## 4 Discussion  
A comparative study of different solvent extraction methods with six different _Eucalyptus_ species [4] examined whether solid-liquid extraction by Soxhlet extraction is the most efficient method, compared to another study [28], in which sample size was also taken into account. Meanwhile, a literature review [3] probed distilled water as the most efficient non-polar solvent. Our results illustrate that the Soxhlet extraction method was the most efficient for all types of sample, obtaining with the _Tradescantia fluminensis_ Soxhlet extraction the highest yield level. These results are also confirmed by the Kruskal-Wallis tests performed. There were highly significant differences (\(p<0.001\)) between Soxhlet extraction and the other \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{6}{c}{**Anthocyanins (mg CC/g of Extract)**} \\ \hline \multirow{2}{*}{**Method**} & _Eucalyptus_ & _Eucalyptus_ & _Tradescantia_ & _Arundo donax_ \\  & _globulus_ **Bark** & _globulus_ **Leaves** & _fluminensis_ & \\ \hline SOX & \(1.29\pm 0.72\) & \(0.61\pm 0.07\) & \(0.13\pm 0.05\) & \(0.70\pm 0.00\) \\ ULS & \(2.64\pm 0.12\) & \(3.18\pm 2.05\) & \(0.27\pm 0.13\) & \(1.46\pm 0.00\) \\ THA & \(3.69\pm 1.24\) & \(6.18\pm 0.82\) & \(0.26\pm 0.02\) & \(2.24\pm 0.00\) \\ IN & \(1.94\pm 0.06\) & \(2.44\pm 0.09\) & \(0.25\pm 0.11\) & \(0.17\pm 0.02\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Anthocyanins obtained, expressed as mg cyanine chloride/g extract. Figure 3: Correlation of extraction yield efficiency by method and species. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{6}{c}{**Total Phenolics (mg GAE/g of Extract)**} \\ \hline \multirow{2}{*}{**Method**} & _Eucalyptus_ & _Eucalyptus_ & _Tradescantia_ & _Arundo donax_ \\  & _globulus_ **Bark** & _globulus_ **Leaves** & _fluminensis_ & _Arundo donax_ \\ \hline SOX & \(9.16\pm 1.64\) & \(29.76\pm 1.86\) & \(5.37\pm 3.03\) & \(9.11\pm 0.00\) \\ ULS & \(11.37\pm 1.31\) & \(94.27\pm 55.83\) & \(3.47\pm 2.34\) & \(13.99\pm 0.00\) \\ THA & \(14.33\pm 1.65\) & \(172.40\pm 44.53\) & \(11.76\pm 0.60\) & \(26.31\pm 0.00\) \\ IN & \(9.09\pm 1.42\) & \(57.39\pm 24.38\) & \(8.67\pm 1.45\) & \(1.39\pm 0.14\) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Total phenolics obtained, expressed as mg gallic acid/g extract. extraction methods, which indicate the influence of this variable in the percentage of yields extracted (Figure 3). However, the Kruskal-Wallis tests showed significant differences between the concentrations for all species (0.001 \(<\)_p_\(<\) 0.05). These results open the discussion to analyze whether plant extractions are more efficient than tree extractions. Other authors suggested yields between 25% and 27% for _Tradescantia fluminensis_[3], making a distinction between leaves and stems, for thermal agitator extractions. In this study, thermal agitator extraction for _Tradescantia_ yield is 35%, and it is higher with Soxhlet extraction, at 42%. Ultrasound extraction is the second most efficient method in contrast with another study [32], which proposes ultrasound-assisted extraction as the most efficient extraction method with water as solvent. _Tradescantia fluminensis_ was the unique species that achieved better results with thermal agitator than ultrasound-assisted method, where it is under the medium level even after repetition of the experiment. Finally, the infusion method was confirmed to be the least efficient method for all samples (0.89-28.64%) [32]. The overall extraction was higher in _Tradescantia fluminensis_ except for ultrasound extraction, where _Eucalyptus globulus_ leaves obtained higher yields. Lowest yield results were in _Eucalyptus globulus_ bark followed by _Arundo donax_. Anthocyanins content was found in higher concentrations in _Eucalyptus globulus_ leaves. As in another study [4] where Soxhlet extraction obtained 0.89 \(\pm\) 0.01 mg CC/g, a medium content of 0.61 \(\pm\) 0.07 mg CC/g was obtained.