## 1 Introduction
Samples of the species' leaves and bark (Table 1) were collected in the riparian forest area of the Umia river in Ribadumia, Galicia, Spain (42\({}^{\circ}\)30\({}^{\circ}\)53.6\({}^{\prime\prime}\) N 8\({}^{\circ}\)45\({}^{\prime}\)58.3\({}^{\prime\prime}\) W) in January and February 2022, and the experiment was carried out simultaneously using the fresh samples, which is why the humidity of the leaves/bark was also taken into account during analysis. Depending on the specific properties of the species, samples were divided into leaves, stems, and bark. For _E. globulus_, we analyzed the bark and the leaves separately, for _A. donax_ only the leaves were analyzed, and for _T. fluminensis_ leaves and stems were analyzed together. The aim of this study was to determine the most efficient pigment extraction method from the leaves and the bark of Eucalyptus globulus, the leaves of _Arundo donax_ L., and the leaves and stem of Tradescantia fluminensis. We also assessed the correlation with extraction method, species used, and phenolic-anthocyanins compounds. For this purpose, four solid-liquid extraction methods have been studied: Soxhlet, thermal agitator, infusion, and ultrasound. As we did not want to introduce chemical compounds into the final bio-solutions, water was chosen for the solvent. We aimed to obtain a bio-compostable liquid that could be used in eco-design and arts, as well as in food and 149 pharmaceutical applications. Phenolic compounds are synthesized in plants partly as a response to ecological and physiological pressures such as pathogens and insect attacks, UV radiation, and wounding [24]. Chemically, phenolic compounds vary widely, although their common characteristic is the presence of one (simple phenolics) or more (polyphenols) aromatic rings with bound hydroxyl groups in their structures. Depending on their structure, they can be grouped into phenolic acids, flavonoids, stilbenoids, and lignan [25]. Phenolic acids with C6-C1 structure are widely distributed in the plant kingdom, with the exception of fungi and algae [25]. In general, phenolic acids are divided into hydroxybenzoic and hydroxycinnamic acids according to their structural characteristics. Polyphenols, which include flavonoids, have at least two phenolic subunits; compounds with three or more phenolic subunits are called tannins (hydrolysable and non-hydrolysable). The basic structure of flavonoids is C6-C3-C6, this basic structure allows a multitude of substitution patterns and variations on the \"C\" ring, giving rise to subclasses [26]. Total phenolic compounds are a diverse group of compounds that include phenolic acids, flavonoids, stilbenoids, and lignans. They are known to have antioxidant properties. Total phenolic content can be measured using various methods, including the Folin-Ciocalteu assay, the ferric reducing antioxidant power (FRAP) assay, and the oxygen radical absorbance capacity (ORAC) assay. They are expressed as milligrams of gallic acid per gram of extract (mg.g\({}^{-1}\)). Anthocyanins are a subclass of flavonoids. They have been shown to have antioxidant, anti-inflammatory, and anti-cancer properties, and may also have neuroprotective and cardiovascular benefits. Anthocyanin content can be measured using spectrophotometry, such as pH differential and high-performance liquid chromatography (HPLC) after separation of \begin{table}
\begin{tabular}{c c c c} \hline
**Family** & **Genus** & **Species** & **Subsp.** \\ \hline Myrtaceae & _Eucalyptus_ & _Eucalyptus globulus_ & subsp. _Globulus_ \\ Poaceae & _Arundo_ & _Arundo donax_ L. & \\ Commelinaceae & _Tradescantia_ & _Tradescantia fluminensis_ Vell. & subsp. _Fluminensis_ \\ \hline \end{tabular}
\end{table} 
Table 1: Taxonomy of the selected species. molecules based on their chemical properties. They are expressed as milligrams of cyanine chloride per gram of extract. Phenolic compounds have the potential to be utilized in various sectors, but their extraction needs to be optimized to achieve high yields that are suitable for large-scale industrial production.