Protective effect of structurally diverse grape procyanidin fractions against UV-induced cell damage and death.

UV radiation leads to the generation of reactive oxygen species (ROS). These molecules exert a variety of harmful effects by altering key cellular functions and may result in cell death. Several studies have demonstrated that human skin can be protected against UV radiation by using plant-derived antioxidants. Here we evaluated the in vitro capacity of several antioxidant polyphenolic fractions from grape, which differ in their degree of polymerization and percentage of galloylation, to protect HaCaT human keratinocytes against UV-induced oxidative damage. These fractions inhibited both basal and UVB- or UVA-induced intracellular ROS generation in this cell line. Consequently, the same fractions inhibited p38 and JNK1/2 activation induced by UVB or UVA radiation. The highest protective effect was for fractions rich in procyanidin oligomers and gallate esters. These encouraging in vitro results support further research and should be taken into consideration into the clinical pharmacology of plant-derived polyphenolic extracts as novel agents for skin photoprotection.

Antiproliferative effect of antioxidant polyphenols from grape in murine Hepa-1c1c7.

BACKGROUND: Grapes and wine contain high concentrations of polyphenolic compounds. Although their cancer protective effect has been well documented, their activity as anticarcinogens should be cautiously considered since the molecular bases of action and their applicability to human cancer prevention are still unclear. AIM OF THE STUDY: We studied the antioxidant/antiradical activity and the antiproliferative effect in vitro of different polyphenolic mixtures, extracted from grapes and fractionated through RP-HPLC. METHODS: The polyphenolic fractions were chemically characterized and their antioxidant/antiradical activity was determined by the DPPH assay. Mouse hepatoma Hepa-1c1c7 cells were used to study the cell growth inhibition capacity of these fractions by MTT assay. Their capacity of altering cell cycle and possible induction of apoptosis was examined using FACS analysis. RESULTS: The original polyphenolic fraction OW, which contained gallic acid (GA), (+)-catechin (Cat), (-)-epicatechin (Ec), glycosylated flavonols (F) and procyanidin oligomers was fractionated into fraction I, composed of monomers and small oligomers, and fraction II that included flavonols and procyanidin oligomers of higher molecular weight. The three polyphenolic fractions tested showed quite similar antiradical activity, although fraction I was the most potent antiradical agent (lowest ED(50) value: 9 microg). Fraction II was the least potent cell growth inhibitor (highest IC(50) value: 100 microg/ml) but showed the strongest effect on the cell cycle of Hepa-1c1c7, inducing apoptosis in those cells. The original fraction OW was demonstrated to have the most potent cell growth inhibition effect (lowest IC(50) value: 43 microg/ml). However, it only appeared to alter cell cycle of Hepa-1c1c7 at concentrations higher than its IC(50) and did not induce apoptosis in those cells. A similar effect on cell cycle and apoptosis was encountered for fraction I. CONCLUSIONS: The polyphenolic fractions tested in this study were potent antiradical agents and exerted an antiproliferative effect in mouse hepatoma Hepa-1c1c7 cells; the fraction with the highest degree of polimerization and galloylation (fraction II) had the most influence on the cell cycle and induction of apoptosis on Hepa-1c1c7.

Valorization of grape (Vitis vinifera) byproducts. Antioxidant and biological properties of polyphenolic fractions differing in procyanidin composition and flavonol content.

Many byproducts and wastes generated by agroindustries contain polyphenols with potential application as food antioxidants and preventive agents against skin cancer and other diseases. The performance of polyphenolic fractions from Parellada grape (Vitis vinifera) pomace as antioxidants in different physicochemical environments was tested. Fractions containing oligomers with mean degree of polymerization between 3 and 4 and percentage galloylation ca. 30% were the most potent free radical scavengers and efficient antioxidants in an oil-in-water emulsion. A fraction including glycosylated flavonols was also efficient in the emulsion. All the fractions showed low aquatic toxicity and weak influence on proliferation of human melanoma cells.