Onions Abstracts 2

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Influence of dietary capsaicin and onion on the metabolic abnormalities associated with streptozotocin induced diabetes mellitus.
            (Babu and Srinivasan, 1997) Download
Effect of feeding 15 mg% capsaicin diet or 3% freeze dried onion powder containing diet were examined in albino rats rendered diabetic with streptozotocin injection. Diabetic rats maintained on onion diet for 8 weeks excreted comparatively less amounts of albumin, urea, creatinine and inorganic phosphorus. Dietary onion also partially reversed the abnormalities in plasma albumin, urea, creatinine and inorganic phosphorus in diabetic animals. Onion also produced a significant reduction in hyperglycemic status of diabetic animals. Diabetic rats maintained on onion diet had a lowered relative liver weight at the end of the study compared to diabetic control group. Diabetic rats fed onion diet also exhibited lowered lipid peroxides in circulation and in urine when compared to diabetic control group. Blood cholesterol was lowered significantly by dietary onion in diabetic animals. Cholesterol decrease was exclusively from LDL-VLDL fraction. Significant decrease in blood phospholipids and triglycerides also brought about by dietary onion. Hepatic cholesterol, triglycerides, phospholipids which were elevated under diabetic condition were countered significantly by dietary onion. Dietary capsaicin did not have any significant influence on any of the parameters tested in diabetic rats. Thus, the study reveals that onion feeding improves the metabolic status in diabetic condition, probably because of its hypoglycemic as well as hypocholesterolemic effect.

New antiasthmatic drugs from traditional medicine
            (Dorsch and Wagner, 1991) Download
Several plants are used in traditional medicine for the treatment of bronchial asthma. We are trying to identify the active compound(s) and their mode of action. For the isolation and identification of the active principles, different chromatographic methods, HPLC, MPLC, elementary analysis, UV, mass, 1H- and 13C-NMR spectroscopy are used. Whole plant extracts, fractionated extracts and pure compounds are tested in the following pharmacological systems: cyclooxygenase and lipoxygenase pathway of arachidonic acid metabolism, bronchial obstruction of guinea pigs after inhalation of allergens, platelet-activating factor (PAF), histamine or acetylcholine, PAF-induced bronchial hyperreactivity of guinea pigs, histamine release, chemoluminescence and chemotaxis of human polymorphonuclear leukocytes as well as thromboxane biosynthesis of human platelets. As active compounds in onion extracts, thiosulfinates and cepaenes could be identified. They exert a wide spectrum of pharmacologic activities, both in vitro and in vivo. Tetragalloyl quinic acid from Galphimia glauca, suppressed allergen- and PAF-induced bronchial obstruction, PAF-induced bronchial hyperreactivity (5 mg/kg orally) in vivo and thromboxane biosynthesis in vitro. Hitherto unknown alkaloids from Adhatoda vasica showed pronounced protection against allergen-induced bronchial obstruction in guinea pigs (10 mg/ml aerosol). Androsin from Picrorhiza kurroa prevented allergen- and PAF-induced bronchial obstruction (10 mg/kg orally; 0.5 mg inhalative). Histamine release in vitro was inhibited by other compounds of the plant extract yet to be identified. Pharmacological effects of plant extracts and pure compounds in man are under investigation.

Dietary antioxidant flavonoids and risk of coronary heart disease: the Zutphen Elderly Study.
            (Hertog et al., 1993) Download
Flavonoids are polyphenolic antioxidants naturally present in vegetables, fruits, and beverages such as tea and wine. In vitro, flavonoids inhibit oxidation of low-density lipoprotein and reduce thrombotic tendency, but their effects on atherosclerotic complications in human beings are unknown. We measured the content in various foods of the flavonoids quercetin, kaempferol, myricetin, apigenin, and luteolin. We then assessed the flavonoid intake of 805 men aged 65-84 years in 1985 by a cross-check dietary history; the men were then followed up for 5 years. Mean baseline flavonoid intake was 25.9 mg daily. The major sources of intake were tea (61%), onions (13%), and apples (10%). Between 1985 and 1990, 43 men died of coronary heart disease. Fatal or non-fatal myocardial infarction occurred in 38 of 693 men with no history of myocardial infarction at baseline. Flavonoid intake (analysed in tertiles) was significantly inversely associated with mortality from coronary heart disease (p for trend = 0.015) and showed an inverse relation with incidence of myocardial infarction, which was of borderline significance (p for trend = 0.08). The relative risk of coronary heart disease mortality in the highest versus the lowest tertile of flavonoid intake was 0.42 (95% CI 0.20-0.88). After adjustment for age, body-mass index, smoking, serum total and high-density-lipoprotein cholesterol, blood pressure, physical activity, coffee consumption, and intake of energy, vitamin C, vitamin E, beta-carotene, and dietary fibre, the risk was still significant (0.32 [0.15-0.71]). Intakes of tea, onions, and apples were also inversely related to coronary heart disease mortality, but these associations were weaker. Flavonoids in regularly consumed foods may reduce the risk of death from coronary heart disease in elderly men.

Onion decreases the ovariectomy-induced osteopenia in young adult rats.
            (Huang et al., 2008) Download
It has been suggested that fruit and vegetable consumption are associated with good bone health. Onion, in particular, has been verified in its efficacy in bone resorption activity. In this study, we further investigated the effects of an onion-containing diet on ovariectomy-induced bone loss using methods of serum marker assay, histomorphometric analysis and biomechanical tests. Sixty-four female Wistar rats (14-week-old) with sham operations or ovariectomy were assigned to 6 groups: CON, sham-operated control group; OVX, ovariectomized group; ALN, ovariectomized rats treated with alendronate (1 mg/kg/day, p.o.); and 3% ON, 7% ON and 14% ON, ovariectomized rats fed with diets containing 3%, 7% and 14% (wt/wt) onion powder, respectively. Animals were sacrificed after a six-week treatment course. In the serum marker assay, alendronate and all three onion-enriched diets significantly decreased serum calcium level (p<0.05). Both 14% ON group and the ALN group even showed similarly lower level of serum osteocalcin (p<0.05), suggesting a down-regulation of bone turnover. The histomorphometric analysis showed that ovariectomy markedly decrease bone trabeculae. The ALN and 14% ON rats were 80% and 46% higher, respectively, in BV/TV than the OVX rats (p<0.05), and the rats fed with onion-enriched food showed a lesser ovariectomy-induced bone loss in a dose-dependent manner. Additionally, both ALN and 14% ON groups had significantly more trabecular number, less separated trabeculae, and fewer osteoclasts (p<0.05), but the protective efficacy from the 14% onion-enriched diet was slightly inferior to that of alendronate. Ovariectomy also significantly decreased tissue weight and biomechanical strength in the OVX group (p<0.05). The ALN and 14% ON groups equivalently showed a lesser decrease in tissue weight, though the difference was not significant. On the other hand, both the ALN and 14% ON groups represented similar biomaterial properties of femurs, and both reduced the ovariectomy-induced decrease in bending load and bending energy (p<0.05). The present study further verified that an onion-enriched diet could counteract ovariectomy-induced bone loss and deterioration of biomechanical properties.

Anti-bacterial action of onion (Allium cepa L.) extracts against oral pathogenic bacteria.
            (Kim, 1997) Download
In this study, the focus was on the antibacterial activity of onions. This study researched the activities of onion extracts on Streptococcus mutans and Streptococcus sobrinus, the main causal bacteria for dental caries, and Porphyromonas gingivalis and Prevotella intermedia, considered to be the main causal bacteria of adult periodontitis. The results showed that the onion extracts possess an effect on all test bacterial strains (S.mutans JC-2, S. sobrinus OMZ176, P. gingivalis ATCC 33277 and P. intermedia ATCC 25611), and the effects were bactericidal against cultured and resting bacterial cells. The activity of the onion extracts was stable even after 48 hours in the culture medium. This result suggests that no decomposition or volatility of onion extracts occurred in the culture medium. The antibacterial activity of onion extracts was not markedly influenced by cysteine (10 mM) treatment. However, activity significantly decreased with alkali treatment. Grated onion left to stand at 37 degrees C for 48 hours did not show antibacterial activity. Also, activity of steam treated (100 degrees C, 10 min.) onion was not observed. Using avicel plate by thin layer chromatography with the solvent of n-butanol:acetic acid:water (3:3:1), the main component of the substance (the substance which develops color with ninhydrin) was observed at an Rf value of about 0.9.

Flavonoid intake and coronary mortality in Finland: a cohort study.
            (Knekt et al., 1996) Download
OBJECTIVE:  To study the association between dietary intake of flavonoids and subsequent coronary mortality. DESIGN:  A cohort study based on data collected at the Finnish mobile clinic health examination survey from 1967-72 and followed up until 1992. SETTINGS:  30 communities from different parts of Finland. SUBJECTS:  5133 Finnish men and women aged 30-69 years and free from heart disease at baseline. MAIN OUTCOME MEASURE:  Dietary intake of flavonoids, total mortality, and coronary mortality. RESULTS:  In women a significant inverse gradient was observed between dietary intake of flavonoids and total and coronary mortality. The relative risks between highest and lowest quarters of flavonoid intake adjusted for age, smoking, serum cholesterol concentration, blood pressure, and body mass index were 0.69 (95% confidence interval 0.53 to 0.90) and 0.54 (0.33 to 0.87) for total and coronary mortality, respectively. The corresponding values for men were 0.76 (0.63 to 0.93) and 0.78 (0.56 to 1.08), respectively. Adjustment for intake of antioxidant vitamins and fatty acids weakened the associations for women; the relative risks for coronary heart disease were 0.73 (0.41 to 1.32) and 0.67 (0.44 to 1.00) in women and men, respectively. Intakes of onions and apples, the main dietary sources of flavonoids, presented similar associations. The relative risks for coronary mortality between highest and lowest quarters of apple intake were 0.57 (0.36 to 0.91) and 0.81 (0.61 to 1.09) for women and men, respectively. The corresponding values for onions were 0.50 (0.30 to 0.82) and 0.74 (0.53 to 1.02), respectively. CONCLUSIONS:  The results suggest that people with very low intakes of flavonoids have higher risks of coronary disease.

Intake of flavonoids and lung cancer.
            (Le Marchand et al., 2000) Download
BACKGROUND:  To investigate the possible relationship between intake of flavonoids-powerful dietary antioxidants that may also inhibit P450 enzymes-and lung cancer risk, we conducted a population-based, case-control study in Hawaii. METHODS:  An in-person interview assessed smoking history and usual intake of 242 food items for 582 patients with incident lung cancer and 582 age-, sex-, and ethnicity-matched control subjects. Subjects who donated a blood sample were genotyped for the P450 enzyme variant allele CYP1A1*2 by use of a polymerase chain reaction-based method. Logistic regression analysis was used to compute odds ratios (ORs) and 95% confidence intervals (CIs). All P values are two-sided. RESULTS:  After adjusting for smoking and intakes of saturated fat and beta-carotene, we found statistically significant inverse associations between lung cancer risk and the main food sources of the flavonoids quercetin (onions and apples) and naringin (white grapefruit). The lung cancer OR for the highest compared with the lowest quartile of intake was 0.5 (95% CI = 0.3-0.9) for onions (P for trend =.001) and 0.6 (95% CI = 0.4-1.0) for apples (P for trend =.03). The OR for the highest compared with the lowest tertile of intake for white grapefruit was 0.5 (95% CI = 0.2-0.9) (P for trend =.02). No association was found for important food sources of other flavonoids. Using published food-composition data for flavonoids, we found an inverse association between intake of quercetin and risk of lung cancer (P for trend =.07) that appears consistent with associations for its food sources. The effect of onions was particularly strong against squamous cell carcinoma (a cell type specifically associated with CYP1A1*2 in our study) and was modified by the CYP1A1 genotype, suggesting that CYP1A1 may play a role in this association. CONCLUSION:  If replicated, particularly in prospective studies, these findings would suggest that foods rich in certain flavonoids may protect against certain forms of lung cancer and that decreased bioactivation of carcinogens by inhibition of CYP1A1 should be explored as underlying mechanisms.

Flavonoid content in fresh, home-processed, and light-exposed onions and in dehydrated commercial onion products.
            (Lee et al., 2008) Download
Onion plants synthesize flavonoids as protection against damage by UV radiation and by intracellular hydrogen peroxide. Because flavonoids also exhibit health-promoting effects in humans, a need exists to measure their content in onions and in processed onion products. To contribute to the knowledge about the levels of onion flavonoids, HPLC and LC-MS were used to measure levels of seven quercetin and isorhamnetin glucosides in four Korean commercial onion bulb varieties and their distribution within the onion, in scales of field-grown onions exposed to home processing or to fluorescent light and in 16 commercial dehydrated onion products sold in the United States. Small onions had higher flavonoid content per kilogram than large ones. There was a graduated decrease in the distribution of the flavonoids across an onion bulb from the first (outside) to the seventh (innermost) scale. Commercial, dehydrated onion products contained low amounts or no flavonoids. Losses of onion flavonoids subjected to "cooking" (in percent) ranged as follows: frying, 33; sauteing, 21; boiling, 14-20; steaming, 14; microwaving, 4; baking, 0. Exposure to fluorescent light for 24 and 48 h induced time-dependent increases in the flavonoid content. The results extend the knowledge about the distribution of flavonoids in fresh and processed onions.


 

Effect of vegetables on bone metabolism.
            (Mühlbauer and Li, 1999) Download
Here we show that a variety of salads, herbs and cooked vegetables that are common in the human diet can alter bone metabolism in rats.

A gamma-glutamyl peptide isolated from onion (Allium cepa L.) by bioassay-guided fractionation inhibits resorption activity of osteoclasts.
            (Wetli et al., 2005) Download
One gram of onion added to the food of rats inhibits significantly (p < 0.05) bone resorption as assessed by the urinary excretion of tritium released from bone of 9-week-old rats prelabeled with tritiated tetracycline from weeks 1 to 6. To isolate and identify the bone resorption inhibiting compound from onion, onion powder was extracted and the extract fractionated by column chromatography and medium-pressure liquid chromatography. A single active peak was finally obtained by semipreparative high-performance liquid chromatography. The biological activity of the various fractions was tested in vitro on the activity of osteoclasts to form resorption pits on a mineralized substrate. Medium, containing the various fractions or the pure compound, was added to osteoclasts of new-born rats settled on ivory slices. After 24 h of incubation, the tartrate-resistant acid phosphatase positive multinucleated cells, that is, osteoclasts, were counted. Subsequently, the number of resorption pits was determined. Activity was calculated as the ratio of resorption pits/osteoclasts and was compared to a negative control, that is, medium containing 10% fetal bovine serum only and to calcitonin (10(-12) M) as a positive control. Finally, a single peak inhibited osteoclast activity significantly (p < 0.05). The structure of this compound was elucidated with high-performance liquid chromatography-electrospray ionization-mass spectrometry, time-of-flight electrospray ionization mass spectrometry, and nuclear magnetic resonance spectroscopy. The single peak was identified as gamma-L-glutamyl-trans-S-1-propenyl-L-cysteine sulfoxide (GPCS). It has a molecular mass of 306 Da and inhibits dose-dependently the resorption activity of osteoclasts, the minimal effective dose being approximately 2 mM. As no other peak displayed inhibitory activity, it likely is responsible for the effect of onion on bone resorption.

 


References
Babu, PS and K Srinivasan (1997), ‘Influence of dietary capsaicin and onion on the metabolic abnormalities associated with streptozotocin induced diabetes mellitus.’, Mol Cell Biochem, 175 (1-2), 49-57. PubMed: 9350033
Dorsch, W and H Wagner (1991), ‘New antiasthmatic drugs from traditional medicine’, Int Arch Allergy Appl Immunol, 94 (1-4), 262-65. PubMed: 1937886
Hertog, MG, et al. (1993), ‘Dietary antioxidant flavonoids and risk of coronary heart disease: the Zutphen Elderly Study.’, Lancet, 342 (8878), 1007-11. PubMed: 8105262
Huang, TH, et al. (2008), ‘Onion decreases the ovariectomy-induced osteopenia in young adult rats.’, Bone, 42 (6), 1154-63. PubMed: 18387868
Kim, JH (1997), ‘Anti-bacterial action of onion (Allium cepa L.) extracts against oral pathogenic bacteria.’, J Nihon Univ Sch Dent, 39 (3), 136-41. PubMed: 9354029
Knekt, P, et al. (1996), ‘Flavonoid intake and coronary mortality in Finland: a cohort study.’, BMJ, 312 (7029), 478-81. PubMed: 8597679
Le Marchand, L, et al. (2000), ‘Intake of flavonoids and lung cancer.’, J Natl Cancer Inst, 92 (2), 154-60. PubMed: 10639518
Lee, SU, et al. (2008), ‘Flavonoid content in fresh, home-processed, and light-exposed onions and in dehydrated commercial onion products.’, J Agric Food Chem, 56 (18), 8541-48. PubMed: 18759442
Mühlbauer, RC and F Li (1999), ‘Effect of vegetables on bone metabolism.’, Nature, 401 (6751), 343-44. PubMed: 10517630
Wetli, HA, et al. (2005), ‘A gamma-glutamyl peptide isolated from onion (Allium cepa L.) by bioassay-guided fractionation inhibits resorption activity of osteoclasts.’, J Agric Food Chem, 53 (9), 3408-14. PubMed: 15853380