Evaluation of the synergistic antioxidant effect of resveratrol and Zataria multiflora Boiss essential oil in sodium alginate bioactive films.

Biodegradable films are the appropriate alternatives to synthetic polymers due to their potential to enhance food safety and their function as carrier for wide range of food additives especially natural antioxidants. The aim of this study was to compare the potential antioxidant activities of sodium alginate films containing resveratrol (RES) alone and in combination with Zataria multiflora essential oil (ZEO) using an in vitro model. At first, the major chemical compositions of ZEO were evaluated by GC/MS. Then, the amount of phenolic compounds of sodium alginate films were evaluated by total phenolic contents assay and antioxidant activities of films were evaluated by DPPH and ABTS assays. Finally, the concentrations of ZEO and RES which showed better antioxidant activities in sodium alginate films, were incorporated to films in combination forms, in order to evaluate their synergistic effects. According to GC/MS analysis, 35 compounds of ZEO were identified and the most important constituent compounds were Thymol (37.94%), p-Cymene (9.50%) and 3-Carene (4.98%), respectively. The results of the radical scavenging evaluations, showed better antioxidant activities of the films containing RES than the films containing ZEO and BHT. Also, the combination use of ZEO and RES into alginate films had the synergistic effects (P<0.05). Therefore, it can be concluded that alginate films incorporated with the combination of ZEO and RES is the appropriate option to postpone the oxidative reactions and can be used as natural antioxidant in food packaging industry.