Thymus dacicus as a new source of antioxidant and antimicrobial metabolites

- Thymus dacicus herb methanol extract and essential oil were investigated.
- HPLC analysis revealed domination of rosmarinic acid in the extract.
- Geranial and neral prevailed in the oil analyzed by GC and GC-MS.
- The extract showed strong antioxidant activity determined by three assays.
- The oil showed synergism with antibiotics on three bacteria in checkerboard test.

In a search for novel food additives/functional food ingredients, chemical composition, and antioxidant and antimicrobial activities of Thymus dacicus Borbás (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, OH radical SC50 of 18.85 μg/mL (determined by 2-deoxyribose assay) and DPPH radical SC50 of 28.04 μg/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.