# Phytochemical Screening and Antioxidant Activity of Selected Estonian _Galium_ Species
## 2 Results and Discussion  
### Colorimetric Assays and Antioxidativity  
The antioxidant activities and the total polyphenolic, flavonoid, and iridoid content of the extracts are shown in Table 1. The Estonian _Galium_ species, especially _Galium verum_, are an excellent source of polyphenols and iridoids. As discussed earlier, this shows the great therapeutic potential of these plants. The results suggest that extraction with 50% acetone yields the highest quantities of polyphenols (up to 25.1 \(\pm\) 0.8 mg GAE/g) and flavonoids (up to 7.3 \(\pm\) 0.5 mg QE/g), whereas 50% ethanol should be used to obtain extracts containing large amounts of iridoids (up to 36.6 \(\pm\) 2.2 mg AE/g). Across the different extracts, both 50% acetone and 50% ethanol extracts are characterised by high antioxidant activities (up to 9.3 \(\pm\) 1.2 and 7.2 \(\pm\) 1.4 mg TE/g, respectively). The colorimetric analyses demonstrated that the extracts of _Galium verum_ blossoms generally contained the highest amounts of bioactives and had the strongest antioxidant properties. Additionally, the results from these experiments exemplify the linear correlation between the total polyphenolic content and the antioxidants of the _Galium_ extracts (correlation graph provided in Supplementary Materials, Figure S1), illustrated by the two extracts with the highest polyphenolic content also having the strongest antioxidative properties (namely, the 50% acetone extracts of _Galium verum_ blossoms and _Galium mollugo_ herb). Therefore, our results confirm the earlier reports of antioxidant properties being attributed to the polyphenolics the extracts contain. Regardless of the extraction solvent used, both _Galium verum_ blossoms and _Galium mollugo_ herb showed high polyphenolic content and strong antioxidant properties.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Plant Species**} & **Extraction** & **Antioxidant Activity,** & **Total Polyphenolic Content,** & **Total Flavonoid Content,** & **Total Iridoid Content,** \\  & **Solvent** & **mg TE/g 1 ** & **mg GE/g 3 ** & **mg AE/g 4 ** \\ \hline \multirow{2}{*}{_Galium verum_ blossoms} & 50\% acetone & 9.3 \(\pm\) 1.2 & 27.2 \(\pm\) 1.5 & 7.3 \(\pm\) 0.5 & 40.8 \(\pm\) 2.9 \\  & 50\% ethanol & 7.2 \(\pm\) 1.4 & 20.7 \(\pm\) 1.4 & 5.6 \(\pm\) 0.5 & 36.6 \(\pm\) 2.2 \\  & 80\% ethanol & 4.3 \(\pm\) 0.7 & 14.8 \(\pm\) 3.4 & 4.6 \(\pm\) 1.4 & 27.2 \(\pm\) 5.6 \\ \hline \multirow{2}{*}{_Galium verum_ herb} & 50\% acetone & 5.5 \(\pm\) 1.4 & 18.3 \(\pm\) 2.3 & 2.8 \(\pm\) 0.3 & 19.1 \(\pm\) 3.0 \\  & 50\% ethanol & 5.1 \(\pm\) 1.4 & 16.8 \(\pm\) 2.0 & 2.6 \(\pm\) 0.1 & 22.7 \(\pm\) 1.6 \\  & 80\% ethanol & 3.5 \(\pm\) 1.5 & 11.5 \(\pm\) 0.6 & 2.6 \(\pm\) 0.7 & 17.4 \(\pm\) 2.6 \\ \hline \multirow{2}{*}{_Galium aparine_ herb} & 50\% acetone & 3.7 \(\pm\) 0.5 & 16.0 \(\pm\) 1.3 & 2.1 \(\pm\) 0.2 & 13.9 \(\pm\) 1.2 \\  & 50\% ethanol & 4.3 \(\pm\) 0.9 & 16.8 \(\pm\) 1.3 & 2.1 \(\pm\) 0.03 & 20.3 \(\pm\) 0.4 \\  & 80\% ethanol & 3.8 \(\pm\) 1.8 & 12.5 \(\pm\) 0.7 & 2.6 \(\pm\) 0.1 & 15.2 \(\pm\) 0.2 \\ \hline \multirow{2}{*}{_Galium mollugo_ herb} & 50\% acetone & 7.6 \(\pm\) 0.3 & 25.1 \(\pm\) 0.8 & 2.9 \(\pm\) 0.2 & 20.6 \(\pm\) 0.7 \\  & 50\% ethanol & 7.1 \(\pm\) 0.7 & 23.1 \(\pm\) 0.5 & 3.0 \(\pm\) 0.3 & 21.8 \(\pm\) 0.9 \\ \hline \multirow{2}{*}{_Galium mollugo_ herb} & 80\% ethanol & 5.5 \(\pm\) 1.4 & 17.6 \(\pm\) 0.5 & 3.0 \(\pm\) 0.2 & 19.8 \(\pm\) 3.0 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Antioxidant activity, and total polyphenolic, flavonoid, and iridoid content of the _Galium_ extracts.