Bioactive Compounds and Antioxidant Activities of T hyme- Enriched Refined Corn Oil

Abstract

J. Agr. Sci. Tech. (2016) Vol. 18: 79-91 79 Bioactive Compounds and Antioxidant Activities of T hyme- Enriched Refined Corn Oil I. Jabri Karoui 1,2 ∗ , K. Msaada 1 , M. Abderrabba 2 , and B. Marzouk 1 ABSTRACT This study was designed to examine bioactive compou nds of the thyme-enriched corn oil and to determine the antioxidant activity of its methan olic extract. Volatile compounds composition was investigated by Gas Chromatography-Mass Spectro metry (GC-MS), whereas phenolic compounds analysis was performed by Reversed-Phase High-Performance Liquid Chromatography (RP-HPLC). Antioxidant activities of the flavoured oil methanolic extract were evaluated using DPPH radical scavenging, β -carotene-linoleic acid bleaching, reducing power and total antioxidant assays. Flavoured oil m ajor volatiles were p -cymene (26.47% ), α - thujene (24.06%) and γ -terpinene (14.30%). Its methanolic extract had hig her Total Phenol Contents (TPCs) (53.99 mg 100 g -1 ) than that of the crude oil (23.63 mg 100 g -1 ). Thymol was the main phenolic compound in the flavoured oil (55 .84% ). Flavoured oil methanolic extract showed higher total antioxidant activity (185.22 mg Gallic Acid Equivalent (GAE) 100 g -1 ) than that of the crude one (100.66 mg GAE 100 g -1 ). In β -carotene-linoleic acid bleaching and DPPH radical scavenging assays, flavoured oil methanolic extract showed higher activities than that of the crude oil based on IC 50 values. Flavoured and crude oils were characterized by a close CE 50 values (1.81 and 1.85 mg mL -1 , respectively). Antioxidant activities of the thym e-enriched oil were mainly due to the presence of phenolic com pounds such as thymol and hydrocarbons such as γ -terpinene and p - cymene. The thyme-enriched oil could be considere d as a new and natural source of antioxidant. Keywords: Antioxidant activity, Corn oil, Essential oil, Pol yphenols, Thymus capitatus .