Phytochemical Composition, Antioxidant and Antimicrobial Activity of the Balkan Endemic Micromeria frivaldszkyana (Degen) Velen. (Lamiaceae).

The current study investigates the content of sugars, organic acids, phenolic acids and flavonoids, as well as antioxidant and antimicrobial activity of Balkan-endemic Micromeria frivaldszkyana. Glucose was the most abundant sugar in the plant (2.77%), followed by fructose (1.18%) and galactose (0.82%). Eight organic acids were detected with quinic acid being in the highest content-556.3 mg/100 g DW. From the individual phenolic acids, rosmarinic acid was found in the most significant amounts (2040.1 ± 1.97 mg/100 g) and hesperidin was the major representative of flavonoids with content 131.2 ± 5.6 mg/100 g DW. The antioxidant activity of the plant was studied by six methods: 2,2'-diphenylpicrylhydrazyl (DPPH)-286.4 ± 10.43 mM TE/g, 2,2'azinobis (3)-ethylbenzthiazoline-6-sulfonic acid (ABTS)-358.4 ± 10.4 mM TE/g, ferric reducing antioxidant power (FRAP)-388.0 ± 32.4 mM TE/g, cupric reducing antioxidant capacity (CUPRAC)-905.6 ± 19.2 mM TE/g, Oxygen Radical Absorbance Capacity (ORAC)-3250.5 ± 208.1 µmol TE/g and Hydroxyl Radical Averting Capacity (HORAC)-306.1 ± 23.5 µmol GAE/g. In vitro antimicrobial activity against nine microorganism was evaluated but the extract displayed antimicrobial activity only against Listeria monocytogenes ATCC 19111 with inhibition zone diameter 9 mm and minimal inhibitory concentration (MIC) 10 mg/mL.