## 3 Discussion
### Theoretical Prediction of Solubility of Wild Thyme Compounds in Green Solvents
#### 3.2.2 Effect of HVED-Assisted Extraction on Recovery of Bioactive Compounds from Wild Thyme  
BACs are generally used in various industries such as food, cosmetic and pharmaceutical industries, especially due to the their antioxidative, antiseptic and antitumor capacity [32]. Extraction of BACs from wild thyme was performed by HVED as a green extraction technology in order to obtain high-quality extracts reach in BACs that could be used for functional food production. The obtained extracts were analyzed for total phenolic content and antioxidant activity (DPPH and FRAP) and compared with modified CE (Figure 2).  
HVED extraction showed higher results for all measured methods including TPC, DPPH and FRAP. The highest content of TPC was found in extract TN7 that was extracted using HVED, nitrogen at 20 kV, and with 50% ethanol (42.86 \(\pm\) 2.38 mg GAE/g, Figure 2c). The highest antioxidant activity was found in extracts obtained by HVED using argon: TA7 and TA9 for DPPH and FRAP methods, respectively. Better extraction of polyphenols and antioxidants was enhanced generally with longer treatment time, higher ethanol content and higher voltage. TPC and DPPH were higher for treatment with nitrogen than argon, while FRAP values were higher for argon treatment. In order to define the best extraction parameters, it is necessary to establish the amount of BACs extracted according to the defined experimental design. Statistically significant influence of ethanol content was noted for TPC and FRAP, while longer treatment time significantly influenced to DPPH results (Table 6). Based on the model, the extraction yield was expressed as percentage of extracted polyphenols per g of sample (g GAE/g of sample). Therefore, yield of extraction was in line with results of TPC and the same trend was noted. The highest yield of extraction was seen for extract TN7 extracted with HVED using nitrogen for 9 min, at 20 kV with 50% of ethanol. In average, HVED extraction showed 2.03 higher yield of extraction compared to CE under same extraction conditions (ethanol content and time of extraction), and it was 2.07 times higher for nitrogen and 1.99 times higher for extraction with argon. A correlation analysis between TPC, DPPH and FRAP showed that the highest correlation was found between TPC and FRAP (0.259). Although these correlations were not high, all methods showed positive correlations. This is not an unusual occurrence since each of this method is based on different mechanism and is performed in different conditions.  
[PERSON] et al. measured TPC in wild thyme extracts after extraction with 1:30 solid-to-solvent ratio and 50% ethanol. With these conditions, results were 26.6, 29.8 and 32.7 mg GAE/L for extraction by maceration, heat and ultrasound-assisted techniques, respectively [5]. These results are much lower compared to HVED, since extract TN7 that had the highest TPC (42.86 \(\pm\) 2.38 mg GAE/g) had the equivalent of 214.31 mg GAE/L. [PERSON] et al. evaluated various conventional (Soxhlet and macerate extraction) and non-conventional extraction (ultrasound, microwave and subcritical water extractions) methods from wild thyme. The results showed that the highest TPC and antioxidant activity was found using subcritical water extraction (141.12 \(\pm\) 0.23 mg GAE/g and 170.32 \(\pm\) 0.87 mg AA/G) [33]. Although these results seems higher compared to our study, no conclusions could be made regarding the best extraction method since different analytical methods were used and different solvents with different solvent to solid ratio were used.