Journal of Food Science and Engineering 8 (2018) 263-270 doi: 10.17265/2159-5828/2018.06.006 Evaluation of the Chemical Profiling, Total Phenolic Composition, the Antioxidant and Antimicrobial Properties of the Essential Oils of Mentha piperita L., Salvia officinalis L., and Thymus vulgaris L. Hulya Demir Faculty of Health Science of Nutrition and Dietetic, Yeditepe University, Istanbul 34755, Turkey Abstract: The purpose of this study was to determine the chemical composition, total phenolic composition, the antioxidant and antimicrobial properties of the essential oils (EOs) of Mentha piperita L., Salvia officinalis L., and Thymus vulgaris L. The essential oils of M. piperita L., S. officinalis L., and T. vulgaris L. were analyzed by means of gas chromatography-mass spectrometry (GC-MS) to demonstrate their chemical composition. The antioxidant properties of the EOs were evaluated with the 2,2-diphenyl-picrylhydrazyl (DDPH) free radical scavenging assay, their total phenolic compound contents were determined by the Folin Ciocalteau method, and their antimicrobial activities were evaluated by the disc diffusion assay. The major compounds in the contents of the essential oils of M. piperita L., S. officinalis L., and T. vulgaris L. were found to be eucalyptol, 1R-α-pinene, and o-cymene, respectively. In the 2,2-diphenyl-picrylhydrazyl (DDPH) assay, the EO of M. piperita L. (8,930.01 µMTE/g) demonstrated the highest antioxidant activity, followed by the activities of the EOs of T. vulgaris L. (157.76 µMTE/g) and S. officinalis L. (115.54 µMTE/g). The total phenolic compound contents of M. piperita L., T. vulgaris L., and S. officinalis L. were measured as 135.074, 0.242, and 0.221 mMGAE/g. All essential oils showed antioxidant activities and antimicrobial activities. The highest antimicrobial activity against S. aureus, A. nigeris, and C. albicans was determined in the EO of M. piperita L. within diameters of 42, 32, and 28 mm, respectively. These properties of essential oils are used in the pharmaceutical and food industries. The essential oils are approved as official medications in many countries and take place in their pharmacopoeias. Key words: Essential oils, chemical composition, total phenolic composition, antioxidant capacity, antimicrobial activity. 1. Introduction The plant life of Turkey, which is called the flora, consists of diverse species. The number of all plant taxa reaches figures over 12,000 and it is estimated that they belong to more than 9,000 species. Of these species, more than 33% are classified under the title “endemic species” and a similar portion is composed of aromatic plants [1]. Essential oils are incorporated as flavouring agents in several industrial products including food, beverages, spirits, perfumes, pharmaceuticals, and cosmetics [2]. A few aromatic and aliphatic Corresponding author: Hulya Demir, PhD, research field: food chemistry. constituents are present in the composition of the EOs, however, the main compounds in the essential oils (EOs) are terpenoids and phenylpropanoids, with monoterpenes, sesquiterpenes, and their oxygenated derivatives composing the largest group of chemical entities [3]. The bioactivity of a particular EO is usually determined by either one or two of its main components, however, the overall activity is not always attributable to the individual molecules in the composition [4]. Rather, it is sometimes yielded as a result of the combination of the activities of the composing molecules or modification of their activities under the effect of several interactions. Natural products and their derivatives are important sources of novel therapeutic molecules [5]. The D DAVID PUBLISHING