Synthesis of new deep eutectic solvents and extraction of some origanum species, GC-MS analysis and biological activity applications

In this thesis, the synthesis of deep eutectic solvents, which is one of the important topics of green chemistry, and their solvent properties compared to general solvents, the extraction of phenolic compounds and their use as a pretreatment reagent in essential oil extraction were evaluated. The antioxidant and antimicrobial activities of the extracts obtained with the volatile components and deep eutectic solvents were examined and compared. Infrared and differential scanning calorimetric analysis and characterization properties of synthesized deep eutectic solvents were elucidated. The plant species used in the thesis study were selected as Origanum micranthum and Origanum minutiflorum from the Labiatae family. p-coumaric acid- tert butyl amonium bromide was used for essential oils. The number of volatile components obtained without pretreatment was determined as 20 and 27, respectively, and the number of volatile components obtained with des was determined as 52 and 58. The antioxidant activities of the essential oils obtained were analyzed by FRAP, CUPRAC and DPPH tests. FRAP and CUPRAC tests are given as trolox equivalent, and DPPH tests are given as SC50 values. For antimicrobial activities, studies were carried out on 1 fungus and 4 bacteria with pathogenic properties. It was observed that the oils obtained without pretreatment had higher antioxidant activity. Essential oils obtained by pretreatment were found to have higher antimicrobial activity. The extraction procedure was optimized using the Design Expert 11.1.2. The most influential parameters on the extraction process were determined as deep eutectic solvent volume, extraction time and temperature. Then, with the Box-Behnken design, multiple regression analysis was applied for 3 parameters with 3 repetitions at the central point. The obtained model gave square and significant results. According to the ANOVA analysis, the R² was 0.9727, the CV was 5.08%, the standard deviation was 3.66, and the signal/noise ratio was 14,474. 1-hexadecanol-thymol and 1-octadecanol-thymol solvents were used as deep eutectic solvents. The method used for the detection of phenolic compounds has been validated. Validation parameters were determined as system suitability, linearity, detection limit and measurement limit, recovery and selectivity.