CATECHINS SPECTROPHOTOMETRICAL DETERMINATION FROM HYDROLYSABLE TANNINS, IN SOME RED GRAPE VARIETIES

Abstract

Among polyphenols compounds, in grapes and wine are found mostly flavanols, catechins and tannins. They are found in greater quantity in red grapes, compared with the whites. Due to their antioxidant activity, up to 25-100 times more than that of vitamins C and E, was studied their anticancer properties, or cardio and immunoprotecto r effect.[1] Polyphenols is gathered in the solid parts of grapes (rachis, peels and seeds) and go in must and wine through the process of macerationfermentation. [2] Catechins content of grape varies with: variety, so il composition, climate, geographic origin, and cultivation practices. This is why we took in study four grape varieties: Cabernet Sauvignon, Merlot, Burgund mare and Muscat Hamburg. The grapes were harvested at complete maturity, from two viticultural areas: West Carpathian Area (Reca � -Timi� ) and South Carpathian Area (Merei-Dealu Mare). The fresh grapes were separated in different parts: rachis, grape skins, seeds and must. The solid parts: rachis, peels and seeds were dried at 65°C, made powder and stocked at 25°C. The must was filtrated and preserved in refrigerator at -20° C. The polyphenolic constituents were extracted fro m the plant material by a series of successive extrac tion. The extracts obtained were analyzed spectrophotometrically at 510 nm. The method consists of tannins precipitation with bovine serum albumin, followed by centrifuge separation and supe rnatant treatment with FeCl 3 solution. The intensity of color produced is proportional to the amount of total catechins (catechins, epicatechins, gallocatechins and epigalocatechins) and is measure d at 510 nm spectrophotometrical. From the samples of seeds, peels and rachis analyzed, were w eighing 0.5 g to add a volume of 10 ml of methyl alcohol with 50% 1% HCl conc. Precipitation of samples was made using ultrasonication over 2 hours. The samples of must or wine were processed in the s ame way. Seeds are rich in catechins than rachis in general 2,5-3:1 report. In samples of peels and wine, catechins content is very low, about 80-100 times s maller than the seeds and present lower interest to catechins. In consequence, to get rich catechins pr eparations are recommended rachis and seeds mixtures. Besides seeds, rachis can be a good sourc e of catechins, representing a proper raw material for the extracts with antioxidant effect. Comparing the values obtained from Merlot in the two winegrowing centers it was established that, in Merei-D ealu Mare gathered the higher content of catechins, both in solids parts as well as in wine.