Identification of Major Constituents of Hypericum perforatum L. Extracts in Syria by Development of a Rapid, Simple, and Reproducible HPLC-ESI-Q-TOF MS Analysis and Their Antioxidant Activities

Abstract

Hypericum perforatum Linn ( St. John’s wort ) is a popular and widespread medicine in Syria, which is used for a wide range of conditions, including gastrointestinal diseases, heart disease, skin diseases, and psychological disorders. This widespread use prompted us to identify the main compounds of this plant from Syria that are responsible for its medicinal properties, especially since its components differ between countries according to the nature of the soil, climate, and altitude. This is, to the best of our knowledge, the first report in which St. John’s wort , a plant native to Syria, is extracted using different solvents and its most important compounds are identified. In this study, the dried above-ground parts, i.e., leaves, stem, petals, and flowers, were extracted using different solvents (water, ethanol, methanol, and acetone) and extraction protocols. By increasing the polarity of the solvent, higher yields were obtained, indicating that mainly hydrophobic compounds were extracted. Therefore, we conclude that extraction using the tea method or using a mixture of water and organic solvents resulted in higher yields compared with pure organic solvents or continuous boiling with water for long periods. The obtained extracts were analyzed using high-performance liquid chromatography equipped with a diode array detector (HPLC–DAD), coupled with UV–visible spectrophotometry at a full spectrum (200–800 nm). The HPLC spectra of the extracts were almost identical at three wavelengths (260 nm for phloroglucinols (hyperforin and derivates), 590 nm for naphthodianthrones (hypericins), and 350 nm for other flavonols, flavones, and caffeoylquinic acids), with differences observed only in the intensity of the peaks. This indicates that the same compounds were obtained using different solvents, but in different amounts. Five standards (chlorogenic acid, quercetin, quercitrin hydrate, hyperoside, and hypericin) were used, and a comparison with retention times and ultraviolet (UV) spectra reported in the literature was performed to identify 10 compounds in these extracts: hyperforin, adhyperforin, hypericin, rutin, quercetin, quercitrin, quercitrin hydrate, hyperoside, biapigenin, and chlorogenic acid. Although the European Pharmacopoeia still describes ultraviolet spectroscopy as a method for determining the quantity of Hyperici herba, interference from other metabolites can occur. Combined HPLC–DAD and electrospray ionization–mass spectrometry (LC-ESI-MS) in the positive mode have therefore also been used to confirm the presence of these compounds in the extracts by correlating known masses with the identified masses or through characteristic fragmentation patterns. Total phenolic contents of the extracts were determined by the Folin–Ciocalteu assay, and antioxidant activity was evaluated as free radical scavenging capacity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays. The resul...

Green Synthesis of Silver Nanoparticles Using Hypericum perforatum L. Aqueous Extract with the Evaluation of Its Antibacterial Activity against Clinical and Food Pathogens

“…Interestingly, the capping of the nanoparticles with moieties of the lipophilic hypericin, hyperforin, and adhyperforin might facilitate their diffusion across the hydrophobic cell membrane of the bacterial cells; meanwhile, the presence of moieties from the flavonoid and phenols such as rutin and quercitrin surrounding their surfaces could increase their capacity to form complexes with extracellular and soluble proteins and with the cell wall [ 97 ]. These chemical constituents were detected among others in the extract of the St. John’s wort in a previous report [ 46 ]. Moreover, AgNPs can bind to sulfur and phosphorus-containing proteins leading to protein and nucleic acids inactivation [ 98 ].…”

“…It is believed that the phloroglucinols (hyperforin, Adhyperforin), the naphthodianthrone hypericin, the flavonoids (rutin, quercetin, quercitrin, quercitrin-hydrate, hyperoside), the bioflavonoid biapigenin, and the phenolic acid chlorogenic acid identified previously in the aqueous St John’s wort extract [ 46 ] played a role in the silver reduction and that the stabilization of the formed nanoelement might endow the AgNPs with advantageous bioactivities, such as antibacterial, antioxidant, and anti-cancer activity. Such an assumption is reinforced by the finding of Pradeep et al [ 45 ], where the polar fraction containing phenolic acids and flavonoids was involved in the reduction of Ag+ ions, while the lower polar one containing biflavonoids, phloroglucinols, and naphthodianthrones acted as a capping agent.…”

“…The ATR-IR diagram shown in Figure 1 d confirmed the existence of St. John’s wort extracted compounds on the surfaces of silver nanoparticles as a reducer and stabilizer. The presence of moieties from Naphthodianthrone, Phloroglucinol, flavonoids, and bioflavonoids derivatives, identified in our previous report on St. John’s wort extract [ 46 ], cause the appearance of well-known signals in the infrared region of the electromagnetic spectrum such as hydroxyl groups, alkyl moiety, and aromatic rings. Indeed, the positions of these bands in the ATR-FTIR spectra are considered a sensitive indicator of the conformational changes in the structure of the plant compounds due to their adsorption on the surfaces of silver nanoparticles [ 62 ].…”

“…Altogether, smaller AgNPs than previously prepared [ 46 ] were synthesized to get a large surface-to-volume ratio. They were functionalized with moieties from H. perforatum aqueous extract that influence NPs’ surface charge, hydrophobicity, and/or solubility, thus influencing the particles’ structure, size, shape, morphology, degree of aggregation, particle dissolution, ion release, and finally the potential bioactivity.…”

“…The phytochemical constituents of H. perforatum extract, which might have a role in reducing AgNO 3 and stabilizing the formed AgNPs, were determined in a previous work by high-performance liquid chromatography equipped with a diode array detector (HPLC-DAD) coupled with UV-visible spectrophotometry at a full spectrum (200–800 nm) [ 46 ]. Detection was carried out at 260 nm for phloroglucinols, 590 nm for naphthodianthrones, and 350 nm for other flavonols, flavones, and chlorogenic acids.…”