garlic
Computational analysis of multivalency in lectins: structures of garlic lectin-oligosaccharide complexes and their aggregates.

Ramachandraiah G, Chandra NR, Surolia A, Vijayan M.

Molecular Biophysics Unit, Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India.

Multivalency in lectins is a phenomenon that has been discussed at considerable length. The structural basis for the role of multivalency in garlic lectin has been investigated here through computational studies. Biochemical studies have shown that the binding affinity of garlic lectin for high mannose oligosaccharides is orders of magnitude greater than that for mannose. Modeling and energy calculations clearly indicate that such increase in affinity cannot be accounted for by binding of these oligosaccharides at any of the six sites of a garlic lectin dimer. These studies also indicate that a given oligosaccharide cannot bind simultaneously to more than one binding site on a lectin dimer. The possibility of a given oligosaccharide simultaneously binding to and hence linking two or more lectin molecules was therefore explored. This study showed that trimannosides and higher oligomers can cross-link lectin dimers, amplifying the protein-oligosaccharide interactions severalfold, thus explaining the role of multivalency in enhancing affinity. A comprehensive exploration of all possible cross-links posed a formidable computational problem. Even a partial exploration involving a carefully chosen region of the conformational space clearly showed that a given dimer pair can be cross-linked not only by a single oligosaccharide molecule but also simultaneously by two oligosaccharides. The number of such possible double cross-links, including those forming interesting tetrameric structures, generally increases with the size of the oligosaccharide, correlating with the biochemical data. In addition to their immediate relevance to garlic lectin, these studies are of general interest in relation to lectin-oligosaccharide interactions.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12851290&dopt=Abstract garlic



garlic
Determination of sulfite in dried garlic by reversed-phase ion-pairing liquid chromatography with post-column detection.

Perfetti GA, Diachenko GW.

U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, 5100 Paint Branch Pkwy, College Park, MD 20740, USA. gperfett cfsan.fda.gov

A method is described for determining sulfite in dried garlic. Garlic is extracted with an HCl solution to inhibit the formation of allicin, which interferes with the determination of sulfite. After cleanup of the extract on a C18 solid-phase extraction column, sulfite is converted to hydroxymethylsulfonate (HMS) by adding formaldehyde and heating to 50 degrees C. HMS is determined by reversed-phase ion-pairing liquid chromatography with post-column detection. The post-column reaction system consists of the addition of KOH to convert HMS to sulfite ion, followed by the addition of 5,5'-dithiobis(2-nitrobenzoic acid) to produce 5-mercapto-2-nitrobenzoic acid which is detected spectrophotometrically at 450 nm. Background levels in unsulfited dried garlic equivalent to < 20 ppm SO2 were found. Recoveries of HMS from spiked garlic averaged 94.8% with a coefficient of variation of 3.8%. Sulfite was found in 13 of 21 samples of dried garlic produced in China, with sulfite ranging from 114 to 445 ppm. Sulfite was found in 60% of commercial dried garlic products purchased locally. The suitability of the Monier-Williams method for determining sulfite in garlic is discussed.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12852574&dopt=Abstract garlic



garlic
[Mutagenicity and cytotoxicity tests of garlic]

[Article in Japanese]

Yoshida S, Hirao Y, Nakagawa S.

Mutagenicity and cytotoxicity of fresh juice and alcohol extract from garlic were studied by Ames' test, Rec assay, Micronucleus test and the check of the influence to HEp 2 and chinese hamster embryo (CHE) primary cultured cells. No evidence of mutagenicity of these samples were observed in Ames' test and Rec assay, while there was dose dependent increase of micronucleated cells and polychromatocytes on the bone marrow cells of mice and chinese hamsters treated with garlic juice. There were severe damages, e.g. growth inhibition and morphological changes of both cultured cells due to garlic juice, but no or slightly cytotoxic signs were observed even in high concentration of garlic extract. A higher sensitivity to the cytotoxic effects of garlic was seen by the present findings with CHE primary cells than HEp 2 cell line.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6471131&dopt=Abstract garlic



garlic
Hypolipidemic effect of garlic and thyroid function.

Chaudhuri BN, Mukherjee SK, Mongia SS, Chakravarty SK.

Male Sprague-Dawley rats were maintained on cholesterol and garlic oil for 12 weeks. Cholesterol induced hyperlipidemia was controlled by garlic feeding. Garlic treatment did not alter the concentrations of circulating thyroid hormones and thyroidal uptake of radioiodine. The results indicate that the hypolipidemic effect of garlic is probably not mediated through the thyroid.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6517887&dopt=Abstract garlic



garlic
Allergic contact dermatitis to garlic (Allium sativum L.). Identification of the allergens: the role of mono-, di-, and trisulfides present in garlic. A comparative study in man and animal (guinea-pig).

Papageorgiou C, Corbet JP, Menezes-Brandao F, Pecegueiro M, Benezra C.

Garlic (Allium sativum L.) water- and ethanol-soluble extracts were prepared and purified by column chromatography. They were tested on garlic-sensitive patients and showed that the allergenic fraction was well located in a few column chromatography fractions. Guinea-pigs were sensitized with garlic water-soluble extracts and tested (open epicutaneous tests) with several fractions. The presence of diallyldisulfide was detected in the sensitizing chromatographic fractions. Guinea-pigs were successfully sensitized to this product and cross-reacted to garlic; animals sensitized to garlic extracts cross-reacted to diallyldisulfide. Both groups reacted to allicin, an oxidized derivative of diallyldisulfide present in garlic. Garlic-sensitive patients showed positive tests to diallyldisulfide, allylpropyldisulfide, allylmercaptan and allicin.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6625648&dopt=Abstract garlic