4.2. Plant Material and Preparation of Essential Oils

The dried aerial parts of O. vulgare and T. vulgaris were purchased from a commercial supplier (U Salvatora, Prague, Czech Republic). Initially, they were homogenized by a Grindomix apparatus (GM100 Retsch, Haan, Germany). Subsequently, the residual moisture contents of both samples were determined gravimetrically at 130 °C for 1 h by Scaltec SMO 01 analyzer (Scaltec Instruments, Gottingen, Germany) in triplicate, and results were expressed as arithmetic averages according to the Official Methods of Analysis of the Association of Official Agricultural Chemists [88]. Both EOs were obtained by hydrodistillation of dried plant material in 1 L of distilled water using a Clevenger-type apparatus (Merci, Brno, Czech Republic) according to the procedure described in the European Pharmacopeia (2013) [89] and stored in sealed glass vials at 4 °C.