The antioxidant activity of Trachyspermum ammi essential oil and thymol in murine macrophages

Essential oils are abundant resources of several bioactive compounds, which possess therapeutic effects and have been at the heart attention of the research as the natural additives for the shelf-life extension of food products. This study aimed to investigate, in vitro radical scavenging and antioxidant capacities of Ttrachyspermum ammi (TEO) and its main components. Furthermore, this study sought to determine the antioxidant enzyme responses to TEO at the gene expression levels. The inhibitory effects of TEO and its main components on superoxide and nitric oxide production and NADH oxidase (NOX) and nitric oxide synthase (NOS) expression examined in lipopolysaccharide (LPS)-stimulated macrophages. TEO and thymol displayed a robust antioxidant activity while γ-terpinene and p-cymene have presented a few antioxidant activities. TEO at 10 μg/mL strongly reduced NO but potently increased reactive oxygen species (ROS) in LPS-stimulated macrophages. TEO significantly decreased inducible nitric oxide synthase (iNOS) mRNA expression but upregulated NOX mRNA in LPS-stimulated macrophages at 10 μg/mL. TEO had strong synergism with LPS to enhance ROS, a condition that is suitable against tumors propagation. Thymol at 10 μg/mL reduced NO, and ROS production and iNOS mRNA and NOX mRNA expression in LPS-stimulated macrophages but γ-terpinene and p-cymene did not show such activities. These differential activities between TEO and its pure chemical components strongly recommend that TEO antioxidant activity may be mainly due to the presence of thymol and also a strong synergism between all monoterpenes and monoterpenoids components of essential oils to the presentation a biological action.