Effects of leucocyanidines on activities of metabolizing enzymes and antioxidant enzymes

Grapes (Vitis vinifera) as a Potential Candidate for the Therapy of the Metabolic Syndrome

Metabolic syndrome is associated with several disorders, including hypertension, diabetes, hyperlipidemia as well as cardiovascular diseases and stroke. Plant-derived polyphenols, compounds found in numerous plant species, play an important role as potential treatments for components of metabolic syndrome. Studies have provided evidence for protective effects of various polyphenol-rich foods against metabolic syndrome. Fruits, vegetables, cereals, nuts, and berries are rich in polyphenolic compounds. Grapes (Vitis vinifera), especially grape seeds, stand out as rich sources of polyphenol potent antioxidants and have been reported helpful for inhibiting the risk factors involved in the metabolic syndrome such as hyperlipidemia, hyperglycemia, and hypertension. There are also many studies about gastroprotective, hepatoprotective, and anti-obesity effects of grape polyphenolic compounds especially proanthocyanidins in the literature. The present study investigates the protective effects of grape seeds in metabolic syndrome. The results of this study show that grape polyphenols have significant effects on the level of blood glucose, lipid profile, blood pressure, as well as beneficial activities in liver and heart with various mechanisms. In addition, the pharmacokinetics of grape polyphenols is discussed. More detailed mechanistic investigations and phytochemical studies for finding the exact bioactive component(s) and molecular signaling pathways are suggested.

Purple grape juice inhibits 7,12-dimethylbenz[a]anthracene (DMBA)-induced rat mammary tumorigenesis and in vivo DMBA-DNA adduct formation

There has been considerable interest in identifying specific foods and phytochemicals that may have breast cancer preventive properties. Concord grapes are rich in polyphenolic chemicals and anthocyanin pigments that may have biological properties which could suppress cancer such as having antioxidant, antiproliferative, and proapoptotic actions. To determine the potential breast cancer protective action of purple grape juice, we examined the effect of grape juice consumption on the initiation stage of 7,12-dimethylbenz[a]anthracene (DMBA)-induced rat mammary tumorigenesis and on the in vivo formation of rat mammary DNA adducts in female Sprague-Dawley rats. Consumption of grape juice significantly inhibited mammary tumor mass at termination and the growth of tumors for the first 5 weeks of detectable tumor development. Consumption of grape juice phenolics by rats also significantly inhibited in vivo mammary DMBA-DNA adduct formation by 34 and 56% for animals fed phenolics at 346 and 692 mg/dL, respectively, compared to controls. Mammary 8-oxo-deoxyguanosine (8-oxo-dG) levels decreased by 25 and 37%, respectively, but the differences were not statistically significant. Liver DMBA-DNA adducts decreased by 10-30%, while 8-oxo-dG adducts remained unchanged, following grape juice intake. Liver glutathione S-transferase activity was significantly increased following grape juice consumption, but only at the highest level of intake. In addition, liver activities of catalase increased and xanthine oxidase decreased significantly, but only at the highest grape juice dose. Thus, these studies indicate that specific constituents or combinations of phytochemicals in purple grape juice can block the initiation stage of DMBA-induced rat mammary tumorigenesis. This tumor inhibitory effect was associated with a suppression of mammary DMBA-DNA adduct formation, which in part may be explained by increased liver activity of the phase II metabolizing enzyme, glutathione S-transferase. Mammary and liver 8-oxo-dG levels were not significantly altered by grape juice consumption. Thus, grape juice constituents appear to have benefit in decreasing susceptibility of the rat mammary gland to the tumor-initiating action of DMBA.