Antioxidant and antiproliferative activities of common vegetables

Antioxidant and antiproliferative activities of common vegetables.

Chu YF, Sun J, Wu X, Liu RH.

Department of Food Science and Institute of Comparative and Environmental Toxicology, Cornell University, Ithaca, New York 14853, USA.

Epidemiological studies have shown that consumption of fruits and vegetables is associated with reduced risk of chronic diseases. Increased consumption of fruits and vegetables containing high levels of phytochemicals has been recommended to prevent chronic diseases related to oxidative stress in the human body. In this study, 10 common vegetables were selected on the basis of consumption per capita data in the United States. A more complete profile of phenolic distributions, including both free and bound phenolics in these vegetables, is reported here using new and modified methods. Broccoli possessed the highest total phenolic content, followed by spinach, yellow onion, red pepper, carrot, cabbage, potato, lettuce, celery, and cucumber. Red pepper had the highest total antioxidant activity, followed by broccoli, carrot, spinach, cabbage, yellow onion, celery, potato, lettuce, and cucumber. The phenolics antioxidant index (PAI) was proposed to evaluate the quality/quantity of phenolic contents in these vegetables and was calculated from the corrected total antioxidant activities by eliminating vitamin C contributions. Antiproliferative activities were also studied in vitro using HepG(2) human liver cancer cells. Spinach showed the highest inhibitory effect, followed by cabbage, red pepper, onion, and broccoli. On the basis of these results, the bioactivity index (BI) for dietary cancer prevention is proposed to provide a simple reference for consumers to choose vegetables in accordance with their beneficial activities. The BI could be a new alternative biomarker for future epidemiological studies in dietary cancer prevention and health promotion.

PMID: 12405796 [PubMed - indexed for MEDLINE]

J Nutr 2002 Oct;132(10):2991-4
Brassica, biotransformation and cancer risk: genetic polymorphisms alter the preventive effects of cruciferous vegetables.

Lampe JW, Peterson S.

Cancer Prevention Research Program, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA. jlampe@fhcrc.org

The chemoprotective effect of cruciferous vegetables is due to their high glucosinolate content and the capacity of glucosinolate metabolites, such as isothiocyanates (ITC) and indoles, to modulate biotransformation enzyme systems (e.g., cytochromes P450 and conjugating enzymes). Data from molecular epidemiologic studies suggest that genetic and associated functional variations in biotransformation enzymes, particularly glutathione S-transferase (GST)M1 and GSTT1, which metabolize ITC, alter cancer risk in response to cruciferous vegetable exposure. Moreover, genetic polymorphisms in receptors and transcription factors that interact with these compounds may further contribute to variation in response to cruciferous vegetable intake. This review outlines the metabolism and mechanisms of action of cruciferous vegetable constituents, discusses the recent human studies testing effects of cruciferous vegetables on biotransformation systems and summarizes the epidemiologic and experimental evidence for an effect of genetic polymorphisms in these enzymes on response to cruciferous vegetable intake. Taken together, genetic differences in biotransformation enzymes and the factors that regulate them, as well as variation in glucosinolate content of cruciferous vegetables and the methods used to prepare these foods underscore the multiple layers of complexity that affect the study of gene-diet interactions and cancer risk in humans.

Publication Types:

Review
Review, Tutorial

PPMID: 12368383 [PubMed - indexed for MEDLINE]

Arch Tierernahr 2001;55(4):333-50
Effects of rapeseed-press cake glucosinolates and iodine on the performance, the thyroid gland and the liver vitamin A status of pigs.

Schone F, Tischendorf F, Leiterer M, Hartung H, Bargholz J.

Agricultural Institute of Thuringia, Jena, Germany.

Rapeseed press cake (per kg DM 181 g EE, 341 g CP and 23.3 mmol glucosinolates) was tested in a long-term experiment with a total of sixty pigs (live weight range 24 to 104 kg). The 3 x 2 factorial design consisted of three rapeseed press cake levels (no rapeseed press cake--control, 75 g or 150 g rapeseed press cake per kg diet) each with two iodine dosages (125 or 250 micrograms supplementary iodine per kg diet). Reduced feed intake and depressed weight gain were found in groups receiving 150 g rapeseed press cake per kg diet, which correspond to 3.2 mmol glucosinolates per kg diet. At an inclusion level of 75 g rapeseed-press cake per kg diet no differences in feed intake and growth intensity were recorded in comparison to the rape feed free control. The rapeseed-press cake diet increased the weight of thyroid gland and liver and decreased the serum thyroxine (T4) concentration. Higher iodine dosage increased the serum T4 concentration of pigs receiving 75 g rapeseed press cake per kg diet (= 1.6 mmol glucosinolates per kg diet) to the level of the control group and retarded the enlargement of the thyroid gland. Intake of rapeseed products lowered the iodine content of the thyroid gland, however, there was no significant difference between groups given 1.6 and 3.2 mmol glucosinolates per kg diet. The vitamin A content of the whole liver and the vitamin A serum concentration were not influenced by the diets tested. However, rapeseed press cake and the glucosinolates, respectively, decreased the vitamin A concentration per gram liver due to the organ enlargement and the resulting dilution effect.

PMID: 12357593 [PubMed - indexed for MEDLINE]

Nutr Cancer 2002;42(1):1-9
Brassica vegetables and prostate cancer risk: a review of the epidemiological evidence.

Kristal AR, Lampe JW.

Cancer Prevention Research Program, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA. akristal@fhcrc.org

Epidemiological studies have yielded conflicting results on the associations of diet with prostate cancer. We review evidence that Brassica vegetables are associated with reduced prostate cancer risk. Brassica vegetables, which include broccoli, cabbage, mustard and collard greens, and bok choy, contain glucosinolates, the metabolic breakdown products of which are potent modulators of xenobiotic-metabolizing enzymes that protect DNA from damage. Twelve published studies give some information about Brassica vegetables and prostate cancer risk; six of these studies can be clearly interpreted. Of these, three reported statistically significant reduced risks (P < 0.05) and one reported a borderline significant reduced risk (P = 0.06) with high Brassica vegetable consumption. The epidemiological literature provides modest support for the hypothesis that high intakes of Brassica vegetables reduce prostate cancer risk.

PMID: 12235639 [PubMed - in process]

Brassica vegetables and prostate cancer risk: a review of the epidemiological evidence.

Kristal AR, Lampe JW.

Cancer Prevention Research Program, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA. akristal@fhcrc.org

Epidemiological studies have yielded conflicting results on the associations of diet with prostate cancer. We review evidence that Brassica vegetables are associated with reduced prostate cancer risk. Brassica vegetables, which include broccoli, cabbage, mustard and collard greens, and bok choy, contain glucosinolates, the metabolic breakdown products of which are potent modulators of xenobiotic-metabolizing enzymes that protect DNA from damage. Twelve published studies give some information about Brassica vegetables and prostate cancer risk; six of these studies can be clearly interpreted. Of these, three reported statistically significant reduced risks (P < 0.05) and one reported a borderline significant reduced risk (P = 0.06) with high Brassica vegetable consumption. The epidemiological literature provides modest support for the hypothesis that high intakes of Brassica vegetables reduce prostate cancer risk.

PMID: 12235639 [PubMed - in process]

J Agric Food Chem 2002 Sep 11;50(19):5490-5
Antioxidant effects of isorhamnetin 3,7-di-O-beta-D-glucopyranoside isolated from mustard leaf (Brassica juncea) in rats with streptozotocin-induced diabetes.

Yokozawa T, Kim HY, Cho EJ, Choi JS, Chung HY.

Institute of Natural Medicine, Toyama Medical and Pharmaceutical University, Sugitani, Toyama 930-0194, Japan. yokozawa@ms.toyama-mpu.ac.jp

To investigate the effects of isorhamnetin 3,7-di-O-beta-D-glucopyranoside (isorhamnetin diglucoside), a major flavonoid compound of mustard leaf, on oxidative stress due to diabetes mellitus, in vivo and in vitro studies were carried out. Oral administration of isorhamnetin diglucoside (10 or 20 mg/kg of body weight/day for 10 days) to rats with streptozotocin-induced diabetes significantly reduced serum levels of glucose and 5-(hydroxymethyl)furfural (5-HMF), which is glycosylated with hemoglobin and is an indicator of oxidative stress. After intraperitoneal administration, isorhamnetin diglucoside did not show these activities. In addition, after oral administration, the thiobarbituric acid-reactive substance levels of serum, and liver and kidney mitochondria declined significantly compared with the control group in a dose-dependent manner, whereas after intraperitoneal administration these levels fell only slightly. On the basis of the oral and intraperitoneal results, it was hypothesized that isorhamnetin diglucoside was converted to its metabolite in vivo, and its conversion to its aglycone, isorhamnetin, by beta-glucosidase was confirmed; isorhamnetin acted as an antioxidant. Moreover, it was observed that isorhamnetin diglucoside had no effect on the 1,1-diphenyl-2-picrylhydrazyl radical, whereas isorhamnetin showed a potent antioxidant effect in vitro. In addition, intraperitoneal administration of isorhamnetin reduced serum glucose and 5-HMF levels. Furthermore, lipid peroxidation in blood, liver, and kidney associated with diabetes mellitus declined after the administration of isorhamnetin. These results suggest that isorhamnetin diglucoside is metabolized in vivo by intestinal bacteria to isorhamnetin and that isorhamnetin plays an important role as an antioxidant.

PMID: 12207497 [PubMed - indexed for MEDLINE]

Cancer Lett 2002 Aug 8;182(1):1-10
Inhibitory effect of whole strawberries, garlic juice or kale juice on endogenous formation of N-nitrosodimethylamine in humans.

Chung MJ, Lee SH, Sung NJ.

Department of Food and Nutrition, Gyeongsang National University, Jinju 660-701, South Korea.

In vitro and in vivo experiments were performed on inhibition of nitrosation by strawberry, garlic, and kale extracts. Strawberry, garlic, and kale extracts inhibited nitrosation in vitro. However, garlic extract has a greater ability to inhibit the chemical nitrosation in vitro than strawberry and kale extracts. The garlic methanol-soluble fraction of the garlic extract was fractionated into G1-G4 fractions by Prep-LC. Fraction G1 inhibited N-nitrosodimethylamine (NDMA) formation by 84+/-1%. We studied the formation of the carcinogen NDMA in humans after administration of nitrate (400 mg/day) in combination with an amine-rich diet and its possible inhibition by administration of whole strawberries (300 g), garlic juice (200 g: 75 g garlic juice in drinking water), or kale juice (200 g) in 27 males and 13 females (ten healthy volunteers in each group) of age 24+/-3 years. Nitrate intake resulted in a significant rise in mean salivary nitrate and nitrite concentrations. Also, nitrate excretion in urine during the experimental day was significantly increased compared with the control days. When whole strawberries, garlic juice, or kale juice was provided immediately after an amine-rich diet with a nitrate, NDMA excretion was decreased by 70, 71, and 44%, respectively, compared with NDMA excretion after ingestion of an amine-rich diet with a nitrate. These results suggest that consumption of whole strawberries, garlic juice, or kale juice can reduce endogenous NDMA formation.

PMID: 12175517 [PubMed - indexed for MEDLINE]

Indian J Med Res 1995 Nov;102:223-6
Role of goitrogens in iodine deficiency disorders & brain development.
Rao PS, Lakshmy R.

National Institute of Nutrition, Hyderabad.

Although iodine deficiency has primarily been implicated in the causation of goitre, the significant role played by food goitrogens in the etiology of iodine deficiency disorder (IDD) is being increasingly recognized. Impaired brain development is the major cause of concern in IDD. Detailed experimental studies were undertaken to ascertain various biochemical changes associated with developing brain in response to treatment with a goitrogens--thiocyanate. Addition of thiocyanate to food deprived of KI brought down significantly the circulating levels of thyroxine (T4) in rats. Nucleic acids and protein content in different regions of brain were significantly lowered in rat pups exposed to thiocyanate. The rate of microtubule assembly, which is detrimental for neurite growth was considerably lowered, thereby influencing both myelin deposition and synaptogenesis in developing brain. Goitrogen intake not only caused an adaptive increase in the activity of type II 5'-deiodinase, which governs availability of triiodothyronine (T3) in brain, it also increased the latter's binding to brain nuclear receptors under conditions of thiocyanate induced hypothyroid state. Addition of adequate quantities of KI mitigated thiocyanate induced alterations by restoring circulating level of thyroxine. These investigations suggest that goitrogens play a significant role in influencing biochemical events unique to developing brain.

Publication Types:

Review
Review, Tutorial

PPMID: 8675242 [PubMed - indexed for MEDLINE]

Horm Metab Res 1995 Oct;27(10):450-4
Iodine metabolism in response to goitrogen induced altered thyroid status under conditions of moderate and high intake of iodine.

Lakshmy R, Rao PS, Sesikeran B, Suryaprakash P.

National Institute of Nutrition, Indian Council of Medical Research, Hyderabad, India.

Metabolic experiments in rats were undertaken to relate excretory pattern of iodine and thiocyanate, with thyroid weight and the circulating levels of thyroxine, in response to moderate and high intake of iodine and under conditions of goitrogen induced altered thyroid status. On a moderate intake of iodine (by depriving diet of KI) 25 mg of thiocyanate or substitution of 1/3rd proportion of casein based diet with dry cabbage, could significantly reduce plasma thyroxine level by 60 days. Neither body weight nor the weights of liver, kidney, heart or spleen were affected due to exposure to goitrogens. A significant increase in thyroid weight as well as higher excretion of iodine and thiocyanate were evident in goitrogen-fed rats. Presence of high amounts of KI, to a certain extent, offered protection from adverse effects of the goitrogens. Semi quantitative assessment of thyroid, indicated hypofunctioning of thyroid with follicular hyperplasia in thiocyanate fed rats. These alterations were of moderate degree in response to cabbage feeding. These results emphasize that, moderate intake of iodine, adequate to meet iodine requirement, may not ensure normal functioning of thyroid in the presence of goitrogens.

PMID: 8575723 [PubMed - indexed for MEDLINE]

Gen Comp Endocrinol 1992 Jan;85(1):147-55
Measurement of plasma thyroxine binding protein in relation to thyroidal condition in the turtle, Trachemys scripta, by radioimmunoassay.

Pavgi S, Licht P.

Department of Integrative Biology, University of California, Berkeley 94720.

Polyclonal (rabbit) antisera were generated against a high-affinity plasma thyroxine (T4) binding protein (TBP) purified from the turtle, Trachemys scripta, and used to develop a specific radioimmunoassay (RIA). The RIA demonstrated the presence of an immunochemically related protein in the plasma of several other species of Trachemys and in members of several other genera from the same family, Emydidae. Plasma from all nonemydids and some emydid genera either showed no competition or nonparallelism in RIA. The presence and level of radioimmunoassayable TBP in diverse species correlated with results of previous comparative measurements of T4 binding activity. However, an immunoreactive protein of the same molecular weight as TBP was identified in all turtles by Western blot analysis. More detailed studies in T. scripta demonstrated that variations in plasma T4 binding activity induced by experimental or environmental manipulations were related to differences in TBP concentrations. The concentration of TBP varied by orders of magnitude (from less than 1 to ca. 150 mg/liter) in euthyroid animals; levels showed ontogenetic changes (virtually absent in hatchlings) and were directly related to thyroidal status. Experimentally induced hypothyroidism (goitrogen treatment or surgical thyroidectomy) resulted in a marked suppression of TBP, and T4 treatment prevented its decline or reinstated it. Thus, in the turtle, this T4 transport protein may exist in higher concentrations and its levels are more variable and show a different relationship to thyroid activity than the analogous T4 binding globulin (TBG) in mammals.

PMID: 1563614 [PubMed - indexed for MEDLINE]