaques and intraneuronal neurofibrillary tangles in brain regions and manifests as a type of dementia in aged individuals that results in memory loss, multiple cognitive abnormalities, and intellectual disabilities that interfere with quality of life. Since the discovery of AD, a wealth of new information has emerged that delineates the causes, mechanisms of disease, and potential therapeutic agents, but an effective remedy to cure the diseases has not been identified yet. This could be because of the complexity of the disease process, as it involves various contributing factors that include environmental factors and genetic predispositions. This review summarizes the current understanding on neurodegenerative mechanisms that lead to the emergence of the pathology of AD.

Plant extracts have gained popularity recently, for their importance as potential antioxidative and antimicrobial agents. These properties have been attributed to their phytochemical content. The extraction solvent and the plant part are among the factors that influence the yield of these phytochemicals This study was therefore undertaken to investigate the antimicrobial and antioxidant activities of extracts of the leaf and stem of Ocimum sanctum (holy basil) and Cymbopogon nardus (citronella grass); two commonly occurring plants in South East Asia. The extracts were obtained by solvent extraction using water, methanol and ethanol. The percentage yield, antimicrobial activity, antioxidant activity and high-performance liquid chromatography (HPLC) analysis was investigated. The organic extracts yielded a higher percentage recovery of phytochemicals compared to the water extracts.  HPLC analysis revealed the presence of chlorogenic acid in all extracts; rutin only in the leaf extracts and the citronella grass leaf extract contained both rutin and gallic acid. Antimicrobial assays were performed using the agar well diffusion method with tetracycline as positive control. Basil extracts exerted a greater inhibitory growth on both S. aureus and E. coli. S. aureus was found to be more susceptible to the presence of plant extracts. Water extracts did not display any zones of inhibition. The DPPH (2,2-diphenyl-1-picrylhydrazyl) assay was used to study the antioxidant effect with Vitamin C (0.1mg/ml) as positive control. The results indicated that the Basil leaf extracts possessed greater antioxidant potential compared to the stem. The study concludes that organic extracts of O. sanctum and C. nardus possess pharmaceutical properties.