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Matthias Hamburger

Publications and source records attributed to Matthias Hamburger.

At least 19 recordsLinked to original sources
PubMed2006

(+)-N-Deoxymilitarinone A, a neuritogenic pyridone alkaloid from the insect pathogenic fungus Paecilomyces farinosus.

A new pyridone alkaloid, (+)-N-deoxymilitarinone A (1), was isolated from Paecilomyces farinosus RCEF 0097 along with the related metabolites, militarinone D and militarinone B. The sterol 22E,4R-ergosta-7,22-diene-3beta,5alpha,6beta,9alpha-tetraol was also identified. The structures were established by spectroscopic methods, in particular with the aid of extensive NMR experiments. Compound 1 induced neurite sprouting in PC 12 cells when tested at 33 and 100 microM concentrations. A cytotoxic effect was observed in human neurons (IMR-32) at a concentration of 100 microM.

Alkaloids↗
PubMed2004

Militarinone A induces differentiation in PC12 cells via MAP and Akt kinase signal transduction pathways.

The fungal metabolite militarinone A (MILI A) promotes neurite outgrowth in PC12 cells. This study was conducted to investigate the signaling pathways involved in the cellular differentiation processes induced by the compound, with a focus on cascades implicated with nerve growth factor (NGF)-mediated neuritogenesis. MILI A possessed pronounced amphiphilic properties. The compound rapidly accumulated in the cell membrane and was slowly released into the cytoplasma. In primed PC12 cells, an early activation of protein kinase B (Akt), representing a downstream target of phosphoinositol 3 (PI3) kinase, and a delayed phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2), and of transcription factor cAMP responsive element binding protein (CREB) was found. The NGF-dependent activation of c-Jun amino terminal kinase (SAPK/JNK1) was potentiated. Morphological differentiation of cells and the phosphorylation of specific signal molecules were blocked by the MAP kinase (MEK1) inhibitor PD098059, the PI3-kinase (PI3K) inhibitor wortmannin and the adenylyl cyclase inhibitor 9-cyclopentyladenine.

Adenylyl Cyclases↗
PubMed2004

Quantitative analysis of anti-inflammatory and radical scavenging triterpenoid esters in evening primrose oil.

Cold pressed, nonraffinated evening primrose oil (EPO) was recently found to contain lipophilic triterpenoidal esters with radical scavenging and anti-inflammatory properties. A simple and robust method for the quantitative analysis of these 3-O-trans-caffeoyl derivatives of betulinic, morolic, and oleanolic acid was developed and validated. Separation was achieved by normal phase chromatography on a Diol column and with hexane/ethyl acetate (50:50) as eluent. The analytes could be determined directly in the oil matrix, without need of a previous removal of the triglycerides. Normal phase LC ESI-MS with a makeup flow of polar modifier was used for checking the identity and purity of analyte peaks. Samples from 22 commercially available EPOs were analyzed. The average caffeoyl ester contents were 58 mg/100 g in cold pressed oils and 4.7 mg/100 g in partially raffinated oils. In fully raffinated EPO samples, the concentration was below the limit of detection. The influence of extraction temperature on the content of caffeoyl esters in nonraffinated EPO was investigated with seeds of Oenothera biennis and Oenothera lamarckiana, respectively. With O. lamarckiana, the concentration of caffeoyl esters in the oil increased with rising pressure and temperature, whereas no such dependency was found with O. biennis. Microscopic analysis revealed some differences in the histology of the seed testa, which may explain in part the differing behaviors in the extraction experiments. There was a difference between O. biennis and O. lamarckiana oils with respect to the relative amounts of the three esters. The temperature of the extraction process had no effect on the ratio of the compounds.

Anti-Inflammatory Agents↗
PubMed2004

Rapid analysis of nucleotide-activated sugars by high-performance liquid chromatography coupled with diode-array detection, electrospray ionization mass spectrometry and nuclear magnetic resonance.

A generally applicable method for HPLC analysis of sugar nucleotides was established. Separation was achieved using ion-pair chromatography on a reversed-phase column. Ion-pair reagents were selected and various parameters optimized with respect to separation of 11 of the most important sugar nucleotides and compatibility with on-line detection by electrospray ionization MS and NMR. The method was applied to the on-line analysis of the GDP-D-mannose-4,6-dehydratase (Gmd) and GDP-4-keto-6-deoxy-D-mannose reductase (Rmd) catalyzed conversion of GDP-D-mannose to GDP-D-rhamnose. By LC-NMR, the intermediate product of the reaction was shown to be a mixture of GDP-4-keto-6-deoxy-D-mannose and GDP-3-keto-6-deoxy-D-mannose. Nucleotide co-factors of enzymatic reactions such as ATP and NADH did not interfere with the analysis of nucleotide-activated sugars.

Carbohydrates↗
PubMed2004

Analysis of aspartyl peptide degradation products by high-performance liquid chromatography and high-performance liquid chromatography-mass spectrometry.

A reversed-phase HPLC method for the analysis of degradation products of the model aspartyl tripeptides Phe-Asp-GlyNH2 and Gly-Asp-PheNH2 after incubation at pH 2 and 10 was developed. Most of the compounds could be separated with a gradient of acetonitrile in water containing 0.1% trifluoroacetic acid. Resolution of the isomeric pairs L-Phe-alpha-L-Asp-GlyNH2/L-Phe-beta-L-Asp-GlyNH2 and L-Phe-alpha-D-Asp-GlyOH/L-Phe-beta-D-Asp-GlyOH was achieved with a gradient of acetonitrile in phosphate buffer, pH 5.0. Under acidic conditions the major degradation pathway was cleavage of the peptide backbone amide bonds yielding dipeptides and amino acids, C-terminal deamidation as well as formation of succidinimyl peptides. At alkaline pH both deamidation of the C-terminal amide as well as isomerization and concomitant enantiomerization of Asp were observed. The peaks were identified both by reference substances and by online electrospray mass spectrometry. The results were compared to a previous developed capillary electrophoresis method. Diastereomeric pairs ofpeptides that could not be separated by capillary electrophoresis were resolved by HPLC while the separation of corresponding pairs of alpha- and beta-Asp peptides was not always achieved by HPLC in contrast to capillary electrophoresis illustrating that both techniques can be complimentary in peptide analysis.

Aspartic Acid↗
PubMed2004

HPLC-based bioactivity profiling of plant extracts: a kinetic assay for the identification of monoamine oxidase-A inhibitors using human recombinant monoamine oxidase-A.

An assay for the HPLC-based search for monoamine oxidase-A (MAO-A) inhibitors in plant extracts was established. It combines human recombinant MAO-A, expressed as GST-fusion protein in yeast, with a kinetic measurement of the conversion of kynuramine to 4-hydroxyquinoline. Substrate selectivity and kinetic parameters of the GST-fusion protein were comparable to the wild-type enzyme. The applicability of the assay to HPLC-based activity profiling was tested with plant extracts spiked with small amounts of known MAO inhibitors.

Chromatography, High Pressure Liquid↗
PubMed2004

The content of indigo precursors in Isatis tinctoria leaves--a comparative study of selected accessions and post-harvest treatments.

We recently clarified the nature of indigo precursors in woad (Isatis tinctoria L.), by identifying the major indoxyl glycoside as isatan A (indoxyl-3-O-(6'-O-malonyl-beta-D-ribohexo-3-ulopyranoside)), and by correcting the structure of the related isatan B (indoxyl-3-O-beta-D-ribohexo-3-ulopyranoside). A quantitative densitometric assay for isatans A and B, and indican, was established and validated. HPTLC separation on silica gel was followed by densitometric analysis of indigoid pigments formed after treatment with dilute acid or base. The seasonal variation of indoxyl glycosides in woad leaves was investigated with first-year plants (rosette stage) of five defined I. tinctoria L. and one I. indigotica L. accessions. Isatan A content reached up to 7.6% of dry weight in I. tinctoria, and up to 21.8% in I. indigotica. The influence of various post-harvest treatments was studied. High concentrations of isatans A and B were found in freeze-dried leaf samples, whereas the content of indican was lowest. Conventional drying at ambient or 40 degrees C led to complete disappearance of isatans A and B. The concentration of indican, in contrast, was 3- to 5-fold higher in leaf samples submitted to drying at ambient and 40 degrees C, respectively.

Chromatography, High Pressure Liquid↗
PubMed2004

Farinosones A-C, neurotrophic alkaloidal metabolites from the entomogenous deuteromycete Paecilomyces farinosus.

Two new yellow pigments, farinosones A (1) and B (2), were isolated from the mycelial extract of the entomogenous fungal strain Paecilomyces farinosus RCEF 0101, together with farinosone C (3), a new metabolite derived from an early step of pyridone alkaloid biosynthesis. The structures were determined by spectroscopic means, in particular by extensive NMR experiments. Compounds 1 and 3 induced neurite outgrowth in the PC-12 cell line at concentrations of 50 microM, while compound 2 was inactive. No cytotoxicity was observed for compounds 1-3 in PC-12 cells when tested at 50 microM concentration in the MTT assay.

Animals↗
PubMed2004

Prevention of experimentally induced irritant contact dermatitis by extracts of Isatis tinctoria compared to pure tryptanthrin and its impact on UVB-induced erythema.

Lipophilic extracts of Isatis tinctoria L. exhibit significant activity against several clinically relevant targets of inflammation. The alkaloid tryptanthrin was identified as one of the active principles in woad and characterised as a potent dual inhibitor of COX-2 and 5-LOX. Here, the anti-inflammatory efficacy of topical application of three different Isatis extracts and tryptanthrin was investigated in human volunteers. Two different models were used, namely the sodium lauryl sulphate (SLS)-induced irritant contact dermatitis (ICD) and UVB-induced erythema. Twenty healthy volunteers without any skin disease participated in the study. Cumulative irritant contact dermatitis was induced on test fields on the volunteers' backs by twice daily application of 0.5 % sodium lauryl sulphate over a period of four days. Half of the test fields were treated with the test substances during the eliciting phase, while the remaining test fields were treated over a period of 4 days after induction of dermatitis. In the second model, a UVB erythema on the volunteers' lower backs was induced using the double minimal erythema dose (MED). Twenty-four hours after irradiation the test fields were treated with the test substances over a period of 3 days. All reactions were assessed visually and by non-invasive bioengineering methods (evaporimetry and chromametry). Treatment with extracts during the ICD eliciting phase led to a significantly smaller increase of visual scores and transepidermal water loss compared to the untreated test field. For tryptanthrin this benefit was also observed, but the improvement was not statistically significant. When treatment was performed after completing the eliciting phase, accelerated resolution of the irritant reaction could not be observed. In the UVB erythema model anti-inflammatory effects of the test substances were not observed.

Adolescent↗
PubMed2004

Tryptanthrin content in Isatis tinctoria leaves--a comparative study of selected strains and post-harvest treatments.

Tryptanthrin is a pharmacologically active compound in the anti-inflammatory herb Isatis tinctoria, with potent inhibitory activity on prostaglandin and leukotriene synthesis and on inducible NO synthase. The tryptanthrin content of five defined woad strains was analyzed in dependence of the time of harvest and post-harvest treatment. Tryptanthrin was determined by a validated ESI-LC-MS isotope dilution assay with d(8)-tryptanthrin as internal standard. The tryptanthrin concentration in freeze-dried leaf samples was low. Drying at ambient temperature led to a significant increase of tryptanthrin concentration, but the highest concentrations were found when leaves were dried at 40 degrees C. Tryptanthrin content in fermented woad leaves was below the limit of quantification. Tryptanthrin appears thus to be a product of post-harvest processes, but details of its formation remain to be elucidated.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2004

HPLC-based activity profiling of Salvia miltiorrhiza for MAO A and iNOS inhibitory activities.

In the course of a screening of plant extracts for potential CNS and anti-inflammatory activities, a dichloromethane extract of Salvia miltiorrhiza showed a pronounced inhibitory effect on recombinant monoamine oxidase A (MAO A) and on inducible NO synthase (iNOS) induction in Raw 267.4 cells. With the aid of HPLC-based profiling techniques, activities could be linked, to a significant extent, to peaks of tanshinone-type diterpenoids, four of which were subsequently isolated. The IC50 of the most active compound, 15,16-dihydrotanshinone I, on human recombinant MAO A was at 23 microM, and 2.4 microM on lipopolysaccharide-mediated iNOS induction in Raw 267.4 cells.

Animals↗
PubMed2003

A simple method for preparation of D-rhamnose.

A rapid procedure for the preparation of D-rhamnose from bacterial lipopolysaccharide (LPS) has been developed. It involves purification of LPS from Pseudomonas syringae pv. phaseolicola by phenol extraction and hydrophobic interaction chromatography (HIC), followed by mild hydrolysis and cleavage of the O-antigen into D-fucose and D-rhamnose. The monosaccharides were separated by column chromatography, and D-rhamnose recovered after filtration over Sephadex-LH 20.

Chromatography↗
PubMed2003

Novel tetramic acids and pyridone alkaloids, militarinones B, C, and D, from the insect pathogenic fungus Paecilomyces militaris.

Three yellow pigments were isolated from a mycelial extract of the entomopathogenic fungus Paecilomyces militaris. With the aid of spectroscopic means, one compound was identified as a new pyridone alkaloid, militarinone D (1). The two other metabolites were characterized as two novel 3-acyl tetramic acids, militarinones B (2) and C (3). In contrast to the structurally related pyridone militarinone A (4), compounds 1-3 showed only negliable neuritogenic activity in PC-12 cells, whereas militarinone D (1) exhibited cytotoxicity. On the basis of a co-occurrence of 3-acyl tetramic acids and biogenetically related pyridone alkaloids in P. militaris, a revised biosynthetic pathway for pyridone alkaloids is proposed.

Alkaloids↗
PubMed2003

Ultraviolet a induces generation of squalene monohydroperoxide isomers in human sebum and skin surface lipids in vitro and in vivo.

At the outermost surface of human skin, skin surface lipids are first-line targets of solar ultraviolet radiation. Therefore, we hypothesized that ultraviolet A and ultraviolet B irradiation induce photo-oxidation of skin surface lipids. To test this, sebum samples were collected from facial skin of 17 healthy volunteers, weighed, and immediately irradiated with either ultraviolet B or ultraviolet A. Squalene, the major sebum lipid, as well as photo-oxidation products were identified in sebum lipid extracts by high-performance liquid chromatography analysis. Upon ultraviolet A exposures squalene was depleted in a concentration-dependent manner, whereas an unidentified sebum lipid photo-oxidation product was detected. Using high-performance thin layer chromatography, high-performance liquid chromatography, atmospheric pressure chemical ionization mass spectrometry, and nuclear magnetic resonance, unidentified sebum lipid photo-oxidation product was identified as a mixture of squalene monohydroperoxide isomers. Squalene monohydroperoxide isomers purified from sebum were identical with squalene monohydroperoxide isomers synthesized by preparative photo-oxidation of squalene. Squalene monohydroperoxide isomers were formed even after small suberythematogenic doses of ultraviolet A (5 J per cm2). Whereas physiologic baseline levels of squalene monohydroperoxide isomers in human skin were only slightly above detection limits, squalene monohydroperoxide isomer levels were strongly increased by suberythematogenic doses of ultraviolet A both in vitro and in vivo. High-performance liquid chromatography results could be complemented by a straightforward thin layer chromatography method for rapid screening of lipid peroxide formation in human sebum/skin surface lipids. In conclusion, specific squalene monohydroperoxide isomers were identified as highly ultraviolet A sensitive skin surface lipid breakdown products that may serve as a marker for photo-oxidative stress in vitro and in vivo.

Adult↗
PubMed2003

A comparative study on the skin penetration of pure tryptanthrin and tryptanthrin in Isatis tinctoria extract by dermal microdialysis coupled with isotope dilution ESI-LC-MS.

The indolo[2,1- b]quinazoline alkaloid tryptanthrin has recently been identified as a pharmacologically active compound in Isatis tinctoria, with potent dual inhibitory activity on prostaglandin and leukotriene synthesis. To investigate the skin penetration of tryptanthrin from solutions of pure compound and Isatis extracts, we developed and validated a cutaneous microdialysis model using ex vivo pig foreleg. Microdialysis was performed by placing linear probes in the dermis of the skin in situ, and tryptanthrin concentrations in the dialysates were determined by isotope dilution electrospray ionization LC-MS in the selected ion mode. Measurable concentrations of tryptanthrin were detected 30 min after application. A dose-dependent increase in tryptanthrin concentrations in the dialysate was observed for the Isatis extracts, but not for pure tryptanthrin. Microscopic analysis showed that the pure compound crystallized from the solution but remained in an amorphous state in the extracts.

Animals↗
PubMed2002

Constituents in evening primrose oil with radical scavenging, cyclooxygenase, and neutrophil elastase inhibitory activities.

Cold-pressed, non-raffinated evening primrose oil was found to contain lipophilic radical scavengers. A highly enriched fraction of these compounds could be obtained from the oil by extraction with aqueous ethanol and subsequent liquid-liquid partitioning with petroleum. LC-DAD-MS analysis revealed that the fraction contained three aromatic compounds with identical UV and ESI-MS spectra. The compounds were isolated by RP-HPLC and their structures established by chemical and spectroscopic means as 3-O-trans-caffeoyl derivatives of betulinic, morolic, and oleanolic acid. The morolic acid derivative was a new compound. The three esters exhibited pronounced radical scavenging activity against the stable 2,2-diphenyl-1-picrylhydrazyl radical and were potent inhibitors of neutrophil elastase and cyclooxygenase-1 and -2 in vitro. Commercial samples of evening primrose oils contained only traces of these lipophilic antioxidants.

Antioxidants↗
PubMed2002

Occurrence of stable foam in the upper Rhine River caused by plant-derived surfactants.

For 30 yr, a persistent foam cover has been observed during the summer months in the Rhine River beneath the Rhine Fall, a waterfall near Schaffhausen, Switzerland. This phenomenon has been a matter of public concern ever since its first appearance, but all previous attempts to clarify the origin of this foam had remained inconclusive. With the aid of electrospray LC-MS,triterpene saponins and mono- and digalactosyldiacylglycerolipids (MGDAG and DGDAG), two classes of tensioactive metabolites occurring in the aquatic plant Ranunculus fluitans Lamk. (Ranunculaceae), were detected in river water and foam samples. Saponin concentrations in water and foam samples were monitored at regular intervals during the years 1998 and 2000. Other compound classes with surfactant properties such as proteins, humic acids, and synthetic detergents were also analyzed. Foam occurrence paralleled with saponin concentration and with the amounts of detached Ranunculus biomass accumulating at the dam of the hydroelectric power plant of Schaffhausen located just above the Rhine Fall but not with the concentration of synthetic detergents. The ecotoxicological potential of Ranunculus constituents, water, and foam samples was checked with a representative range of aquatic indicator organisms. No acute toxicity was observed at concentrations that were at least 50-fold higher than those found in the environmental samples.

Biomass↗