Neuroprotective Effects of Garlic : A Review

Garlic has been investigated extensively for health benefits; resulting in more than one thousand publications over the last decade alone. It is considered one of the best disease preventive foods; based on its potent and varied effects. Midlife risk factors for cardiovascular diseases; such as high serum total cholesterol; raised LDL; increased LDL oxidation; increased platelet aggregation; impaired fibrinolysis; hypertension and homocystinemia are important risk factors for dementia in later years. These risk factors play a major role in the genesis of atherosclerosis of vital arteries causing both cardiovascular and cerebrovascular disease. Garlic is best known for its lipid lowering and anti-atherogenic effects. Possible mechanisms of action include inhibition of the hepatic activities of lipogenic and cholesterogenic enzymes that are thought to be the genesis for dyslipidemias; increased excretion of cholesterol and suppression of LDL-oxidation. Oxidative stress caused by increased accumulation of reactive oxygen species (ROS) in cells has been implicated in the pathophysiology of several neurodegenerative diseases including Alzheimer's disease (AD). Several studies have demonstrated the antioxidant properties of garlic and its different preparations including Aged Garlic Extract (AGE). AGE and S-allyl-cysteines (SAC); a bioactive and bioavailable component in garlic preparations have been shown in a number of in vitro studies to protect neuronal cells against beta-amyloid (A ) toxicity and apoptosis. Thus the broad range of anti-atherogenic; antioxidant and anti-apoptotic protection afforded by garlic may be extended to its neuroprotective action; helping to reduce the risk of dementia; including vascular dementia and AD

Neuroprotective Effects of Garlic: A Review

Garlic has been investigated extensively for health benefits; resulting in more than one thousand publications over the last decade alone. It is considered one of the best disease preventive foods; based on its potent and varied effects. Midlife risk factors for cardiovascular diseases; such as high serum total cholesterol; raised LDL; increased LDL oxidation; increased platelet aggregation; impaired fibrinolysis; hypertension and homocystinemia are important risk factors for dementia in later years. These risk factors play a major role in the genesis of atherosclerosis of vital arteries causing both cardiovascular and cerebrovascular disease. Garlic is best known for its lipid lowering and anti-atherogenic effects. Possible mechanisms of action include inhibition of the hepatic activities of lipogenic and cholesterogenic enzymes that are thought to be the genesis for dyslipidemias; increased excretion of cholesterol and suppression of LDL-oxidation. Oxidative stress caused by increased accumulation of reactive oxygen species (ROS) in cells has been implicated in the pathophysiology of several neurodegenerative diseases including Alzheimer's disease (AD). Several studies have demonstrated the antioxidant properties of garlic and its different preparations including Aged Garlic Extract (AGE). AGE and S-allyl-cysteines (SAC); a bioactive and bioavailable component in garlic preparations have been shown in a number of in vitro studies to protect neuronal cells against beta-amyloid (A ) toxicity and apoptosis. Thus the broad range of anti-atherogenic; antioxidant and anti-apoptotic protection afforded by garlic may be extended to its neuroprotective action; helping to reduce the risk of dementia; including vascular dementia and AD

Cholesterol-lowering effect of organosulphur compounds from garlic: a possible mechanism of action.

OBJECTIVES: Hyperlipidemia constitutes a major etiopathological factor for atherosclerosis. The medicinal value of garlic is best known for its lipid lowering effects and antiatherogenic effects. The mechanism by which lipid soluble organosulphur compounds from garlic reduce plasma lipids has not been fully investigated. The author had previously shown that the hepatic activity of beta-hydroxy-beta-methylglutaryl-CoA (HMG-CoA) reductase, the rate limiting enzyme in cholesterol biosynthesis and the incorporation of radiolabeled (1, 2 14C), acetate into hepatic free and esterified cholesterol was significantly decreased in rat treated with garlic derived organosulphur compounds. We hypothesised that the antiatherogenic effect of the organosulphur compounds may be attributed to the formation of protein internal disulphide and thus inactivation of thiol (-SH) group enzymes such as HMG-CoA reductase and the multienzyme complex of fatty acid synthesis. The objective of the present study is to elucidate the inhibitory mechanism by in vitro studies. METHOD: Lipid soluble organosulphur compounds from garlic were treated in vitro with Luke's cysteine reagent (representing the thiol (-SH) group of enzymes) and the interaction products were separated by paper chromatography. RESULT: The result indicated that the organosulphur compounds were capable of interacting with the thiol (-SH) group of cysteine and thus forming cysteine derivatives. CONCLUSION: The antiatherogenic effects of these organosulphur compounds can be attributed to such reactions that inhibit HMG-CoA reductase and other lipogenic enzymes. The anticarcinogenic effects of these compounds may also be due to inhibitory reactions on enzymes that activate carcinogens.

Antioxidant effect of two flavonoids from the bark of Ficus bengalensis Linn in hyperlipidemic rats.

Two flavonoid compounds, viz. 5,7-dimethyl ether of leucopelargonidin 3-0-alpha-L rhamnoside and 5,3'-dimethyl ether of leucocyanidin 3-0-alpha-D galactosyl cellobioside obtained from the bark of F. bengalensis were evaluated for their antioxidant action in hyperlipidemic rats. The results were compared with the activity of a structurally similar flavonoid, quercetin, a known antioxidant. The Ficus compounds showed significant antioxidant effects which may be attributed to their polyphenolic nature. The methylation of two hydrozyl groups in the Ficus flavonoids might have slowed down their antioxidant action as compared to quercetin.

Hypolipidemic effect of garlic protein substituted for casein in diet of rats compared to those of garlic oil.

Garlic (Allium sativum Linn.) is ascribed with many therapeutic effects. For the present study, the water soluble proteins and the essential oil of garlic were investigated for their hypolipidemic effect on hyperlipidemia induced by cholesterol containing diet in albino rats. Both garlic protein (16% of diet) and garlic oil (100 mg/kg body weight/day) exhibited significant lipid lowering effects. The hypolipidemic action is primarily due to a decrease in hepatic cholesterogenesis in the treated rats. Even though garlic oil was found to be more effective, the garlic protein is more palatable and free from an obnoxious smell.

Biochemical effects of garlic protein diet and garlic oil on glycosaminoglycan metabolism in cholesterol fed rats.

Garlic protein diet or daily administration of garlic oil to 2% cholesterol fed rats controlled significantly the increases in sulphated glycosaminoglycans in their heart and aorta. However hyaluronic acid level increased. UDPG dehydrogenase decreased and several degrading enzymes increased in the aorta on treatment. The effects of treatment were just the reverse in liver. The high percentage of cysteine in garlic protein and the reactive disulphide group in the oil may be responsible for their beneficial effects.

Antidiabetic and hypolipidemic effects of S-methyl cysteine sulfoxide isolated from Allium cepa Linn.

S-methyl cysteine sulphoxide (SMCS), a sulphur containing amino acid isolated from onion (Allium cepa Linn) showed antidiabetic and antihyperlipidemic effects. Oral administration of SMCS daily at a dose of 200 mg/kg body weight for a period of 45 days to alloxan diabetic rats controlled significantly their blood glucose and lipids in serum and tissues and altered the activities of liver hexokinase, glucose 6-phosphatase and HMG CoA reductase towards normal. The above effects of SMCS were comparable to those of glibenclamide and insulin.

Hypoglycemic effects of leucodelphinidin derivative isolated from Ficus bengalensis (Linn).

A Leucodelphinidin derivative isolated from the bark of Ficus bengalensis Linn demonstrated hypoglycemic action at a dosage of 250 mg/kg given both in normal and alloxan diabetic rats. It's action is closely similar to that of an effective dose of glibenclamide (2 mg/kg) tested under the same conditions. However, after a glucose load the plant product is only just significantly active but not as effective as the sulphonylurea. The efficacy of the plant product as a hydroglycemic agent adds to its other therapeutic effects, as it belongs to the class of flavonoids.