## 3 Results and Discussion
### UHPLC-MS/MS Analysis of Phenolic Compounds  
A total of thirty-eight different polyphenolic compounds in three purified St. John's work extracts were quantified (Table 6). Numerous papers have been written on _H. perforatum_ extracts, however, most of them have only reported the analyses of some individual compounds, such as hyperforins and hypericins [32; 33]. Among the total 38 polyphenols tested, 26 were detected and quantitated. The extracts were generally very rich in polyphenols and followed the results obtained with spectrophotometric assays; in fact, the extracts obtained from full bloom plants are richer in molecules than the sample III, with 65,275, 38,799 and 22,857 ug/g of dried weight extract, respectively. Considering the plant with the higher amount of polyphenols determined by UHPLC-MS/MS, among them, hyperoside, isoquercitrin and deplbindin-3,5-diglucoside resulted as predominant, with their concentrations being 18,726.59, 11,895.02 and 10,619.51 ug/g of dried weight extract, respectively. It is clear that _H. perforatum_ extract contains a good amount of isoquercitrin; [PERSON] et al. [34] also studied the correlation between the phenolic content of a full ethanolic extract of _H. perforatum_ and fractions with antioxidant potentials, and found the presence of this molecule. Our experimental work revealed that the _H. perforatum_ II extract is predominantly constituted of rutin (9573.17 ug/g), quercetin (4195.62 ug/g), quercetin (2069.36 ug/g), neochlorogenic acid (4095.9 ug/g) and procyanidin B2 (1184.41 ug/g). These findings are aligned with those reported by [PERSON] et al. [35], where hyperoside and rutin were two of the most important polyphenols in the extract and neochlorogenic acid occurred in smaller amounts. Rutin was found to be the most predominant compound in _H. perforatum_ extract obtained from MAE extraction [36]. However, all of the researchers mentioned above focused their investigation on the major polyphenols occurring in this plant, and generally, different polyphenols compared with those analyzed in the present research. Moreover, [PERSON] et al. [37] also quantified 26 different compounds in _H. perforatum_, but only 12 analytes corresponded to those quantified in the present work. For those compounds, the reported values by [PERSON] et al. [37] were in agreement with the outcomes found in the current paper. Generally, quercetin is one of the main phenolic compounds in different species of Hypericum extract. [PERSON] et al. [38] analyzed 11 Hypericum species (_H. perforatum_ L., _H. aegypti_ L., _H. oxysporum_ L., _H. calvicinum_ L., _H. hircinum_ L., _H. intrutum_ L., _H. montanum_ L., _H. putulum_ Thunb., _H. perfoliation_ L., _H. pubescens_ Boiss., _H. tetrapertum_ Fr.). In all species, except _H. androsanemtum_ H. _hircinum_, where hydroxycinamic acids were the most prevalent polyphenols, quercetin derivatives are one of the main phenolic compounds. However, the value we found for quercetin appears to be higher than all those reported in this article for all the species. Nevertheless, our results are consistent with data on _H. perforatum_ obtained from [PERSON] et al. [39]. Furthermore, our values of chlorogenic acid, hyperoside and quercetin were generally higher than the values found in _H. hircinum_, but lower than those found in _H. scrapili_ by [PERSON] et al. [39]. Multiple research studies have conducted a comparison of various polyphenols in different _Hypericum_ species, thereby validating that a wide range of polyphenol concentrations could change in relation to numerous internal or external factors, including the phenological stage, the species of the plant, the genetic profile, the growing site, the harvest period and the type of soil in which the plant grows [40].