Evaluation of antioxidant activity of chlorogenic acids and coffee extracts by an electrochemical DNA-based biosensor

Sensitivity of dsDNA structure towards OH radicals as the pro-oxidants has been utilized as the detection principle of an analytical procedure applied for the first time to the evaluation of antioxidant activity (AOA) of 6 chlorogenic acids (CGAs) and extracts of 10 coffees. A nanostructured electrochemical DNA-based biosensor was prepared using a commercial electrode assembly and treated in the DNA cleavage agent formed by the Fenton type reaction. An addition of CGAs and aqueous coffee extracts significantly diminishes the degree of DNA degradation determined using cyclic voltammetry (CV) with the redox indicator [Fe(CN)₆]^3-/4-. The AOA decreases in order caffeic acid, CFA, >caffeoylquinic acids, CQAs, >dicaffeoylquinic acids, diCQAs, exhibiting the relative portion of survived DNA of about 71%, 70% and 69%, respectively, and of about 72% for C. robusta, Cherry, India (green bean) to 49% for Nescafé Espresso. Mechanisms of antioxidative properties are discussed.