## 3 Discussion
### Theoretical Prediction of Solubility of Wild Thyme Compounds in Green Solvents  
#### 3.1.1 Wild Thyme Compounds Solubility in Green Solvents by HSPs  
The solubility of wild thyme compounds in selected green solvents assessed by HSPs is given in Table 1 and presented as a comparison with conventionally used \(n\)-hexane (first column). Results are shown as a RED value that estimates the potential of a solvent to dissolve solutes. RED values from 0-1 present very good solubility, medium solubility is 1-3, and poor solubility \(>\) 3. It is clear that some alternative (green) solvents have better solubility then n-hexane and for that reason, it is not the best solvent for extraction of wild thyme BACs from theoretical perspective. According to solvent with highest number of very good soluble compounds, followed by medium and poor solubility, the order of solvents that could be used for better solubility of wild thyme compounds was as following: CPME  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Pesticides** & **MRL (mg/kg)** & **Content (mg/kg)** \\ \hline Lindane (\(\gamma\)-isomer of hexachlorocyclohexane ) & 0.01 & \textless{}0.002 \\ \hline Methoxychlor & 0.01 & \textless{}0.010 \\ \hline Tolylfluanid (sum of toyllfluanid and dimethylaminosulfotoluidide expressed as toyllfluanid) & 0.05 & \textless{}0.020 \\ \hline Vinclozolin & 0.02 & \textless{}0.002 \\ \hline MRL—maximum residue level, DDT—dichlorophenyltrichloroethane, DDE—dichlorophenyldichloroethylene, TDE—tetrachloropiphenylethane, DDD—dichlorophenyldichloroethane. & \\ \hline \hline \end{tabular}
\end{table}
Table 7: _Cont._  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Metals** & **MRL (mg/kg)** & **Dried Wild Thyme (mg/kg)** & **Extract (mg/kg)** \\ \hline Lead (Pb) & 3.000 & \textless{}0.050 & / \\ \hline Cadmium (Cd) & 1.000 & 0.120 & / \\ \hline Mercury (Hg) & 0.100 & 0.019 & / \\ \hline Chromium (Cr) & / & 12.000 & 56.550 \\ \hline Nickel (Ni) & / & 20.060 & 6.450 \\ \hline Manganese (Mn) & / & 115.000 & 40.750 \\ \hline Iron (Fe) & / & 1581.000 & 25.350 \\ \hline Copper (Cu) & / & 8.400 & 5.700 \\ \hline Zinc (Zn) & / & 42.000 & 13.000 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Residule levels and maximum residue levels (MRL) of metals (mg/kg) in dried wild thyme and in wild thyme extract.  
\(>\) limonene \(>\) ethyloleate \(>\) cymene \(>\)\(\beta\)-myrcene \(>\) MeTHF \(>\)\(\alpha\)-pinene \(>\)\(n\)-hexane \(>\) ethylacetate \(>\) DMC \(>\) methylacetate \(>\) 1-butanol \(>\) isopropanol \(>\) ethanol \(>\) methanol \(>\) water. It can be concluded from the results that wild thyme compounds have the lowest solubility in water, followed by primary alcohols (ethanol, 1-butanol and methanol) and secondary alcohol isopropanol. On the other side, these solvents are the cheapest green solvents that is the great advantage for their usage. CPME showed the highest theoretical prediction for solution of wild thyme compounds.  
A classical rule \"like dissolves like\" can be applied to theoretical prediction for solvent-solute solubility. According to this rule, more polar solvents will have higher probability of solubility for polar compounds, while non-polar solvents will have a tendency to dissolve less polar or non-polar solutes. This was shown with HSPs results, where non-polar (or weakly polar) solvents like n-hexane, limonene, CPME, methylacetate, ethyleneate, cymene, \(\beta\)-myrcene and \(\alpha\)-pinene had higher probability of solubility of less polar compounds such as hydrophobic thymol, \(\alpha\)-thujene, piperitone and other.