## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c} \hline
**Fruit Matrix** & **Analyte** & **Content [ug/g]** & **Country of Origin** & **Source** \\ \hline \multirow{8}{*}{Elderberry} & \multirow{4}{*}{EA} & 6.0 ug/g & Argentina & [51] \\  & & n.d. & Canada & [44] \\  & & n.d. & Croatia & [46] \\  & & n.d. & Germany & [48] \\ \cline{2-5}  & \multirow{4}{*}{Q} & 14.0 & Argentina & [51] \\  & & n.d.—256.0 ug/g fw * & Canada & [6] \\  & & 3.3 ug/g fw & Canada & [44] \\  & & 144.0 ug/g & Croatia & [45] \\  & & 138.0 ug/g fw & Croatia & [46] \\  & & 5.5 ug/g * & Romania & [52] \\  & & 28.9–45.0 ug/g fw * & Slovenia & [53] \\  & & 331.0 ug/g fw & Sweden & [42] \\ \hline \multirow{8}{*}{Hawthorn} & \multirow{4}{*}{EA} & 169 ug/g dw & Bulgaria & [43] \\ \cline{3-5}  & \multirow{4}{*}{Q} & 303 ug/g & Romania & [41] \\ \cline{3-5}  & & n.d. & Bulgaria & [43] \\  & & 0.015 ug/g & Romania & [41] \\  & & n.d.—0.1 ug/g dw & Spain & [28] \\ \hline \multirow{8}{*}{Lingonberry} & \multirow{4}{*}{Q} & 2.3 ug/g fw & Canada & [44] \\  & & 74.0–146.0 ug/g * & Finland & [50] \\ \cline{3-5}  & & 131.0 ug/g fw & Finland & [42] \\  & & 2.0–14.1 ug * & USA & [54] \\ \hline \multirow{8}{*}{Rowanberry} & \multirow{4}{*}{Q} & \multirow{4}{*}{n.d.} & Bulgaria & [43] \\  & & 12.0 ug/g dw & Estonia & [55] \\ \cline{3-5}  & & 63.0 ug/g * & Finland & [50] \\ \cline{3-5}  & & 510.0 ug/g dw & Poland & [56] \\ \hline \multirow{8}{*}{Sea-buckthorn} & \multirow{4}{*}{EA} & n.d. & Canada & [57] \\  & & <LOD & Finland & [39] \\ \cline{3-5}  & & 0.4–12.1 ug/g fw & Slovakia & [58] \\ \cline{3-5}  & \multirow{4}{*}{Q} & 67.0–175.0 ug/g fw * & Canada & [57] \\ \cline{3-5}  & & 62.0 ug/g * & Finland & [50] \\ \cline{3-5}  & & 172.0 ug/g fw & Finland & [42] \\ \cline{3-5}  & & 106.4–122.6 ug/g & Romania & [59] \\ \cline{3-5}  & & n.d. & Slovakia & [58] \\ \hline \end{tabular} The asterisk (*) indicates the content in acidified methanolic extract (acetic, hydrochloric, or formic acid); <LOD— the content was below the limit of detection; n.d.—not detected; fw—fresh weight; dw—dry weight.  
\end{table} 
Table 4: _Cont._According to [PERSON] and co-workers [45], elderberry is a rich source of flavonoids, with Q being the most dominant, reaching 144 \(\mu\)g/g fw. It is a higher value than that observed in our elderberry samples, which had a mean Q content of 17.81 \(\mu\)g/g dw (Figure 2B). Similarly, the high Q contents in elderberries have been determined in studies from Canada [6] and Sweden [42], where levels ranged from below LOD to as high as 256 and 331 \(\mu\)g/g fw, respectively. The mean value of Q in chokeberry (calculated from four samples)was 48.40 \(\mu\)g/g dw, which is lower than the value obtained by [PERSON] and co-workers [45], who found it to be 92.15 \(\pm\) 0.5 \(\mu\)g/g fw. In another study by the same research group, wild chokeberry was investigated over 2 years, with determined Q levels at a much lower level, in the range from 5 to 17.4 \(\mu\)g/g fw [49]. In contrast, a higher value of Q content of 148 \(\mu\)g/g dw was reported by [PERSON] et al. [43]. According to [PERSON] and co-workers, Q content amounted to 89, 63, and 62 mg/kg of fresh weight in chokeberry, rownberry, and sea-buckthorn berry, respectively [50]. The Q content in fruit reported in review articles is often misleading, because some authors did not distinguish between content in extract and in acidified extract, which corresponds to Q released after acid hydrolysis from the flavonoid glycosides. According to [PERSON] et al. [42], approximately 97% of the total Q in linguonberry is delivered from glycosides. Moreover, it also happens that in the same papers, amounts of quercetin as aglycons and glycosides are given, which would mean that despite the addition of acid and being left for 24 h, hydrolysis did not occur entirely [49]. Phenolic compounds and flavonoids represent major classes of natural antioxidants. Estimation of TPC and TFC provides valuable information regarding the phenolic composition of plant material and facilitates the prediction of its bioactive properties.