Different effects of heating and freezing treatments on the antioxidant properties of broccoli, cauliflower, garlic and onion. An experimental in vitro study

ABSTRACT BACKGROUND: Vegetables have some beneficial effects on human health due to their antioxidant compounds, like polyphenols. Cooking leads to many physical and chemical changes to plant structure that can alter the phytochemical compounds of vegetables. OBJECTIVES: To investigate the effects of heat treatment and freezing on the antioxidant properties of garlic, onion, broccoli and cauliflower. DESIGN AND SETTING: Experimental in vitro study in a university laboratory. METHODS: Fresh broccoli (Brassica oleracea var. italica), cauliflower (Brassica oleracea var. botrytis), garlic (Allium sativum) and onion (Allium cepa) were obtained from a local store. These vegetables were divided into three treatment groups: raw, heated and frozen. The heat treatment consisted of heating them in a drying oven at 150 °C for 20 minutes. The freezing treatment consisted of keeping them frozen at -20 °C until analysis. The total phenolic content, antioxidant activity and malondialdehyde levels of the vegetables were measured using the Folin-Ciocalteu phenol reagent, 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity and thiobarbituric acid reactive substances, respectively. RESULTS: Heat treatment had deleterious effects on the antioxidant properties of onion and garlic; and it decreased the antioxidant activity of broccoli. Freezing improved the antioxidant activity of broccoli and garlic, but had detrimental effects for cauliflower and onion. CONCLUSIONS: Heat treatment and freezing exhibit different effects on the antioxidant properties of broccoli, cauliflower, garlic and onion. Convenient cooking and storage patterns should be identified for each vegetable, to obtain the best nutritional benefit from the antioxidant compounds of vegetables.

Aqueous extract of Allium sativum L bulbs offer nephroprotection by attenuating vascular endothelial growth factor and extracellular signal-regulated kinase-1 expression in diabetic rats.

To investigate the nephroprotective effect of garlic and elucidate the mechanism by which it prevents the progression of diabetic nephropathy in diabetic rats, diabetes was induced by a single ip injection of streptozotocin (45 mg/kg body weight). Garlic extract (500 mg/kg body weight) and aminoguanidine (1 g/L) were supplemented in the treatment groups. Histopathological examination using H&E, PAS staining and the immunohistochemical analysis of vascular endothelial growth factor (VEGF) and extracellular signal-regulated kinase-1 (ERK-1) expression were performed on kidney sections at the end of 12 weeks. Significant change in both, the urine and serum biochemistry confirmed kidney damage in diabetic animals which was further confirmed by the histological changes such as mesangial expansion, glomerular basement membrane thickening, glycosuria and proteinuria. However, the diabetic animals treated with garlic extract showed a significant change in urine and serum biochemical parameters such as albumin, urea nitrogen and creatinine compared to that of diabetic rats. Further, the garlic supplemented diabetic rats showed a significant decrease in the expression of VEGF and ERK-1 compared to diabetic rats, attenuating mesangial expansion and glomerulosclerosis. Thus, garlic extract rendered nephroprotection in diabetic rats.

Hypouricemic and antioxidant activities of Allium cepa Lilliaceae and quercetin in normal and hyperuricemic rats

To evaluate the hypouricemic and antioxidant effects of Allium cepa Lilliaceae [Allium cepa L.] and quercetin in normal and hyperuricemic rats. The following study was conducted in the Department of Nutrition and Biochemistry, Tehran University of Medical Science, Iran, between May 2007 and March 2008. A total of 48 male Wistar rats [body weights: 180-200 g] were randomly divided into 8 equal groups including normal; normal + Allium cepa L. [5g/kg]; normal + quercetin [5mg/kg]; normal + allopurinol [5mg/kg]; hyperuricemic; hyperuricemic + Allium cepa L. [5g/kg]; hyperuricemic + quercetin [5mg/kg]; hyperuricemic + allopurinol [5mg/kg] once a day for 14 days. Experimentally, hyperuricemia in rats was induced by intraperitoneal injection of potassium oxonate [250mg/kg]. Allium cepa L. and quercetin treatments for 14 days significantly reduced [p=0.000] the serum uric acid levels of hyperuricemic rats in a time-dependent manner. All treatments significantly inhibited hepatic xanthine oxidase/xanthine dehydrogenase activity. Allium cepa L. and quercetin treatments led also to a significant improvement in biomarkers of oxidative stress in hyperuricemic rats [p=0.000]. Although the hypouricemic effect of allopurinol was much higher than that of Allium cepa L. and quercetin, it could not significantly change oxidative stress biomarkers. These results may be responsible partly for the beneficial effects of Allium cepa L. and its major flavonoid on hyperuricemia and oxidative stress

Evaluation of antimitotic activity of Rotula aquatica (Lour): a traditional herb used in treatment of cancer.

Rotula aquatica was extensively used by vaidyas (Ayurvedic practioners) in holistic treatment of cancer. In the present study, an attempt has been made to evaluate the antimitotic activity of R. aquatica. Preliminary antimitotic screening was done using Allium cepa root tip assay. The mitotic index of the root tips markedly decreased with increasing concentration of the aqueous extract. The different fractions obtained by successive extraction of R. aquatica using solvents of increasing polarity were also evaluated for their antimitotic activity. Tannins were isolated which showed a better activity than the non-tannin fraction. Experiments were also carried out with incorporation of folic acid in the aqueous extract. Folic acid inhibited the antimitotic activity of aqueous extract of R. aquatica in a dose dependent manner. The results obtained were compared with methotrexate--a known drug available in market as anti-cancer agent. The studies were extended to human cells using 3 pancreatic cancer cell lines, viz: HPAF-II, BxPC-3, and CAPAN-2. Extract of R. aquatica was found to be extremely effective in the prevention of cell proliferation of the pancreatic cancer cell lines. The phytochemical evaluation revealed presence of polyphenols (tannins) and steroids. A HPTLC fingerprinting was developed and studied. Two compounds were isolated and subjected to spectral studies like UV, IR and mass spectrums. The empirical formula was derived by considering this data with elemental analysis of the compounds.

Allium vegetables in cancer prevention: an overview.

The Allium genus includes approximately 500 species. Commonly used allium vegetables include garlic, onion, leeks, chives, scallions which are used all over the world in different delicacies. Some allium vegetables have been employed for millenia in the traditional medical practice to treat cardiovascular diseases. They have been shown to have applications as antimicrobial, antithrombotic, antitumor, hypolipidaemic, antiarthritic and hypoglycemic agents. In recent years, extensive research has focused on the anticarcinogenic potential of allium vegetables and their constituents, viz., allylsulfides and flavonoids (particularly quercetin which is present abundantly in onion). Epidemiological studies have shown that higher intake of allium products is associated with reduced risk of several types of cancers. These epidemiological findings are well correlated with laboratory investigations. Organosulfur compounds present in Allium vegetables, are considered to be responsible for the beneficial effects of these herbs. Several mechanisms have been proposed to explain the cancer-preventive effects of Allium vegetables and related organosulfur compounds. These include inhibition of mutagenesis, modulation of enzyme activities, inhibition of DNA adduct formation, free-radical scavenging, and effects on cell proliferation and tumor growth. Although there is a large body of evidence supporting these mechanisms, they are still speculative, and further research is needed to support causality between such properties and cancer-preventive activity in experimental animals. This article reviews current knowledge concerning allium vegetables and cancer prevention.

Therapeutic values of onion (Allium cepa L.) and garlic (Allium sativum L.).

Onion and garlic contain many sulfur containing active principles mainly in the form of cysteine derivatives, viz. S-alkyl cysteine sulfoxides which decompose into a variety of thiosulfinates and polysulfides by the action of an enzyme allinase on extraction. Decomposed products are volatile and present in the oils of onion and garlic. They possess antidiabetic, antibiotic, hypocholesterolaemic, fibrinolytic and various other biological actions. In addition to free sulfoxides in alliums, there are nonvolatile sulfur-containing peptides and proteins which possess various activities and thus make these vegetables as an important source of therapeutic agents. As allyl and related sulfoxides are inhibiting thiol group enzymes, alliums are to be used only in limited quantities.

Antiperoxide effects of S-allyl cysteine sulphoxide isolated from Allium sativum Linn and gugulipid in cholesterol diet fed rats.

Cholesterol containing diet significantly increased not only the body weight, but also the weight of liver and adipose tissue of rats. This is accompanied by a significant increase in blood lipids, atherogenic index and lipid peroxidation and a significant decrease in reduced glutathione level, superoxide dismutase and catalase activities in tissues. Treatment with S-allyl cysteine sulphoxide reverses the deleterious effects of cholesterol diet significantly and almost as effectively as gugulipid.

Antidiabetic and hypolipidemic effects of S-methyl cysteine sulfoxide isolated from Allium cepa Linn.

S-methyl cysteine sulphoxide (SMCS), a sulphur containing amino acid isolated from onion (Allium cepa Linn) showed antidiabetic and antihyperlipidemic effects. Oral administration of SMCS daily at a dose of 200 mg/kg body weight for a period of 45 days to alloxan diabetic rats controlled significantly their blood glucose and lipids in serum and tissues and altered the activities of liver hexokinase, glucose 6-phosphatase and HMG CoA reductase towards normal. The above effects of SMCS were comparable to those of glibenclamide and insulin.