## 4 Discussion
It has antiviral effects against several viruses, including HIV [54,55], adenovirus [56], hepatitis B virus [56], and HSV [57], and also inhibits inflammation caused by viral infections [57]. The presence of various phenolic components such as flavonol derivatives in _Samucus_ species has been previously reported. A number of studies have investigated the flavonoid content and composition of SN and have demonstrated the presence of flavones, flavonoids, and flavonol glycosides. The main phenolic components in black elderberry flowers are flavonoids, namely quercetin-3-rutinoside (rutin), quercetin-3-glucose (isoquercetin), kaempfer-3-glucoside, kaempfer-3-rutinoside, and isorhamnetin-3-rutinoside [58]. In our study, significant differences in the content of the investigated flavonoids among the studied extracts were observed. Quercetin and its glycosides (flavonols) were present in all extracts. PSNFIE was distinctive with the highest content of quercetin-3-rutinoside (14,232.1 \(\pm\) 648.9 mg/100 g DW), followed by PSNLE (7004.1 \(\pm\) 235.3 mg/100 g DW) and PSNFFE (4623.0 \(\pm\) 283.7 mg/100 g DW). The content of isoquercetin was also higher (2963.0 \(\pm\) 132.7 mg/100 g DW, 2028.2 \(\pm\) 94.3 mg/100 g DW, 1513.3 \(\pm\) 68.8 mg/100 g DW--determined for PSNFIE, PSEFIE, and PSNFFE, respectively). In addition, rutin and isoquercetin, the other flavonoids, appeared to be minor constituents. Despite the differences in the flavonoid content and composition, all extracts were distinctive with a very high content of rutin, which was the predominant flavonoid in all extracts. The highest amount of rutin (14,232.1 mg/100 g DW) found in PSNFIE significantly exceeds the available results in the literature from 11.6 mg/100 g DW to 42.3 mg/100 g DW [59], and 14.93 mg/100 g DW [60], which is due the purification using solid-phase extraction. Previous studies indicate that SN flowers are the richest part of the plant in flavonoids [61], which is in agreement with our results. [PERSON] et al. reported that quercetin-3-rutinoside, kaempfer-3-rutinoside, and isorhamnetin-3-rutinoside are the major flavonoids composing over 90% of the total flavonoid content in black elderberry flowers [60]. Determining plant anthocyanin content is of great importance from both a nutritional and pharmacological point of view. We detected cyanidin-3-glucoside, cyanidin-3-sambubioside, cyanidin-3,5-diglucoside, cyanidin-3-galactoside, cyanidin-3-O-rutinoside, cyanidin-3-arabinoside, and pelargonidin-3-glucoside. The PSNFrE contained 24,341.1 mg/100 g DW cyanidin-3-glucose and 21,051.4 mg/100 g DW cyanidin-3-sambubioside. The remaining anthocyanin representatives were in smaller quantities. Pelargonidin-3-glucose was only found in SN fruit extracts, and cyanidin-3-arabinoside was only found in SE extracts. In order to reveal whether glycosides of other anthocyanins were present, we hydrolyzed the investigated extracts and revealed that besides cyanididin, SN extract also contains small amounts of delphinidin, pelargonidin, and malvidin. After hydrolysis, SE extract revealed a slightly higher content of cyanidin, which indicates that it contains additional cyanidin glycosides. However, aglycones unlike cyanidin were not detected in SE extract. It is known that berry fruits are particularly rich in anthocyanins, whose content, however, depends mostly on the plant species and climate characteristics [62]. According to the literature data, the predominant anthocyanin in _S. nigra_ fruit is cyanidin-3-glucose (204.6-481.4 mg CGE/100 g FW), followed by cyanidin-3-sambubioside (122.2-269.1 mg CGE/100 g FW) [43]. Other cyanidin glycosides reported include cyanidin-3-sambubioside-5-glucoside, cyanidin-3,5-diglucoside, cyanidin-3-rutinoside, pelargonidin-3-glucose, and pelargonidin-3-sambubioside [15; 21]. In agreement with these results, in our study, cyanidin glycosides were found to be the predominant anthocyanins in both SN and SE extracts. However, SN fruit extract was a very rich source of anthocyanins.