Marta K. Dudek

Effects of Geum urbanum L. root extracts and its constituents on polymorphonuclear leucocytes functions. Significance in periodontal diseases.

ETHNOPHARMACOLOGICAL RELEVANCE Geum urbanum L. (wood avens) root infusions and decoctions have been used externally for reducing the bleeding and inflammation of gums (gingivitis), and mucous membranes. AIM OF THE STUDY Taking into account that primed and hyperactivated neutrophils are an important factor in the transition from gingivitis to periodontitis, we investigated the effects of phytochemically characterised (HPLC-DAD-MS(n)) extracts of different polarity from Geum urbanum root on oxidative burst, elastase, metalloproteinase 9 (MMP-9), interleukin 8 (IL-8) and 1β (IL-1β), tumour necrosis factor (TNF-α) release, expression of adhesion molecules (CD62L and CD11b) and delayed apoptosis in stimulated neutrophils. As gemin A is a dominating compound in a raw material, so we considered its activity in parallel with the positive control quercetin. MATERIALS AND METHODS The extracts were characterised by HPLC-DAD- MS(n) method. The inhibition of ROS production by stimulated neutrophils was determined using luminol dependent chemiluminescence method. The effect on MMP-9, IL-1β, TNF-α and IL-8 production by neutrophils was measured by enzyme-linked immunosorbent assay (ELISA). Neutrophil elastase release was established spectrophotometrically. The expression of adhesion molecules and the apoptosis of neutrophils was analyzed with flow cytometry. RESULTS The main compounds detected in the extract belong mainly to the group of ellagitannin: pedunculagin, stachyurin, casuarynin and gemin A, and ellagic acid derivatives. Procyanidins and one complex tannin were found as minor compounds. Gemin A significantly affected the functions of stimulated neutrophils by reducing the surface expression of CD11b, and inhibiting the release of reactive oxygen species, and proteases (elastase, MMP-9), chemokines and cytokines (interleukins IL-8, IL-1β). Interestingly, gemin A stimulated the release of TNF-α, which may be one of the stimulators of apoptosis of neutrophil cells. The primary aqueous extract, the ethyl acetate and the butanolic fractions, all containing the highest level of gemin A, have exerted similar but weaker activity. CONCLUSION The modulating effect on the neutrophils function of extracts, and its main constituent gemin A, support the traditional use of this plant material in cavity inflammation including mucositis, gingivitis and periodontosis.

Computational and experimental study of reversible hydration/dehydration processes in molecular crystals of natural products – a case of catechin

When employing a complementary approach that joins theoretical (crystal structure prediction, CSP, gauge-including projector-augmented wave density functional theory, GIPAW DFT) and experimental (solid-state nuclear magnetic resonance, SSNMR) techniques, we prove that detectable changes in the water content in a crystal lattice can be monitored as a continuous or quantum process by using border values of the measurable number of water molecules in the crystal, depending on the observation probe. In the case of a 13C nucleus, which “feels” the presence of water in its nearest neighbourhood, the subtle changes in the structure of the water channel during the dehydration/rehydration process are not reflected until the water loss exceeds a certain number of molecules. Here, the dehydration of (+)-catechin 4.5-hydrate with a loss of ca. 1–1.5 and 2–2.5H2O molecules leads to microcrystalline form II (partially dehydrated) or amorphous form III, respectively. The CSP calculations for the partially dehydrated (+)-catechin (form II), as verified by experimental 1H and 13C shieldings, resulted in two similar probable crystal structures, which have 2 and 2.5 water molecules in the unit cell.

Hydroxycinnamoyl derivatives and secoiridoid glycoside derivatives from Syringa vulgaris flowers and their effects on the pro-inflammatory responses of human neutrophils

Thirteen new compounds including caffeoyl-glucaric and p-coumaroyl-altraric acid derivatives, one monoterpenoid glucoside, four secoiridoid glycosides, and three hydroxycinnamoyl phenylpropanoid glycosides esterified with an oleoside 11-methyl ester along with fifteen known compounds were isolated from flowers of Syringa vulgaris L. (Oleaceae). Their structures were elucidated by high-resolution spectroscopic methods. The tested compounds were able to decrease the production of reactive oxygen species. Moreover, oleoechinacoside (13), demethylhydroxyoleonuezhenide (14), demethyloleonuezhenide (15), syringaoleoacteoside (25) and oleoacteoside (26) at the concentration of 50μM, moderately suppressed the LPS-stimulated release of pro-inflammatory chemokine IL-8 and TNF-α from human neutrophils. Moreover, oleonuezhenide (12), oleoside 11-methyl ester (16) and oleoacteoside (26) at the concentration of 50μM were able to induce the surface expression of interleukin 10 receptor, which is suppressed by the incubation of monocyte/macrophage cells with LPS.

Experimental tests for quality validation of computationally predicted crystal structures – a case of a conformationally flexible procyanidin A-2 dihydrate

Crystal structure prediction (CSP) of large, flexible, multi-component crystals is currently one of the most challenging computational tasks. In this work, we present a new approach to the CSP procedure, in which computationally generated crystal structures are evaluated not only on the basis of lattice energy, but also by the similarity of their theoretical NMR parameters and PXRD diffractograms with the experimental results. We employ procyanidin A-2 dihydrate as a model structure, and prove that even for such large and flexible systems with multiple possibilities of hydrogen bond formation it is possible to obtain a true crystal structure without single crystal diffraction experiments, on the condition that all three measures, i.e. lattice energy, NMR and PXRD similarity, are accounted for in an appropriate manner, so that they can guide us through a labyrinth of CSP-generated structures. The similarity of NMR parameters allows for unambiguous identification of the conformation of a molecule inside the crystal, whereas the PXRD data plainly indicates the true space group and, when combined with the crystal lattice energy, also the correct packing arrangement. Such an approach allows for faster elimination of incorrect structures, which in particular cases may be the only chance to obtain the true crystal structure within reasonable time and effort.

Approach toward the Understanding of Coupling Mechanism for EDC Reagent in Solvent-Free Mechanosynthesis

A unique approach in mechanosynthesis, joining solid-state NMR spectroscopy, X-ray crystallography, and theoretical calculations, is employed for the first time to study the mechanism of the formation of the C-N amide bond using EDC·HCl as a coupling reagent. It has been proved that EDC·HCl, which in the crystal lattice exists exclusively in the cyclic form (X-ray data), easily undergoes transformation to a pseudocyclic stable intermediate in reaction with carboxylic acid forming a low-melt phase (differential scanning calorimetry, solid-state NMR). The obtained intermediate is reactive and can be further used for synthesis of amides in reaction with appropriate amines.

Trimeric and Tetrameric A-Type Procyanidins from Peanut Skins

Peanut skins are a rich source of oligomeric and polymeric procyanidins. The oligomeric fractions are dominated by dimers, trimers, and tetramers. A multistep chromatographic fractionation led to the isolation of four new A-type procyanidins of tri- and tetrameric structures. The structures of the new trimers were defined by NMR, electronic circular dichroism, and MS data as epicatechin-(4β→8,2β→O→7)-epicatechin-(4β→8,2β→O→7)-catechin, peanut procyanidin B (3), and epicatechin-(4β→8,2β→O→7)-epicatechin-(4β→6)-catechin, peanut procyanidin C (4). The new tetramers were defined as epicatechin-(4β→8,2β→O→7)-epicatechin-(4β→6)-epicatechin-(4β→8,2β→O→7)-catechin, peanut procyanidin E (1), and epicatechin-(4β→8,2β→O→7)-epicatechin-(4β→6)-epicatechin-(4β→8,2β→O→7)-epicatechin, peanut procyanidin F (2). In addition, both A-type dimers A1, epicatechin-(4β→8,2β→O→7)-catechin, and A2, epicatechin-(4β→8,2β→O→7)-epicatechin, as well as two known peanut trimers, ent-epicatechin-(4β→6)-epicatechin-(4β→8,2β→O→7)-catechin, peanut procyanidin A (5), and epicatechin-(4β→8)-epicatechin-(4β→8,2β→O→7)-catechin, peanut procyanidin D (6), were also isolated. Dimer A1, the four trimers, and two tetramers were evaluated for anti-inflammatory activity in an in vitro assay, in which LPS-stimulated macrophages were responding with secretion of TNF-α, a pro-inflammatory cytokine. Tetramer F (2) was the most potent, suppressing TNF-α secretion to 82% at 8.7 μM (10 μg/mL), while tetramer E (1) at the same concentrations caused a 4% suppression. The results of the TNF-α secretion inhibition indicate that small structural differences, as in peanut procyanidin tetramers E and F, can be strongly differentiated in biological systems.

Expedient synthesis of V-shaped bifunctional N,N-bis-oligoelthyleneglycol-amines and their use for the preparation of multifunctional OEG-based platforms.

We designed a convergent synthesis pathway that provides access to trifunctional oligoethyleneglycol-amine (OEG-amine) linkers. By applying the reductive coupling of a primary azide to bifunctional OEG-azide precursors, the corresponding symmetrical dialkylamine bearing two homo-functional end chain groups and a central nitrogen was obtained. These building blocks bear minimal structural perturbation compared to the native OEG backbone which makes them attractive for biomedical applications. The NMR investigations of the mechanism process reveal the formation of nitrile and imine intermediates which can react with the reduced free amine form. Additionally, these trifunctional OEG-amine linkers were employed in a coupling reaction to afford branched multifunctional PEG dendrons which are molecularly defined. These discrete PEG-based dendrons (n = 16, 18 and 36) could be useful for numerous applications where multivalency is required.

Effects of Phytochemically Characterized Extracts From Syringa vulgaris and Isolated Secoiridoids on Mediators of Inflammation in a Human Neutrophil Model

Aim of the study: The aim of the present study was to investigate the effects of phytochemically characterized extracts connected with the traditional use (infusions and ethanolic extracts) of different parts of Syringa vulgaris (common lilac) on the pro-inflammatory functions of neutrophils. Active compounds were isolated from the most promising extract(s) using bioassay-guided fractionation, and their activity and molecular mechanisms of action were determined. Methods: The extracts were characterized using a HPLC-DAD- MSn method. The effects on ROS, MMP-9, TNF-α, IL-8, and MCP-1 production by neutrophils were measured using luminol-dependent chemiluminescence and enzyme-linked immunosorbent assay (ELISA) methods. The effects on p38MAPK, ERK1/2, JNK phosphorylation, and NF-kB p65 translocation were determined using western blots. Results: The major compounds detected in the extracts and infusions belong to structural groups, including caffeic acid derivatives, flavonoids, and iridoids. All extracts and infusions were able to significantly reduce ROS and IL-8 production. Bioassay-guided fractionation led to the isolation of the following secoiridoids: 2″-epiframeroside, oleonuezhenide, oleuropein, ligstroside, neooleuropein, hydroxyframoside, and framoside. Neooleuropein appeared to be the most active compound in the inhibition of cytokine production by attenuating the MAP kinase pathways. Conclusion: The present study demonstrated that common lilac, which is a traditionally used medicinal plant in Europe, is a valuable source of active compounds, especially neooleuropein.

The influence of procyanidins isolated from small-leaved lime flowers (Tilia cordata Mill.) on human neutrophils

Linden flower is a wildly used plant material among patients in the treatment of common cold symptoms and mucosa inflammations. However, the structure and bioactivity of flavan-3-ol derivatives present in infusions from flowers of Tilia cordata have not been studied so far. The aim of current study was to isolate and identify main procyanidins present in the flowers of small-leaved lime and to evaluate their influence on the inflammatory response of human neutrophils ex vivo. The chemical structure of isolated compounds was established by 1D and 2D NMR experiments. The bioactivity of obtained compounds was tested in human neutrophils model. Cytotoxicity and influence of compounds on apoptosis was established by flow cytometry. The levels of produced cytokines were established by ELISA after stimulation with lipopolysaccharide (LPS). The inhibition of the production of reactive oxygen species was checked by luminol-dependent chemiluminescence method after N-formylmethionyl-leucyl-phenylalanine (f-MLP) induction. The phytochemical work resulted in the isolation of 10 compounds. Compounds were identified as oligomeric procyanidins and their precursor epicatechin. The potential anti-inflammatory activity of compounds was evaluated in the concentration range 5-20 μM. All compounds were able to decrease the production of ROS from f-MLP-stimulated neutrophils. Most of compounds were able to inhibit the LPS-induced release of IL-8. Some trimeric and tetrameric derivatives were also able to decrease the production of MIP-1β. Obtained results partially support the traditional usage of infusion from lime flowers in the treatment of symptoms of inflammation and irritation of mucosa in common cold, pharyngitis and tonsillitis.

Structural studies on radiopharmaceutical DOTA-minigastrin analogue (CP04) complexes and their interaction with CCK2 receptor

BackgroundThe cholecystokinin receptor subtype 2 (CCK-2R) is an important target for diagnostic imaging and targeted radionuclide therapy (TRNT) due to its overexpression in certain cancers (e.g., medullary thyroid carcinoma (MTC)), thus matching with a theranostic principle. Several peptide conjugates suitable for the TRNT of MTC have been synthesized, including a very promising minigastrin analogue DOTA-(DGlu)6-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH2 (CP04). In this contribution, we wanted to see whether CP04 binding affinity for CCK-2R is sensitive to the type of the complexed radiometal, as well as to get insights into the structure of CP04-CCK2R complex by molecular modeling.ResultsIn vitro studies demonstrated that there is no significant difference in CCK-2R binding affinity and specific cellular uptake between the CP04 conjugates complexed with [68Ga]Ga3+ or [177Lu]Lu3+. In order to investigate the background of this observation, we proposed a binding model of CP04 with CCK-2R based on homology modeling and molecular docking. In this model, the C-terminal part of the molecule enters the cavity formed between the receptor helices, while the N-terminus (including DOTA and the metal) is located at the binding site outlet, exposed in large extent to the solvent. The radiometals do not influence the conformation of the molecule except for the direct neighborhood of the chelating moiety.ConclusionsThe model seems to be in agreement with much of structure-activity relationship (SAR) studies reported for cholecystokinin and for CCK-2R-targeting radiopharmaceuticals. It also explains relative insensitivity of CCK-2R affinity for the change of the metal. The proposed model partially fits the reported site-directed mutagenesis data.