## 4 Discussion  
Due to their specific physicochemical and biological characteristics, sulphated phenolic conjugates are undoubtedly an interesting class of compounds. Unfortunately, they are generally not very common in nature. Sulphated flavonoids, which are by far the most prevalent group, have been found in over 250 species [23]. Some sulphate derivatives of phenolic acids, anthraquinones, and coumarins have also been identified [24]. Only eight species from five different families were reported to contain ellagic acid sulphates. This paper is the first report of that type of compounds in the genus _Geum_, and second in the Rosaceae family. Compound **1** has previously only been isolated from _Tamarix tetragyna_ and _Euphorbia sororia_, whereas compound **2** has previously been isolated from the latter species and _Potentilla candicans_[9; 10; 13]. The results of quantitative analysis confirmed that the rhizome of _G.__rivale_ is a good source of the investigated compounds. On the other hand, only trace amounts of the analytes were found in the aerial parts of the plant, which demonstrates that accumulation of the sulphates is organ-specific. As the production of particular metabolites is often taxonomically dependent, the rhizome and aerial parts of closely related species--_G.__urbanum_--were also investigated. The compounds were detectable only in the rhizome of _G.__urbanum_, but the content below the quantification limit excludes the plant material as an alternative source of the analytes. The relatively high yields from the isolation procedure (6.00 mg/g; 71.5% of the factual content) indicate that the developed simple separation procedure might be successfully applied for cost-effective production and purification of these natural chemicals. Previously, the highest yield was obtained from _Potentilla candicans_--1.6 g of compound **2** was isolated from 5 kg of dry plant material [9] which corresponds to the content of only 0.3 mg/g dw. However, the methods used in the study were multi-step general isolation procedures, not targeted at any particular compound. Thus, the recovery of those methods may underestimate the actual content of the isolates. The role of phenolic sulphates in plant metabolism remains yet to be fully explained although some specific compounds were found to have significance in plant growth, development, and adaptation to stress [25; 26]. It was postulated before for sulphated flavonoids that their occurrence in plants is rather an ecological adaptation than a taxonomical trait [27]. The differences in the sulphates content between two closely related species examined in our study seems to confirm this assumption. However, the most common hypothesis about their role in adaptation to water-stress [27; 28], does not appear to be valid here--in contrast to many of the plants containing sulphate derivatives of ellagic acid, e.g., _Tamarix_ sp., _Raumuria vermiculata_, and _Frankenia laevis_ that thrive on dry or salty soils [12; 15; 29], _G.__rivale_ prefers slow draining soils where water is in abundance [1]. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Analytic**} & \multicolumn{3}{c}{**IC\({}_{50}\) [uM] a**} \\ \cline{2-4}  & **HL-60** & **NALM-6** & **WM 115** \\ \hline Ellagic acid & 300.6 \(\pm\) 12.3 A  & 124.9 \(\pm\) 50.5 A  & 62.3 \(\pm\) 9.7 A  \\
**1** & 365.3 \(\pm\) 34.3 B  & 358.4 \(\pm\) 61.7 C  & 306.4 \(\pm\) 57.3 B  \\
**2** & 391.0 \(\pm\) 54.7 B  & 473.8 \(\pm\) 41.5 B  & 333.3 \(\pm\) 22.2 B  \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Cytotoxic activity of the isolated compounds **1** and **2** and ellagic acid. As far as pharmacological effect on human organism is considered, several biological activities were found for sulphated phenolics including anticoagulant, antiviral, antitumor, antibacterial, and anti-inflammatory capacity. On the other hand, the knowledge on the biological properties of sulphate ellagic acid derivatives is very limited.