Method for Measuring Antioxidant Activity and Its Application to Monitoring the Antioxidant Capacity of Wines

TLDR

Antioxidant capacity of wines is strictly related to the amount of phenolic compounds. The study developed a novel method for measuring antioxidant activity using N,N‑dimethyl‑p‑phenylenediamine (DMPD). The DMPD method employs the stable radical cation of N,N‑dimethyl‑p‑phenylenediamine, with linear inhibition of color formation by 0.2–11 µg TROLOX, and a rapid, inexpensive protocol that ensures sensitivity and reproducibility for hydrophilic antioxidants, validated on wine samples from Campania, Italy. The DMPD assay produced results comparable to the established ABTS method on the same wine samples. Keywords include antioxidant activity, DMPD, radical cation, ABTS, and wine.

Abstract

A novel method for measuring the antioxidant activity using N,N-dimethyl-p-phenylenediamine (DMPD) was developed. The radical cation of this compound gives a stable colored solution and a linear inhibition of color formation can be observed in the presence of 0.2−11 μg of TROLOX. The experimental protocol, which is rapid and inexpensive, ensures sensitivity and reproducibility in the measure of antioxidant activity of hydrophilic compounds. The effectiveness of the DMPD method on real foods was verified by evaluating the antioxidant ability of wine samples coming from different areas of Campania, Italy. Antioxidant capacity of wines is strictly related to the amount of phenolic compounds. The results obtained by the DMPD method are very similar to those obtained on the same samples when the radical cation of 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (Miller et al., 1996) was used. Keywords: Antioxidant activity; DMPD; radical cation; ABTS; wine