## 3 Discussion
The statistically significant greatest amounts of cyanidin 3-\(O\)-glucose and rutin detected by RP-HPLC and HPLC determinations (Table S1) might be positively correlated with the reduced viability of MCF7 breast cell lines by elderberry cookies (Table 3). Cytotoxic activity of elderberry flower extracts could only be observable in T24 bladder carcinoma cells but not in MRC-5 human normal fibroblast cells [9]. On the contrary, elderberry and chokeberry extracts exerted greater cytotoxic properties on BJ normal human fibroblasts (mean values for all extracts' concentrations--46.35%) than on the WM793 melanoma cell line (mean values for all extracts' concentrations--36.60%) as documented in this study (Tables 2 and 3). However, this phenomenon has been observed and described in the literature by several researchers for dietary polyphenols [43; 44; 45; 46; 47; 48; 49; 50]. Some polyphenols may be carcinogenic or genotoxic at high concentrations [43; 45]. Caffeic acid, for instance, induced gastric and renal tumors in rats and mice at a dietary dose of 2% [50]. Quercetin inactivated the \(O\)-methylation of catechol estrogens and elevates the urinary concentration of 2- and 4-hydroxyestrodiol by 60-80%, which may lead to increased redox cycling of catechol estrogens and estradiol-induced tumor development, indicating that the genotoxic effects reported in vitro may be due to the high levels used, at which polyphenols can act as prooxidants [48; 49; 51]. The RP-HPLC determinations in the tested cookies indicated significantly highest concentrations of quercetin in chokeberry and sea-buckthorn extracts (\(p<0.05\)) together with considerable amounts of quercetin-3-\(O\)-galactosidase in chokeberry, hawthorn and sea-buckthorn extracts. In elderberry extracts the latter has not been detected, while quercetin was found in moderate amounts (Table S1). The formation of glutathioneyl-quercetin adducts has been demonstrated in tyrosinase-rich B16F-10 melanoma cells and in the myeloperoxidase-rich human HL-60 cell line, which provide important evidence for the prooxidative metabolism of quercetin in cellular in vitro models. This also implies that tissues abundant in oxidative enzymes may be especially vulnerable to the prooxidative damage caused by quercetin [44]. And finally, green tea catechins (1% or 0.1% of the diet) have been shown to promote tumor formation in the colon of F344 male rats, and though quercetin may reduce cancer cell propagation at high concentrations, it has been found to promote cell growth at low concentrations (1-5 mol/L) [46; 47]. The existing contradicted results among the pro-healthy and potential toxic properties of dietary polyphenols and containing them edibles need thorough research in order to estimate the proper pharmaceutical dosages. Last, the extracts from hawthorn enriched cookies were least effective in inhibiting proliferation of MCF7 human breast and WM793 melanoma cell lines (Tables 2-4; Figures 1 and 2). It is surprising because this plant belonging to the _Rosaceae_ family, has a great nutritious value, rich in bioactive components (chlorogenic acid, proanthocyanidin B2, epicatechin, proanthocyanidin, mucoxanthin, quercetin, rutin, unsolic acid, hawthornic acid, oleanolic acid) and is characterized by a high therapeutic and health value [16]. In the literature [PERSON] et al. [52] found that unsolic acid, a triterpenoid, induced apoptosis of human breast and hepatocellular carcinoma cells via the mitochondrial pathway. Hawthorn polysaccharide inhibited the proliferation of human colon cancer cells by increasing the rate of cancer cell apoptosis [53], while isolated compounds have shown anti-tumor activity both in vivo and in vitro against melanoma [54]. In the present study, these beneficial properties of hawthorn extracts have not been observed. One of the possible explanations is the form of fruits used for extract preparations (raw plant materials vs. processed in the form of baked cookies).