Role of garlic and onion for better cognition and maintenance of neurodegenerative diseases

A wide variety of acute and chronic neurodegenerative diseases, including Alzheimer's disease (AD), and Parkinson's disease (PD), and ischemic/traumatic brain injury etc. share common characteristics, such as oxidative stress, misfolded proteins, excitotoxicity, neuroinflammation, and neuronal loss. Because no drugs are available to prevent the progression of these neurological disorders, intervention strategies using phytochemicals may show promise as an alternative form of treatment. Modulation of endogenous cellular defence mechanisms represents an innovative approach to therapeutic intervention in diseases causing chronic tissue damage, such as in neurodegeneration. In several in vitro and in vivo studies, the phytochemicals of garlic and onion have dem¬onstrated significant neuroprotective effects. The garlic (Allium sativum L.) contains diverse phytoconstituents namely sulfur containing water-soluble compounds [cysteine derivatives such as S-allyl cysteine (SAC), S-allyl mercaptocysteine (SAMC), and S-methyl cysteine (SMC)]; lipid-soluble compounds such as diallyl sulfide (DAS), diallyl disulfide (DADS), diallyl trisulfide (DATS), allyl methyl trisulfide (AMTS), dithiins, and ajoene isomers, which are used as nutraceuticals. It also contains various enzymes such as allinase, peroxidase, and miracynase), carbohydrates (sucrose and glucose), minerals (selenium), amino acids (such as cysteine, glutamine, isoleucine, and methionine), and vitamins (C, E, and A). The presence of bioflavonoids (quercetin and cyanidin, allistatin I, and allistatin II) and vitamins (C, E, and A) in garlic also protects from oxidation agents and free radicals. Similarly, Onion (Allium cepa) contains flavonoids and sulfur-containing com¬pounds like dipropyl sulfide, dipropyl disulfide, dipropenyl sulfide, and dipropenyl disulfide are the best-known organosulfur substances, responsible for the neuroprotective effect.