Testing the Simplified Molecular Dynamics Approach to Improve the Reproduction of ECD Spectra and Monitor Aggregation.

A simplified molecular-dynamics-based electronic circular dichroism (ECD) approach was tested on three condensed derivatives with limited conformational flexibility and an isochroman-2H-chromene hybrid, the ECD spectra of which could not be precisely reproduced by the conventional ECD calculation protocol. Application of explicit solvent molecules at the molecular mechanics (MD) level in the dynamics simulations and subsequent TDDFT-ECD calculation for the unoptimized MD structures was able to improve the agreements between experimental and computed spectra. Since enhancements were achieved even for molecules with limited conformational flexibility, deformations caused by the solvent molecules and multitudes of conformers produced with unoptimized geometries seem to be key factors for better agreement. The MD approach could confirm that aggregation of the phenanthrene natural product luzulin A had a significant contribution to a specific wavelength range of the experimental ECD. The MD approach has proved that dimer formation occurred in solution and this was responsible for the anomalous ECD spectrum. The scope and limitations of the method have also been discussed.

Phytochemical Investigation of Carex praecox Schreb. and ACE-Inhibitory Activity of Oligomer Stilbenes of the Plant.

Phenolic compounds are the main special metabolites of Cyperaceae species from phytochemical, pharmacological, and chemotaxonomical points of view. The present study focused on the isolation, structure determination, and pharmacological investigation of constituents from Carex praecox. Twenty-six compounds, including lignans, stilbenes, flavonoids, megastigmanes, chromenes, and phenylpropanoids, were identified from the methanol extract of the plant. Five of these compounds, namely, carexines A-E, are previously undescribed natural products. All compounds were isolated for the first time from C. praecox. The ACE-inhibitory activity of seven stilbenoid compounds was tested, and (-)-hopeaphenol proved to be the most active (IC50 7.7 ± 0.9 µM). The enzyme-kinetic studies revealed a mixed-type inhibition; therefore, domain-specific studies were also conducted. The in silico docking of (-)-hopeaphenol to the ACE affirmed some favorable interactions. In addition, the antiproliferative and antibacterial effects of some compounds were also evaluated.

Isolation and NMR Scaling Factors for the Structure Determination of Lobatolide H, a Flexible Sesquiterpene from Neurolaena lobata.

A new flexible germacranolide (1, lobatolide H) was isolated from the aerial parts of Neurolaena lobata. The structure elucidation was performed by classical NMR experiments and DFT NMR calculations. Altogether, 80 theoretical level combinations with existing 13C NMR scaling factors were tested, and the best performing ones were applied on 1. 1H and 13C NMR scaling factors were also developed for two combinations utilizing known exomethylene containing derivatives, and the results were complemented by homonuclear coupling constant (JHH) and TDDFT-ECD calculations to elucidate the stereochemistry of 1. Lobatolide H possessed remarkable antiproliferative activity against human cervical tumor cell lines with different HPV status (SiHa and C33A), induced cell cycle disturbance and exhibited a substantial antimigratory effect in SiHa cells.

Chemistry and Pharmacology of Cyperaceae Stilbenoids: A Review.

Cyperaceae is a cosmopolitan plant family with approx. 5000 species distributed worldwide. Several members of this family are used in traditional medicines for the treatment of different diseases. In the last few decades, constituents with great chemical diversity were isolated from sedges, and a wide range of biological activities were detected either for crude extracts or for pure compounds. Among the isolated compounds, phenolic derivatives are the most important, especially stilbenoids, and flavonoids. To date, more than 60 stilbenoids were isolated from 28 Cyperaceae species. Pharmacological investigation of Cyperaceae stilbenoids revealed that several compounds possess promising activities; mainly antiproliferative, antibacterial, antioxidant and anthelmintic effects. Isolation, synthesis and pharmacological investigation of stilbenes are increasing constantly. As Cyperaceae species are very good sources of a wide variety of stilbenes, and several of them occur in large amount worldwide, they are worthy for phytochemical and pharmacological investigations. Moreover, stilbenes are important from chemotaxonomical point of view, and they play a key role in plant defense mechanisms as well. This review summarizes the stilbenoids isolated from sedges, and their biological activities.

Juncaceae Species as Promising Sources of Phenanthrenes: Antiproliferative Compounds from Juncus maritimus Lam.

Juncaceae family represents an abundant source of phenanthrenes. In continuation of our work aiming at the isolation of biologically active compounds from Juncaceae species, Juncus maritimus Lam. was subjected to phytochemical and pharmacological investigations. The isolation process was carried out by using combined extraction and chromatographic methods. The structures of the obtained chemical compounds were elucidated by spectroscopic analysis, including HRESIMS, 1D (1H, 13C-JMOD), and 2D (1H-1H-COSY, HSQC, HMBC, NOESY) NMR spectra. Four new [maritins A-D (1-4)] and seven known phenanthrenes (5-11) were isolated from the plant, of which two (4 and 11) are phenanthrene dimers composed of effusol monomers. Maritin C (3) has an unusual 4,5-ethanophenanthrene skeleton most likely produced by biosynthetic incorporation of a vinyl group into a cyclohexadiene ring. Compounds 1-11 were tested for their antiproliferative activity on seven human tumor cell lines (HeLa, HTM-26, T-47D, A2780, A2780cis, MCF-7, KCR) and one normal cell line (MRC-5) using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The dimeric phenanthrenes showed strong antiproliferative activity against T-47D cells with IC50 values of 9.1 and 6.2 µM, respectively.

Oxidized Juncuenin B Analogues with Increased Antiproliferative Activity on Human Adherent Cell Lines: Semisynthesis and Biological Evaluation.

Phenanthrenes have become the subject of intensive research during the past decades because of their structural diversity and wide range of pharmacological activities. Earlier studies demonstrated that semisynthetic derivatization of these natural compounds could result in more active agents, and oxidative transformations are particularly promising in this regard. In our work, a natural phenanthrene, juncuenin B, was transformed by hypervalent iodine(III) reagents using a diversity-oriented approach. Eleven racemic semisynthetic compounds were produced, the majority containing an alkyl substituted p-quinol ring. Purification of the compounds was carried out by chromatographic techniques, and their structures were elucidated by 1D and 2D NMR spectroscopic methods. Stereoisomers of the bioactive derivatives were separated by chiral-phase HPLC and the absolute configurations of the active compounds, 2,6-dioxo-1,8a-dimethoxy-1,7-dimethyl-8-vinyl-9,10-dihydrophenanthrenes (1a-d), and 8a-ethoxy-1,7-dimethyl-6-oxo-8-vinyl-9,10-dihydrophenanthrene-2-ols (7a,b) were determined by ECD measurements and TDDFT-ECD calculations. The antiproliferative activities of the compounds were tested on different (MCF-7, T47D, HeLa, SiHa, C33A, A2780) human gynecological cancer cell lines. Compounds 1a-d, 4a, 6a, and 7a possessed higher activity than juncuenin B on several tumor cell lines. The structure-activity relationship studies suggested that the p-quinol (2,5-cyclohexadien-4-hydroxy-1-one) moiety has a considerable effect on the antiproliferative properties, and substantial differences could be identified in the activities of the stereoisomers.

Gerardiins A-L and Structurally Related Phenanthrenes from the Halophyte Plant Juncus gerardii and Their Cytotoxicity against Triple-Negative Breast Cancer Cells.

Species in the Juncaceae accumulate different types of secondary metabolites, among them phenanthrenes and 9,10-dihydrophenanthrenes in substantial amounts. These compounds have chemotaxonomic significance and also possess interesting pharmacological activities. The present study has focused on the isolation, structure determination, and pharmacological investigation of phenanthrenes from Juncus gerardii. Twenty-six compounds, including 23 phenanthrenes, have been isolated from a methanol extract of this plant. Twelve compounds, the phenanthrenes gerardiins A-L (1-12), were obtained as new natural products. Eleven phenanthrenes [effusol (13), dehydroeffusol (14), effususin A (15), compressin A, 7-hydroxy-2-methoxy-1-methyl-5-vinyl-9,10-dihydrophenanthrene, juncusol, 2-hydroxy-7-hydroxymethyl-1-methyl-5-vinyl-9,10-dihydrophenanthrene, 2,7-dihydroxy-5-formyl-1-methyl-9,10-dihydrophenanthrene, effususol A, 2,7-dihydroxy-5-hydroxymethyl-1-methyl-9,10-dihydrophenanthrene, and jinflexin C], 1-O-p-coumaroyl-3-O-feruloyl-glycerol, and the flavones apigenin and luteolin were isolated for the first time from this plant. The cytotoxicity of the 23 isolated phenanthrenes in both mouse (4T1) and human (MDA-MB-231) triple-negative breast cancer cells and in a nontumor (D3, human cerebral microvascular endothelial) cell line was tested using an MTT viability assay. The results obtained showed that the dimeric compounds gerardiins I (9), J (10), K (11), and L (12), derived biogenetically from effusol and dehydroeffusol, were cytotoxic to both tumor and nontumor cell lines, while the monomeric compounds exerted no or very low cytotoxicity. Impedance measurements were consistent with the results of the MTT assays performed.

Antiproliferative Phenanthrenes from Juncus tenuis: Isolation and Diversity-Oriented Semisynthetic Modification.

The occurrence of phenanthrenes is limited in nature, with such compounds identified only in some plant families. Phenanthrenes were described to have a wide range of pharmacological activities, and numerous research programs have targeted semisynthetic derivatives of the phenanthrene skeleton. The aims of this study were the phytochemical investigation of Juncus tenuis, focusing on the isolation of phenanthrenes, and the preparation of semisynthetic derivatives of the isolated compounds. From the methanolic extract of J. tenuis, three phenanthrenes (juncusol, effusol, and 2,7-dihydroxy-1,8-dimethyl-5-vinyl-9,10-dihydrophenanthrene) were isolated. Juncusol and effusol were transformed by hypervalent iodine(III) reagent, using a diversity-oriented approach. Four racemic semisynthetic compounds possessing an alkyl-substituted p-quinol ring (1-4) were produced. Isolation and purification of the compounds were carried out by different chromatographic techniques, and their structures were elucidated by means of 1D and 2D NMR, and HRMS spectroscopic methods. The isolated secondary metabolites and their semisynthetic analogues were tested on seven human tumor cell lines (A2780, A2780cis, KCR, MCF-7, HeLa, HTB-26, and T47D) and on one normal cell line (MRC-5), using the MTT assay. The effusol derivative 3, substituted with two methoxy groups, showed promising antiproliferative activity on MCF-7, T47D, and A2780 cell lines with IC50 values of 5.8, 7.0, and 8.6 µM, respectively.

Cirsiliol Suppressed Epithelial to Mesenchymal Transition in B16F10 Malignant Melanoma Cells through Alteration of the PI3K/Akt/NF-κB Signaling Pathway.

Malignant melanoma is a highly aggressive form of skin cancer which has a propensity for metastasis. Epithelial mesenchymal transition (EMT) plays a primordial role in the progression of metastatic disease. Metastatic melanoma is resistant to conventional therapies. Hence, researchers have been exploring alternative approaches, including the utility of bioactive phytochemicals to manage metastatic disease. In the present study, we investigated the potential of cirsiliol, a flavonoid isolated from Centaurea jacea L., in modulating the aggressive behavior of B16F10 metastatic melanoma cells, including EMT, and associated molecular mechanisms of action. Cirsiliol was found to be effective in restraining the colony formation and migration of fibronectin-induced B16F10 metastatic melanoma cells. Cirsiliol inhibited the activity and expression of matrix metalloproteinase-9 (MMP-9). Cirsiliol also suppressed the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (also known as Akt)/nuclear factor-κB (NF-κB) signaling pathway which, in turn, caused upregulation of E-cadherin and downregulation of N-cadherin, Snail and Twist. Based on these results, cirsiliol may be considered a promising compound against EMT in the therapeutic management of malignant melanoma.

Phenanthrenes: A Promising Group of Plant Secondary Metabolites.

Although phenanthrenes are considered to constitute a relatively small group of natural products, discovering new phenanthrene derivatives and evaluating their prospective biological activities have become of great interest to many research groups worldwide. Based on 160 references, this review covers the phytochemistry and pharmacology of 213 naturally occurring phenanthrenes that have been isolated between 2008 and 2016. More than 40% of the 450 currently known naturally occurring phenanthrenes were identified during this period. The family Orchidaceae is the most abundant source of these compounds, although several new plant families and genera have been involved in the search for phenanthrenes. The presence of certain substituent patterns may be restricted to specific families; vinyl-substituted phenanthrenes were reported only from Juncaceae plants, and prenylated derivatives occur mainly in Euphorbiaceae species. Therefore, these compounds also can serve as chemotaxonomic markers. Almost all of the newly isolated compounds have been studied for their biological activities (e.g., potential cytotoxic, antimicrobial, anti-inflammatory, and antioxidant effects), and many of them showed multiple activities. According to the accumulated data, denbinobin, with a novel mechanism of action, has great potential as a lead compound for the development of a new anticancer agent.

Phenanthrenes from Juncus Compressus Jacq. with Promising Antiproliferative and Anti-HSV-2 Activities.

Juncaceae species are rich sources of phenanthrenes. The present study has focused on the isolation and structure determination of biologically active components from Juncus compressus. Eleven compounds (nine phenanthrenes and two flavonoids) have been isolated from the plant by the combination of different chromatographic methods. Two compounds (compressins A (Compound 1) and B (Compound 2)) are novel natural products, while seven phenanthrenes (effusol (Compound 3), effususol (Compound 4), juncusol (Compound 5), 2-hydroxy-1-methyl-4-oxymethylene-5-vinyl-9,10-dihydrophenanthrene (Compound 6), 7-hydroxy-1-methyl-2-methoxy-5-vinyl-9,10-dihydrophenanthrene (Compound 7), effususin A (Compound 8), and dehydroeffusol (Compound 9)), and two flavonoids (apigenin (Compound 10) and luteolin (Compound 11) were isolated for the first time from the plant. Compressin B (Compound 2) is a dimeric phenanthrene, in which two juncusol monomers (Compound 5) are connecting through their C-3 atoms. The structure elucidation of the isolated compounds was carried out using 1D, 2D NMR spectroscopic methods and HR-MS measurements. In vitro investigation of the antiproliferative effect of the phenanthrenes on two cervical (HeLa and SiHa) and an ovarian human tumor cell line (A2780) revealed that compounds have remarkable antiproliferative activity, mainly on the HeLa cell line. Moreover, juncusol (Compound 5) proved to possess significant antiviral activity against the herpes simplex 2 virus (HSV-2).

Phytochemical investigation of Rumex thyrsiflorus Fingerh.

In the course of our pharmacological screening of Polygonaceae species occurring in the Carpathian Basin the extracts prepared from the roots of Rumex thyrsiflorus showed promising antiproliferative, xanthine oxidase inhibitory and antibacterial activities. The present work deals with the isolation of compounds from the root of the plant. After multistep separation process, four compounds were obtained from the n-hexane, chloroform and ethyl acetate soluble fractions of the methanol extract of the root. The structures of the isolated compounds were determined as 1-palmitoylglycerol, ß-sitosterol, (-)-epicatechin, and procyanidin B5.

Myrsinane, Premyrsinane, and Cyclomyrsinane Diterpenes from Euphorbia falcata as Potassium Ion Channel Inhibitors with Selective G Protein-Activated Inwardly Rectifying Ion Channel (GIRK) Blocking Effects.

GIRK channels are activated by a large number of G protein-coupled receptors and regulate the electrical activity of neurons, cardiac atrial myocytes, and ß-pancreatic cells. Abnormalities in GIRK channel function have been implicated in the pathophysiology of neuropathic pain, drug addiction, and cardiac arrhythmias. In the heart, GIRK channels are selectively expressed in the atrium, and their activation inhibits pacemaker activity, thereby slowing the heart rate. In the present study, 19 new diterpenes, falcatins A-S (1-19), and the known euphorprolitherin D (20) were isolated from Euphorbia falcata. The compounds were assayed on stable transfected HEK-hERG (Kv11.1) and HEK-GIRK1/4 (Kir3.1 and Kir3.4) cells. Blocking activity on GIRK channels was exerted by 13 compounds (61-83% at 10 µM), and, among them, five possessed low potency on the hERG channel (4-20% at 10 µM). These selective activities suggest that myrsinane-related diterpenes are potential lead compounds for the treatment of atrial fibrillation.

Isolation of Phorbol Esters from Euphorbia grandicornis and Evaluation of Protein Kinase C- and Human Platelet-Activating Effects of Euphorbiaceae Diterpenes.

Human platelets contain conventional (α and ß) and novel isoforms of PKC (δ and θ), and PKC activation can result in platelet aggregation and secretion reaction that are important for thrombus formation. Several tumor-promoting Euphorbiaceae diterpenes are known to act as direct activators of PKC, but many types of such diterpenes have not been studied as platelet stimulators. In the present study, two new and five known phorbol esters were isolated from Euphorbia grandicornis. Two of the isolated phorbol esters together with compounds representing ingenane, jatrophane, and myrsinane structural types were studied on PKC activation and platelet stimulation. The investigated phorbol esters and ingenane esters induced blood platelet aggregation and ATP secretion. PKC activation was demonstrated by inducing membrane translocation of PKCs, phosphorylation of PKC substrates, and activation of PKC signaling pathways. The PKC-activating effect of the compounds correlated well with their efficacy to cause platelet stimulation. Moreover, by using an isoform-specific PKC inhibitor, it was found that besides conventional PKCs novel PKCs also play a positive role in platelet activation caused by phorbol/ingenane esters, especially in regulating platelet aggregation. The present results suggest that platelets afford a useful model for studying PKC activators of natural origin or their chemical derivatives.

Phenanthrenes from Juncus inflexus with Antimicrobial Activity against Methicillin-Resistant Staphylococcus aureus.

The present study has focused on an investigation of the antibacterial effects of Juncus inflexus and the isolation and identification of its active compounds. Eleven phenanthrenes were isolated from a methanolic extract of the roots. Four compounds (jinflexins A-D, 1-4) are new natural products, while seven phenanthrenes [juncuenins A (5), B (6), and D (8), juncusol (7), dehydrojuncuenins A (9) and B (11), and dehydrojuncusol (10)] were isolated for the first time from the plant. Jinflexin D (4) is a dimer with an unprecedented heptacyclic ring system. The absolute configurations of the new compounds were determined by TDDFT-ECD calculations, and their enantiomeric purity was checked by chiral HPLC analysis. Extracts of different polarity (n-hexane, dichloromethane, and ethyl acetate) were evaluated for their antimicrobial effects against methicillin-resistant Staphylococcus aureus, extended-spectrum ß-lactamase (ESBL)-producing Citrobacter freundii, Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, multiresistant Acinetobacter baumannii, and Pseudomonas aeruginosa. The MIC values of the isolated compounds were determined by a microdilution method. Jinflexin B (2), juncusol (7), juncuenin D (8), and dehydrojuncuenin B (11) showed significant activity (MIC value range 12.5-100 µg/mL) against MRSA strains.

Inhibition of COX-2 and NF-κB1 Gene Expression, NO Production, 5-LOX, and COX-1 and COX-2 Enzymes by Extracts and Constituents of Onopordum acanthium.

The present study focused on the investigation of the inhibition of cyclooxygenase-2 and nuclear factor kappa B1 gene expression, nitric oxide production, leukotriene biosynthesis (5-lipoxygenase), and cyclooxygenase-1 and cyclooxygenase-2 enzymes of Onopordum acanthium, and the isolation and identification of its active compounds. From the chloroform soluble part of the MeOH extract prepared from aerial parts, lignans [pinoresinol (1), syringaresinol (2), and medioresinol (3)] and flavonoids [hispidulin (4), nepetin (5), apigenin (6), and luteolin (7)] were isolated by a combination of different chromatographic methods. The structures of the compounds were determined by means of mass spectrometry and 1D- and 2D-nuclear magnetic resonance spectroscopy, and by comparison of the spectral data with literature values. Extracts of different polarity and the isolated compounds obtained from the aerial parts, together with those previously isolated from the roots of the plant [4ß,15-dihydro-3-dehydrozaluzanin C (8), zaluzanin C (9), 4ß,15,11ß,13-tetrahydrozaluzanin C (10), nitidanin diisovalerianate (11), 24-methylenecholesterol (12), and 13-oxo-9Z,11E-octadecadienoic acid (13)], were evaluated for their inhibitory effects on cyclooxygenase-2 and nuclear factor kappa B1 gene expression, inducible nitric oxide synthase, 5-lipoxygenase, and cyclooxygenase-1 and cyclooxygenase-2 enzymes in in vitro assays. It was found that O. acanthium extracts exert strong inhibitory activities in vitro and some lignans, flavonoids, and sesquiterpenes may play a role in these activities. 4ß,15-Dihydro-3-dehydrozaluzanin C and zaluzanin C at 20 µM were the most active constituents tested against lipopolysaccharide/interferon-γ-induced nitric oxide production (100.4 ± 0.5 % and 99.4 ± 0.8 %) in the inhibition of cyclooxygenase-2 (98.6 ± 0.2 % and 97.0 ± 1.1 %) and nuclear factor kappa B1 gene expression (76.7 ± 7.3 % and 69.9 ± 3.4 %). Furthermore, it was shown that these inhibitory effects are not due to cytotoxicity of the compounds.

Xanthine oxidase inhibitory activity of extracts prepared from Polygonaceae species.

The xanthine oxidase (XO) inhibitory activity of aqueous and organic extracts of 27 selected species belonging in five genera (Fallopia, Oxyria, Persicaria, Polygonum and Rumex) of the family Polygonaceae occurring in the Carpathian Basin were tested in vitro. From different plant parts (aerial parts, leaves, flowers, fruits and roots), a total of 196 extracts were prepared by subsequent extraction with methanol and hot H2O and solvent-solvent partition of the MeOH extract yielding n-hexane, chloroform and 50% MeOH subextracts. It was found that the chloroform subextracts and/or the remaining 50% MeOH extracts of Fallopia species (F. bohemica, F. japonica and F. sachalinensis), Rumex species (R. acetosa, R. acetosella, R. alpinus, R. conglomeratus, R. crispus, R. hydrolapathus, R. pulcher, R. stenophyllus, R. thyrsiflorus, R. obtusifolius subsp. subalpinus, R. patientia) and Polygonum bistorta, Polygonum hydropiper, Polygonum lapathifolium and Polygonum viviparum demonstrated the highest XO inhibitory activity (>85% inhibition) at 400 µg/mL. The IC50 values of the active extracts were also determined. On the basis of the results, these plants, and especially P. hydropiper and R. acetosella, are considered worthy of activity-guided phytochemical investigations.

Sesquiterpenes from Neurolaena lobata and their antiproliferative and anti-inflammatory activities.

Five new sesquiterpenes, neurolobatin A (1), neurolobatin B (2), 5ß-hydroxy-8ß-isovaleroyloxy-9α-hydroxycalyculatolide (3), 3-epi-desacetylisovaleroylheliangine (4), and 3ß-acetoxy-8ß-isovaleroyloxyreynosin (5), were isolated from the aerial parts of Neurolaena lobata. The structures were established by means of a combined spectroscopic data analysis, including ESIMS, APCI-MS, and 1D- and 2D-NMR techniques. Neurolobatin A (1) and B (2) are unusual isomeric seco-germacranolide sesquiterpenes with a bicyclic acetal moiety, compounds 3 and 4 are unsaturated epoxy-germacranolide esters, and compound 5 is the first eudesmanolide isolated from the genus Neurolaena. The isolated compounds (1-5) were shown to have noteworthy antiproliferative activities against human tumor cell lines (A2780, A431, HeLa, and MCF7). The anti-inflammatory effects of 1-5, evaluated in vitro using LPS- and TNF-α-induced IL-8 expression inhibitory assays, revealed that all these compounds strongly down-regulated the LPS-induced production of IL-8 protein, with neurolobatin B (2) and 3-epi-desacetylisovaleroylheliangine (4) being the most effective.

Investigation of the Allelopathic Effect of Two Invasive Plant Species in Rhizotron System.

A key question in plant invasion biology is why invasive plants are more competitive in their introduced habitat than in their native habitat. Studies show that invasive species exhibit allelopathy, influencing other plants by releasing chemicals. Research on allelopathy uses in vitro tests, investigating effects on seed germination and seedling development. Although soil plays a role in modifying allelopathic effects, observations with soil are rare and almost nothing is known about the root development of test plants developing in soil and the effects of allelopathic compounds on root architecture. Our study evaluates the allelopathic effects of false indigo-bush (Amorpha fruticosa L.) and common milkweed (Asclepias syriaca L.) on oilseed rape growth as a model plant. The rhizotron system was used to study the effect of morphology and root architecture. Leaf-soil mixtures at 0.5%, 1%, and 5% concentrations were used. Shoot and root development was strongly inhibited at 5%. But there was no difference between the allelopathy of the two species, and the application of lower concentrations did not show any effect, demonstrating that soil has a significant modifying effect on their allelopathy. Our results highlight that the development of roots growing in the soil is also worth investigating in connection with allelopathy, which can strengthen the ecological importance of allelochemicals during successful invasions.

Inhibition of G protein-activated inwardly rectifying K+ channels by extracts of Polygonum persicaria and isolation of new flavonoids from the chloroform extract of the herb.

The G protein-activated inwardly rectifying K+ channel-modulatory activities of Polygonum persicaria extracts were investigated by using an automated patch-clamp method, with the aim of identifying natural sources of promising ion channel-blocking compounds. The chloroform extract of the whole plant at 0.1 mg/mL exhibited high G protein-activated inwardly rectifying K+ channel-inhibitory activity. Fractionation of this extract by vacuum liquid chromatography on RP-silica gel resulted in 6 fractions, which were evaluated for G protein-activated inwardly rectifying K+ channel-modulatory activity. RP-HPLC of the most active fractions afforded the main compounds 1-4 in pure form and a mixture containing the minor constituents. The structures were identified by means of UV, HRMS, and advanced NMR methods as 3-O-senecioyl-isorhamnetin (1), 3-O-angeloyl-isorhamnetin (2), 5,3',4',5'-tetramethoxy-6,7-methylenedioxyflavone (3), and 3,5,3',4',5'-pentamethoxy-6,7-methylenedioxyflavone (4). Compounds 1-4 are new natural products, though 4 was reported earlier as a synthetic compound. Neither the individual, nor the combined application of compounds 1-4 modified the G protein-activated inwardly rectifying K+ channel activity. However, a marked G protein-activated inwardly rectifying K+ current-inhibitory effect was detected on use of the HPLC eluates containing the minor compounds. These results indicate the presence of electrophysiologically active agents among the minor compounds.