Tungtungmadic acid (3-caffeoyl-4-dihydrocaffeoyl quinic acid) is a new chlorogenic acid derivative that was isolated from the Salicomia herbacea. The structure of tungtungmadic acid was determined using chemical and spectral analysis. The antioxidant activity of tungtungmadic acid was evaluated using various antioxidant assays, including free radical scavenging, lipid peroxidation and hydroxyl radical-induced DNA strand breaks assays. Tungtungmadic acid ($IC_{50};=;5.1;{mu}M;and;9.3;{mu}M$) was found to have higher antioxidant activity in the DPPH scavenging assay as well as in the iron-induced liver microsomal lipid peroxidation system. In addition, the tungtungmadic acid was also effective in protecting the plasmid DNA against strand breakage induced by hydroxyl radicals.