In Vitro Antioxidant Activities, Total Phenolic Contents and Main Phenolic Compounds of Essential Oil Blend and Grape Seed Extract

Objective: This study was conducted to assess antioxidant activities, total phenolic contents and main phenolic compounds of essential oil blend (EOB) and grape seed extract (GSE). Material and Methods: The antioxidant activites of EOB (composed of oregano, clove and cumin essential oils) and GSE were determined by in vitro methods such as 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and trolox equivalent antioxidant capacity (TEAC). The total phenolic contents of EOB and GSE were determined by the Folin-Ciocalteu method and calculated as gallic acid equivalents (GAE). The main phenolic compounds of EOB calculated from the individual essential oils compounds analyzed by GC/MS. The condensed tannin concentration of GSE was measured by the butanol/HCl method. Results: The antioxidant activities of EOB and GSE were determined by two different in vitro methods provided the values of 79.0 % and 74.7 % for DPPH, and 276.51 µM/100 g and 83.0 µM/100 g for TEAC, respectively. The total phenolic contents of EOB and GSE were 437.84 mg GAE/g and 175.50 mg GAE/g, respectively. The main phenolic compounds of the EOB were carvacrol (42.08 %), thymol (4.17 %), eugenol (22.38 %), cuminaldhyde (5.04 %) and safranal (2.69 %). The condensed tannin concentration in GSE was 45.88 g/100g Conclusion: In this study, EOB showed higher total phenolic content and antioxidant activity determined by two methods (DPPH radical scavenging activity and trolox equivalent antioxidant capacity) than GSE. The results obtained by both methods are compatible and quite similar. According to these findings, EOB and GSE could be used as potential sources of natural antioxidants in food, feed and pharmaceutical industries.