Allicin, an Antioxidant and Neuroprotective Agent, Ameliorates Cognitive Impairment

Abstract

Allicin (diallylthiosulfinate) is a defense molecule produced by cellular contents of garlic (Allium sativum L.). On tissue damage, the non-proteinogenic amino acid alliin (S-allylcysteine sulfoxide) is converted to allicin in an enzyme-mediated process catalysed by alliinase. Allicin is hydrophobic in nature, can efficiently cross the cellular membranes and behaves as a reactive sulfur species (RSS) inside the cells. It is physiologically active molecule with the ability to oxidise the thiol groups of glutathione and between cysteine residues in proteins. Allicin has shown anticancer, antimicrobial, antioxidant properties and also serves as an efficient therapeutic agent against cardiovascular diseases. In this context, the present review describes allicin as an antioxidant, and neuroprotective molecule that can ameliorate the cognitive abilities in case of neurodegenerative and neuropsychological disorders. As an antioxidant, allicin fights the reactive oxygen species (ROS) by downregulation of NOX (NADPH oxidizing) enzymes, it can directly interact to reduce the cellular levels of different types of ROS produced by a variety of peroxidases. Most of the neuroprotective actions of allicin are mediated via redox-dependent pathways. Allicin inhibits neuroinflammation by suppressing the ROS production, inhibition of TLR4/MyD88/NF-κB, P38 and JNK pathways. As an inhibitor of cholinesterase and (AChE) and butyrylcholinesterase (BuChE) it can be applied to manage the Alzheimer’s disease, helps to maintain the balance of neurotransmitters in case of autism spectrum disorder (ASD) and attention deficit hyperactive syndrome (ADHD). In case of acute traumatic spinal cord injury (SCI) allicin protects neuron damage by regulating inflammation, apoptosis and promoting the expression levels of Nrf2 (nuclear factor erythroid 2-related factor 2). Metal induced neurodegeneration can also be attenuated and cognitive abilities of patients suffering from neurological diseases can be ameliorates by allicin administration.

Evaluation of the Effect of Garlic Tablet as a Complementary Treatment for Patients with Diabetic Retinopathy

“…It has also been shown that the antiangiogenic effect of garlic compounds is due to its inhibitory effect on particular signaling pathways in nondiabetic cell models, including VEGF, AKT/ERK, and NO pathways [27]. Moreover, several reports are indicating the neuroprotective and neuroregenerative effects of garlic [28][29][30][31]. Accordingly, garlic is suggested to enhance the antiangiogenic effect of intravitreal anti-VEGF agents, protect the neural retina from oxidant damages, suppress the inflammation process that is responsible for the pathogenesis of DME, and can be an effective complementary treatment in the management of diabetic retinopathy.…”

Therapeutic Potential of Allicin and Aged Garlic Extract in Alzheimer’s Disease

“…Alliinase and alliin form an enzyme-substrate complex in the presence of water, at an optimum temperature of 33 • C and pH of 6.5. Indeed, the enzyme is sensitive to acids, suggesting the employment of enteric-coated formulations of garlic supplements [11,31,32]. Allicin (the most abundant thiosulfinate formed via allinase reactions, approximately 70%) is poorly soluble in water and is responsible for a pungent and unpleasant flavor, but it is very unstable and easily transformed into a high number of products, classified as oilsoluble compounds, mainly including dithiins (formed by the dimerization of thioacrolein created via allicin β-elimination), followed by ajoene, allyl methyl trisulfide (AMTS), diallyl sulfide (DAS), diallyl disulfide (DADS), and diallyl trisulfide (DATS).…”

“…Recently, the healthy properties of allicin have been widely characterized in terms of neuroprotection for AD therapy [11,88]. A comparison between raw and steamed garlic has been performed in terms of anti-inflammatory activities in LPS-stimulated BV2 microglial cells.…”

“…In ancient times, garlic was frequently used as a remedy for intestinal disorders, flatulence, worms, respiratory infections, skin diseases, wounds, symptoms of aging and many other ailments, and abundant literature supports the health-promoting effects of garlic and its by-products, which are associated with the bioactive compounds present in their matrix [3][4][5]. It has been used to reduce triglycerides and low-density cholesterol in the human body [6,7], to lower blood pressure [8], for antithrombotic activity [9], and to increase blood insulin levels [10,11]. In recent years, garlic organosulfur derivatives and garlic supplements have been shown to negatively affect the growth of tumor cells and the risk of cancer [12][13][14][15][16][17][18][19].…”

Structured Long-Chain Omega-3 Fatty Acids for Improvement of Cognitive Function during Aging

“…As the brain is highly susceptible to oxidative damage, it has been suggested that inadequate antioxidant defences might mediate the pathogenesis and progression of dementia [ 61 ]. Many antioxidant nutrients such as vitamin C, vitamin E [ 62 ], zinc [ 63 ] (cofactor for enzymes with antioxidative activity) and carotenoids [ 64 ], and non-nutrient food ingredients like polyphenols [ 65 ], anthocyanins [ 66 ], lignans [ 67 ] or allicin [ 68 ] have been proven to be beneficial for age-related cognitive impairment. But, as far as there is not a deficit of the mentioned nutrients or a pathological situation, clinical trials with supplementation of these mentioned antioxidant compounds have not demonstrated a beneficial effect on any cognitive outcome in healthy patients [ 10 ].…”