Multivariate analysis of antioxidant power and polyphenolic composition inred wines

It has been demonstrated that the dietary intake of compounds having antiox idant activity is very important, and various chemical, biological, and ele ctrochemical methods have been proposed to evaluate the antioxidant power o f compounds such as polyphenols. Wine, although nonessential, has a high po lyphenol content up to 2-3 g/L in red wines obtained by traditional macerat ion. The polyphenol content of wines is usually evaluated by the Folin reag ent, which provides an appropriate response to the requirements of wine man ufacturers. Because the presence of individual polyphenols may be evaluated by HPLC, more or less selective methods toward the various chemical classe s of polyphenols have been developed. An HPLC method set up recently was ap plied to evaluate how individual polyphenols contributed to the overall ant ioxidant power (AOP) of 60 Italian red wines, trying to identify the effect that individual compounds may have on the total AOP. Application of the mu ltivariate analysis allowed us to detect some determining compounds such as gallic acid and some flavonols. On the basis of the correlation between tw o traditional chemical methods, namely the total polyphenol determination b y the Folin reagent and the flavanol determination by the condensation reac tion with p-(dimethylamino)-cinnamaldehyde, it was shown that the use of th ese two merely chemical methods is well correlated (r = 0.83 and 0.87) to a n AOP evaluation of red wines.