Essential Oil Composition, Total Phenolic Content, and Antioxidant Activity - Determined from Leaves, Flowers and Stems of Origanum Vulgare L. Var. Aureum

Origanum vulgare L. var. aureum is an aromatic medicinal plant belonging to the Lamiaceae family, rich in essential oils and antioxidants. Its specific chemical composition represents an important source of biologically active principles with diverse applications in food products and nutraceuticals. The aim of this study was to determine the differences between chemical composition of volatile oils, phenolic content and antioxidant activity of different plants parts: leaves, flowers, and stems. Essential oils from leaves and flowers had similar compositions with only few differences between γ-terpinene and trans-ß-ocimene. Total phenolic content and antioxidant activity were determined for the hydro-alcoholic extract obtained from post-distillation oregano waste material. The total phenolic content was determined using Folin-Ciocalteu reagent and varied from 3173 to 6522 mg GAE/L. The major compounds identified by HPLC were syringic acid, pyrocatechol, and catechin. Furthermore, all extracts showed high antioxidant activity, ranging from 31.3 to 44.5 mg GAE/L, with an inhibition percent varying from 63.1 to 88.6%.