Allicin

The bulb of Allium sativum L.

Allicin from garlic strongly inhibits cysteine proteinases and cytopathic effects of Entamoeba histolytica.[Pubmed:9333064]

Antimicrob Agents Chemother. 1997 Oct;41(10):2286-8.

The ability of Entamoeba histolytica trophozoites to destroy monolayers of baby hamster kidney cells is inhibited by Allicin, one of the active principles of garlic. Cysteine proteinases, an important contributor to amebic virulence, as well as alcohol dehydrogenase, are strongly inhibited by Allicin.

Allicin induces apoptosis of the MGC-803 human gastric carcinoma cell line through the p38 mitogen-activated protein kinase/caspase-3 signaling pathway.[Pubmed:25523417]

Mol Med Rep. 2015 Apr;11(4):2755-60.

Gastric cancer is one of the most common forms of malignant tumor, and the development of antigastric cancer drugs with minimal toxicity is of clinical importance. Allicin is extracted from Allium sativum (garlic). Recent research, including clinical experiments, has shown that garlic has anticancer and tumor suppressive effects. The present study aimed to investigate the effects of Allicin on the MGC803 human gastric carcinoma cell line, and to further explore the possible mechanisms of its tumor suppressor effects. The effects of Allicin on the MGC803 cells were initially examined using an 3(4,5dimethylthiazol2yl)2,5diphenyltetrazolium bromide assay. Hoechst staining was also used, in order to demonstrate the impact of Allicin on MGC803 cell apoptosis. In addition, western blot analysis was performed to determine the abnormal expression levels of apoptosisassociated proteins, following the treatment of MGC803 cells with Allicin. Western blotting was also used to investigate the specific mechanisms underlying Allicininduced apoptosis of MGC803 cells. The rate of MGC803 apoptosis was significantly increased, when the concentration and treatment time of Allicin were increased. Hoechst staining detected an enhanced rate of apoptosis, and enhanced expression levels of cleaved caspase 3 were determined by western blotting. Notably, the protein expression levels of p38 were increased when the MGC803 cells were treated with Allicin. The results of the present study suggest that Allicin may inhibit the proliferation and induce the apoptosis of MGC803 human gastric carcinoma cells, and this may partially be achieved through the enhanced expression of p38 and cleaved caspase 3.

Allicin from garlic inhibits the biofilm formation and urease activity of Proteus mirabilis in vitro.[Pubmed:25837813]

FEMS Microbiol Lett. 2015 May;362(9). pii: fnv049.

Several virulence factors contribute to the pathogenesis of Proteus mirabilis. This study determined the inhibitory effects of Allicin on urease, hemolysin and biofilm of P. mirabilis ATCC 12453 and its antimicrobial activity against 20 clinical isolates of P. mirabilis. Allicin did not inhibit hemolysin, whereas it did inhibit relative urease activity in both pre-lysed (half-maximum inhibitory concentration, IC50 = 4.15 mug) and intact cells (IC50 = 21 mug) in a concentration-dependent manner. Allicin at sub-minimum inhibitory concentrations (2-32 mug mL(-1)) showed no significant effects on the growth of the bacteria (P > 0.05), but it reduced biofilm development in a concentration-dependent manner (P < 0.001). A higher concentration of Allicin was needed to inhibit the established biofilms. Using the microdilution technique, the MIC90 and MBC90 values of Allicin against P. mirabilis isolates were determined to be 128 and 512 mug mL(-1), respectively. The results suggest that Allicin could have clinical applications in controlling P. mirabilis infections.

Allicin enhances chemotherapeutic response and ameliorates tamoxifen-induced liver injury in experimental animals.[Pubmed:24646302]

Pharm Biol. 2014 Aug;52(8):1009-14.

CONTEXT: Tamoxifen (TAM) is widely used for treatment of hormone-dependent breast cancer; however, it may be accompanied with hepatic injury. Allicin is the most abundant thiosulfinate molecule from garlic with the potential to provide beneficial effects on various diseases. OBJECTIVE: To elucidate the effect of commercially available Allicin on both antitumor activity and liver injury of TAM. MATERIALS AND METHODS: The cytotoxicity of TAM and/or Allicin was evaluated in vitro using cultured Ehrlich ascites carcinoma (EAC) cells and in vivo against murine tumor (solid) model of EAC. TAM induced liver injury in rats by intraperitoneally (i.p.) injection at a dose of 45 mg/kg, for 7 successive days. RESULTS: TAM at a dose of 3 microM (IC50) significantly decreased percent survival of EAC to 52%. TAM combination with Allicin (5 or 10 microM) showed a significant cytotoxic effect compared with the TAM-treated group as manifested by a decrease in percent survival of EAC to 35% and 29%, respectively. Allicin (10 mg/kg, orally) enhanced the efficacy of TAM (1 mg/kg, i.p.) in mice as manifested by a significant increase in solid tumor growth inhibition by 82% compared with 70% in the TAM group. In rats, TAM intoxication resulted in a significant decline in SOD, GSH, and total protein with significant elevation in TBARS, ALT and AST, ALP, LDH, total bilirubin, gammaGT, and TNF-alpha levels. These changes are abrogated by Allicin treatment. DISCUSSION AND CONCLUSION: The results suggest the beneficial role of Allicin as an adjuvant to TAM in cancer treatment by alleviating liver injury.

Allicin inhibits spontaneous and TNF-alpha induced secretion of proinflammatory cytokines and chemokines from intestinal epithelial cells.[Pubmed:15380914]

Clin Nutr. 2004 Oct;23(5):1199-208.

BACKGROUND & AIMS: Allicin, the active substance of fresh crushed garlic has different biological activities and was implicated as an anti-inflammatory agent. Epithelial cells have an important role in intestinal inflammation. The aim of this study was to assess the immunomodulatory effect of Allicin on intestinal epithelial cells. METHODS: The spontaneous and TNF-alpha-stimulated secretion of IL-1beta, IL-8, IP-10 and MIG from HT-29 and Caco-2 cells was tested with, or without pretreatment with Allicin. Cytokine secretion was assessed using ELISA and expression of mRNA was determined by an RNA protection assay. RESULTS: Allicin markedly inhibited the spontaneous and TNF-alpha -induced secretion of IL-1beta, IL-8, IP-10 and MIG from the two different cell lines in a dose-dependent manner and suppressed the expression of IL-8 and IL-1beta mRNA levels. In addition, Allicin suppressed the degradation of IkappaB. No effect on cell viability was noted. CONCLUSIONS: These observations indicate that Allicin exerts an inhibitory immunomodulatory effect on intestinal epithelial cells and suggest that Allicin may have the potential to attenuate intestinal inflammation.

Allicin protects rat cardiomyoblasts (H9c2 cells) from hydrogen peroxide-induced oxidative injury through inhibiting the generation of intracellular reactive oxygen species.[Pubmed:24945597]

Int J Food Sci Nutr. 2014 Nov;65(7):868-73.

Oxidative stress is considered an important factor that promotes cell death in response to a variety of pathophysiological conditions. This study investigated the antioxidant properties of Allicin, the principle ingredient of garlic, on preventing oxidative stress-induced injury. The antioxidant capacities of Allicin were measured by using 1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay and hydrogen peroxide (H(2)O(2))-induced cell damage on H9c2 cardiomyoblasts. Allicin (0.3-10 muM) pre-incubation could concentration-dependently attenuate the intracellular reactive oxygen species (ROS) increase induced by H(2)O(2) on H9c2 cells. It could also protect H9c2 cells against H(2)O(2)-induced cell damage. However, the DPPH free radical scavenging activity of Allicin was shown to be low. Therefore, it is believed that the protective effect of Allicin on H9c2 cells could inhibit intracellular ROS production instead of scavenging extracellular H(2)O(2) or free radicals. For the observed protective effect on H9c2 cells, Allicin might also be effective in reducing free radical-induced myocardial cell death in ischemic condition.

The antioxidant properties of garlic compounds: allyl cysteine, alliin, allicin, and allyl disulfide.[Pubmed:16822206]

J Med Food. 2006 Summer;9(2):205-13.

Garlic and garlic extracts, through their antioxidant activities, have been reported to provide protection against free radical damage in the body. This study investigated antioxidant properties of garlic compounds representing the four main chemical classes, alliin, allyl cysteine, allyl disulfide, and Allicin, prepared by chemical synthesis or purification. Alliin scavenged superoxide, while allyl cysteine and allyl disulfide did not react with superoxide. Allicin suppressed the formation of superoxide by the xanthine/xanthine oxidase system, probably via a thiol exchange mechanism. Alliin, allyl cysteine, and allyl disulfide all scavenged hydroxyl radicals; the rate constants calculated based on deoxyribose competitive assay were 1.4-1.7 x 10(10), 2.1-2.2 x 10(9), and 0.7-1.5 x 10(10) M (1) second(1), respectively. Contrary to previous reports, Allicin did not exhibit hydroxyl radical scavenging activity in this study. Alliin, Allicin, and allyl cysteine did not prevent induced microsomal lipid peroxidation, but both alliin and allyl cysteine were hydroxyl scavengers, and allyl disulfide was a lipid peroxidation terminator. In summary, our findings indicated that allyl disulfide, alliin, Allicin, and allyl cysteine exhibit different patterns of antioxidant activities as protective compounds against free radical damage.

Analyzing the antibacterial effects of food ingredients: model experiments with allicin and garlic extracts on biofilm formation and viability of Staphylococcus epidermidis.[Pubmed:25838894]

Food Sci Nutr. 2015 Mar;3(2):158-68.

To demonstrate different effects of garlic extracts and their main antibiotic substance Allicin, as a template for investigations on the antibacterial activity of food ingredients. Staphylococcus epidermidis ATCC 12228 and the isogenic biofilm-forming strain ATCC 35984 were used to compare the activity of Allicin against planktonic bacteria and bacterial biofilms. The minimal inhibitory concentration (MIC) and the minimum biofilm inhibitory concentration (MBIC) for pure Allicin were identical and reached at a concentration of 12.5 mug/mL. MBICs for standardized garlic extracts were significantly lower, with 1.56 and 0.78 mug/mL Allicin for garlic water and ethanol extract, respectively. Biofilm density was impaired significantly at a concentration of 0.78 mug/mL Allicin. Viability staining followed by confocal laser scanning microscopy showed, however, a 100% bactericidal effect on biofilm-embedded bacteria at a concentration of 3.13 mug/mL Allicin. qRT-PCR analysis provided no convincing evidence for specific effects of Allicin on biofilm-associated genes. Extracts of fresh garlic are more potent inhibitors of Staphylococcus epidermidis biofilms than pure Allicin, but Allicin exerts a unique bactericidal effect on biofilm-embedded bacteria. The current experimental protocol has proven to be a valid approach to characterize the antimicrobial activity of traditional food ingredients.

Effect of allicin from garlic powder on serum lipids and blood pressure in rats fed with a high cholesterol diet.[Pubmed:10882191]

Prostaglandins Leukot Essent Fatty Acids. 2000 Apr;62(4):253-9.

The use of fresh aqueous garlic extract is known to be effective in reducing thromboxane formation by platelets in both in vivo and in vitro animal models of thrombosis. In the present study, we studied the effect of Lichtwer garlic powder (containing 1.3% alliin equivalent to 0.6% Allicin) on the serum cholesterol, triglyceride, glucose, protein, and systolic blood pressure in rats fed with a high cholesterol diet. Experimental rats were fed a 2% high cholesterol diet with and without garlic powder for 6 weeks. Control rats were fed a normal diet. The aqueous garlic powder extract was given orally to rats on a daily basis. It was observed that cholesterol-fed animals had a significant increase in serum cholesterol compared to the control group of rats fed on a normal diet. However, when the rats were fed with a high cholesterol diet mixed with garlic powder, there was a significant reduction in their serum cholesterol levels compared with the group which were on a diet containing high cholesterol without garlic powder. Serum triglyceride levels were also significantly lowered by garlic powder when compared to control and high cholesterol diet group rats. The blood pressure of the high cholesterol diet animals was significantly higher compared to the animals receiving the control diet. The blood pressure of the animals receiving garlic powder and high cholesterol diet was significantly lower as compared to the high cholesterol and control diet group. No significant changes were observed in the serum glucose and protein in all of the rats. These results show that garlic is beneficial in reducing blood cholesterol, triglycerides levels and systolic blood pressure in hypercholesterolemic rats. Our experimental results show that garlic may beneficially affect two risk factors for atherosclerosis--hyperlipidemia and hypertension.

Allicin (diallyl thiosulfinate) is isolated from garlic including Diallyl monosulfide, Diallyl disulfide, Diallyl trisulfide, Diallyl tetrasulfide, and Methyl allyl disulphide etc. They accounts for 98% of the extract. Allicin (diallyl thiosulfinate) has highly potent antimicrobial activity, and inhibits growth of a variety of microorganisms, among them antibiotic-resistant strains.

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