Thymus dacicus as a new source of antioxidant and antimicrobial metabolites

In a search for novel food additives functional food ingredients, chemical composition, and antioxidant and antimicrobial activities of Thymus dacicus Borbas (Lamiaceae) flowering aerial parts dry methanol extract and essential oil were tested for the first time. HPLC analysis of the extract revealed that among dominant polyphenols, rosmarinic acid was the most abundant (71.33 +/- 1.11 mg/g). Monoterpenes geranial (34.4%) and neral (23.9%) prevailed in the oil, analyzed by GC and GC-MS. The extract showed pronounced antioxidant activity, with FRAP value of 5.16 +/- 0.19 mmol Fe2+/g, center dot OH radical SC50 of 18.85 mu g/mL (determined by 2-deoxyribose assay) and DPPH radical SC50 of 28.04 mu g/mL. Eight out of ten tested microbial strains were susceptible to the oil in microdilution test. Furthermore, for the combination of the oil and vancomycin/gentamicin, synergism was demonstrated against MRSA, Klebsiella pneumoniae and Escherichia coli in checkerboard test. Obtained results encourage further research of this herb as potentially beneficial ingredient in foodstuffs. (C) 2016 Elsevier Ltd. All rights reserved.