Green tea (Camellia sinensis), rosemary (Rosmarinus officinalis) and oak fruit (Quercus branti) are of known medicinal plants used in traditional medicine. They provide substantial antioxidant activities but the possible antioxidant interaction between them has not been studied. In the present study first the bioactive compounds from these three plants were first extracted and thereafter assayed for total phenols, 2, 2-diphenyl-1- picrylhydrazyl (DPPH) radical scavenging activity, total antioxidant capacity (TAOC) and reducing power. In addition, the antioxidant properties of the extracts individually and in combinations were evaluated in soy bean oil as food system. There was a direct relation between total phenolics and antioxidant activities of extracts. Green tea and oak fruit extracts had the highest and least activity, respectively. All three kinds of interactions (synergistic, antagonistic and additive) were observed. In soy bean oil, the only effect was antagonism but even with this effect, combined extract was significantly (P < 0.05) better than butylated hydroxytoluene (BHT) and control sample. Results showed that these three natural extracts and their combination can be effectively used as a substituent of synthetic antioxidant BHT.
Keywords: Antagonism; Green tea; Oak fruit; Rosemary; Synergism.