Chemical composition and antioxidant activity of O. vulgare var. vulgare and var. heracleoticum

Abstract

Oregano (Origanum vulgare) is an aromatic plant from the Lamiaceae family. Due to its rich content of polyphenols, flavonoids and other important secondary metabolites, oregano have anti-inflammatory, antioxidant, and antimicrobial properties. This research was aimed to compare the chemical composition of O. vulgare var. vulgare and var. heracleoticum and their antioxidant activity. Investigated extracts were prepared by ethanol maceration. The total phenolic content was determined by the Folin-Ciocalteu method. The total amount of flavonoids was determined spectrophotometrically by analysing flavonoid complex formation with AlCl3. Chemical characterization was performed by high-performance liquid chromatography. The ability of the tested extract to neutralize 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl (OH•) and nitroso (NO•) radicals was tested by the spectrophotometric methods. The total phenolic content was аpproximately equal in both, O. vulgare var. vulgare and var. heracleoticum (87.53 and 90.5 mg of the gallic acid equivalents/g dry extract, respectively). Also, the total amount of flavonoids was аpproximately equal in both, O. vulgare var. vulgare and var. heracleoticum (21.8 and 23.23 mg of the quercetin equivalents/g dry extract, respectively). Rosmarinic, ferulic and chlorogenic acids, and rutin were identified as dominant polyphenolic compounds. Moreover, antioxidant activity of both extracts was similar. Half-maximal inhibitory concentration (IC50) for DPPH was 2.28 mg/mL for O. vulgare var. vulgare and 2.59 mg/mL for O. vulgare var. heracleoticum. The ability of the tested extract to neutralize NO• was similarly good for both extracts (IC50= 17.71 and 20.53 mg/mL). The tested extracts showed weaker activity in neutralizing OH• (IC50= 285.37 and 192.24 mg/mL). Due to the similarity in chemical composition and antioxidant activity both varieties can be used as medicinal herbal drugs.