## 3 Results  
### Total Phenolic and Total Flavonoid Content  
Results demonstrated that the extract of _H. perforatum_ was the most abundant in phenolic compounds (86 \(\pm\) 13.34 mg GAE/g dry plant material), while the lowest TPC was determined in the extract of _H. vesiculosum_ (26.92 \(\pm\) 10.32 mg GAE/g dry plant material). For the total flavonoid content shown in Table 2, the most abundant extract in flavonoids was that of _H. tetrapertum_ (1.58 \(\pm\) 0.08 mg RE/g dry plant material). Similarly, the lowest TFC was calculated for _H. perfolatum_ (0.21 \(\pm\) 0.14 mg RE/g dry plant material). The UV-Vis spectra of some of the _Hypericum_ species studied are presented in Figure 2. Figure 2 presents the UV-Vis spectra of the less studied species of _Hypericum_, namely _H. cycladicum_, _H. delplicum_, and _H. fragile_, as well as the UV-Vis spectrum of _H. perforatum_, to allow comparison with the other species. Figure 2 presents the UV-Vis spectra of the same species after complexing with AlCl\({}_{3}\). As shown in Figure 2a, the UV-Vis spectra of _H. cycladicum_ and _H. fragile_ present a \(\lambda\)max at 334 nm and 330 nm, respectively. This  
Figure 1: UV-Vis spectrum of quercetin and rutin standard solutions after complexing with AlCl\({}_{3}\) reagent.  
range of absorption is typical for flavones and flavonoids [28]. To distinguish between these two groups, [PERSON] et al. [29] observed that the UV wavelength of the B ring is near 304-350 nm for flavones, while flavonoids absorb at a longer wavelength of 328-357 nm. Therefore, according to the literature data, flavonoids are compounds that seem to prevail in the extracts of \(H\). _cycladicum_ and \(H\). _fragile_. Moreover, the hypysochromic shift at band I in the case of \(H\). _deplticum_ is attributed to the presence of sugar moieties, more probably attached at position 3 of the C ring [29].  
As demonstrated in Table 2, there seems to be no proportional relationship between TPC and TFC. The mechanism of action of the Folin Ciocalteu assay is the transfer of electrons from phenolic compounds. Nevertheless, non-phenolic compounds such as ascorbic acid, aromatic amines, and sugars can also reduce the Folin Ciocalteu reagent, resulting in an additive effect on the interpreted results [30]. Consequently, a high TPC is not always accompanied by a high TFC, as in the case of \(H\). _perforatum_. Fewer limitations exist for the AlCl\({}_{3}\) colorimetric assay. This method is accepted among researchers for the determination of total flavonoid content because the reagent does not interfere with other subclasses of phenolic compounds. On the contrary, AlCl\({}_{3}\) forms stable complexes with flavonoids by binding at position 4 of the cheto-group (C ring) and occupying at the same time hydroxyl groups from positions 5 or 3. The other binding site is at positions 3\({}^{\prime}\) and 4\({}^{\prime}\) [Figure 3]. However, most of the flavonoids are produced as glycosides. A glycosidic moiety or moieties may occupy one or more of the binding sites of AlCl\({}_{3}\); therefore, AlCl\({}_{3}\) will not bind the positions occupied by the sugar moiety [31].Phenolic compounds are produced mostly in their glycosylated form [32]. Hence, it is possible that the stereochemistry of glycosylated flavonoids presented in the extracts hinders the binding of AlCl\({}_{3}\).