Mycophenolic Acid: a one hundred year odyssey from antibiotic to immunosuppressant

2D Quantitative structure-property relationship study of mycotoxins by multiple linear regression and support vector machine

In the present work, support vector machines (SVMs) and multiple linear regression (MLR) techniques were used for quantitative structure–property relationship (QSPR) studies of retention time (t_R) in standardized liquid chromatography–UV–mass spectrometry of 67 mycotoxins (aflatoxins, trichothecenes, roquefortines and ochratoxins) based on molecular descriptors calculated from the optimized 3D structures. By applying missing value, zero and multicollinearity tests with a cutoff value of 0.95, and genetic algorithm method of variable selection, the most relevant descriptors were selected to build QSPR models. MLR and SVMs methods were employed to build QSPR models. The robustness of the QSPR models was characterized by the statistical validation and applicability domain (AD). The prediction results from the MLR and SVM models are in good agreement with the experimental values. The correlation and predictability measure by r² and q² are 0.931 and 0.932, repectively, for SVM and 0.923 and 0.915, respectively, for MLR. The applicability domain of the model was investigated using William’s plot. The effects of different descriptors on the retention times are described.

Inhibition of inosine monophosphate dehydrogenase reduces adipogenesis and diet-induced obesity

We previously described a putative role for inosine monophosphate dehydrogenase (IMPDH), a rate-limiting enzyme in de novo guanine nucleotide biosynthesis, in lipid accumulation. Here we present data which demonstrate that IMPDH activity is required for differentiation of preadipocytes into mature, lipid-laden adipocytes and maintenance of adipose tissue mass. In 3T3-L1 preadipocytes inhibition of IMPDH with mycophenolic acid (MPA) reduced intracellular GTP levels by 60% (p<0.05) and blocked adipogenesis (p<0.05). Co-treatment with guanosine, a substrate in the salvage pathway of nucleotide biosynthesis, restored GTP levels and adipogenesis demonstrating the specificity of these effects. Treatment of diet-induced obese mice with mycophenolate mofetil (MMF), the prodrug of MPA, for 28 days did not affect food intake or lean body mass but reduced body fat content (by 36%, p=0.002) and adipocyte size (p=0.03) and number. These data suggest that inhibition of IMPDH may represent a novel strategy to reduce adipose tissue mass.

Mycophenolic derivatives from Eupenicillium parvum

A new compound, euparvic acid (1, C(14)H(16)O(6)), and the known compounds 5,7-dihydroxy-4-methylphthalide (2), 6-(3-carboxybutyl)-7-hydroxy-5-methoxy-4-methylphthalan-1-one (3), 6-(5-carboxy-3-methylpent-2-enyl)-7-hydroxy-5-methoxy-4-methylphthalan-1-one (4), and 6-(5-carboxy-4-hydroxy-3-methylpent-2-enyl)-7-hydroxy-5-methoxy-4-methylphthalan-1-one (5) were isolated from the EtOAc extract of Eupenicillium parvum. The structure of 1 was determined by interpretation of MS and homo- and heteronuclear 2D NMR spectroscopic data and confirmed by X-ray crystallography. The absolute configuration of 5 was determined via MPA ester derivatization.

Enzyme immunoassay for mycophenolic acid in milk and cheese

Mycophenolic acid (MPA) was reacted with N-hydroxysuccinimide and conjugated to keyhole limpet hemocyanin (KLH), and to horseradish peroxidase (HRP), respectively. The MPA-KLH was used to produce anti-MPA antiserum in rabbits. A competitive direct enzyme immunoassay (EIA) for MPA was established with anti-MPA antiserum and MPA-HRP conjugate. The mean 50% inhibition and detection limit of MPA standard curves (n = 103) were 197 +/- 67 and 81 +/- 48 pg/mL, respectively. The EIA was specific for MPA and its synthetic 2-morpholinoethyl ester, mycophenolate mofetil (91% relative cross-reactivity). Raw bulk milk and pasteurized milk, with and without beta-glucuronidase pretreatment, were analyzed by EIA. No MPA was found in milk, at a detection limit of 100 pg/mL (recovery 58-66% at 0.125-2 ng/mL). Blue-veined cheese from the German market (n = 53) was analyzed by EIA, and the detection limit was at 0.5 ng/g (recovery 68-79% at 5-100 ng/g). All but two cheeses contained MPA, although mostly (66%) at levels of <10 ng/g. MPA at 400-1200 ng/g was found in Roquefort cheeses. Highest levels (4-11 microg/g) were found in a German soft cheese preparation. MPA levels in mycelium-rich parts of cheese were 3 times higher than in mycelium-free parts.

Synthesis of methylenebis(phosphonate) analogs of dinucleotide pyrophosphates

A facile method is described for preparation of nonsymmetrical P1,P2-methylenebis(phosphonate) diesters based on the 31P-NMR-controlled reaction of methylenebis(phosphonate) monoesters with diisopropylcarbodiimide, resulting in the formation of the intermediate P1,P4-disubstituted bicyclic trisanhydride. This intermediate, after treatment with an another nucleoside, carbohydrate, or alcohol followed by hydrolysis, is converted into the corresponding methylenebis(phosphonate) diester. An analog of a natural dinucleotide pyrophosphate can be obtained when a nucleoside 5'-methylenebis(phosphonate) is coupled with another nucleoside. This method is suitable for preparation of metabolically stable (resistant to phosphodiesterase cleavage) analogs of NAD, FAD, and related natural pyrophosphates. The resulting compounds are useful for mechanistic studies of enzymes that use the natural pyrophosphates as cofactors or substrates, and in development of inhibitors that have potential applications as therapeutic agents.

Bis(sulfonamide) isosters of mycophenolic adenine dinucleotide analogues: inhibition of inosine monophosphate dehydrogenase

Synthesis of novel inhibitors of human IMP dehydrogenase is described. These inhibitors are isosteric methylenebis(sulfonamide) analogues 5-8 of earlier reported mycophenolic adenine methylenebis(phosphonate)s 1-3. The parent bis(phosphonate) 1 and its bis(sulfonamide) analogue 5 showed similar sub-micromolar inhibitory activity against IMPDH2 (K(i) approximately 0.2 microM). However, the bis(sulfonamide) analogues 6 and 8 substituted at the position 2 of adenine were approximately 3- to 10-fold less potent inhibitors of IMPDH2 (K(i)=0.3-0.4 microM) than the corresponding parent bis(phosphonate)s 2 and 3 (K(i)=0.04-0.11 microM), respectively.

Contamination of fresh and ensiled maize by multiple penicillium mycotoxins

Toxins produced by Penicillium species are reported in maize silage and have been associated with health problems in cattle. Our objectives were to evaluate the prevalence and dynamics of patulin (PAT), mycophenolic acid (MPA), cyclopiazonic acid (CPA), and roquefortine C (ROC) in fresh and ensiled maize. To achieve these objectives we developed a high-performance liquid chromatography method coupled with mass spectrometry to detect all four toxins simultaneously in silage. In addition we collected weather data, information on agronomic practices, and silage fermentation characteristics for each study site. Silage was collected at harvest and after ensiling in 2001 and 2002 from 30 Pennsylvania dairies. The average concentration of toxins (range in parentheses) was: PAT 0.08 microg/g (0.01 to 1.21), MPA 0.16 microg/g (0.02 to 1.30), CPA 0.12 microg/g (0.02 to 1.43), and ROC 0.38 microg/g (0.01 to 5.71). ROC was the most frequently detected toxin (60%), followed by MPA (42%), CPA (37%), and PAT (23%). Of 120 samples tested, 15% contained no detectible levels of toxin, 25% were contaminated with one toxin, 32% with two, 18% with three, and 10% with all four toxins. All four mycotoxins were found in freshly harvested material, contradicting the belief that Penicillium toxin formation occurs exclusively during storage. We observed that weather conditions during specific growth stages of the crop affected the final concentration of toxins in freshly harvested maize. In ensiled material, PAT levels were affected by concentrations of propionic and isobutyric acids. Based on our data, Penicillium mycotoxins can form while the crop is in the field and after ensiling, suggesting that preventative measures should begin prior to ensiling.

Probing binding requirements of type I and type II isoforms of inosine monophosphate dehydrogenase with adenine-modified nicotinamide adenine dinucleotide analogues

Novel tiazofurin adenine dinucleotide (TAD) analogues 25-33 containing a substituent at C2 of the adenine ring have been synthesized as inhibitors of the two isoforms of human IMP-dehydrogenase. The 2-ethyl TAD analogue 33 [Ki = 1 nM (type I), Ki = 14 nM (type II)] was found to be the most potent. It did not inhibit three other cellular dehydrogenases up to 50 microM. Mycophenolic adenine bis(phosphonate)s containing a 2-phenyl (37) or 2-ethyl group (38), were prepared as metabolically stable compounds, both nanomolar inhibitors. Compound 38 [Ki = 16 nM (type I), Ki = 38 nM (type II)] inhibited proliferation of leukemic K562 cells (IC50 = 1.1 microM) more potently than tiazofurin (IC50 = 12.4 microM) or mycophenolic acid (IC50 = 7.7 microM).

Synthesis of azole nucleoside analogues of d-pinitol as potential antitumor agents

A convenient strategy is reported for the synthesis of azole nucleoside analogues of D-pinitol (=3-O-methyl-D-chiro-inositol). The key intermediate 3-O-methyl-4,5-epoxy-D-chiro-inositol was obtained in excellent yield via an epoxidation from mono-methanesulfonate of D-pinitol. The process of opening of the epoxy ring by azole-bases appeared strongly regioselective in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene. All newly synthesized carbocyclic azole nucleosides were assayed against lung and bladder cancer in vitro. Only the triazole and benzotriazole nucleoside analogues inhibited the growth of human lung cancer cell lines (PG) with EC(50) of 11.3 and 22.6 microM, respectively, and showed much less inhibitory activity against human bladder cell lines (T(24)).

Polymerase chain reaction (PCR) identification ofPenicillium brevicompactum, a grape contaminant and mycophenolic acid producer

Penicillium brevicompactum is a ubiquitous fungal species that contaminates diverse substrates and commodities and produces an array of metabolites toxic to human and animals. The present work has obtained evidence, by liquid chromatography (LC)-ion-trap mass spectrometry, of the ability of P. brevicompactum strains isolated from grapes to produce mycophenolic acid, a potent immunosuppressor. In order to facilitate early diagnosis of this species on commodities for human and animal consumption, a rapid, sensitive and specific polymerase chain reaction (PCR) assay for P. brevicompactum was developed. The specific primers were designed based on the ITS1-5.8S-ITS2ITS (Internal Transcribed Spacers of rRNA genes) multicopy region. This method provides a useful aid to detect the presence of this fungal species in grapes and other commodities in order to prevent the toxins produced entering the food chain.

Mycotoxins and other secondary metabolites produced in vitro by Penicillium paneum Frisvad and Penicillium roqueforti Thom isolated from baled grass silage in Ireland

Secondary metabolites produced by Penicillium paneum and Penicillium roqueforti from baled grass silage were analyzed. A total of 157 isolates were investigated, comprising 78 P. paneum and 79 P. roqueforti isolates randomly selected from more than 900 colonies cultured from bales. The findings mostly agreed with the literature, although some metabolites were not consistently produced by either fungus. Roquefortine C, marcfortine A, and andrastin A were consistently produced, whereas PR toxin and patulin were not. Five silage samples were screened for fungal metabolites, with two visually moldy samples containing up to 20 mg/kg of roquefortine C, mycophenolic acid, and andrastin A along with minor quantities (0.1-5 mg/kg) of roquefortines A, B, and D, festuclavine, marcfortine A, and agroclavine. Three visually nonmoldy samples contained low amounts of mycophenolic acid and andrastin A. The ability of both molds to produce a diverse range of secondary metabolites in vitro and in silage should be a concern to livestock producers.

From miso, saké and shoyu to cosmetics: a century of science for kojic acid

This article reviews the curious history of kojic acid, discovered as a fungal natural product in 1907. It was one of the first secondary metabolites to have its biosynthetic pathway studied by the isotope tracer technique, and, more recently, has been of interest as a skin lightening agent. There are 112 references.

Novel methylenephosphophosphonate analogues of mycophenolic adenine dinucleotide. Inhibition of inosine monophosphate dehydrogenase

Novel methylenephosphophosphonate analogues of mycophenolic adenine dinucleotide (MAD) have been prepared as potential inhibitors of IMP dehydrogenase. A coupling of the mycophenolic (hydroxymethyl)phosphonate 6 with the phosphitylated adenosine analogue 11 followed by oxidation and deprotection afforded the phosphophosphonate 8. A similar coupling between adenosine (hydroxymethyl)phosphonate 10 and phosphitylated mycophenolic alcohol 5 gave the corresponding phosphophosphonate 13. Both 8 and 13 (Ki = 20-87 nM) were found to be the most potent cofactor type inhibitors of IMP dehydrogenase.

Production of metabolites from the Penicillium roqueforti complex

Penicillium roqueforti comprises three accepted species: P. carneum, which is associated with meat, cheese, and bread; P. paneum, associated primarily with bread and silage; and P. roqueforti, which is associated with various processed foods and silage. This paper reports the use of HPLC-MS and HPLC-NMR to investigate the metabolites of silage-derived strains from two areas where silage toxicoses are regularly observed (Scandinavia and eastern Canada). Only modest differences were seen between the metabolites produced by strains from Canada and Scandinavia; however, silage strains of P. paneum isolated from Quebec were poor producers of patulin. This paper reports for the first time the production of festuclavine from P. paneum. This may be important as a possible explanation for the ill thrift observed when this species is dominant in poorly ensiled materials fed to dairy cows.

Effects of Mycophenolic Acid on Inosine Monophosphate Dehydrogenase I and II mRNA Expression in White Blood Cells and Various Tissues in Sheep

Mycophenolic acid (MPA) is a mycotoxin commonly found as Penicillium genus secondary metabolite in feedstuffs and silages. Feeding with MPA contaminated silages may modulate the immune system in the farm animals and can cause appetite lost, ketosis, paralysis and abortion. The aim of the present study was to characterize the long-term MPA effect on both the inosine monophosphate dehydrogenase (IMPDH) isoforms I and II mRNA expression in white blood cells (WBC) and various tissue of healthy sheep. In treated animals 300 mg MPA/day/sheep was applied. In all investigated tissues the IMPDH I and II mRNA was abundant: WBC, spleen, thymus, ileum, jejunum, kidney, liver, pharyngeal and mesenterial lymph node. An efficiency-corrected relative quantification of the IMPDH types I and II isoforms mRNA were performed by normalizing with the constant reference gene expression of beta-actin. High IMPDH I mRNA expression levels were seen in kidney > mesenterial lymph node > jejunum > spleen > pharyngeal lymph node. Medium and low abundance was found in ileum > WBC > liver > thymus. Type II mRNA was highly expressed in liver > thymus > jejunum. In pharyngeal lymph node > spleen > ileum > mesenterial lymph node > kidney > WBC medium to low IMPDH II mRNA concentrations were detected. Under MPA treatment the IMPDH I mRNA expression was not significantly regulated in WBC, only trends of down- and upregulation were observed. Surprisingly in jejunum an upregulation could be observed (P < 0.05). In pharyngeal lymph node a tendency to downregulation was shown. This may be due to frequent ruminant activities and frequent exposition of MPA to the pharyngeal lymph nodes. In contrast to type I mRNA expression, IMPDH II mRNA was significantly downregulated in ileum (3.4-fold, P < 0.01) and tendencies in downregulation could be seen in jejunum (5.1-fold, P = 0.14). In addition, significant downregulation of IMPDH II gene expression over the entire feeding experiment could be shown in WBC of MPA-treated animals compared with untreated animals (P < 0.05). In conclusion, the recent study demonstrates that feeding sheep with MPA-contaminated silage did not induce IMPDH I mRNA expression in various tissues and blood, except in jejunum, but has suppressive effects on IMPDH II mRNA expression in WBC and ileum.

Synthesis of some monocyclic analogues of mycophenolic acid via the Johnson ortho ester Claisen rearrangement

The synthesis of some monocyclic analogues of mycophenolic acid in which the lactone ring has been eliminated, leaving the aromatic ring intact and the same oxygenated substituents flanking the hexenoic acid side chain with an (E)-geometry at the double bond, has been accomplished via the Johnson ortho ester Claisen rearrangement. The synthetic methodology reported here allows the preparation of mycophenolic acid analogues bearing alkyl substituents at the alpha- and beta-positions on the side chain.

Phenotypic taxonomy and metabolite profiling in microbial drug discovery

Microorganisms and in particular actinomycetes and microfungi are known to produce a vast number of bioactive secondary metabolites. For industrially important fungal genera such as Penicillium and Aspergillus the production of these compounds has been demonstrated to be very consistent at the species level. This means that direct metabolite profiling techniques such as direct injection mass spectrometry or NMR can easily be used for chemotyping/metabolomics of strains from both culture collections and natural samples using modern informatics tools. In this review we discuss chemotyping/metabolomics as part of intelligent screening and highlight how it can be used for identification and classification of filamentous fungi and for the discovery of novel compounds when used in combination with modern methods for dereplication. In our opinion such approaches will be important for future effective drug discovery strategies, especially for dereplication of culture collections in order to avoid redundancy in the selection of species. This will maximize the chemical diversity of the microbial natural product libraries that can be generated from fungal collections.

Determination of selected mycotoxins in mould cheeses with liquid chromatography coupled to tandem with mass spectrometry

A simple and feasible method is described for analysing nine mycotoxins in cheese matrix. The method involves liquid extraction followed by high performance liquid chromatographic separation and mass spectrometric detection of the analytes, and allows the determination of aflatoxins B1, B2, G1, G2 and M1, ochratoxin A, mycophenolic acid, penicillic acid and roquefortine C simultaneously. Average recoveries of the mycotoxins from spiked samples at concentration levels of 5-200 microg kg(-1) ranged from 96-143%. Within-day relative standard deviations at these concentration levels varied from 2.3-12.1%. The limit of quantification for aflatoxin M1 was 0.6 microg kg(-1) and for the other compounds 5 microg kg(-1). The method developed was applied for analysing these mycotoxins in blue and white mould cheeses purchased from Finnish supermarkets. Roquefortine C was detected in all of the blue mould cheese samples in concentrations of 0.8-12 mg kg(-1). One blue cheese contained also 0.3 mg kg(-1) mycophenolic acid. The other investigated mycotoxins were absent in the samples.

Inflammatory and Cytotoxic Responses in Mouse Lungs Exposed to Purified Toxins from Building Isolated Penicillium brevicompactum Dierckx and P. chrysogenum Thom

In vitro and in vivo studies have shown that building-associated Penicillium spores and spore extracts can induce significant inflammatory responses in lung cells and animal models of lung disease. However, because spores and spore extracts comprise mixtures of bioactive constituents often including toxins, it is impossible to resolve which constituent mediates inflammatory responses. This study examined dose-response (0.5 nM, 2.5 nM, 5.0 nM, 12.5 nM/g body weight (BW) animal) and time-course (3, 6, 24 and 48 h post instillation (PI)) relationships associated with inflammatory and cytotoxic responses in mouse lungs intratracheally instilled with pure brevianamide A, mycophenolic acid, and roquefortine C. High doses (5.0 nM and/or 12.5 nM/g BW animal) of brevianamide A and mycophenolic acid, the dominant metabolites of P. brevicompactum, and roquefortine C, the dominant metabolite of P. chrysogenum, induced significant inflammatory responses within 6 h PI, expressed as differentially elevated macrophage, neutrophil, MIP-2, TNF, and IL-6 concentrations in the bronchioalveolar lavage fluid (BALF) of intratracheally exposed mice. Macrophage and neutrophil numbers were maximal at 24 h PI; responses of the other inflammatory markers were maximal at 6 h PI. Except for macrophage numbers in mycophenolic acid-treatment animals, cells exhibited significant dose-dependent-like responses; for the chemo-/cytokine markers, dose dependency was lacking except for MIP-2 concentration in brevianamide A-treatment animals. It was also found that brevianamide A induced cytotoxicity expressed as significantly increased LDH concentration in mouse BALF, at concentrations of 12.5 nM/g BW animal and at 6 and 24 h PI. Albumin concentrations, measured as a nonspecific marker of vascular leakage, were significantly elevated in the BALF of mice treated with 12.5 nM/g nM brevianamide A/animal from 6 to 24 h PI and in > or =5.0 nM/g mycophenolic acid-treated animals at 6 to 24 h PI. These results suggest that these three toxins from Penicillium species common on damp materials in residential housing provoke compound-specific toxic responses with different toxicokinetics. Moreover, that these toxins can stimulate significant inflammatory responses in vivo might help explain some of the indoor effects associated with Penicillium spore exposures in indoor environments.

Andrastins A-D, Penicillium roqueforti Metabolites consistently produced in blue-mold-ripened cheese

This is the first finding of andrastins in blue cheese as well as any other sample type. Here, they were produced by the secondary starter culture Penicillium roqueforti. After purification by normal-phase chromatography followed by combined reverse-phase ion-exchange chromatography, the andrastins A-D were detected by liquid chromatography combined with UV and high-resolution mass spectrometry. In 23 representative samples of European blue cheeses, andrastin A was consistently found in quantities between 0.1 and 3.7 microg/g of cheese (median 2.4 microg/g). Assuming the same molar response factors as for andrastin A, the B, C, and D analogues were present in approximately 5-, 3-, and 5-20-fold lower amounts than andrastin A, respectively. The andrastins are protein farnesyltransferase inhibitors and are capable of inhibiting the efflux of anticancer drugs from multidrug-resistant cancer cells. Thus, their presence in common blue cheese suggests a potential for a positive or negative impact on human health.

Byssochlamys nivea as a source of mycophenolic acid

Byssochlamys species are responsible for spoilage and degradation of fruits and silages and can also produce the mycotoxin patulin. We analyzed secondary metabolite production by Byssochlamys nivea. Mycophenolic acid and its precursors, 5-methylorsellinic acid and 5,7-dihydroxy-4-methylphthalide, were identified in all of the B. nivea strains that we examined.

Natural products to drugs: natural product derived compounds in clinical trials

Natural product and natural product-derived compounds that are being evaluated in clinical trials or in registration (current 31 December 2004) have been reviewed. Natural product derived drugs launched in the United States of America, Europe and Japan since 1998 and new natural product templates discovered since 1990 are discussed.

Mycotoxin production and postharvest storage rot of ginger (Zingiber officinale) by Penicillium brevicompactum

Twenty naturally infected ginger (Zingiber officinale) rhizomes displaying visible mold growth were examined to identify the fungi and to evaluate the presence of fungal secondary metabolites. Penicillium brevicompactum was the predominant species isolated from 85% of the samples. Mycophenolic acid was identified from corresponding tissue extracts. Because mycophenolic acid is a potent immunosuppressant and synergistic mycotoxicosis studies involving human consumption have not been carried out on this metabolite, spoilage of commercially marketed produce caused by P. brevicompactum is a concern. This is the first reported occurrence of mycophenolic acid in commercially sold plant food products.

Synthesis, molecular modeling, and evaluation of nonphenolic indole analogs of mycophenolic acid

Based on the promising activity of an indole-3-carboxamide derivative, a nonphenolic analog of mycophenolic acid (MPA), we report herein the synthesis of a compound containing two important features for the activity of MPA, the ring methoxy and methyl. The synthesis was accomplished using two strategies; a method dependent on stepwise building of the hexenoate side chain followed by the indolecarboxamide ring system, and a convergent route that depended on 1,3-sigmatropic rearrangement as a key step. Docking experiments on both Chinese Hamster and Human Type-II inosine monophosphate dehydrogenase (IMPDH) showed that this compound has potential binding interactions with the NAD site. The analogs showed no activity against MCF7-S, MCF7-R, or IGR-OV1 cancer cells.

The role of natural product chemistry in drug discovery

Although traditionally natural products have played an important role in drug discovery, in the past few years most Big Pharma companies have either terminated or considerably scaled down their natural product operations. This is despite a significant number of natural product-derived drugs being ranked in the top 35 worldwide selling ethical drugs in 2000, 2001, and 2002. There were 15 new natural product-derived drugs launched from 2000 to 2003, as well as 15 natural product-derived compounds in Phase III clinical trials or registration at the end of 2003. Recently, there has been a renewed interest in natural product research due to the failure of alternative drug discovery methods to deliver many lead compounds in key therapeutic areas such as immunosuppression, anti-infectives, and metabolic diseases. To continue to be competitive with other drug discovery methods, natural product research needs to continually improve the speed of the screening, isolation, and structure elucidation processes, as well addressing the suitability of screens for natural product extracts and dealing with issues involved with large-scale compound supply.

Petrosifungins A and B, novel cyclodepsipeptides from a sponge-derived strain of Penicillium brevicompactum

A strain of Penicillium brevicompactum derived from a specimen of the Mediterranean sponge Petrosia ficiformis was investigated for its secondary metabolites. Using fast centrifugal partitioning chromatography (FCPC) two previously unknown cyclodepsipeptides, petrosifungins A (1) and B (2), were isolated, both containing two neighboring units of the nonproteinogenic amino acid l-pipecolinic acid. The absolute configurations of all amino acids were established to be l using GITC derivatization and Marfey's method. Furthermore, the known metabolite brevianamide A (3) was isolated. The likewise known compounds mycophenolic acid (4) and asperphenamate (5) were identified from their spectroscopic properties directly in the extract using HPLC-UV, -MS, and -NMR coupling.

Mycotoxin production by indoor molds

Fungal growth in buildings starts at a water activity (a(w)) near 0.8, but significant quantities of mycotoxins are not produced unless a(w) reaches 0.95. Stachybotrys generates particularly high quantities of many chemically distinct metabolites in water-damaged buildings. These metabolites are carried by spores, and can be detected in air samples at high spore concentrations. Very little attention has been paid to major metabolites of Stachybotrys called spirocyclic drimanes, and the precise structures of the most abundant of these compounds are unknown. Species of Aspergillus and Penicillium prevalent in the indoor environment produce relatively low concentrations of mycotoxins, with the exception of sterigmatocystins that can represent up to 1% of the biomass of A. versicolor at a(w)'s close to 1. The worst-case scenario for homeowners is produced by consecutive episodes of water damage that promote fungal growth and mycotoxin synthesis, followed by drier conditions that facilitate the liberation of spores and hyphal fragments.

Quantification of the influence of mycophenolic acid on the release of endothelial adhesion molecules

BACKGROUND

Mycophenolic acid selectively inhibits inosine 5'-monophosphate dehydrogenase leading to a shortage of guanosine nucleotides. Since GTP is required for the synthesis of glycoproteins, this immunosuppressive drug also influences the production of several cell adhesion molecules.

METHOD

Soluble endothelial cell adhesion molecules released into cell culture supernatants after an incubation period of 16 h are assessed via a standard ELISA procedure applying test kits for E-selectin, VCAM-1 and ICAM-1.

RESULTS

Treatment with TNF-alpha leads to the induction of E-selectin and causes a significant increase in VCAM-1 and ICAM-1 content in the supernatant in relation to the level of unstimulated cells. Due to the inhibitory effects of MPA-applied either alone or in combination with cyclosporin A and prednisolone-sE-selectin is significantly reduced and sVCAM-1 is slightly but not significantly decreased, whereas sICAM-1 levels remain unchanged.

CONCLUSIONS

We demonstrate that the influence of MPA on endothelial cell adhesion molecules can readily be determined via ELISA. The results indicate that the immunosuppression by MPA is also achieved by slightly reducing the expression and consequent release of E-selectin, a pivotal molecule in the first step of leucocyte-endothelial interactions.

Discovery of N-[2-[2-[[3-methoxy-4-(5-oxazolyl)phenyl]amino]-5-oxazolyl]phenyl]-N-methyl-4- morpholineacetamide as a novel and potent inhibitor of inosine monophosphate dehydrogenase with excellent in vivo activity

Inosine monophosphate dehydrogenase (IMPDH) is a key enzyme that is involved in the de novo synthesis of purine nucleotides. Novel 2-aminooxazoles were synthesized and tested for inhibition of IMPDH catalytic activity. Multiple analogues based on this chemotype were found to inhibit IMPDH with low nanomolar potency. One of the analogues (compound 23) showed excellent in vivo activity in the inhibition of antibody production in mice and in the adjuvant induced arthritis model in rats.

Influence of mycophenolic acid on inosine 5'-monophosphate dehydrogenase activity in human peripheral blood mononuclear cells

BACKGROUND

Inosine 5'-monophosphate dehydrogenase (IMPDH) catalyses the oxidation of inosine 5'-monophosphate (IMP) to xanthosine 5'-monophosphate (XMP). Thus, this enzyme plays an important role in the rate-limiting step of the de novo guanine nucleotide biosynthesis, making it a potent target for immunosuppressive drugs. Mycophenolic acid (MPA) is the most potent and specific inhibitor of IMPDH.

METHOD

IMPDH activity is determined via evaluation of XMP formation and the inhibitory influence of MPA in human peripheral blood mononuclear cells (PBMCs) is assessed by means of high-performance liquid chromatography (HPLC). For this objective, we have optimised a method based on solvent-generated ion exchange chromatography by cautiously varying mobile phase parameters.

RESULTS

The optimised method renders it possible to separate 18 analytes in 54 min in a single isocratic experiment and to measure the IMPDH activity in the lysate of human PBMCs in dependence on incubation time, substrate, co-substrate and inhibitor concentrations. In this way, we have determined the Michaelis-Menten constants K(M) and V(max) for IMP and beta-NAD+ and the inhibitor constant K(i) for MPA.

CONCLUSIONS

The chromatographic method presented in this report allows a rapid, reliable and reproducible quantification of IMPDH activity in PBMCs and therefore represents an attractive tool for the pharmacodynamic monitoring of the effects of MPA in patients under immunosuppressive therapy.