## 3 Results and Discussion
Phenolic compounds were also identified (Table 3, Figure 2). The antioxidant activity described as ABTS was lower than the one found by other authors and was 14.64 \(\upmu\)M \(\mathrm{Trolox}/100\) g. Guelder rose fruit is characterized by high antioxidant activity and the results obtained by us are different. [PERSON] et al. [2] determined the ABTS value at 26.57 \(\pm\) 1.71 \(\upmu\)M \(\mathrm{Trolox}/100\) g (DM). In the study by [PERSON] et al. [31], the ABTS value of six VO genotypes ranged from 31.95 to 109.81 \(\upmu\)M \(\mathrm{Trolox}/1\) g.  
The obtained result for the FRAP assay was 211.14 \(\upmu\)M \(\mathrm{Trolox}/100\) g, while another study by [PERSON] et al. [2] observed the value of 19.29 \(\upmu\)M \(\mathrm{Trolox}/100\) g. Moreover, there are significant differences in the results obtained in another study by [PERSON] et al. [3]. The content of polyphenols in VO fruit was 1695.99 mg GAE/100 g DM. In other studies, a lower amount of TPC in frozen fruits was reported as compared to our study. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Unit** & **Guelder Rose Fruit** \\ \hline ABTS & \(\upmu\)M \(\mathrm{Trolox}/100\) g & 14.63 \(\pm\) 0.61 \\ FRAP & \(\upmu\)M \(\mathrm{Trolox}/100\) g & 211.14 \(\pm\) 1.04 \\ TPC & mg GAE/100 g & 1695.88 \(\pm\) 0.86 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The values of ABTS, FRAP and TPC in guelder rose fruit. Figure 2: Representative UPLC–MS chromatogram of VO fruit. It complements Table 3.  
These differences may be due to different growing conditions or a different climate. [PERSON] et al. [5] reported a polyphenol content of 621 to 987 mg GAE/100 g, [PERSON] et al. [4] reported TPC of 1106 mg GAE/100g, [PERSON] et al. [25] reported the content of 829 mg/100 g in V. opulus Tajoznye Rubiny', and [PERSON] et al. [32] reported the content of 325 mg/100 g. In comparison to popular fruits in Poland, guelder rose fruit has a higher polyphenol content than e.g., apples 60-210 60 mg/100 g or plums 220-500 mg/100 g [33]. The identification of phenolic compounds is presented in Table 3 and Figure 2. The main phenolic compound identified in the studied fruits was chlorogenic acid. Moreover, as in the study conducted by [PERSON] et al. [10], chlorogenic acid occurs in the form of dimers and one negative molecular ion. Additionally, in this study, like in previous studies, the peak was dominant [1,3,10]. Moreover, we found the following components in VO fruits: quinic acid, apigenin -7-0-glucoside, p-coumaric acid cinnamyl ester, loganic acid, pelargonidin 3-O-robinobioside, procyanidin B1, procyanidin C, and quercetin 3-rutinoside (commonly called ruin). B- and C-type procyanidin identified under this study was also mentioned in a review study by [PERSON] et al. [3]. Moreover, ruin [1,10] and quinic acid [10] were also identified by other authors. We also observed small amounts of compounds that are not presented in the table. These were: syringetin-3-O-galactoside, hydrate (RT 2.791 min, _m/z_ 525.2838), vitexin-2\({}^{\prime\prime}\)-O-rhammoside (RT 3.808, _m/z_ 413.2820), quercetin-3-galactoside-6\({}^{\prime\prime}\)-rhammoside-3\({}^{\prime\prime}\)-rhammoside (RT 3.808/9.457; _m/z_ 771.2408/769.2241), (+)-catechin hydrate (RT 4.307, _m/z_ 291.3129), and quercetin-3-O-alpha-L-rhamnopyranosyl(1-2)-beta-D-glucopyranoside-7-O-alpha-L-rhamnopyranoside (RT 5.547, _m/z_ 757.1452) [34,35].