Role of galloylation and polymerization in cytoprotective effects of polyphenolic fractions against hydrogen peroxide insult.

Byproducts and wastes generated by agricultural, food, and forestry industries contain large amounts of polyphenols, which can be potentially used as sources of natural or semisynthetic antioxidants. This study examined and compared the protection against peroxidative damage induced in erythrocytes and 3T3 cell line of polyphenolic fractions from white grape pomace, pine bark, and witch hazel bark. The work pays special attention to the different degrees of polymerization and galloylation of the extracts to contribute to the understanding of their mechanisms of action. Fractions demonstrated different protections against erythrocyte lipid peroxidation, hemolysis, and 3T3 cytotoxicity caused by H(2)O(2). Galloylation is claimed to be related to antioxidant protective capacity, and it is also responsible for the pro-oxidant effect observed at high doses. The results show that not only the percentage of galloylation but also the degree of polymerization are important modulators of their antioxidant capacity. In this sense, it is crucial that novel polyphenolic fractions were prepared attending a value of 3 for the mean degree of polymerization and did not exceed a 30% of galloylation to reach the highest antioxidant capacity with the lowest cytotoxic effects. For this reason, the grape extracts appear to be the best strategy to fight against hydrogen peroxide cell damage.

Biobased epicatechin conjugates protect erythrocytes and nontumoral cell lines from H2O2-induced oxidative stress.

This paper reports the study of the protective action of epicatechin and epicatechin derivatives, obtained by depolymerizing polymeric flavanols in the presence of cysteine or cysteamine, on red blood cells (RBC) and nontumoral cell lines challenged by exogenous H(2)O(2). The epicatechin derivatives showed more effective antioxidant properties than epicatechin. Among them, 4ß-(2-aminoethylthio)epicatechin 3-O-gallate showed the highest antioxidant activity against three markers of oxidative stress: hemolysis, lipid peroxidation, and cytotoxicity. Furthermore, as this compound lacks the pyrogallol group on the condensed flavanic structure, it might be safer than other potent gallocatechin-type polyphenols. These findings indicate that these epicatechin derivatives, which are byproducts of the agro-food industry show potential for application in the food and drug industries.

Low cytotoxicity of creams and lotions formulated with Buriti oil (Mauritia flexuosa) assessed by the neutral red release test.

The aim of this work was to evaluate possible cytotoxic effects of topical creams and lotions produced with Buriti oil and commercial surfactants on human keratinocytes HaCat and 3T3 embryonic mouse fibroblast cultures. We also aimed to assess the cytotoxicity of the surfactants used to produce the emulsions. The neutral red release (NRR) assay was performed as an in vitro method to evaluate the cytotoxicity of the emulsions in HaCat and 3T3 cell lines and predict potential skin irritation. The Buriti oil emulsions presented low cytotoxicity to the cells at high concentrations and the addition of Vitamin E increased cell viability. Among the surfactant tested, Unitol CE 200F proved to be the most cytotoxic, presenting an IC(50) significantly lower than the others. Emulsions formulated with Buriti oil and commercial surfactants could be non irritant to the skin due to their low cytotoxicity, especially when enhanced with vitamin E. When emulsified with Buriti oil, water and Brij 72, Unitol CE 200F showed less cytotoxic effects than when tested alone.

Highly galloylated tannin fractions from witch hazel (Hamamelis virginiana) bark: electron transfer capacity, in vitro antioxidant activity, and effects on skin-related cells.

Witch hazel ( Hammamelis virginiana) bark is a rich source of both condensed and hydrolizable oligomeric tannins. From a polyphenolic extract soluble in both ethyl acetate and water, we have generated fractions rich in pyrogallol-containing polyphenols (proanthocyanidins, gallotannins, and gallates). The mixtures were highly active as free radical scavengers against ABTS, DPPH (hydrogen donation and electron transfer), and HNTTM (electron transfer). They were also able to reduce the newly introduced TNPTM radical, meaning that they included some highly reactive components. Witch hazel phenolics protected red blood cells from free radical-induced hemolysis and were mildly cytotoxic to 3T3 fibroblasts and HaCat keratinocytes. They also inhibited the proliferation of tumoral SK-Mel 28 melanoma cells at lower concentrations than grape and pine procyanidins. The high content in pyrogallol moieties may be behind the effect of witch hazel phenolics on skin cells. Because the most cytotoxic and antiproliferative mixtures were also the most efficient as electron transfer agents, we hypothesize that the final putative antioxidant effect of polyphenols may be in part attributed to the stimulation of defense systems by mild prooxidant challenges provided by reactive oxygen species generated through redox cycling.

Comparative antioxidant and cytotoxic effects of lignins from different sources.

The potential antioxidant activity of industrial lignins obtained from different sources and their potential cytotoxic effect on two immortalized cell lines is studied. In addition the stability of aqueous preparations of these lignins is studied together with the effect on them of ultraviolet irradiation. The lignins studied show a high antioxidant capacity over a range of concentrations that are not harmful to normal human cells. The stability of the lignin solutions when they are exposed to UVA light is confirmed. These findings suggest new uses for lignins in cosmetic and topical medical formulations. This study aims to demonstrate the antioxidant activity and stability of several lignins from different sources. It assesses their suitability for new commercial applications, mainly in cosmetics and pharmaceuticals, by discarding any possible cytotoxic properties.

Comparative antioxidant and cytotoxic effect of procyanidin fractions from grape and pine.

There is a great interest in characterizing the biological properties of natural compounds obtained from plants, especially polyphenols. We studied the structure-activity-cytotoxicity relationships of polyphenolic fractions obtained from grape pomace and pine bark. These fractions contained similar polymerised flavonoids but different percentages of pyrogallol groups that confer on them different biological properties. The human keratinocyte cell line HaCaT and the mouse fibroblast cell line 3T3 were used to study the cytotoxicity of the different fractions after 24, 48, and 72 h of exposure. Antioxidant activity of the fractions was evaluated by measuring the inhibition of hemolysis mediated by AAPH. Our results demonstrate that the polyphenolic fractions studied show high antioxidant capacity in a concentration range that is not harmful to normal human cells. Pine fractions presented slightly lower antioxidant activity than grape fractions but are less cytotoxic. This data provides useful information to help design safe antioxidant products that act without altering critical cell functions.

Comparative study of the cytotoxicity induced by antioxidant epicatechin conjugates obtained from grape.

We studied the cytotoxicity of epicatechin conjugates obtained by depolymerization of grape polymeric flavanols in the presence of cysteamine or cysteine and the resulting conjugates purified by ion exchange and/or reversed-phase high-resolution chromatography and compared it to their antioxidant capacity. The studies were carried out on fibroblast and keratinocyte cell lines. The cytotoxic effects of these products were observed at concentrations 3-7-fold higher than the antioxidant concentration after exposure for 24, 48, and 72 h. The compounds with a gallate group were more toxic than the corresponding products without one. It is interesting to note that the esther ethyl derivative exhibited low cytotoxicity but had the most potent antioxidant activity. The results indicated that effective antioxidant activity can be obtained from these products in a concentration range that is safe for the normal cell. This finding suggests new pharmaceutical applications and may also help us to identify the potential therapeutic dose.