Chemical, molecular and structural studies of Boswellia species: β-Boswellic Aldehyde and 3-epi-11β-Dihydroxy BA as precursors in biosynthesis of boswellic acids

The distribution and biosynthesis of boswellic acids (BAs) is scarce in current literature. Present study aims to elucidate the BAs biosynthetic and its diversity in the resins of Boswellia sacra and Boswellia papyrifera. Results revealed the isolation of new (3β, 11β-dihydroxy BA) and recently known (as new source, β-boswellic aldehyde) precursors from B. sacra resin along with α-amyrin. Following this, a detailed nomenclature of BAs was elucidated. The quantification and distribution of amyrins (3-epi-α-amyrin, β-amyrin and α-amyrin) and BAs in different Boswellia resins showed highest amyrin and BAs in B. sacra as compared with B. serrata and B. papyrifera. Distribution of BAs significantly varied in the resin of B. sacra collected from dry mountains than coastal trees. In B. sacra, high content of α-amyrin was found in the roots but it lacked β-amyrin and BAs. The leaf part showed traces of β-ABA and AKBA but was deficient in amyrins. This was further confirmed by lack of transcript accumulation of amyrin-related biosynthesis gene in leaf part. In contrast, the stem showed presence of all six BAs which are attributed to existence of resin-secretory canals. In conclusion, the boswellic acids are genus-specific chemical constituents for Boswellia species albeit the variation of the amounts among different Boswellia species and grades.

Development and validation of a novel LC-MS/MS method for simultaneous determination of abiraterone and its seven steroidal metabolites in human serum: Innovation in separation of diastereoisomers without use of a chiral column

Abiraterone acetate (AA), the prodrug of abiraterone, is FDA-approved for the treatment of castration-resistant prostate cancer. Abiraterone is metabolized in patients to a more potent analogue, D4A. However, we have recently reported that this analogue is further metabolized to additional metabolites in patients treated with AA. Here, we present a liquid chromatography-tandem mass spectrometry method developed to resolve and detect abiraterone and its seven metabolites in human serum using an AB Sciex Qtrap 5500 mass analyzer coupled with a Shimadzu Nexera UPLC station. Analytes and the internal standard (abiraterone-d4) were extracted from human serum using the liquid-liquid extraction procedure. The analytes were separated using a Zorbax Eclipse Plus C18 150×2.1mm, 3.5μm column at 40°C and an isocratic mobile phase 35% A (0.1% formic acid in water), 65% B (0.1% formic acid in methanol:acetonitrile; 60:40). Electrospray ionization in positive mode was applied with multiple reaction monitoring in a total run time of 13min. Abiraterone detection was linear in the range 2-400ng/mL and all metabolites from 0.1-20ng/mL. The method was validated following US FDA guidelines for bioanalytical method validation, and all the metabolite results were within the acceptance limits. Despite the similarity in structure and mass transition between the metabolites, the validated method separated all the metabolites, including diastereomers, to allow accurate identification and quantitation of each compound.

Rejection of pharmaceutically-based N-nitrosodimethylamine precursors using nanofiltration

N-Nitrosodimethylamine (NDMA) is a disinfection by-product (DBP) with many known precursors such as amine-containing pharmaceuticals that can enter the environment via treated wastewater. Reverse osmosis and tight nanofiltration membranes (MW cutoff < 200 Da) are treatment technologies that demonstrate high removal of many compounds, but at relatively high energy costs. Looser membranes (>200 Da) may provide sufficient removal of a wide range of contaminants with lower energy costs. This study examined the rejection of pharmaceuticals that are known NDMA precursors (∼300 Da) using nanofiltration (MW cutoff ∼350 Da). MQ water was compared to two raw water sources, and results illustrated that NDMA precursors (as estimated by formation potential testing) were effectively rejected in all water matrices (>84%). Mixtures of pharmaceuticals vs. single-spiked compounds were found to have no impact on rejection from the membranes used. The use of MQ water vs. surface waters illustrated that natural organic matter, colloids, and inorganic ions present did not significantly impact the rejection of the amine-containing pharmaceuticals. This study illustrates that NDMA formation potential testing can be effectively used for assessing NDMA precursor rejection from more complex samples with multiple and/or unknown NDMA precursors present, such as wastewater matrices.

Targeting thapsigargin towards tumors

The skin irritating principle from Thapsia garganica was isolated, named thapsigargin and the structure elucidated. By inhibiting the sarco/endoplasmic reticulum Ca(2+) ATPase (SERCA) thapsigargin provokes apoptosis in almost all cells. By conjugating thapsigargin to peptides, which are only substrates for either prostate specific antigen (PSA) or prostate specific membrane antigen (PSMA) prodrugs were created, which selectively affect prostate cancer cells or neovascular tissue in tumors. One of the prodrug is currently tested in clinical phase II. The prodrug under clinical trial has been named mipsagargin.

[Separation of enantiomers of three chiral drugs by capillary electrophoresis based on achiral ionic liquid]

Using an achiral ionic liquid, 1-butyl-3-methylimidazolium chlorine ([ BMIM] Cl), as an additive and beta-cyclodextrin (beta-CD) as a chiral selector, the enantiomers of chlorpheniramine, the precursor of chloramphenicol and of loxacin were separated by capillary zone electrophoresis. This work was directed to the study of the association of [BMIM] Cl to the chiral selector beta-CD and the possible effects of [BMIM] Cl on chiral separation. Simultaneously, the separation performances were studied when only containing beta-CD in the buffer. The results showed that there are synergistic effects of [BMIM] Cl as an additive for the enantiomeric separations. [BMIM] Cl can not only remarkably increase the separation selectivity and resolution of the enantiomers, but also effectively restrain the adsorption of the sample molecules and improve the peak shape. [BMIM] Cl as an additive of chiral separation can provide a new method for the separation of chiral drugs which are hard separable under common electrophoresis conditions.

Endophyte fungal isolates from Podophyllum peltatum produce podophyllotoxin

The lignan podophyllotoxin (1) is highly valued as the precursor to clinically useful anticancer drugs. Substantial drug development of this compound class continues, including potential new use for inflammatory disease. We have isolated two endophyte fungi, both strains of Phialocephala fortinii, from rhizomes of the plant Podophyllum peltatum. The fungi were identified through DNA sequencing and morphology. Both strains of fungi are slow-growing and produce 1 at low but measurable amounts in broth culture. The compound was confirmed through matching HPLC retention times, absorption spectra, and MS data to authentic 1. The yield of 1 has ranged from 0.5 to 189 microg/L in 4 weeks of culture. These fungi have implications for the sustained production of 1 independent of wild populations of the source plants.

Column selection and method development for the separation of nucleoside phosphotriester diastereoisomers, new potential anti-viral drugs. Application to cellular extract analysis

Analytical HPLC methods using derivatized cellulose and amylose chiral stationary phases used in normal and reversed-phase modes were developed for the diastereoisomeric separation of mononucleotide prodrugs (pronucleotides) of 3'-azido-2',3'-dideoxythymidine (AZT). The resolutions were performed with two silica-based celluloses using normal and reversed-phase methodologies: Tris-3,5-dimethylphenylcarbamate (Chiralcel OD-H and Chiracel OD-RH) and Tris-methylbenzoate (Chiralcel OJ and OJ-R). Two amyloses phases, Tris-3,5-dimethylphenylcarbamate (Chiralpak AD) and Tris-(S)-1-phenylethylcarbamate (Chiralpak AS), were used in normal-phase mode. Additionally, we developed separation using two stationary phases with immobilized cyclodextrins in reversed-phase and polar-organic modes. The mobile phase and the chiral stationary phase were varied to achieve the best resolution. Different types and concentration of aliphatic alcohols, acetonitrile or water in the mobile phase were also tested for the different separation modes. An optimal baseline separation (Rs > 1.5) was readily obtained with all silica-based celluloses and amyloses using a normal-phase methodology. The different columns gave complementary results in term of resolution. Limits of detection and quantification were 0.12-0.20 and 0.40-0.67 microm, respectively. This analytical method was applied in a preliminary study for the pronucleotide 2 quantification in cellular extract.

Novel amino acid derived natural products from the ascidian Atriolum robustum: identification and pharmacological characterization of a unique adenosine derivative

Investigation of the methanolic extract of the Australian ascidian Atriolum robustum led to the isolation and characterization of five new amino acid derived structures (1-5). The structures were elucidated employing spectroscopic techniques (NMR, MS, UV, and IR). The absolute stereochemistry of 1 and 2 was established by chemical degradation, derivatization, and chiral GC-MS analysis. Structures 4 and 5 are complex nucleosides containing rare methylthioadenosine and methylsulfinyladenosine moieties, respectively. In radioligand binding studies the 5'-deoxy-5'-methylthioadenosine-2',3'-diester 4 exhibited affinity for A(1) and A(3) adenosine receptors with K(i) values below 10 microM. Its affinity was somewhat lower for A(2A) (K(i) = 17 microM) and much lower for A(2B) adenosine receptors. Analytical experiments using capillary electrophoresis showed that compound 4 was stable under the conditions of radioligand binding studies. Incubation with carboxylesterase resulted in slow hydrolysis of the adenosine derivative to 5'-deoxy-5'-methylthioadenosine (MTA), which was about 10-fold more potent at adenosine receptors than compound 4. Thus, the 2',3'-diester derivative 4 may act as a lipophilic prodrug of MTA in addition to its own adenosine receptor activity. GTP shift experiments indicated that the adenosine derivative was a partial agonist at A(1) adenosine receptors of rat brain cortical membranes. Compound 4 inhibited cAMP accumulation in Chinese hamster ovary (CHO) cell membranes recombinantly expressing the human A(3) adenosine receptor, thus indicating that the adenosine derivative also acted as a partial agonist at A(3)ARs. Homology models of the A(1) and the A(3) adenosine receptors in their putative active and inactive conformations were built and used for docking of the sterically demanding compound 4. It was found that this ligand fit well into the binding pockets of both receptor subtypes because of its highly flexible structure, although in somewhat different binding modes.

Strategies for access to enantiomerically pure ecadotril, dexecadotril and fasidotril: a review

Ecadotril and dexecadotril are powerful and selective inhibitors of neprilysin (NEP, EC 3.4.24.11) and are being developed as therapeutic agents, since they behave as prodrugs of the enantiomers of thiorphan. They exhibit different pharmaceutical profiles (intestinal antisecretatory action for the (R) enantiomer, i.e. dexecadotril, and cardiovascular activity for the (S) enantiomer, i.e. ecadotril). Fasidotril is a related compound which has special interest as an equipotent dual inhibitor of NEP and ACE (EC 3.4.15.1). This behavior confers on fasidotril powerful pharmaceutical properties in the cardiovascular field. This review deals with various synthetic approaches, either published or patented, for access to the enantiomerically pure or highly enriched forms of these drugs. Thus, different methods have been studied, which are taken from different methodologies of resolution procedures and asymmetric synthesis, namely : i- Synthesis from a chiron from the chiral pool ii- Chemical resolution of racemic precursors iii- Enzymatic resolution and desymmetrization of meso starting materials iv- Asymmetric synthesis, including enantioselective catalytic hydrogenation, alkaloid catalyzed asymmetric Michael additions, and diastereoselective alkylation of a chiral derivative. Some of these methods are used in industrial processes leading to the indicated compounds.

Effective enzymatic resolution of rac-1-(3-trifluoromethylphenyl)propan-2-ol, precursor of fenfluramine

Lipases from Candida antarctica and from Mucor miehei efficiently catalyze the enantioselective esterification of rac-1-(3-trifluoromethylphenyl)propan-2-ol. The obtained enantioforms are suitable to prepare both enantiomers of fenfluramine.

Design and production of genetically modified soybean protein with anti-hypertensive activity by incorporating potent analogue of ovokinin(2-7)

The potent anti-hypertensive peptide, RPLKPW, has been designed based on the structure of ovokinin(2-7). The sequence encoding this peptide was introduced into three homologous sites in the gene for soybean beta-conglycinin alpha' subunit. The native alpha' subunit as well as the modified, RPLKPW-containing alpha' subunit were expressed in Escherichia coli, recovered from the soluble fraction and then purified by ion-exchange chromatography. The RPLKPW peptide was released from recombinant RPLKPW-containing alpha' subunit after in vitro digestion by trypsin and chymotrypsin. Moreover, the undigested RPLKPW-containing alpha' subunit given orally at a dose of 10 mg/kg exerted an anti-hypertensive effect in spontaneously hypertensive rats, unlike the native alpha' subunit. These results provide evidence for the first time that a physiologically active peptide introduced into a food protein by site-directed mutagenesis could practically function in vivo even at a low dose.

Practical synthesis, separation, and stereochemical assignment of the PMPA pro-drug GS-7340

The practical synthesis of a mixed phenoxy-amidate derivative of PMPA with high oral bioavailability and favorable pharmacokinetics is described. The non-stereoselective synthetic route produces a 1:1 mixture of two diastereomers at phosphorous. Simulated moving bed chromatography using Chiralpak AS enabled kilo-scale isolation of the more potent diastereomer (GS-7340). The GS-7340 phosphorous chiral center was found to be (S) by X-ray crystallography.

Purification of PMPA amidate prodrugs by SMB chromatography and x-ray crystallography of the diastereomerically pure GS-7340

The diastereomers of GS-7171, aryl phosphoramidate derivatives of the anti-HIV nucleotide analog 9-[2-R-(phosphonomethoxy)propyl]adenine (tenofovir, PMPA), were isolated by batch elution chromatography and continuous simulated moving bed chromatography. The absolute configuration of the more pharmacologically active diastereomer, GS-7340, was determined to be (R,S,S) by single crystal x-ray crystallography.

Liquid extraction and ion-pair HPLC for determination of hydrophilic 3-hydroxypyridin-4-one iron chelators

Hydrophilic 3-hydroxypyridin-4-ones (HPOs), such as 1-(2'-carboxyethyl)-2-methyl-3-hydroxypyridin-4-one (CP38), 1-(3'-hydroxypropyl)-2-methyl-3-hydroxypyridin-4-one (CP41) and 1-(2'-hydroxyethyl)-2-ethyl-3-hydroxypyridin-4-one (CP102), are orally active iron chelators and ester prodrugs of these molecules are currently under investigation. A liquid extraction method using acetonitrile and 2-propanol (80:20 v/v) under acidic and NaCl-saturated conditions has been developed in order to efficiently extract these HPOs from various matrices. The extracted HPOs were determined using a reversed phase polymer HPLC column (PLRP-S 100 A) and the gradient ion-pair mobile phase containing tetrabutylammonium chloride (5 mM) and EDTA (0.5 mM). The extraction recovery of these chelators in phosphate buffer, rat blood and liver homogenate varied from 85 to 94%. The coefficients of variation (C.V.) for within-day determination were in the range of 1.4-3.3% at 1 mM and 2.0-4.7% at 0.1 mM. High accuracy of determination was also achieved.

20-O-beta-glucopyranosyl camptothecin from mostuea brunonis: A potential camptothecin pro-drug with improved solubility

Bioassay-guided fractionation of the organic extracts of whole plants of Mostuea brunonis (Loganiaceae), using the National Cancer Institute's (NCI) human tumor-based in vitro antitumor screen, led to the isolation and identification of camptothecin 20-O-beta-D-glucoside (1) and three moderately cytotoxic alkaloids, the known deoxypumiloside (2) and strictosamide (3), and the new 2'-O-acetylstrictosamide (4), from the cytotoxic alkaloid fractions. While the previously unknown 20-O-beta-D-glucopyranosyl camptothecin exhibited greater solubility in alcohol, DMSO-H(2)O and H(2)O than camptothecin, it was essentially inactive in the NCI's in vitro 60-cell line primary antitumor screen. However, it could be vulnerable to de-glucosidation in vivo, and may, therefore, merit additional evaluation as a potential prodrug of camptothecin that could be more readily formulated than the parent agent.

Antineoplastic agents 393. Synthesis of the trans-isomer of combretastatin A-4 prodrug

The (E)-stilbene isomer (2a) of the (Z)-combretastatin A-4 prodrug (1b) was efficiently prepared from (E)-combretastatin A-4 by a reaction sequence employing phosphorylation (dibenzyl chlorophosphite), cleavage (trimethyliodosilane) of the benzyl ester and reaction of the resulting phosphoric acid with sodium methoxide. The sodium phosphate product (2c) was also found to be an important side-product, presumably from iodine-catalyzed isomerization, when the analogous synthetic route was used to obtain the combretastatin A-4 prodrug (1b). The phosphoric acid precursor of prodrug 1b derived from (Z)-combretastatin A-4 (1a) was converted into a series of metal cation and ammonium cation salts to evaluate effects on human cancer cell growth, antimicrobial activities and solubility behavior.

Synthesis and in vitro evaluation of potential antichagasic dipeptide prodrugs of primaquine

American trypanosomiasis (Chagas' disease) is an endemic parasitic disease afflicting more than 20 million people in Latin America. Currently, therapy is unsatisfactory and only two drugs are available. Primaquine, an antimalarial drug, has trypanocidal activity. Dipeptide derivatives of primaquine, Phe-Arg-PQ, Lys-Arg-PQ, and Phe-Ala-PQ, were synthesized. The choice of the peptides was based on the primary specificity of cruzipain, the major cysteine proteinase from T cruzi. The prodrugs obtained were tested on the LLC-MK2 cell culture infected with trypomastigotes forms of T. cruzi. Phe-Arg-PQ, Lys-Arg-PQ, and Phe-Ala-PQ were active in all stages.

Esters of cephalosporins. Part III. Separation and properties of the R and S isomers of the 1-acetoxyethyl ester of cefuroxime

Two separation methods for the R and S isomers of the 1-acetoxyethyl ester of cefuroxime [I] were evaluated. Physico-chemical and biological properties of these isomers were studied. It was found that the R isomer after oral administration to rats is absorbed better and faster than the isomer S.

Bacterial mutagenicity of cigarette smoke and its interaction with ethanol

The mutagenicities of mainstream cigarette smoke (CS), a cigarette smoke condensate (CSC) and smokers' urines were investigated by using batteries of Salmonella typhimurium and Escherichia coli strains. The S9-mediated mutagenicity of CSC was remarkably enhanced when using nitroreductase- and especially O-acetyltransferase-overproducing derivatives of the classical strains TA98 and TA100, with the following rank of sensitivity: YG1024 > YG1029 > YG1021 > TA98NR > YG1026 > TA98 > TA100 > TA100-DNP6 > TA100NR > TA98-1,8-DNP6. With YG1024, a doubling of spontaneous revertants was observed with as little as 1/110 of the smoke condensate recovered from one cigarette under our experimental conditions. Similarly, the S9-mediated mutagenicity of mainstream CS was considerably increased in YG1024 and YG1029, the O-acetyltransferase-overproducing derivatives of TA98 and TA100, respectively. In the absence of S9 mix, the concentrates of 23 urine specimens from five smokers failed to revert S. typhimurium TA98 and YG1024, and were equitoxic in E. coli WP2 and its repair-deficient counterpart CM871 (uvrA-, recA-, lexA-). In the presence of S9 mix, all specimens were mutagenic, with an average YG1024:TA98 ratio of 6.6:1. These patterns suggest that the bacterial mutagenicity of smoke-associated complex mixtures is mainly due to aromatic amines. The mutagenicities of other typical constituents of CS, i.e. the polycyclic aromatic hydrocarbon benzo[a]pyrene (BP) and the tobacco specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), were not appreciably enhanced in the O-acetyltransferase-overproducing strain YG1029, compared to its parental strain TA100. Moreover, BP and NNK induced less than additive mutagenic responses when combined at high doses.(ABSTRACT TRUNCATED AT 250 WORDS)

[Recent progress in the study on chemical constituents of herba Cistanche]

The constituents of Herba Cistanche (C. salsa used in Japan and C. deserticola used in China) are described. The review indicates that some cistanosides are the main active constituents of Herba Cistanche, and may be taken as the guide and precursor compounds for synthesizing new tonic drugs.

High-performance liquid chromatographic method for the separation of chlorambucil and its N-oxide prodrug

A reversed-phase high-performance liquid chromatographic method is described to distinguish chlorambucil N-oxide from the parent chlorambucil and quantitate both after separation from biological samples. The influence of solvent pH, alcohol, acid and ion-pairing agent on the separation is described. The stability of chlorambucil and its N-oxide in buffers and alcohols, as well as stability during filtration is discussed with potential application for metabolic studies.

Biphenomycin C, a precursor of biphenomycin A in mixed culture

A precursor of biphenomycin A in mixed culture of Streptomyces griseorubiginosus No. 43708 with Pseudomonas maltophilia No. 1928 was isolated and characterized. The structure of the precursor, designated biphenomycin C was determined to be a peptide which is composed of biphenomycin A and arginylserine residue (Fig. 1), on the basis of chemical and spectroscopic evidence.

Synthesis and analysis of O,O'-dicarboxylate (dibenzyl) bispilocarpates as possible prodrugs of pilocarpine

As a part of a series of studies to develop prodrug derivatives of pilocarpine, the O,O'-succinyl (dibenzyl), O,O-adipoyl (dibenzyl), O,O-fumaryl (dibenzyl), and O,O-terephthaloyl (dibenzyl) bispilocarpate fumarates were synthesized as a new class of pilocarpine prodrugs. The compounds were prepared from pilocarpic acid benzyl monoester by coupling two pilocarpic acid benzyl monoesters together with spacer chains by usual esterification methods. Liquid chromatography, thermospray liquid chromatography-mass spectrometry, high-resolution mass spectrometry, and NMR spectroscopy were applied to the identification and the purity evaluation of the synthetic products.

Synthesis and identification of pilocarpic acid diesters, prodrugs of pilocarpine

A series of new pilocarpic acid diesters were synthesized to obtain prodrugs for pilocarpine with varying physico-chemical properties. Thermospray liquid chromatography-mass spectrometry (TSP-LC-MS), liquid chromatography with UV-detection (LC-UV) and NMR-spectroscopy were used for the identification of the synthetic products and for evaluation of their purity including typical impurities (pilocarpic acid monoester, pilocarpine). TSP-LC-MS-analysis was performed in the reversed-phase mode using acetonitrile (60%)-0.2 M ammonium acetate (40%) as mobile phase. In LC-UV-analysis chromatographic separation was carried out on a reversed-phase column and the mobile phase consisted of methanol (71%) and 0.02 M potassium dihydrogen phosphate, pH 4.5 (29%). Electron ionization-mass spectrometry (EI-MS) was used for elucidation of structures. Elemental compositions of the substances were verified with high resolution-mass spectrometry (HR-MS). The complete establishment of structures presented was based on 1H-, and COSY-NMR-spectroscopy joined to TSP-LC-MS-analysis.