Μελέτη συστατικών του οίνου με αντιοξειδωτική δράση

Abstract

The beneficial effect of wine consumption to human health has been widely accepted. Indeed, epidemiological studies showed a decrease in susceptibility of Low-Density Lipoprotein (LDL) to oxidation, which implies the contribution of wine consumption to the prevention of arteriosclerosis development and to the increase of serum antioxidant capacity. Furthermore, wine consumption has been associated with decrease in incidence of chronic inflammatory diseases and even cancer. This action can be attributed to antioxidant activity of wine, due to its content of many polyphenolic antioxidants. However, the polyphenolic and, hence the antioxidant profile of wines differs essentially between red and white wines and it is also greatly affected by the vinification technology used.According to the literature, the antioxidant activity of wines is affected by several parameters including among others the aging. However no references exist in the literature referring to the influence of wines‟ disposal conditions and, particularly, the effect of air exposure of wines to their antioxidant profile.In the present study, the effect of aging in bottles to the antioxidant content of twelve popular Greek wine varieties from South and North Greece was investigeated. The assessment of the antioxidant activity of wine samples can be carried out by means of in vitro cell free experimental protocols, among others the reducing ability against the stable diphenylpicrylhydrazyl ( DPPH ) free radical. Also determination of total polyphenols was carried out using Folin Ciocalteu method. Furthermore the antioxidant activity of discolored wines samples was calculated. Finally the effect of contact with atmospheric air to the antioxidant profile of the twelve investigated wines was studied by disposal in open bottles at two different conditions ( room temperature 25ν C / fridge temperature 4ν C ).However, the determination of the reducing ability towards DPPH can be considered as a tedious and time-consuming technique, especially for large-scale investigations needing a lot of data. For this purpose, an attempt was made to develop an alternative measure for the evaluation of antioxidant activity of wine samples. Electroanalytical techniques were selected as the oxidation ability of a chemical by a free radical can be associated with its reactivity with an electrode.The results according to DPPH reactivity showed that the antioxidant activity of red wines is ten times higher than white wines. Furthermore, aging leads to a moderate decrease in antioxidant activity of the investigated Greek wines, which can be attributed to the reduction of their anthocyanines content and to possible decrease in their total phenolic content. According to the Folin Ciocalteau method the total polyphenols of wines is reduced with aging. Disposal of wine samples in an open bottle provokes a considerable decrease on their antioxidant properties, possibly due to reactions with atmospheric oxygen. An elimination of about 50% of the antiradical activity of the investigated wine samples is observed in 8-12 days at 25oC and in 11-16 days at 4oC.Cyclic voltammograms of wine samples having the higher antioxidant activity ( Cabernet -Merlot, Cabernet - N. Drys, Metohi, Semeli, Syrah, Nemea and Megas Oinos ) did not show distinct peak, but rather a plateau at a similar voltage range, implying complex electrochemical behaviour and the presence of oxidation mechanisms with successive oxidation steps. The absence of distinct peak does not permit correlation with the results obtained by DPPH investigations.However, chronoamperometric data in one step ( 800 mV ) and in two steps ( 500 mV and 800 mV ) were found to be consistent with reactivity towards DPPH, expressed as Trolox equivalents. Chronoamperometric signals of all investigated wine samples from different vintages were further correlated with antiradical activity against DPPH with satisfactory statistics, despite the possible difference in their total chemical content. Thus chronoamperometric signal of wines at 800 mV can be considered as a quick measure for the evaluation of antioxidant activity of wine samples, especially for large-scale investigations needing a lot of data.