Abstract
Hypericum triquetrifolium and H. neurocalycinum were evaluated for their phytochemical content and in vitro bioactivity. NMR analyses were performed on the methanol extract of the aerial parts of H. triquetrifolium to establish the main classes of phytoconstituents. Then, LC-DAD-MSn analyses were performed in order to compare the composition of aerial parts and roots extracts of both Hypericum species, obtained using either methanol or water as solvents. Results, processed using multivariate data analysis, showed a significantly higher phenolic content of methanol extracts compared to water extracts, while minor qualitative differences were observed between the two. Distinctive flavonoid and PAC patterns were observed for H. triquetrifolium and H. neurocalycinum, and specific compounds were exclusively detected in one or the other species. Specifically, the phloroglucinols 7-epiclusianone, hyperfirin and hyperforin were present only in H. neurocalycinum, while hyperforin was detected only in H. triquetrifolium. Extracts were assayed using different in vitro tests to evaluate their antioxidant properties and their inhibitory activity against several enzymes, showing significant antioxidant and metal chelating activities. Furthermore, inhibitory properties against acetylcholinesterase, butyrylcholinesterase and tyrosinase were observed. Multivariate approaches were used to correlate biological data with the phytochemical composition of the different extracts. The results, showing positive correlations between specific chemical constituents and the measured bioactivities, represent preliminary data that could guide future studies aimed at isolating bioactive constituents from H. neurocalycinum and H. triquetrifolium for further pharmacological evaluations.
Highlights
Hypericum genus (Hypericaceae) encompasses 465 species distributed worldwide and of which nearly 100 taxa are grouped under 19 sections in Turkey (Öztürk et al, 2009; Eroglu Ozkan et al, 2018)
NMR data allowed to set up an appropriate integrated liquid chromatography coupled to diode array detector and multi-step tandem mass spectrometry (LC-DAD-MSn) and LC coupled to quadrupoletime of flight MS (QTOF) method for the comprehensive phytochemical characterization of methanol and water extracts prepared from both aerial parts and roots of the two Hypericum species
Considering the variable importance on projection (VIP) coefficients (>1) and the significance level calculated comparing methanol vs. water samples, we summarised the findings supporting the compounds related to different extraction solvents for the two considered plant parts in Supplementary Table S4
Summary
Hypericum genus (Hypericaceae) encompasses 465 species distributed worldwide and of which nearly 100 taxa (out of which 45 are endemic) are grouped under 19 sections in Turkey (Öztürk et al, 2009; Eroglu Ozkan et al, 2018). The methanol extract of H. triquetrifoium Turra aerial parts, a species known as curled-leaved St. John’s Wort and distributed in the Mediterranean basin (Volkov, 2018), has been reported to exert anti-inflammatory activity in carrageenan-induced paw edema rats and antinociceptive activity in mouse model challenged with formalin (Apaydın et al, 1999; Ozturk et al, 2002). The present study aimed at investigating and comparing the phytochemical composition and the antioxidant and enzyme inhibitory potential of two Hypericum species of the Turkish flora, namely H. neurocalycinum and H. triquetrifolium. NMR data allowed to set up an appropriate integrated liquid chromatography coupled to diode array detector and multi-step tandem mass spectrometry (LC-DAD-MSn) and LC coupled to quadrupoletime of flight MS (QTOF) method for the comprehensive phytochemical characterization of methanol and water extracts prepared from both aerial parts and roots of the two Hypericum species. The results from phytochemical screening and in vitro bioassays were analyzed using multivariate techniques, in order to find correlations between specific chemical constituents and the monitored bioactivities
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