Antioxidant activity of naturally occurring phenols and their corresponding biphenols as individual compounds and in mixtures with anticancer drug 5-fluorouracil

The opportunity of combination therapies based on natural products and approved drugs, such as the combination of 5-fluorouracil (5-FU), an antineoplastic drug, with phenols has been successfully investigated. Although the growing interest in these mixtures and their potential use in medicinal applications, no information has been reported on their antioxidant activity in term of additivism or synergism that results from the combinations of these compounds. The present study aimed to investigate the antioxidant effect of 5-FU as individual compound and in equimolar mixture with some natural phenols and their corresponding biphenols. Electrochemical behavior of 5-FU and its antioxidant power on the oxidative environment produced by hydrogen peroxide (HP) have been assessed. Moreover, the eventual synergism produced by the co-presence of 5-FU and one of the most important physiological antioxidant compounds as ascorbic acid (AA) has been studied. Results showed that 5-FU did not show any antioxidant activity, not affecting the HP current, while AA was able to significantly reduce the signal produced by HP. The co-presence of 5-FU and AA determined a slightly higher decrease in the HP signal, if compared with AA alone. Protective effect of some naturally occurring phenols and their biphenols as individual compounds and as equimolar binary mixture with 5-FU were studied during bulk lipid autoxidation. Syntheses of biphenols were carried out under sustainable conditions by C-C coupling reaction of the corresponding monomer. The results of this study showed that the inhibitory effect of the mixtures was similar to those of the individual phenols and even weaker i.e. neither synergism, nor additivism were obtained.