Toxicological evaluation of oregano oil

Abstract

The present study evaluated the mutagenic and toxicological potential of a proprietary organic oregano/olive oil mix sold under the trade name Oreganano™. The test article was investigated for its potential to induce gene mutations according to the plate incorporation and preincubation test by Salmonella typhimurium strains TA98, 100, 1535 and 1537 and tester strain Escherichia coli WP2uvrA at concentrations of 3.16, 10.0, 31.6, 100, 316, 1000, 2500 and 5000 μg/plate with and without metabolic activation. Although toxic effects were noted in all tester strains, no biologically relevant increases in revertant colony numbers of any of the five tester strains were observed. Therefore, Oreganano™ did not cause gene mutations by base pair changes or frame shifts in the genome of the strains used and were considered to be non-mutagenic in the bacterial reverse mutation assay. In a 14-day feeding study of dietary levels of 0, 1.25, 2.5 and 5.0% in Sprague-Dawley rats, there were no adverse clinical, body weight, food consumption or macroscopic changes associated with the administration of Oreganano™. Body weight gain and food consumption was statistically reduced over the 14 days in both male and female animals; however, body weight and food efficiency was unaffected. There were no macroscopic findings attributable to test article administration. Therefore, the no-observed adverse- effect level (NOAEL) was 5.0% in the diet, the highest dose tested and OregananoTM is considered safe and suitable for consumption. Key words: Toxicology, oregano, genotoxicity.