garlic
The effects of garlic preparations against human tumor cell proliferation.

Siegers CP, Steffen B, Robke A, Pentz R.

Department of Toxicology, Medical University of Luebeck, Germany. siegers medinf.mu-luebeck.de

Epidemiological studies in China provide reason to suspect that a rich garlic content in the diet might reduce the proliferation of tumors in humans. We conducted experiments on human tumor cell lines and determined the influence of a garlic powder preparation, a garlic extract (reported as 8-10% L(+)-alliin enriched), and a combination thereof, on cellular proliferation in cell cultures, employing the widely used indirect neutral red procedure. Garlic powder failed to inhibit the growth of human hepatoma HepG2 or human colorectal carcinoma Caco2 cells at concentrations of up to 1000 micrograms/ml. Garlic extract, in which the alliin content was highly enriched was also unable to inhibit the growth of these cells. However, when the garlic extract was supplemented with garlic powder (to 10% final concentration) there was a concentration-dependent clear inhibition of tumor cell growth (IC50 values of 330 micrograms/ml for HepG2 and 480 micrograms/ml for Caco-2 cells). The growth of the human lymphatic leukemia cell line CCRF CEM was significantly inhibited in a dose-dependent manner by both garlic powder and garlic extract at concentrations as low as 30 micrograms/ml. However, no potentiation of this effect occurred upon mixing of the two preparations. Our results suggest that the antiproliferative effects of garlic may be due to breakdown products of alliin, such as allicin or polysulfides, rather than alliin itself, since the addition of an alliinase system (garlic powder) to an alliin enriched preparation without alliinase (garlic extract) potentiated the effects observed with the two preparations alone.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10228605&dopt=Abstract garlic



garlic
Effects of garlic preparations on superoxide production by phorbol ester activated granulocytes.

Siegers CP, Robke A, Pentz R.

Department of Toxicology, Medical University of Luebeck, Germany. siegers medinf.mu-luebeck.de

Sulfur containing constituents of garlic are considered responsible for conveying the antioxidative properties of garlic preparations. The radical scavenging properties of garlic preparations against oxygen radicals, specifically their ability to inhibit the formation of superoxide anions, were investigated using human granulocytes activated with 10 nM phorbol myristyl acetate (PMA). A garlic powder preparation inhibited the production of superoxide with a calculated IC50 of 390 micrograms/ml. An 8-10% alliin enriched garlic extract (alliinase inactivated) did not inhibit superoxide production even at concentrations as high as 1000 micrograms/ml. When the extract was mixed with garlic powder (90% garlic powder, 10% garlic extract), there was a clear inhibition of superoxide production with an IC50 value of 295 micrograms/ml. An even stronger inhibitory effect could be achieved when garlic powder was added to garlic extract (10% garlic powder, 90% extract, IC50 = 160 micrograms/ml). These experimental results suggest that the alliin metabolite allicin may be responsible for the oxygen radical scavenging properties of garlic.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10228606&dopt=Abstract garlic



garlic
Stabilization and pharmaceutical use of alliinase.

Krest I, Keusgen M.

Institut fur Pharmazeutische Biologie, Universitat Bonn, Germany.

In recent years, numerous clinical trials were undertaken in order to elucidate the active principle of garlic (Allium sativum L., Alliaceae). The most prominent effect of garlic preparations is a contribution to the prevention of stroke and arteriosclerosis. Allicin[(2-propenyl)-2-propenethiosulfinate] and other sulfur containing compounds were suggested as active compounds. The extremely unstable allicin itself is liberated from the more stable alliin [S-(+)-2-propenyl-L-cysteine sulfoxide] by the enzyme alliinase (EC 4.4.1.4) if fresh garlic is crunched or garlic powder is moistened. Therefore, an active enzyme is required in alliin containing remedies like those prepared from garlic powder. In order to investigate enzyme stability, alliinase was isolated from garlic powder. The partially purified enzyme could be stabilized over several months by addition of sodium chloride, sucrose, and pyridoxal-5'-phosphate. Alliinase may also be freeze-dried. This allows combinations of synthetic alliin and purified alliinase as components of an acid resistant tablet or capsule. In the intestine, the pro-drug alliin would be enzymatically converted to allicin. In clinical trials, highly dosed preparations of this kind should yield a precise information about the physiological effects of allicin. In addition, alliin-homologues substances which bear a modified alkyl side chain and do not occur in nature may be tested.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10234740&dopt=Abstract garlic



garlic
Effect of raw versus boiled aqueous extract of garlic and onion on platelet aggregation.

Ali M, Bordia T, Mustafa T.

Department of Biological Sciences, Faculty of Science, Safat, Kuwait.

The effects of aqueous extracts of raw and boiled garlic and onions were studied in vitro on the collagen-induced platelet aggregation using rabbit and human platelet-rich plasma. A dose dependant inhibition of rabbit platelet aggregation was observed with garlic. Onion also showed dose-dependent inhibitory effects on the collagen-induced platelet aggregation but this inhibition was of a lesser magnitude compared to garlic when related to dose. The concentration required for 50% inhibition of the platelet aggregation for garlic was calculated to be approximately 6.6 mg ml(-1) plasma, whereas the concentration for onion was 90 mg ml(-1) plasma. Boiled garlic and onion extracts showed a reduced inhibitory effect on platelet aggregation. Garlic but not onion significantly inhibits human platelet aggregation in a dose-dependent fashion. The potency of garlic in inhibiting the collagen-induced platelet aggregation is approximately similar to that of rabbit platelets (8.8 mg ml(-1) produced 50% inhibition of platelet aggregation). The results of this study show that garlic is about 13 times more potent than onion in inhibiting platelet aggregation and suggest that garlic and onion could be more potent inhibitors of blood platelet aggregation if consumed in raw than in cooked or boiled form.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10319916&dopt=Abstract garlic



garlic
Effects of garlic extract on oxidant/antioxidant status and atherosclerotic plaque formation in rabbit aorta.

Durak I, Ozturk HS, Olcay E, Can B, Kavutcu M.

Ankara University Medical Faculty, Department of Biochemistry, Ankara, Turkey. durak medicine.ankara.edu.tr

BACKGROUND AND AIM: The results of a number of studies suggest that garlic (or garlic extracts) may have favourable effects against the development of atherosclerosis. The aim of this study was to investigate the effects of garlic extract supplementation on oxidant/antioxidant status and atherosclerotic plaque formation in rabbit aortic tissue. METHODS: AND RESULTS: Twenty-two male New Zealand White rabbits were fed a cholesterol-supplemented diet (0.5 g/Kg/day) and nine control rabbits a regular diet for four months. At the end of this period, atherosclerotic plaque formation and antioxidant activity were measured in the aortic tissue of the controls and seven of the cholesterol-fed animals. Of the remaining 15 experimental animals, seven were fed normal laboratory diet and eight a normal diet plus garlic extract (1.5 ml/Kg/day) for a further three months before atherosclerotic plaque formation and antioxidant activity were measured in the aortic tissue of both groups. The cholesterol-fed animals showed a significantly impaired antioxidant system associated with increased plaque formation. However, garlic extract supplementation significantly improved antioxidant status and reduced the plaque surface area. CONCLUSIONS: In this experimental model, garlic extract dietary supplementation activated the antioxidant system and decreased peroxidation in aortic tissue. There was also a reduction in atherosclerotic plaque area. Although further studies are required to elucidate the mechanisms involved, the protective activity of garlic extract may be due to its antioxidant properties.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12325471&dopt=Abstract garlic