Synthesis and antioxidant study of new polyphenolic hybrid-coumarins

Abstract

The antioxidant capacity of hydroxylated coumarins and hydroxybenzoic acids has been widely described. However, there is little information on the antioxidant activity when both systems are functionalized. In this work, new hybrid compounds synthesis with a common coumarin scaffold and hydroxybenzoic acids is described. Their antioxidant capacity was evaluated against reactive oxygen species (ROS) using oxygen radical absorbance capacity-fluorescein (ORAC-FL), electron spin resonance (ESR) spin trapping, quenching of superoxide anion, cellular antioxidant activity (CAA) and a ferric reducing ability of plasma (FRAP assay). Additionally, the local reactivity indicator (Fukui index) was calculated to discriminate different reactive sites in the new molecules in which the oxidative process occurs. Likewise, the BDE values were calculated in order to obtain information about the antioxidant capacity for HAT mechanisms. The insertion of organic phenols in a simple coumarin structure produced new derivatives with an improved antioxidant capacity in relation to coumarin 1a. For compound 3c, a synergy phenomenon in ORAC-FL and the FRAP test was observed. For compound 3b, this phenomenon was observed in the superoxide scavenging test. According to the CAA assay results, the activity of the new compounds is limited to those oxidative processes in lipophilic media (e.g., bio membranes). Keywords: Polyphenol, Hybrid coumarin, Antioxidant capacity, ROS, Fukui index