Radical-scavenging activity of dietary phytophenols in combination with co-antioxidants using the induction period method.

ABSTRACT

The radical-scavenging activity of dietary phytophenols has been investigated by many researches due to their antioxidant, anti-inflammatory and anticancer property but the radical-scavenging effect of 2-phytophenol and the phytophenolco-antioxidants, vitamin C and thiol combination under nearly anaerobic conditions still remains unknown. The radical-scavenging activity for seventeen phytophenols and for six synthetic phenols (positive controls) was investigated using the induction period method in the polymerization of methyl methacrylates (MMA) initiated by thermal decomposition of benzoyl peroxide (BPO) by monitoring differential scanning calorimetery (DSC). The k(inh) for the phytophenols was likely with the range 0.5 × 10³ M⁻¹s⁻¹-2.2 × 10³ M⁻¹s⁻¹, whereas that for synthetic phenols, hydroquinone and galvinoxyl, was with the range 7 × 10³ M⁻¹s⁻¹-8 × 10³ M⁻¹s⁻¹. Also, the additive scavenging effect of the (-)-epigallocatechin (EGC)(-)-epicatechin (EC) and the (+)-catechinepicatechin (EC) combination was observed at 11 molar ratio, whereas that of the ECquercetin combination showed the cancel (prooxidative) effect. Furthermore, the EGCASDB (L-ascorbyl 2,6-dibutylate) or 2-ME (2-mercaptoethanol) combination showed the prooxidative effect. Such enhancement of prooxidation in the combination may increase their toxic effects due to their cooxidation. Also, the synergic, additive or cancel effects of the flavonoidvitamins E combination on the induction period in the BPO (a PhCOO* radical) and 2,2'-azobisisobutyronitrile (AIBN, an R* radical) systems are discussed.