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PubMed2004

Genomic organization of a novel root alliinase gene, ALL1, in onion.

Alliinase operates in the biochemical pathway that produces the compounds responsible for the characteristic flavor of onion. We isolated and characterized the 86-kb BAC clone containing a novel onion alliinase gene, ALL1. Identity of deduced amino acid sequence of ALL1 with a bulb alliinase is 65.4% and with a root alliinase is 67.3%. The ALL1 gene is expressed specifically in onion roots and estimated pI value of mature ALL1 protein is similar to that of root alliinase isoform I, which is an uncharacterized protein having alliinase activity. The highly repetitive sequences around the ALL1 gene was observed from sequence and DNA gel blot analyses. The 33.2% G+C content of the 35-kb ALL1 region is similar to that of dicot plants and lower than that of monocot cereal plants, although onion is classified into monocots. The present study shows the first evidence of the onion genomic sequences around genes differed from the cereal genome.

Base Sequence↗
PubMed2005

Molecular and biochemical characterisation of a serine acetyltransferase of onion, Allium cepa (L.).

We have previously cloned a cDNA, designated SAT1, corresponding to a gene coding for a serine acetyltransferase (SAT) from onion (Allium cepa L.). The SAT1 locus was mapped to chromosome 7 of onion using a single-stranded conformation polymorphism (SSCP) in the 3' UTR of the gene. Northern analysis has demonstrated that expression of the SAT1 gene is induced in leaf tissue in response to low S-supply. Phylogenetic analysis has placed SAT1 in a strongly supported group (100% bootstrap) that comprises sequences that have been characterised biochemically, including Allium tuberosum, Spinacea oleracea, Glycine max, Citrullus vulgaris, and SAT5 (AT5g56760) of Arabidopsis thaliana. This group can be divided further with the SAT1 of A. cepa sequence grouping strongly with the A. tuberosum sequence. Translation of SAT1 from onion generates a protein of 289 amino acids with a calculated molecular mass of 30,573 Da and pI of 6.52. The conserved G277 and H282 residues that have been identified as critical for L-cysteine inhibition are observed at G272 and H277. SAT1 has been cloned into the pGEX plasmid, expressed in E. coli and SAT activity of the recombinant enzyme has been measured as acetyl-CoA hydrolysis detected at 232 nm. A Km of 0.72 mM was determined for l-serine as substrate, a Km of 92 microM was calculated with acetyl-CoA as substrate, and an inhibition curve for L-cysteine generated an IC50 value of 3.1 microM. Antibodies raised against the recombinant SAT1 protein recognised a protein of ca. 33 kDa in whole leaf onion extracts. These properties of the SAT1 enzyme from onion are compared with other SAT enzymes characterised from closely related species.

Acetyltransferases↗
PubMed2004

An onion variety has natural antithrombotic effect as assessed by thrombosis/thrombolysis models in rodents.

INTRODUCTION: Prevention of arterial thrombotic diseases has a high priority in developed countries. As inappropriate diet has been shown to be an important risk factor for thrombotic events, regular antithrombotic diet may offer a convenient and effective way of prevention. The aim of the present study was to test onion extracts for antithrombotic effect and to identify the effective varieties in Allium cepa. MATERIALS AND METHODS: A shear-induced platelet function test (haemostatometry) was used to screen for antithrombotic potential. Onion extracts showing significant antithrombotic activity in vitro were further assessed in vivo by using a laser-induced thrombosis test in mice. RESULTS AND CONCLUSIONS: An onion variety, Toyohira, showed significant antithrombotic activity both in vitro and in vivo. Toyohira showed thrombolytic activity in addition to the antiplatelet effect. Superkitamomiji, 2935A, and K83211 showed only thrombolytic activity. Quercetin, the richest flavonoid in onion, was measured, but no correlation was found between quercetin content and antithrombotic activity. It is concluded that onion A. cepa can be classified into varieties with or without antithrombotic and thrombolytic effects. This should be taken into account in future population studies on the antithrombotic effects of vegetables.

Animals↗
PubMed2000

Garlic and onion oils inhibit proliferation and induce differentiation of HL-60 cells.

Phytochemicals present in the genus Allium have potential pharmacological effects, such as antimicrobial, antithrombotic, antitumor, hypolipidaemic and hypoglycemic activities. In this present study, we examined the effects of garlic and onion oils on human promyelocytic leukemia cells, HL-60. Incubation of HL-60 with garlic or onion oil (20 microg/ml) caused a marked suppression of HL-60 proliferation; the suppression was almost identical with those obtained by all-trans-retinoic acid (ATRA) or dimethyl sulfoxide (DMSO) used as positive controls. These oils induced the generation of nitroblue tetrazolium (NBT)-reducing activity, and about 20% of the HL-60 cells became NBT positive. CD11b, another marker of the differentiation of these cells, was also significantly induced by garlic oil or onion oil. The combination of garlic or onion oil with ATRA was more effective than either alone. These data suggest that garlic and onion oils have the ability to induce differentiation of HL-60 cells into those of the granulocytic lineage.

Cell Count↗
PubMed1998

Effects of aqueous extract of onion on the liver and lung of rats.

The toxic effects of oral and intraperitoneal administration of onion extracts on lung and liver tissue of rats were investigated. Oral or intraperitoneal administration of low doses of onion (50 mg/kg) to rats had little effect on lung and liver tissues when compared to control animals. In contrast, administration of high doses of onion (500 mg/kg) resulted in apparent histological changes in lung and liver tissues of rats. Intraperitoneal administration of the high dose of onion was more damaging to lung and liver tissue than oral administration and resulted in a 25% rate of mortality in this treatment group. These results suggest that low doses of onion are nontoxic and may be administered with few ill effects.

Animals↗
PubMed1998

Mutagenicity of cooked hamburger is reduced by addition of onion to ground beef.

Addition of onion effectively reduced mutagenicity of cooked hamburger when tested on Salmonella typhimurium TA98 strain with metabolic activation. The components of onion that participated in the reduction of mutagenicity were sugars. Addition of starch or glucose to ground beef the amount equivalent to that in onion reduced the mutagenicity of cooked hamburger. Addition of onion may cause imbalance of the sugar content of ground beef that effectively produces mutagenicity. Mutagenicity of the heated model mixture of glucose/glycine/creatinine in diethyleneglycol-water was reduced by an excessive amount of glucose. Hence, Japanese cooking-style with addition of onion can reduce mutagenicity of hamburger.

Animals↗
PubMed2004

Uptake of quercetin and quercetin 3-glucoside from whole onion and apple peel extracts by Caco-2 cell monolayers.

Evidence suggests that regular consumption of fruits and vegetables may reduce the risk of chronic diseases, and phytochemicals from fruits and vegetables may be responsible for this health benefit. However, there is limited knowledge on the bioavailability of specific phytochemicals from whole fruits and vegetables. This study used Caco-2 cells to examine uptake of quercetin aglycon and quercetin 3-glucoside as purified compounds and from whole onion and apple peel extracts. Pure quercetin aglycon was absorbed by the Caco-2 cells in higher concentrations than quercetin 3-glucoside (p < 0.05). Caco-2 cells treated with quercetin 3-glucoside accumulated both quercetin 3-glucoside and quercetin. Caco-2 cells absorbed more onion quercetin aglycon than onion quercetin 3-glucoside (p < 0.05), and the percentage of onion quercetin absorbed was greater than that of pure quercetin, most likely due to enzymatic hydrolysis of quercetin 3-glucoside and other quercetin glucosides found in the onion by the Caco-2 cells. Caco-2 cells absorbed low levels of quercetin 3-glucoside from apple peel extracts, but quercetin aglycon absorption was not detected. Caco-2 cell homogenates demonstrated both lactase and glucosidase activities when incubated with lactose and quercetin 3-glucoside, respectively. This use of the Caco2 cell model appears to be a simple and useful system for studying bioavailability of whole food phytochemicals and may be used to assess differences in bioavailability between foods.

Biological Availability↗
PubMed2000

Chronic consumption of raw but not boiled Welsh onion juice inhibits rat platelet function.

Welsh onion has been consumed for prevention of cardiovascular disorders. To study if it has antithrombotic effects, 9-wk-old male Sprague-Dawley rats were studied. Some rats were fed raw or boiled Welsh onion juice (2 g. kg(-1). d(-1)) for 4 wk, and the remaining acted as the control. Before and after feeding, their systolic blood pressure was measured by a tail-cuff method. Two days after the treatment period, tail bleeding time, platelet function (including platelet aggregation and adhesion), plasma levels of prostaglandins, and platelet cyclic nucleotide levels were determined. In comparison to the control, raw Welsh onion juice consumption significantly (1) lowered resting systolic blood pressure; (2) prolonged the bleeding time; (3) diminished platelet adhesion on a fibrinogen-coated surface, ADP-evoked platelet aggregation and ADP-stimulated thromboxane release; (4) elevated the concentration of cyclic AMP, but not cyclic GMP, in platelets; (5) increased the plasma level of 6-keto-prostaglandin F(1alpha), the stable prostacyclin metabolite, but not the plasma nitrite level. On the contrary, boiled Welsh onion juice consumption was totally ineffective. In conclusion, consuming raw Welsh onion juice, but not boiled juice, has blood pressure lowering and antithrombotic effects in rats. These effects may be mediated by PGI(2)-cAMP pathway.

6-Ketoprostaglandin F1 alpha↗
PubMed2004

QTL affecting soluble carbohydrate concentrations in stored onion bulbs and their association with flavor and health-enhancing attributes.

Onion bulbs accumulate fructans, a type of soluble carbohydrate associated with lower rates of colorectal cancers. Higher fructan concentrations in bulbs are correlated with higher pungency, longer dormancy, and greater onion-induced antiplatelet activity (OIAA). We analyzed replicated field trials of a segregating family for types and concentrations of soluble carbohydrates in onion bulbs 90 days after harvest. Means were adjusted using dry weight as the covariant to reveal highly significant (P < 0.001) differences among parents and families for glucose, fructose, sucrose, and the fructans 1-kestose, neokestose, and (6G,1)-nystose. Fructan concentrations showed significant (P < 0.05) phenotypic correlations with each other and with sucrose, pungency, and OIAA. These observations are consistent with the hypothesis that onion bulbs accumulating fructans take up or retain less water, concentrating both soluble carbohydrates and thiosulfinates responsible for pungency and OIAA. Interval mapping of family means from the covariant analyses revealed regions on linkage groups A and D significantly (LOD > 2.68) affecting soluble carbohydrate concentrations. The enzyme catalyzing the first step of fructan polymerization, 1-sucrose-sucrose fructosyltransferase (1-SST), mapped independently of these genomic regions. One region on linkage group D near an acid-invertase gene was significantly (LOD = 3.45) associated with sucrose concentrations. This study reveals that the accumulation of sucrose in stored onion bulbs may allow for the combination of sweeter flavor with significant OIAA.

Carbohydrate Metabolism↗
PubMed1999

Rumen bacteria are involved in the onset of onion-induced hemolytic anemia in sheep.

The mechanism of onion-induced hemolytic anemia in ruminants was investigated. The ether-extract obtained from the mixture of rumen fluid and onion juice incubated at 38.5 degrees C for 9 hr induced oxidative damage in sheep erythrocytes in vitro, indicating the production of certain oxidants in the mixture. The increase of the oxidative effect in the mixture was inhibited completely by the removal of rumen microorganisms and partly by treatment with antibiotics and by oxygen gas. The sheep fed onions (50 g/kg body weight/day) for 15 days developed more severe Heinz body hemolytic anemia than did the sheep fed the equivalent amount of onions with 5 g/day ampicillin sodium salt. The results indicated that certain rumen bacteria appear to be involved in the onset of onion-induced hemolytic anemia in sheep.

Anemia, Hemolytic↗
PubMed2001

Various cooking methods and the flavonoid content in onion.

Onion is a major source of flavonoids and is cooked in various ways in the world. The major flavonoids in onion are two quercetin glycosides, quercetin 4'-O-beta-glucoside (Q4'G) and quercetin 3,4'-O-beta-diglucosides (Q3,4'G), which are recognized as bioactive substances that are good for our health. We have investigated the effect of cooking procedures on the content of antioxidants. We selected quercetin conjugates, total phenol compounds, and ascorbic acid to estimate the amount of flavonoid ingestion from onion. We examined the following cooking methods: boiling, frying with oil and butter, and microwave cooking. Various cooking methods do not consider the degradation of quercetin conjugates when cooking onion. Microwave cooking without water better retains flavonoids and ascorbic acid. Frying does not affect flavonoid intake. The boiling of onion leads to about 30% loss of quercetin glycosides, which transfers to the boiling water. At that time, the effect of additives on the quercetin conjugates is different according to the compounds. The hydrolysis of quercetin glycosides for daily cooking might occur with the addition of seasonings such as glutamic acid. Additional ferrous ions accelerated the loss of flavonoids.

Antioxidants↗
PubMed2004

Fate of Escherichia coli O157:H7 in manure compost-amended soil and on carrots and onions grown in an environmentally controlled growth chamber.

Studies were done to determine the fate of Escherichia coli O157:H7 in manure compost-amended soil and on carrots and green onions grown in an environmentally controlled growth chamber. Commercial dairy cattle manure compost was inoculated with a five-strain mixture of green fluorescent protein-labeled E. coli O157:H7 at 10(7) CFU g(-1) and mixed with unsterilized Tifton sandy loam soil at a ratio of 1:5. Baby carrot or green onion seedlings were planted into the manure compost-amended soil in pots, and soil samples surrounding the plant, edible carrot roots and onion bulb samples, and soil immediately beneath the roots were assayed for E. coli O157:H7 in triplicate at weekly intervals for the first 4 weeks, and every 2 weeks for the remainder of the plant growth cycle (up to 3 months). E. coli O157:H7 cell numbers decreased within 64 days by 3 log CFU/g in soil and soil beneath the roots of green onions and by more than 2 log CFU/g on onions. E. coli O157:H7 survived better during the production of carrots, with a 2.3-log CFU/g reduction in soil and a 1.7-log CFU/g reduction on carrots within 84 days. These results indicate that the type of plant grown is an important factor influencing the survival of E. coli O157:H7 both on the vegetable and in the soil in which the vegetable is grown.

Agriculture↗
PubMed1999

Antioxidant role of oils isolated from garlic (Allium sativum Linn) and onion (Allium cepa Linn) on nicotine-induced lipid peroxidation.

Nicotine, a major component of tobacco, is partly responsible for the development of atherosclerosis. It has been suggested that antioxidant nutrients are protective against degenerative diseases. So we have studied the antioxidant effect of oils isolated from onion and garlic on nicotine-induced lipid peroxidation in rat tissues. The lipid peroxidation products and scavenging enzymes were assessed in liver, lungs, heart and kidney. The rats were treated with 0.6 mg nicotine/kg bw and simultaneously given 100 mg garlic or onion oils/kg bw for 21 d. Thiobarbituric acid reactive substances, conjugated dienes and hydroperoxides concentrations were significantly increased in the tissues of nicotine-treated rats. Both the garlic oil and onion oil supplementation to nicotine-treated rats increased resistance to lipid peroxidation. The activities of catalase, superoxide dismutase and glutathione peroxidase decreased in nicotine-treated rats, but there was a trend to increased glutathione content. With garlic oil or onion oil supplementation, nicotine-treated rats had increased activities of antioxidant enzymes and increased concentrations of glutathione. These results indicate that oils of garlic and onion are effective antioxidants against the oxidative damage caused by nicotine.

Animals↗
PubMed2002

The use of cytoplasmic markers in onion hybrid breeding.

We applied the RFLP approach to identify the cytoplasmic genotypes of selected onion breeding materials from Poland. For this purpose, mitochondrial DNA from cytoplasmic male-sterile (CMS) and male-fertile onions were hybridized with the probes for the following mitochondrial genes: atpA, atp6, atp9, cob, cox1, nad3, nad4 and nad6. S-, T- or C-cytoplasm was represented in each analyzed sterile accession. Some new polymorphisms shared by S- and C-cytoplasmic onions were identified. We also used currently available PCR markers to test if cytoplasmic heterogenity occurs within onion inbreds. A fraction of the plants bearing S-cytoplasm were found within two male-fertile lines, but such plants were not detected in the open-pollinated cultivars Sochaczewska, Wolska and Zytawska. Both the RFLP and PCR approaches gave some proof of existing mitochondrial heteroplasmy in onions

Breeding↗
PubMed1996

Onion bulb cells in mice deficient for myelin genes share molecular properties with immature, differentiated non-myelinating, and denervated Schwann cells.

Onion bulb formation is a pathological feature observed in peripheral nerves of patients suffering from inherited peripheral neuropathies such as Charcot-Marie-Tooth and Déjérine-Sottas diseases. An onion bulb consists of small circumferentially oriented (supernumerary) cells and their processes surrounding a large caliber axon. In the present study, we investigated the molecular phenotype of supernumerary cells at the light and electron microscopic levels. The major motor (quadriceps muscle) branch of the femoral nerve from 16- to 24-month-old mice with an inactivated allele of the myelin protein zero gene or deficient for myelin-associated glycoprotein (MAG; P0(+)- and MAG--mice, respectively), which have numerous onion bulbs, was teased to obtain single nerve fibers, which were then processed for immunocytochemistry. Corresponding nerves from wild-type mice served as controls. In both P0(+)- and MAG--mice, supernumerary cells expressed S-100, the low-affinity nerve growth factor receptor (p75, NGFr), the cell adhesion molecule L1, the neural cell adhesion molecule (N-CAM), and glial fibrillary acidic protein (GFAP). At the electron microscopic level, the cell surface of supernumerary cells was NGFr immunoreactive and L1 and N-CAM were expressed at points of contact between supernumerary cells. NGFr, L1, and N-CAM were also present in the basal lamina surrounding myelinated axons associated with onion bulbs. Both S-100 and GFAP immunoreactivities were seen in the cytoplasm of supernumerary cells. In contrast, in wild-type mice myelinating Schwann cells only expressed S-100 intracellularly and L1 and N-CAM in their basal lamina, whereas non-myelinating Schwann cells expressed all five molecules investigated. The present study indicates that supernumerary cells in onion bulbs have a molecular phenotype characteristic of immature, differentiated non-myelinating, and denervated Schwann cells, thus excluding the possibility that supernumerary cells are perineurial cells.

Animals↗
PubMed1991

Onion bulb formation in the initial complex of neurons in human dorsal root ganglion: their significance and alterations in amyotrophic lateral sclerosis.

We have demonstrated onion bulb-like structures in human dorsal root ganglia (DRG). These onion bulbs morphologically consist of non-continuous layers of supporting-cell cytoplasms that encase thinly myelinated axons and are immunocytochemically recognized by anti-S-100 protein and anti-glial fibrillary acidic protein antibodies. These structures are present in normal controls and preferentially involve the initial complex of the large, light, neurofilament-rich neurons. The number of onion bulbs and their average number of lamellae reach a peak in the third decade and then decline. In three cases of amyotrophic lateral sclerosis (ALS), the onion bulbs involve non-myelinated axons as well as the thinly myelinated portion of the initial complex and are increased both in frequency and in average number of lamellae. Our studies suggest that these onion bulbs represent a normal biological process of DRG neurons that may be accentuated in ALS.

Amyotrophic Lateral Sclerosis↗
PubMedDate not supplied

The protective action of essential oils of onion and garlic in cholesterol-fed rabbits.

The effects of the essential oils of onion and garlic have been investigated in cholesterol-fed rabbits and have been compared with the effects of clofibrate. The marked rise in serum cholesterol and blood coagulability that followed 3 months of cholesterol feeding (0.2 g/kg/day) was significantly reduced by the essential oils of both onion and garlic. Fibrinolytic activity was actually increased even above the normal control levels. The essential oils of onion and garlic (equivalent to 1 g/kg/day of raw bulbs) proved more effective than clofibrate in the usual clinical dose of 33 mg/kg/day. Garlic was even more effective than onion. Cholesterol feeding increased the average lipid content of aorta from 5.95 to 13.75 mg/100 mg dry weight. With addition of clofibrate, onion or garlic the values were 7.79, 6.23 and 5.28 mg/100 ml, respectively. Thus it can be seen that the essential oils effectively prevent lipid acculation in the rabbit oarta.

Animals↗
PubMedDate not supplied

Effect of the essential oils of garlic and onion on alimentary hyperlipemia.

SUMMARY: The effect of garlic and onion on alimentary hyperlipemia, induced by feeding 100 g butter, has been studied in 10 healthy subjects. The freshly extracted juice of 50 g of garlic or onion, as well as an equivalent amount of their ether-extracted essential oils, was administered randomly on four different days during a one-week period. Garlic and onion have a significant protective action against fat-induced increases in serum cholesterol and plasma fibrinogen and decreases in coagulation time and fibrinolytic activity. The essential oil fraction, which contains all the taste and odour, exactly duplicated the beneficial effects of whole garlic and onion. It is, therefore, concluded that the active principle of garlic and onion is the essential oil, which chemically is a combination of sulphur-containing compounds, mainly allyl propyl disulphide and diallyl disulphide.

Adult↗