Proteoglycans from Boswellia serrata Roxb. and B. carteri Birdw. and identification of a proteolytic plant basic secretory protein

Galactomannan and Vicilin from Fenugreek Seeds (Trigonella foenum-graecum) Impair Early Pathogen-Host Interaction of Campylobacter jejuni with Intestinal Cells via JlpA

Campylobacter jejuni is the leading cause of severe enteritis worldwide. Identification of natural products against C. jejuni that inhibit early-stage host-pathogen interactions is a promising strategy, particularly by blocking bacterial adhesion to and invasion into the host cells. This should help to reduce the bacterial load in vector animals. From the seeds of Trigonella foenum-graecum, an aqueous extract (fenugreek high molecular fraction) of high-molecular compounds (polysaccharides, proteins) was obtained. The polysaccharide was characterized as galactomannan (1,4-mannose backbone, substituted at O-6 with single galactose residues and galactose oligosaccharide chains). The protein part consisted of 50 kDa vicilin as the main compound. The fenugreek high molecular fraction did not influence proliferation of C. jejuni and viability of Caco-2 cells (1 - 1000 µg/mL). The fenugreek high molecular fraction reduced bacterial adhesion to Caco-2 significantly (500 - 1000 µg/mL), which was due to an interaction with the bacterial adhesin JlpA, preventing the interaction of this outer membrane protein to its ligand HSP90α (IC50 = 23.4 µg/mL). Bacterial invasion was reduced significantly. Both polysaccharides as well as vicilin contribute to the observed antiadhesive effect. As vicilin-like proteins are widely found in plants from the Fabaceae family, a vicilin-enriched protein preparation from Pisum sativum was investigated for antiadhesive activity. These findings suggest that fenugreek seeds or vicilin-rich plant extracts could be used to develop novel strategies to control C. jejuni infections in food-producing animals, ultimately helping to decrease the prevalence of campylobacteriosis in humans.

Plants arabinogalactans: From structures to physico-chemical and biological properties

Arabinogalactans (AGs) are plant heteropolysaccharides with complex structures occasionally attached to proteins (AGPs). AGs in cell matrix of different parts of plant are freely available or chemically bound to pectin rhamnogalactan. Type I with predominantly β-d-(1 → 4)-galactan and type II with β-d-(1 → 3) and/or (1 → 6)-galactan structural backbones construct the two main groups of AGs. In the current review, the chemical structure of AGs is firstly discussed focusing on non-traditional plant sources and not including well known industrial gums. After that, processes for their extraction and purification are considered and finally their techno-functional and biological properties are highlighted. The role of AG structure and function on health advantages such as anti-tumor, antioxidant, anti-ulcer- anti-diabetic and other activites and also the immunomodulatory effects on in-vivo model systems are overviewed.

Considerations to Be Taken When Carrying Out Medicinal Plant Research-What We Learn from an Insight into the IC50 Values, Bioavailability and Clinical Efficacy of Exemplary Anti-Inflammatory Herbal Components

Medicinal plants represent a big reservoir for discovering new drugs against all kinds of diseases including inflammation. In spite the large number of promising anti-inflammatory plant extracts and isolated components, research on medicinal plants proves to be very difficult. Based on that background this review aims to provide a summarized insight into the hitherto known pharmacologically active concentrations, bioavailability, and clinical efficacy of boswellic acids, curcumin, quercetin and resveratrol. These examples have in common that the achieved plasma concentrations were found to be often far below the determined IC50 values in vitro. On the other hand demonstrated therapeutic effects suggest a necessity of rethinking our pharmacokinetic understanding. In this light this review discusses the value of plasma levels as pharmacokinetic surrogates in comparison to the more informative value of tissue concentrations. Furthermore the need for new methodological approaches is addressed like the application of combinatorial approaches for identifying and pharmacokinetic investigations of active multi-components. Also the physiological relevance of exemplary in vitro assays and absorption studies in cell-line based models is discussed. All these topics should be ideally considered to avoid inaccurate predictions for the efficacy of herbal components in vivo and to unlock the "black box" of herbal mixtures.

Spectral quality overrides software score-A brief tutorial on the analysis of peptide fragmentation data for mass spectrometry laymen

The use of mass spectrometry has dramatically increased the research pace in the life sciences. The influence of the technique is enormous and its results can have far-reaching consequences such as jail time when applied in forensics. Therefore, analytical chemists trained in proper procedure know that they must validate their experiments. However, those quality measures have not been adopted in a similar manner in the omics technologies even though the stakes are equally high. Reasons are, among others, the segregation of the data generation and data mining functions and an undue belief in software capabilities. In this article, problematic issues such as false or overinterpretation of data are discussed, and assistance is provided for mass spectrometry laymen to evaluate the quality of their results; a quick guide to mass spectral data interpretation of peptide fragmentation experiments, the basis of bottom-up proteomics, is offered. Good science can only be generated in tight collaboration of principal investigator, analytical chemist, and bioinformatician so that the limits and the potential of each method and approach can be responsibly communicated.

Smart drug delivery against Helicobacter pylori: pectin-coated, mucoadhesive liposomes with antiadhesive activity and antibiotic cargo

The first step in the development of Helicobacter pylori pathogenicity is the receptor-mediated adhesion to the gastric epithelium. Inhibition of outer membrane proteins of H. pylori (e.g. BabA) by antiadhesive drugs will contribute to reduced recolonization and infection. Pectin from apple inhibits the BabA and LPS-mediated adhesion of H. pylori to human stomach cells. Pectin-coated liposomes with encapsulated amoxicillin were characterized for polydispersity, zeta potential, encapsulation efficiency, stability, and amoxicillin release. Coated liposomes did not influence the viability of AGS and HT29-MTX cells up to 100 μg/mL but exert cytotoxicity against H. pylori at 10 μg/mL. Pectin-coating of liposomes provoked direct interaction and subsequent binding of the particles to surface structures of H. pylori, and interaction with mucus from porcine stomach and mucus secreted by HT29-MTX cells. Laser scanning microscopy of H. pylori and AGS cells together with liposomes indicated co-aggregation. The mucoadhesive effect seems interesting as stomach cells are covered by a mucus layer. H. pylori is able to penetrate and cross the mucin rapidly to reach pH-neutral epithelium to escape the acidic environment, followed by interaction with epithelial cells. In summary, all experimental evidence is consistent with a specific interaction of pectin-coated liposomes with mucins and surface structures of H. pylori. As the coated liposomes show mucoadhesion to the negatively charged mucins, docking to stomach mucin, mucus penetration, and recognition of and adhesion to H. pylori, they can be considered a novel type of multifunctional drug carriers for local antibiotic therapy against H. pylori. KEY POINTS: • Smart, multifunctional mucoadhesive liposomes • Specific targeting against BabA/LPS of Helicobacter pylori • Inhibition of bacterial adhesion of H. pylori to human host cells • Release of antibiotic cargo.

BabA and LPS inhibitors against Helicobacter pylori: pectins and pectin-like rhamnogalacturonans as adhesion blockers

The first step in the development of Helicobacter pylori pathogenicity is receptor-mediated adhesion to gastric epithelium. Adhesins of H. pylori not only enable colonisation of the epithelium, with BabA interacting with Lewis^b, but also interaction of lipopolysaccharide (LPS) with galectin-3 contributes to attachment of H. pylori to the host cells. Anti-adhesive compounds against H. pylori have been described, but specific analytical assays for pinpointing the interaction with BabA are limited. LPS-galectin-3 inhibitors have not been described until now. A sandwich ELISA with recombinant BabA₅₄₇-6K was developed to investigate the interaction of BabA with Lewis^b-HSA. Isothermal titration calorimetry gave thermodynamic information on the interaction between BabA, Lewis^b-HSA and anti-adhesive compounds. A highly esterified rhamnogalacturonan from Abelmoschus esculentus inhibited the adhesion of H. pylori to adherent gastric adenocarcinoma (AGS) cells (IC₅₀ 550 μg/mL) and interacted with BabA (IC₅₀ 17 μg/mL). Pectins with similar rhamnogalacturonan structure showed weak anti-adhesive activity. Highly branched rhamnogalacturonans with low uronic acid content and high degree of esterification are potent BabA inhibitors. BabA represents a promising target for the development of anti-adhesive drugs against H. pylori. The rhamnogalacturonan influenced also the binding affinity of H. pylori to recombinant galectin-3 in a concentration-dependent manner with an IC₅₀ of 222 μg/mL. Similar effects were obtained with pectin from apple fruits, while pectins from other sources were inactive.

Polysaccharides from lichen Xanthoria parietina: 1,4/1,6-α-d-glucans and a highly branched galactomannan with macrophage stimulating activity via Dectin-2 activation

Hot-water soluble polysaccharides H-1-3 and H-2-1 were isolated from the thalli of the lichen Xanthoria parietina (L.) Th. Fr. and purified by ion exchange and gel permeation chromatography. Structure elucidation was mainly based on 2D-NMR and nano-ESI-Q-TOF MS/MS experiments. H-1-3 (13.7 kDa) was shown to be linear α-glucan with α-d-Glcp-(1 → [→[4)-α-d-Glcp-(1]₂ → [6)-α-d-Glcp-(1]₃ → 4)]_n core backbone. The (1,4)- and (1,6)-α-d-Glcp linkages were in a 2:3 M ratio. H-2-1 (525 kDa) was characterized as a complex branched β-galacto-α-mannan with →[6)-α-d-Manp-(1 → [2,6)-α-d-Manp-(1]₂ → [2)-α-d-Manp-(1]₂→]_n core units and main side chains of (1,3)-β-d-Galf linked at O-6 to →2)-α-d-Manp-(1→, together with minor terminal units of 1,4/1,6-α-D -Glcp units attached to the core chain at O-6 position and α-L-Rhap linked to Galf side chain at O-2 position (Manp: Galf: Glcp: Rhap linkage ratio = 9:3:2:1). H-2-1 exerted strong immunoactivity in vitro and activated murine RAW macrophages 264.7 towards significantly increased phagocytosis, TNF-α and IL-1β secretion. These effects are due to an interaction of the galactomannan with the transmembrane pattern-recognition protein Dectin-2 of the macrophages.

Isolation, structure elucidation, and immunostimulatory activity of polysaccharide fractions from Boswellia carterii frankincense resin

Frankincense has a long history in religious, cultural, and medicinal use. In this study polysaccharides were extracted from frankincense from Boswellia carterii. The polysaccharides were purified by anion exchange chromatography on a DEAE-Sepharose Fast Flow 16/10 FPLC column. Six fractions were obtained and the three most active immunomodulatory fractions were further purified by size exclusion chromatography on a Superdex-200 column. The composition showed the monosaccharides present were predominantly galactose, arabinose, and glucuronic acid along with small amounts of rhamnose and glucose. The monosaccharide composition and glycosyl linkage analysis revealed the polysaccharides belong to the type II arabinogalactans. Fourier-transform infrared spectroscopy and bicinchoninic acid assay showed that the amount of protein in the samples was <1 wt%. One-dimensional ¹H NMR were consistent with high molecular weight compounds. The monosaccharides were primarily in the β conformation. The three fractions exhibited an immunostimulatory effect on RAW 264.7 murine macrophage cells. The most active immunostimulatory fraction FA2, stimulated a range of pro-inflammatory mediators including iNOS, NO, TNF-α, and IL-6 in RAW 264.7 cells. The fractions were effective in proliferating primary murine splenocytes. The results indicate that the polysaccharides isolated from frankincense have the potential to be used as an immunological stimulant or nutraceutical.

γ-Propoxy-Sulfo-Lichenan Induces In Vitro Cell Differentiation of Human Keratinocytes

Background: As non-cellulosic β-d-glucans are known to exert wound-healing activity by triggering keratinocytes into cellular differentiation, the functionality of a semisynthetic lichenan-based polysaccharide on skin cell physiology was investigated. Methods: γ-Propoxy-sulfo-lichenan (γ-PSL, molecular weight 52 kDa, β-1,3/1,4-p-d-Glucose, degree of substitution 0.7) was prepared from lichenan. Differentiation of primary human keratinocytes was assayed by the protein analysis of differentiation specific markers and by gene expression analysis (qPCR). The gene array gave insight into the cell signaling induced by the polysaccharide. Results: γ-PSL (1 to 100 μg/mL) triggered keratinocytes, in a concentration-dependent manner, into the terminal differentiation, as shown by the increased protein expression of cytokeratin 1 (KRT1). Time-dependent gene expression analysis proved differentiation-inducing effects, indicating strong and fast KRT1 gene expression, while KRT10 expression showed a maximum after 12 to 24 h, followed by downregulation to the basal level. Involucrin gene expression was only changed to a minor extent, which was similar to loricrin and transglutaminase. Gene array indicated the influence of γ-PSL on MAP kinase and TGF-β mediated signaling towards keratinocyte differentiation. Conclusion: The propoxylated lichenan may improve wound healing by topical application to promote the terminal barrier formation of keratinocytes.

Cell wall extensins in root-microbe interactions and root secretions

Extensins are cell wall glycoproteins, belonging to the hydroxyproline-rich glycoprotein (HRGP) family, which are involved in many biological functions, including plant growth and defence. Several reviews have described the involvement of HRGPs in plant immunity but little focus has been given specifically to cell wall extensins. Yet, a large set of recently published data indicates that extensins play an important role in plant protection, especially in root-microbe interactions. Here, we summarise the current knowledge on this topic and discuss the importance of extensins in root defence. We first provide an overview of the distribution of extensin epitopes recognised by different monoclonal antibodies among plants and discuss the relevance of some of these epitopes as markers of the root defence response. We also highlight the implication of extensins in different types of plant interactions elicited by either pathogenic or beneficial micro-organisms. We then present and discuss the specific importance of extensins in root secretions, as these glycoproteins are not only found in the cell walls but are also released into the root mucilage. Finally, we propose a model to illustrate the impact of cell wall extensin on root secretions.

Phytochemical Characterization of Low Molecular Weight Constituents from Marshmallow Roots (Althaea officinalis) and Inhibiting Effects of the Aqueous Extract on Human Hyaluronidase-1

Extract RE was obtained from the roots of Althaea officinalis in a yield of 8.1%, related to the dried plant material, by extraction with MeOH-H₂O (1:1), followed by precipitation with EtOH to remove high molecular weight constituents. Phytochemical investigation of RE revealed the presence of N-phenylpropenoyl-l-amino acid amides 1-5, 8% glycine betaine 6, about 9% total amino acids with proline as the main compound, and about 61% mono- and oligomeric carbohydrates with sucrose as the main compound. Further fractionation revealed the presence of a hypolaetin diglycoside (12) and four hypolaetin glycosides (7-9 and 11) with O-sulfocarbohydrate moieties; additionally, 4'-O-methylisoscutellarein-8-O-β-d-(3″-O-sulfo)glucuronopyranoside (10) and the diglycosylated coumarin haploperoside D (13) were identified. The hypolaetin-O-sulfoglycosides 7-10 are new natural products. RE inhibited the enzymatic activity of surface-displayed human hyaluronidase-1 on Escherichia coli F470 cells with an IC₅₀ of 7.7 mg/mL. RE downregulated mRNA expression of hyal-1 in HaCaT keratinocytes at 125 and 250 μg/mL, respectively. These data contribute to a deeper phytochemical understanding of marshmallow root extracts and to the positive influence of extracts used for therapy of irritated and inflamed buccal tissue and cough.

Arabinosylation Plays a Crucial Role in Extensin Cross-linking In Vitro

Extensins (EXTs) are hydroxyproline-rich glycoproteins (HRGPs) that are structural components of the plant primary cell wall. They are basic proteins and are highly glycosylated with carbohydrate accounting for >50% of their dry weight. Carbohydrate occurs as monogalactosyl serine and arabinosyl hydroxyproline, with arabinosides ranging in size from ~1 to 4 or 5 residues. Proposed functions of EXT arabinosylation include stabilizing the polyproline II helix structure and facilitating EXT cross-linking. Here, the involvement of arabinosylation in EXT cross-linking was investigated by assaying the initial cross-linking rate and degree of cross-linking of partially or fully de-arabinosylated EXTs using an in vitro cross-linking assay followed by gel permeation chromatography. Our results indicate that EXT arabinosylation is required for EXT cross-linking in vitro and the fourth arabinosyl residue in the tetraarabinoside chain, which is uniquely α-linked, may determine the initial cross-linking rate. Our results also confirm the conserved structure of the oligoarabinosides across species, indicating an evolutionary significance for EXT arabinosylation.

Acetylated Rhamnogalacturonans from Immature Fruits of Abelmoschus esculentus Inhibit the Adhesion of Helicobacter pylori to Human Gastric Cells by Interaction with Outer Membrane Proteins

Polysaccharide containing extracts from immature fruits of okra (Abelmoschus esculentus) are known to exhibit antiadhesive effects against bacterial adhesion of Helicobacter pylori (H. pylori) to stomach tissue. The present study investigates structural and functional features of polymers responsible for this inhibition of bacterial attachment to host cells. Ammonium sulfate precipitation of an aqueous extract yielded two fractions at 60% and 90% saturation with significant antiadhesive effects against H. pylori, strain J99, (FE_60% 68% ± 15%; FE_90% 75% ± 11% inhibition rates) after preincubation of the bacteria at 1 mg/mL. Sequential extraction of okra fruits yielded hot buffer soluble solids (HBSS) with dose dependent antiadhesive effects against strain J99 and three clinical isolates. Preincubation of H. pylori with HBSS (1 mg/mL) led to reduced binding to 3ʹ-sialyl lactose, sialylated Le^a and Le^x. A reduction of bacterial binding to ligands complementary to BabA and SabA was observed when bacteria were pretreated with FE_90%. Structural analysis of the antiadhesive polysaccharides (molecular weight, monomer composition, linkage analysis, stereochemistry, and acetylation) indicated the presence of acetylated rhamnogalacturonan-I polymers, decorated with short galactose side chains. Deacetylation of HBSS and FE_90% resulted in loss of the antiadhesive activity, indicating esterification being a prerequisite for antiadhesive activity.

Xyloglucan from Tropaeolum majus Seeds Induces Cellular Differentiation of Human Keratinocytes by Inhibition of EGFR Phosphorylation and Decreased Activity of Transcription Factor CREB

Xyloglucan XG (molecular weight 462 kDa, 1,4-/1,4,6-(pGlc) linked backbone, side chains of 1-pXyl, 1,2-pXyl, 1-p-Gal) was isolated from the seeds of Tropaeolum majus. XG (100 μg/mL) induced terminal cellular differentiation of human keratinocytes, as demonstrated by immunofluorescence staining and Western blot using cytokeratin 10 and involucrin as marker proteins. Differentiation was also induced by XG-derived oligosaccharides (degree of polymerization 7-9). Quantitative real-time polymerase chain reaction (qPCR) revealed the induction of gene expression of typical differentiation markers (cytokeratin, filaggrin, involucrin, loricrin, transglutaminase) in a time-dependent manner. Whole human genome microarray indicated that most of upregulated genes were related to differentiation processes. Microarray findings on selected genes were subsequently confirmed by qPCR. For identification of the molecular target of xyloglucan PAGE of keratinocyte membrane preparations was performed, followed by blotting with fluorescein isothiocyanate-labeled XG. XG interacting proteins were characterized by MS. Peptide fragments of epidermal growth factor receptor (EGFR) and integrin β4 were identified. Subsequent phospho-kinase array indicated that phosphorylation of EGFR and transcription factor cAMP response element-binding protein (CREB) was decreased in the XG-treated cells. Thus, the XG-induced differentiation of keratinocytes is proposed to be mediated by the inhibition of the phosphorylation of EGFR, leading to a dimished CREB activation, which is essential for the activation of cellular differentiation.

Gastroprotection as an example: antiadhesion against Helicobacter pylori, anti-inflammatory and antioxidant activities of aqueous extracts from the aerial parts of Lippia integrifolia Hieron

ETHNOPHARMACOLOGICAL RELEVANCE

The aerial parts of Lippia integrifolia (Gris.) Hieronymus (Verbenaceae), known as incayuyo, are used by the peasant population of Argentina for treatment of diseases related to a gastrointestinal system, mainly for inflammation of the stomach and have also been included into the Argentina Food Code. This study aimed to investigate the phytochemical profile of hydrophilic extracts from the herbal material by LC-MS and to evaluate potential pharmacological mechanisms rationalizing the traditional use of incayuyo aqueous extracts potential anti-inflammatory treatment of gastrointestinal disorders.

MATERIALS AND METHODS

Phytochemical profiling: LC-MS of an aqueous decoction. Antiadhesive effects against Helicobacter pylori: in vitro FACS assay using FITC-labeled bacteria and AGS human stomach cells. Influence of extracts on stomach cells and RAW 264.7 macrophages: MTT viability assay and BrdU proliferation ELISA. Influence of extracts on IL-6 and IL-8 secretion from stomach cells was quantitated by ELISA after infection of the cells with Helicobacter pylori. Influence of test extracts on macrophages: phagocytosis of FITC-labeled Zymosan particles and NO production. Antioxidative capacity: DPPH assay and O2-induced caroten oxidation.

RESULTS

LC-MS profiling indicated the presence of compounds 1-20 with flavonoid hexosides, phenylethanoides (acteoside, isoacteoside) and sesquiterpenes [(epi)lippidulcine, peroxylippidulcine] in the decoction extract and subfraction PhF. The extract exhibits strong in vitro antioxidative capacity and inhibited adhesion of Helicobacter pylori to stomach cells up to 40%, while an EtOH-soluble fraction showed inhibition rates of up to 60%. Decoction increased the cellular viability of AGS cells significantly at >10 μg/mL, while proliferation rate was not influenced. Helicobacter pylori induced IL-8 secretion was significantly reduced by coincubation of AGS cells with the extracts. Aqueous extracts stimulated phagocytosis rate of macrophages and inhibited the LPS-induced NO-secretion.

CONCLUSIONS

The traditional use of aqueous extracts from Lippia integrifolia for gastric inflammation seems to be rationalized: besides anti-inflammatory effects on stomach cells antiadhesive properties of the extracts against the main bacterial inductor of gastritis Helicobacter pylori were identified. Additional effects for stimulation of innate immunity and potential radical scavenging effects may additionally contribute to the activity of the extracts.

Antiadhesive properties of arabinogalactan protein from ribes nigrum seeds against bacterial adhesion of Helicobacter pylori

Fruit extracts from black currants (Ribes nigrum L.) are traditionally used for treatment of gastritis based on seed polysaccharides that inhibit the adhesion of Helicobacter pylori to stomach cells. For detailed investigations an arabinogalactan protein (F2) was isolated from seeds and characterized concerning molecular weight, carbohydrate, amino acid composition, linkage, configuration and reaction with β-glucosyl Yariv. Functional testing of F2 was performed by semiquantitative in situ adhesion assay on sections of human gastric mucosa and by quantitative in vitro adhesion assay with FITC-labled H. pylori strain J99 and human stomach AGS cells. Bacterial adhesins affected were identified by overlay assay with immobilized ligands. ¹²⁵I-radiolabeled F2 served for binding studies to H. pylori and interaction experiments with BabA and SabA. F2 had no cytotoxic effects against H. pylori and AGS cells; but inhibited bacterial binding to human gastric cells. F2 inhibited the binding of BabA and fibronectin-binding adhesin to its specific ligands. Radiolabeled F2 bound non-specifically to different strains of H. pylori; and to BabA deficient mutant. F2 did not lead to subsequent feedback regulation or increased expression of adhesins or virulence factors. From these data the non-specific interactions between F2 and the H. pylori lead to moderate antiadhesive effects.

Arabinogalactan protein cluster from Jatropha curcas seed embryo contains fasciclin, xylogen and LysM proteins

An non-GPI-anchored AGP cluster (Y2) was isolated from the seeds of Jatropha curcas L. (Euphorbiaceae) composed of 4.8% polypeptides (mainly Ala, Ser, Gly, Hyp, Glu) and a carbohydrate moiety composed of Gal, Ara, GlcA, Rha, Man and GlcN. Besides the typical structural features of arabinogalactan proteins, typical N-glycan linker of the complex type (GlcNAc4Man3Gal2Fuc1Xyl1) were identified. O-glycosylation occurred mainly via Hyp and to a lesser extent via Thr and Ser. N-glycans from the complex type, carrying at the innermost GlcNAc at position O-3 one α-Fuc-residue, were also present. MS analysis of the tryptic digest assigned peptides of three major protein groups: fasciclin-like arabinogalactan proteins, xylogen-like proteins and LysM domain-containing proteins. They could not be separated further and it is indicated that various homologous protein forms co-exist. Histological investigation of J. curcas seeds revealed the presence of AGPs in the vessels of cotyledons and in the procambium ring of the embryo.