garlic
Toxic effect of garlic extracts on the eggs of Aedes aegypti (Diptera: Culicidae): a scanning electron microscopic study.

Jarial MS.

The surface features of the eggs of Aedes aegypti (L.) and the effect of garlic extracts on their hatching were studied by scanning electron microscopy. The exochorion and endochorion layers of the eggshells display an essentially pentagonal reticulation. The exochorion meshwork exhibits large and small papillae interconnected by horizontal struts. At higher magnification, the large papillae show aeropyles on their rough surface. Eggs hatched in deionized water undergo complete fracture near the anterior poles producing free shell caps. In contrast, eggs placed in 6% reconstituted Kyolic garlic extract are only partially fractured, display attached shell caps, and the larvae remain trapped within the shells. In the natural garlic bulb extract, the eggs show no fracture lines in their shells. No larvae were observed either alive or dead in the garlic extracts, suggesting the embryos were disabled before they could escape from their eggshells as viable larvae. It is concluded that aqueous extracts of garlic inhibit hatching of Aedes eggs. Thus, compounds in garlic may be beneficial in the control of mosquitoes.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11372972&dopt=Abstract garlic



garlic
Water-soluble organosulfur compounds of garlic inhibit fatty acid and triglyceride syntheses in cultured rat hepatocytes.

Liu L, Yeh YY.

Nutrition Department, The Pennsylvania State University, University Park 16802, USA.

The putative hypolipidemic effect of garlic remains controversial. To gain further insight into the effect of garlic on lipid metabolism, the present study determined the inhibitory effects of water-soluble organosulfur compounds present in garlic on triglyceride (TG) and fatty acid synthesis in cultured rat hepatocytes. When incubated at 0.05 to 4.0 mmol/L with cultured hepatocytes, S-allyl cysteine (SAC) and S-propyl cysteine (SPC) decreased [2-14C]acetate incorporation into triglyceride in a concentration-dependent fashion achieving a maximal inhibition at 4.0 mmol/L of 43 and 51%, respectively. The rate of [2-14C]acetate incorporation into phosphlipids was depressed to a similar extent by SAC and SPC. SPC, SAC, S-ethyl cysteine (SEC), and gamma-glutamyl-S-methyl cysteine decreased [2-14C]acetate incorporation into fatty acid synthesis by 81, 59, 35, and 40%, respectively, at 2.0-4.0 mmol/L concentrations. Alliin, gamma-glutamyl-S-allyl cysteine, gamma-glutamyl-S-propyl cysteine S-allyl-N-acetyl cysteine, S-allylsulfonyl alanine, and S-methyl cysteine had no effect on fatty acid synthesis. The activities of lipogenic enzymes, fatty acid synthase (FAS), and glucose-6-phosphate dehydrogenase (G6PDH) were measured in cultured hepatocytes treated with the inhibitors. The activity of FAS in cells treated with 4.0 mmol/L SAC and SPC, respectively, was 32 and 27% lower than that of nontreated cells. Neither SAC nor SPC affected G6PDH activity. The results indicate that SAC, SEC, and SPC inhibit lipid biosynthesis in cultured rat hepatocytes, and further suggest that these S-alk(en)yl cysteines of garlic impair triglyceride synthesis in part due to decreased de novo fatty acid synthesis resulting from inhibition on FAS. Whether tissue concentrations of active garlic components can achieve levels required to inhibit TG synthesis in vivo warrants further investigation.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11383692&dopt=Abstract garlic



garlic
Garlic and garlic-derived compounds inhibit human squalene monooxygenase.

Gupta N, Porter TD.

Division of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY 40536-0082, USA.

Although extracts of garlic inhibit cholesterol biosynthesis in cultured hepatocytes, the inhibitory components of garlic and the site or sites of inhibition in the cholesterol biosynthetic pathway have not been established. To elucidate potential mechanisms of inhibition, we examined the effect of fresh garlic extract and 16 water- or lipid-soluble compounds derived from garlic on purified recombinant human squalene monooxygenase. Squalene monooxygenase catalyzes the second and likely rate-limiting step in the downstream pathway for cholesterol biosynthesis. A 50% inhibitory concentration (IC(50)) of squalene epoxidation was achieved with 1 g/L of fresh garlic extract; of the 16 garlic compounds tested, only selenocystine (IC(50) = 65 micromol/L), S-allylcysteine (IC(50) = 110 micromol/L), alliin (IC(50) = 120 micromol/L), diallyl trisulfide (IC(50) = 195 micromol/L), and diallyl disulfide (IC(50) = 400 micromol/L) substantially inhibited the enzyme. Kinetic analysis showed that the inhibition by garlic and by these compounds was slow and irreversible, suggestive of covalent binding to the enzyme; the ability of thiol-containing compounds such as glutathione and 2,3-dimercaptopropanol to prevent and reverse the inhibition indicated that the garlic compounds were reacting with sulfhydryl groups on the protein. Dithiols were better reversal agents than monothiols, further suggesting that these inhibitors bind to the proposed vicinal sulfhydryls present on this enzyme. These results indicate that squalene monooxygenase may be one of the target enzymes through which garlic inhibits cholesterol biosynthesis.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11385050&dopt=Abstract garlic



garlic
Morphological changes in garlic (Allium sativum L.) microbulblets during dormancy and sprouting as related to peroxidase activity and gibberellin A3 content.

Arguello JA, Falcon LR, Seisdedos L, Milrad S, Bottini R.

Facultad de Ciencias Agropecuarias, Universidad Nacional de Cordoba, Cordoba, Argentina. jarguell agro.uncor.edu

The aim of this work was to study the physiological mechanisms of dormancy and sprouting during post-harvest of garlic (Allium sativum L.) microbulblets produced by meristem culture of garlic seed cloves. The morphological changes occurring in garlic microbulblets were assessed from harvest till sprouting in relation with peroxidase activity and levels of gibberellins. Also the effect of a cold treatment (30 days at 4 degrees C) given 30 days after harvest was studied. The results showed that during the state of dormancy in garlic microbulblets formation of the leaf primordia and vascular differentiation of the storage leaf occurred, while increases of peroxidase activity and low levels of GA3 (the only active gibberellin identified) were found. At the end of dormancy the sprouting channel was formed, vascular differentiation established, and peaks of soluble peroxidase activity as well as of GA3 were observed. At day 90 post-harvest, garlic microbulblets showed physiologically mature and able to sprout. Further on, bud expansion and decrease of GA3 levels characterized sprouting of the microbulblets. The cold treatment enhanced GA3 levels and anticipated the sprouting process.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11387870&dopt=Abstract garlic



garlic
Prophylactic action of garlic on the histological and histochemical patterns of hepatic and gastric tissues in rats injected with a snake venom.

Rahmy TR, Hemmaid KZ.

Zoology Department, Faculty of Science, Suez Canal University, Ismailia, Egypt.

The present study aimed to examine the prophylactic action of oral administration of two doses of garlic on the histological and histochemical patterns of the gastric and hepatic tissues in rats envenomed with cobra snake. The study included the following groups: Group I contained control rats orally administered distilled water for ten days. Group II included rats orally administered daily for ten days with the equivalent therapeutic dose of garlic to rat (18 mg/kg body weight). Group III included rats orally administered daily for ten days with double the equivalent therapeutic dose of garlic to rat (36 mg/kg body weight). Group IV contained rats intramuscularly (i.m.) injected with 1/2 LD50 of cobra venom (0.0125 microg venom/gm body weight) and dissected after 6 hr from injection. Groups V and VI contained rats daily administered with the previous two doses of garlic for ten days, respectively, followed by a single i.m. injection of the above dose of cobra venom after 24 hr from the last garlic application. Rats of these two groups were dissected after 6 hr from venom injection. Administration of the therapeutic dose of garlic induced slight cytoplasmic granulation in some hepatic cells. However, administration of double the therapeutic dose caused swelling, necrosis, and damage of the gastric glandular epithelia together with signs of erosion, exfoliation, and necrosis of the surface mucosal cells. It also induced swelling and coalescence of the hepatic cells, loss of the normal arrangement of the hepatic cords, and hypertrophy of Kupffer cells. Injection with cobra venom caused loss of the normal characteristic appearance of the gastric glands and the epithelial lining cells of the gastric folds and the appearance of numerous inflammatory cells in the lamina properia. It also induced the occurrence of highly swollen hepatic cells, hepatic cellular necrosis and damage, as well as activated Kupffer cells. Nevertheless, pretreatment with the therapeutic dose of garlic for ten days induced a prophylactic activity against the pathogenic effects of the venom in both tissues, which appeared more or less normal except for very minor abnormalities. However, application of double the therapeutic dose of garlic for the same duration did not induce any prophylactic activity. Histochemically, slight alterations were noticed in the polysaccharide, protein, and nucleic acid contents of the gastric mucosa and the hepatic tissues due to administration of the therapeutic doses of garlic. However, severe depletions of these components were recorded in both tissues due to administration of double the therapeutic doses of garlic or injection of cobravenom or the application of both of them together. On the contrary, minor changes were noticed in the histochemical patterns of both tissues in rats pretreated with the therapeutic doses of garlic prior to venom application. It could be concluded that oral administration of the therapeutic dose of garlic for ten days has no serious side effects on gastric and hepatic tissues and could be used as a prophylactic tool against cobra snake envenomation.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11405277&dopt=Abstract garlic