Inhibition of Candida adhesion to buccal epithelial cells by an aqueous extract of Allium sativum (garlic)

The effect of pre-incubation of either Candida or buccal epithelial cells (BEC) with different concentrations of aqueous garlic extract (AGE) was investigated, as well as the effect of mouth rinse with AGE on the adhesion of yeast to BEC. Adhesion of Candida spp. to BEC was significantly reduced after both short and long time exposure of yeast to AGE. A similar inhibition of adherence was observed upon preincubation of BEC with AGE. The adherence-inhibition activity of AGE treatment was antagonized by thiols such as L-cysteine, glutathione and 2-mercaptoethanol. In addition, germ-tube formation was suppressed when C. albicans cells were pretreated with AGE. There was a significant reduction in the adherence of yeasts to BEC collected immediately or 15 min after an oral rinse with AGE. No statistical significance in the adhesion of BEC collected 30 min after oral rinse with AGE and control BEC was observed. The diminished adherence of C. albicans to BEC after exposure to various concentrations of garlic may have clinical relevance.     

Inhibition of Helicobacter pylori by garlic extract (Allium sativum)

Abstract The antibacterial effect of aqueous garlic extract (AGE) was investigated against Helicobacter pylori . Sixteen clinical isolates and three reference strains of H. pylori were studied. Two different varieties of garlic were used. The concentration of AGE required to inhibit the bacterial growth was between 2–5 mg ml⁻¹. The concentration, for both AGE types, to inhibit 90% (MIC₉₀) of isolates was 5 mg ml⁻¹. The minimum bactericidal concentration (MBC) was usually equal to, or two-fold higher than, minimum inhibitory concentration (MIC). Heat treatment of extracts reduced the inhibitory or bactericidal activity against H. pylori ; the boiled garlic extract showed a loss of efficacy from two-to four-fold the values of MIC and the MBC obtained with fresh AGR. The antibacterial activity of garlic was also studied after combination with a proton pump-inhibitor (omeprazole) in a ratio of 250:1. A synergistic effect was found in 47% of strains studied; an antagonistic effect was not observed.     

Inhibition of adhesion to buccal epithelial cells of Pseudomonas aeruginosa by dextran

Adhesion of Pseudomonas aeruginosa strains to buccal epithelial cells appears to be a necessary precondition for colonization and infection of respiratory tract. There are many strategies to prevent host organisms for Pseudomonas aeruginosa. The purpose of these studies was to evaluate the potential for preventing adhesion of Pseudomonas aeruginosa to epithelial cells with dextran. Dextran (5,000 MW) inhibited adhesion of Pseudomonas aeruginosa to buccal cells, at 20 mM was most inhibitory. The inhibitory effect appeared to be nonspecific because other neutral polysaccharides (glycogen and mannan) were also inhibitory. Dextran is an inexpansive and nontoxic agent and may be useful to prevent colonization and infection of respiratory tract with Pseudomonas aeruginosa.     

Antimicrobial properties of Allium sativum (garlic)

Although garlic has been used for its medicinal properties for thousands of years, investigations into its mode of action are relatively recent. Garlic has a wide spectrum of actions; not only is it antibacterial, antiviral, antifungal and antiprotozoal, but it also has beneficial effects on the cardiovascular and immune systems. Resurgence in the use of natural herbal alternatives has brought the use of medicinal plants to the forefront of pharmacological investigations, and many new drugs are being discovered. This review aims to address the historical use of garlic and its sulfur chemistry, and to provide a basis for further research into its antimicrobial properties.     

Sensitivity of food pathogens to garlic (Allium sativum)

The inhibitory activity of garlic ( Allium sativum ) against Staphylococcus aureus, Salmonella typhi, Escherichia coli and Listeria monocytogenes was measured by the 'turbidity' method. Minimum inhibitory concentration (MIC) of garlic at 80% inhibition level was calculated for these bacteria. All bacterial pathogenic strains tested were inhibited by garlic; E. coli was most sensitive and Listeria monocytogenes was least sensitive. Therefore, garlic has potential for the preservation of processed foods.     

Inhibition of skin tumors in DMBA-induced complete carcinogenesis system in mice by garlic (Allium sativum)

The chemopreventive action of garlic extract on DMBA-induced complete skin carcinogenesis system was studied in random bred, 6-7 weeks old, male Swiss albino mice. Topical weekly application of DMBA for 25 weeks at two dose levels, i.e. 200 nmol during the first week followed by 100 nmol during subsequent weeks, or 400 nmol during the first week followed by 200 nmol during subsequent weeks, resulted in 73.9% and 100% tumor incidences respectively. When garlic extract was topically applied twice daily for 3 days every week prior to above-stated dose schedules of DMBA, the incidences of tumors were reduced to 31.8% (P less than 0.01) and 43.4% (P less than 0.01) respectively.     

Agrobacterium tumefaciens-mediated transformation of leek (Allium porrum) and garlic (Allium sativum)

Transgenic leek (Allium porrum) and garlic (Allium sativum) plants have been recovered by the selective culturing of immature leek and garlic embryos via Agrobacterium-mediated transformation using a method similar to that described by Eady et al. (Plant Cell Rep 19:376–381, 2000) for onion transformation. This method involved the use of a binary vector containing the m-gfp-ER reporter gene and nptII selectable marker, and followed the protocol developed previously for the transformation of onions with only minor modifications pertaining to the post-transformation selection procedure which was simplified to have just a single selection regime. Transgenic cultures were selected for their ability to express the m-gfp-ER reporter gene and grown in the presence of geneticin (20 mg/l). The presence of transgenes in the genome of the plants was confirmed using TAIL-PCR and Southern analysis. This is the first report of leek and true seed garlic transformation. It now makes possible the integration of useful agronomic and quality traits into these crops.     

Correlation between cell-surface hydrophobicity of Candida albicans and adhesion to buccal epithelial cells

Adhesion of four isolates of Candida albicans to buccal epithelial cells was determined after growth of the yeasts in defined medium containing 50 mM glucose or 500 mM galactose as the carbon source. With each isolate, adhesion of galactose-grown yeasts was significantly higher than that of glucose-grown organisms. Yeast cell-surface hydrophobicity was assessed by two methods, a modified hydrocarbon adhesion assay and a more sensitive polystyrene microsphere assay. All four isolates were significantly more hydrophobic after growth on 500 mM galactose than after growth on 50 mM glucose. Overall, a strong positive correlation between adhesion and surface hydrophobicity was observed (r = 0.965). These results are discussed in relation to the role of yeast-surface hydrophobicity in pathogenesis.     

Susceptibility to purple blotch (Alternaria porri) in garlic (Allium sativum)

Experiments were conducted to study the progress of purple blotch disease of garlic caused by Alternuria porri in the field, to determine the relationship between garlic leaf age and susceptibility to Alternaria porri, and also to assess loss in bulb characters due to purple blotch of garlic. Per cent disease severity and number of purple blotch lesions on four garlic genotypes of known susceptibility, Sel-10 (highly susceptible), G-41 (highly susceptible), IC-49382 (moderately susceptible) and IC-49373 (moderate to less susceptible) were monitored from bulb formation to bulb maturity at weekly intervals. Lesions appeared early on highly susceptible cultivars, Sel-10 and G-41. Rapid progress of disease development was noticed during the last 3 wk before bulb maturity. Peak severity at the maturity of the crop was significantly higher on highly susceptible genotypes. No definite correlation could be established between number of lesions and disease severity. A logistic curve was fitted to predict the disease progress on different weeks before bulb maturity. Levels of leaf tissue found damaged by A. porri at weekly intervals from bulb initiation to bulb maturity were significantly lower on younger leaves than on older leaves. Leaves that emerged 7 wk before bulb maturity required more than a 5 wk period to reach 50% leaf damage, whereas leaves emerging 2, 3 and 4 wk before bulb maturity exceeded 50% leaf damage within a 2–3 wk period. Individual garlic leaves became more susceptible to purple blotch as they aged and emerging leaves were more susceptible the closer they emerged to bulb maturity. Per cent loss in bulb weight and bulb volume was found to be significantly higher on highly susceptible genotypes. No significant reduction in number of cloves/bulb was observed. We propose 4 wk before bulb maturity as the action threshold for initiation of fungicidal application to prevent damaging levels of disease.     

Organosulfur compounds from garlic (Allium sativum) oxidizing canine erythrocytes

The sulfurous acid ester, trans-sulfurous acid allyl ester 3-allylsulfanyl-allyl ester 8, along with two known thiosulfinates was isolated from the aqueous ethanol extract of garlic (Allium sativum). The chemical structure of 8 was determined on the basis of spectroscopic data including high resolution mass and two-dimensional NMR techniques. All of these compounds induced methemoglobin formation in a canine erythrocyte suspension in vitro resulting in the oxidation of canine erythrocytes. This is the first report of sulfurous acid ester showing oxidant activity in canine erythrocytes.     

The influence of garlic (Allium sativum) extract on interleukin 1alpha-induced expression of endothelial intercellular adhesion molecule-1 and vascular cell adhesion molecule-1.

Inflammation plays an important role in both the initiation of atherosclerosis and development of atherothrombotic events. The adherence of leukocytes/monocytes to the endothelium is an early event in atherogenesis. Phytotherapeutica as garlic and garlic extracts were shown to have beneficial modulating effects in patients with atherosclerotic disease. The aim of this study was to evaluate in vitro the influence of water-soluble garlic (Allium sativum) extract on the cytokine-induced expression of endothelial leukocyte adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1, CD54) and vascular cell adhesion molecule-1 (VCAM-1, CD106). Cytokine-induced expression of cellular adhesion molecules was measured on primary human coronary artery endothelial cell (HCAEC) cultures. HCAEC were cultured in microvascular endothelial cell growth medium and preincubated with garlic extract at various concentrations (0.25-4.0 mg/ml), after which human interleukin-1alpha (IL-1alpha, 10 ng/ml) was added for 1 day. Fluorescein isothiocyanate (FITC)-labeled anti-ICAM-1 and FITC-labeled anti-VCAM-1 were used to analyze the IL-1alpha-induced expression of ICAM-1 and VCAM-1 by flow cytometry. Incubation of HCAEC with garlic extract significantly decreased ICAM-1 and VCAM-1 expression induced by IL-1alpha. In addition, we examined the effects of garlic extract on the adhesion of monocytes to endothelial cells, using the monocytic U937 cell line. The presence of garlic extract significantly inhibited the adhesion of monocytes to IL-1alpha-stimulated endothelial cells. These results indicate that garlic extract modulates the expression of ICAM-1 and VCAM-1, thus potentially contributing to the beneficial effects traditionally attributed to garlic.     

Sister chromatid exchanges in garlic (Allium sativum L.) callus cells

A technique is described for differential staining of sister chromatids and the study of sister chromatid exchanges (SCEs) in garlic (Allium sativum L.) callus cells. BrdU incorporation into newly synthesized DNA was ensured by culturing calli on medium containing 100 M BrdU+0.01 M FudR+1 M Urd. SCEs were visualized by FPG staining technique and their frequency was analysed. Mean frequency of SCEs in callus cells was higher than that in meristem root-tip cells. Using the same staining method, cell cycle time of callus cells was analysed. It was found that it ranges from 48 to 132 hrs. The method described represents a new approach in the study of genetic instability of plant cells cultured in vitro.Abbreviations BrdU 5-bromo-2-deoxyuridine - 2,4-D 2,4-dichlorophenoxyacetic acid - FPG fluorescent-plus-Giemsa - FudR 5-fluoro-2-deoxyuridine - SCE sister chromatid exchange - SSC 0.15 M NaCl + 0.015 M Na-citrate - T thymidine-containing strand of the DNA duplex - B 5-bromo-2-deoxyuridine-containing strand of the DNA duplex - Urd uridine     

Cadmium accumulation and oxidative burst in garlic (Allium sativum)

To investigate the temporal sequence of physiological reactions of garlic (Allium sativum) to cadmium (Cd) treatment, seedlings developed from cloves were grown in increasing concentrations of CdCl2, ranging from 1-10 mM, for up to 8 days in sand. Analysis of Cd uptake indicated that most Cd accumulated in roots, but some was also translocated and accumulated in leaves at longer exposure time (after 12h) and higher concentrations (5 and 10mM) of CdCl2. Changes in activities of antioxidative enzymes, including superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), were characterized in leaves of garlic seedlings. Cd (5 and 10 mM) initially inhibited the activities of SOD and CAT but thereafter recovered or even increased compared with control plants. POD activities at 5 and 10 mM of Cd increased more than 3-4 times over control plants within 12 h and then dropped, but were still higher than controls at the end of the experiment. Otherwise lipid peroxidation enhanced with the increasing of incubation time and concentrations of external Cd. Leaves exposed to 1 mM CdCl2 showed a less pronounced response and only a small reduction in shoot growth. These results suggested that in leaves of garlic seedlings challenged by CdCl2 at higher concentrations, induction of these various enzymes is part of a general defense strategy to cope with overproduction of reactive oxygen. The possible mechanism of antioxidative enzymes changing before Cd accumulation in leaves of garlic seedlings is discussed.     

New mannose-specific lectins from garlic (Allium sativum) and ramsons (Allium ursinum) bulbs.

Two new mannose-binding lectins were isolated from garlic (Allium sativum, ASA) and ramsons (Allium ursinum, AUA) bulbs, of the family Alliaceae, by affinity chromatography on immobilized mannose. The carbohydrate-binding specificity of these two lectins was studied by quantitative precipitation and hapten-inhibition assay. ASA reacted strongly with a synthetic linear (1----3)-alpha-D-mannan and S. cerevisiae mannan, weakly with a synthetic (1----6)-alpha-D-mannan, and failed to precipitate with galactomannans from T. gropengiesseri and T. lactis-condensi, a linear mannopentaose, and murine IgM. On the other hand, AUA gave a strong reaction of precipitation with murine IgM, and good reactions with S. cerevisiae mannan and both synthetic linear mannans, suggesting that the two lectins have somewhat different binding specificities for alpha-D-mannosyl units. Of the saccharides tested as inhibitors of precipitation, those with alpha-(1----3)-linked mannosyl units were the best inhibitors of ASA, the alpha-(1----2)-, alpha-(1----4)-, and alpha-(1----6)-linked mannobioses and biosides having less than one eighth the affinity of the alpha-(1----3)-linked compounds. The N-terminal amino acid sequence of ASA exhibits 79% homology with that of AUA, and moderately high homology (53%) with that of snowdrop bulb lectin, also an alpha-D-mannosyl-binding lectin.     

Structure of the d-galactan isolated from garlic (Allium sativum) Bulbs

Hot-water extraction of defatted garlic-bulbs yielded a mixture of polysaccharides containing a d-galactan, a d-galacturonan, an l-arabinan a d-glucan, and a d-fructan. A trace of l-rhamnose was also detected in the polysaccharide by hydrolyzate. The pectic acid was partially removed by precipitation with aqueous calcium chloride; from the remaining polysaccharide mixture a pure d-galactan containing 97.3% of d-galactose was isolated by fractional precipitation repeated chromatography through a column of DEAE-cellulose. Methanolysis and hydrolysis of the permethylated d-galactan yielded 2,3,4,6-tetra-,2,3,6-tri-, and 2,3-di-O-methyl-d-galactose in the molar proportions of 1:2:1. On periodate oxidation the d-galactan reduced 1.18 molar equivalents of the oxidant per d-galactosyl residue, and liberated one molar equivalent or formic acid per 4.13 d-galactosyl residues. Smith degradation of the d-galactan was also conducted. From these results, a structure has been assigned to the repeating unit of the d-galactan.     

A new high molecular weight agglutinin from garlic (Allium sativum)

Erythrocyte agglutination by lectins from Allium sativum was inhibited only by mannose of the sugars tested. However, asialofetuin was more effective inhibitor of agglutination as compared to mannose. This led to the use of an asialofetuin-silica affinity column to isolate agglutinins of 110 and 25 kDa (ASA110 and ASA25). While ASA25 is a dimeric protein comprising of subunits of 12.5 and 13.0 kDa, ASA110 is a glycoprotein of two identical subunits of 47 kDa. ASA110 revealed to have a high content of aspartic acid, glycine, leucine and serine but low content of cysteine and methionine. It contains 14 residues of neutral sugars in addition to 43 residues of hexosamines per mole of lectin and requires metal ions for its functional conformation. Serological cross-reactions with other species showed some common epitopes of ASA110 and ASA25 present in A. porrum, A. ascalonicum, Narcissus alba, PHA and Con A but not in A. cepa. ASA110 with CHO cells indicated it to be weakly cytotoxic with LD50 of 160 µg/ml. (Mol Cell Biochem 166: 1-9, 1997)