Isolation and identification of phenolic compounds fromHypericum richeriVill. and their antioxidant capacity

Unveiling myricetin's pharmacological potency: A comprehensive exploration of the molecular pathways with special focus on PI3K/AKT and Nrf2 signaling

Myricetin can be found in the traditional Chinese medicinal plant, Myrica rubra. Myricetin is a flavonoid that is present in many vegetables, fruits, and plants and is considered to have strong antioxidant properties as well as a wide range of therapeutic applications. Growing interest has been piqued by its classification as a polyphenolic molecule because of its potential therapeutic benefits in both the prevention and management of numerous medical conditions. To clarify myricetin's traditional medical uses, modern research has investigated various pharmacological effects such as antioxidant, anticancer, anti-inflammation, antiviral, antidiabetic, immunomodulation, and antineurodegenerative effects. Myricetin shows promise as a nutritional flavonol that could be beneficial in the prevention and mitigation of prevalent health conditions like diabetes, cognitive decline, and various types of cancer in humans. The findings included in this study indicate that myricetin has a great deal of promise for application in the formulation of medicinal products and nutritional supplements since it affects several enzyme activities and alters inflammatory markers. However, comprehensive preclinical studies and research studies are necessary to lay the groundwork for assessing myricetin's possible effectiveness in treating these long-term ailments. This review summarizes both in vivo and in vitro studies investigating myricetin's possible interactions through the nuclear factor-E2-related factor 2 (Nrf2) as well as PI3K (phosphatidylinositol 3-kinase)/AKT (protein kinase B) signaling pathways in an attempt to clarify the compound's possible clinical applicability across a range of disorders.

Unravelling Phytochemical and Bioactive Potential of Three Hypericum Species from Romanian Spontaneous Flora: H. alpigenum, H. perforatum and H. rochelii

Hypericum perforatum L., also known as St. John’s Wort, is recognized worldwide as a valuable medicinal herb; however, other Hypericum species were intensively studied for their bioactive potential. To fill the research gap that exists in the scientific literature, a comparative evaluation between H. alpigenum Kit., H. perforatum L. and H. rochelii Griseb. & Schenk was conducted in the present study. Two types of herbal preparations obtained from the aerial parts of these species were analyzed: extracts obtained through maceration and extracts obtained through magnetic-stirring-assisted extraction. LC-DAD-ESI-MSn analysis revealed the presence of phenolic acids, flavan-3-ols and flavonoid derivatives as the main constituents of the above-mentioned species. Moreover, all extracts were tested for their antioxidant, enzyme-inhibitory and antimicrobial potential. Our work emphasizes for the first time a detailed description of H. rochelii phenolic fractions, including their phytochemical and bioactive characterization. In comparison with the other two studied species, H. rochelii was found as a rich source of phenolic acids and myricetin derivatives, showing important antioxidant, anticholinesterase and antibacterial activity. The study offers new perspectives regarding the chemical and bioactive profile of the less-studied species H. alpigenum and H. rochelii.

Pharmacokinetic properties of phytochemicals in Hypericum perforatum influence efficacy of regulating oxidative stress

BACKGROUND

Hypericum perforatum is used in ethnopharmacology and has recently become popular in conventional medicine for treatment of mild to moderate depression. The abundance of potentially functional phytochemicals and their broader utilizations in traditional medicine suggests that ingestion of H. perforatum may impart additional secondary health benefits.

HYPOTHESIS/PURPOSE

Considering that many phytochemicals are known to display antioxidant activity, it was hypothesized that H. perforatum ingestion may inhibit oxidative stress and inflammation (OSI) which occurs in transient cycles following exercise and consumption of meals. The aim of this study was to explore the pharmacokinetics of H. perforatum phytochemicals after ingestion to predict the absorption timing of putative medicinal phytochemicals.

STUDY DESIGN/METHODS

In silico analyses of previously published plant extract phytochemical profiles were performed, wherein the Phytochemical Absorption Prediction (PCAP) model was used to predict the pharmacokinetics of phytochemicals. The predicted times for phytochemicals to reach maximum plasma concentration (T_max), and associated antioxidant activities, were compared to prior clinical in vivo studies to assess the accuracy and applicability of predictions.

RESULTS

The PCAP model identified that phytochemicals with antioxidant activity concurrently accumulate in plasma with T_max in the range of 1.6-2.3 h after ingestion. Comparison with previously published results identified that attenuation of OSI following H. perforatum ingestion aligns with the predicted T_max of antioxidant phytochemicals.

CONCLUSION

Based on these results it is therefore recommended that H. perforatum administration occurs 2 h before meals to provide optimal secondary health benefits associated with inhibition of postprandial stress. Additionally, these results highlight the use of in silico analyses to inform ingestion time and optimize the health benefits from ingestion of plant-based foods and medicines.

Inhibition of human monoamine oxidase A and B by flavonoids isolated from two Algerian medicinal plants

BACKGROUND

Monoamine oxidases (MAOs) are outer mitochondrial membrane flavoenzymes. They catalyze the oxidative deamination of a variety of neurotransmitters. MAO-A and MAO-B may be considered as targets for inhibitors to treat neurodegenerative diseases and depression and for managing symptoms associated with Parkinson's and Alzheimer's diseases.

PURPOSE

The objective was to evaluate the inhibitory effect of Hypericum afrum and Cytisus villosus against MAO-A and B and to isolate the compounds responsible for the MAO-inhibitory activity.

METHODS

The inhibitory effect of extracts and purified constituents of H. afrum and C. villosus were investigated in vitro using recombinant human MAO-A and B, and through bioassay-guided fractionation of ethyl acetate fractions of areal parts of the two plants collected in northeastern Algeria. In addition, computational protein-ligand docking and molecular dynamics simulations were carried out to explain the MAO binding at the molecular level.

RESULTS

The ethyl acetate (EtOAc) fractions of H. afrum and C. villosus showed the highest MAO inhibition activity against MAO A and B with IC50 values of 3.37 µg/ml and 13.50 µg/ml as well as 5.62 and 1.87 µg/ml, respectively. Bioassay-guided fractionation of the EtOAc fractions resulted in the purification and identification of the known flavonoids quercetin, myricetin, genistein and chrysin as the principal MAO-inhibitory constituents. Their structures were established by extensive 1 and 2D NMR studies and mass spectrometry. Quercetin, myricetin and chrysin showed potent inhibitory activity towards MAO-A with IC50 values of 1.52, 9.93 and 0.25 µM, respectively, while genistein more efficiently inhibited MAO-B (IC50 value: 0.65 µM). The kinetics of the inhibition and the study of dialysis dissociation of the complex of quercetin and myricetin and the isoenzyme MAO-A showed competitive and mixed inhibition, respectively. Both compounds showed reversible binding. Molecular docking experiments and molecular dynamics simulations allowed to estimate the binding poses and to identify the most important residues involved in the selective recognition of molecules in the MAOs enzymatic clefts.

CONCLUSION

Quercetin and myricetin isolated from H. afrum together with genistein and chrysin isolated from C. villosus have been identified as potent MAO-A and -B inhibitors. H. afrum and C. villosus have properties indicative of potential neuroprotective ability and may be new candidates for selective MAO-A and B inhibitors.

Comparative Analysis of Phenolic Compounds in Seven Hypericum Species and Their Antioxidant Properties

A comparative analysis of the phenolic compounds in the 70% EtOH extracts of Hypericum acutum, H. androsaemum, H. barbatum, H. hirsutum, H. maculatum, and H. richeri has been carried out using high-performance liquid chromatography coupled with photodiode array UV detection and high resolution TOF mass spectrometry. Quercetin, astilbin, I3, II8-biapigenin, orientin, 2”- O-acetylorientin, three phenolcarboxylic acids, and eight flavonols 3- O-glycosides were identified in the extracts on the basis of their on-line UV spectra, accurate mass spectral data, and in comparison of retention times with those from the standards. Fingerprint analysis of the extracts revealed significant differences in the qualitative and quantitative chemical composition of the studied species. Antioxidant assays with various reaction mechanisms were used including ferric reducing antioxidant power (FRAP) assay, DPPH, ABTS, superoxide anion radical scavenging capacity and inhibition of liposome peroxidation induced by Fe2+. The most potent were extracts of H. acutum and H. maculatum indicating this Hypericum species interesting for further research aimed as a potentially new source of biologically active compounds.

Molecular mechanisms underlying anticancer effects of myricetin

Dietary guidelines published in the past two decades have acknowledged the beneficial effects of myricetin, an important and common type of herbal flavonoid, against several human diseases such as inflammation, cardiovascular pathologies, and cancer. An increasing number of studies have shown the beneficial effects of myricetin against different types of cancer by modifying several cancer hallmarks including aberrant cell proliferation, signaling pathways, apoptosis, angiogenesis, and tumor metastasis. Most importantly, myricetin interacts with oncoproteins such as protein kinase B (PKB) (Akt), Fyn, MEK1, and JAK1-STAT3 (Janus kinase-signal transducer and activator of transcription 3), and it attenuates the neoplastic transformation of cancer cells. In addition, myricetin exerts antimitotic effects by targeting the overexpression of cyclin-dependent kinase 1 (CDK1) in liver cancer. Moreover, it also targets the mitochondria and promotes different kinds of cell death in various cancer cells. In the present paper, a critical review of the available literature is presented to identify the molecular targets underlying the anticancer effects of myricetin.

On-line activity screening for radical scavengers from Baccharis chilco

Baccharis plants have been used since ancient times in American traditional medicine. Baccharis chilco is a perennial shrub of temperate regions of South America that grows well in rainfall forests of Colombia. Neither chemical composition nor biological studies of this plant have ever been reported. Two caffeoylquinic acid (CQA) derivatives, 5-O-[(E)-caffeoyl]quinic acid (1) and 3,5-di-O-[(E)-caffeoyl]quinic acid (3), and rosmarinic acid (2) have been isolated from B. chilco growing wild in Colombia, using the on-line HPLC-DAD-DPPH radical-scavenging detection technique as guidance. In the course of the purification work, L-chiro-inositol (4) was also isolated. Structures of the four isolated compounds were determined by spectroscopic methods. Antioxidants 2 and 3 exhibited high antiradical activities evaluated by the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH(.)) assay, although somewhat lower than that of the reference compound ascorbic acid. The on-line HPLC-DAD-DPPH technique allowed a rapid pinpointing of antioxidants in the studied EtOH extract, and the facile guided isolation of the target molecules.