A new inhibitor for fructosamine 3‐kinase (Amadorase)

Non‐enzymatic glycation is a Maillard reaction that occurs spontaneously between glucose and proteins and results in the accumulation of advanced glycation end products (AGEs), which are believed to be one of the causes for age‐related tissue damage. Fructosamine 3‐kinase (FN3K) is an enzyme involved in the protein deglycation process by fructosyl phosphorylation, returning amino acid residues to their pristine state with 3‐deoxyglucosone (3‐DG) and inorganic phosphate as by‐products. 3‐DG is a very reactive electrophile that is even more potent at generating AGEs than glucose; therefore, inhibitors specific to FN3K have been suggested as a means to suppress 3‐DG formation. Dyn‐12 is a substrate mimicking inhibitor with an IC₅₀ value of approximately 6 mM. We report a new hydrophobic competitive inhibitor with respect to fructolysine that has an IC₅₀ of 1.7 mM. Drug Dev. Res. 67:448–455, 2006. © 2006 Wiley‐Liss, Inc.     

Hepatitis Caused by Lotus‐f3?

Abstract: We present a case of hepatitis and jaundice are associated with ingestion of Lotus‐f3 submitted to our regional pharmacovigilance centre. A 56‐year‐old woman with psoriatic arthritis developed increased liver enzymes and jaundice 3 weeks after having started to take the product. The woman had been treated with etanercept for more than a year. She was hospitalized with hepatitis, and viral causes were ruled out. Liver biopsy suggested autoimmune or toxic hepatitis. Both etanercept and Lotus‐f3 were withdrawn, and 6 weeks later the liver enzymes were normalized without any treatment. Etanercept was subsequently successfully reintroduced, and based on the rapid resolution of the hepatitis, a toxic effect of Lotus‐f3 was suggested. This was the first report in the national adverse drug reaction database for this product, but three similar cases have now been reported. Lotus‐f3 contains an extract of green tea, which has been associated with hepatotoxicity. The Norwegian adverse drug reaction database contains nine reports of hepatitis or jaundice associated with natural products. Four different natural products containing extracts of green tea have been suspected in eight out of these nine reports.     

Synthesis of [18F]‐labeled N‐3(substituted) thymidine analogues: N‐3([18F]fluorobutyl) thymidine ([18F]‐FBT) and N‐3([18F]fluoropentyl) thymidine ([18F]‐FPT) for PET

Syntheses of N‐3(substituted) analogues of thymidine, N‐3([¹⁸F]fluorobutyl)thymidine ([¹⁸F]‐FBT) and N‐3([¹⁸F]fluoropentyl)thymidine ([¹⁸F]‐FPT) are reported. 1,4‐Butane diol and 1,5 pentane diol were converted to their tosyl derivatives 2 and 3 followed by conversion to benzoate esters 4 and 5, respectively. Protected thymidine 1 was coupled separately with 4 and 5 to produce 6 and 7 , which were hydrolyzed to 8 and 9 , then converted to their mesylates 10 and 11 , respectively. Compounds 10 and 11 were fluorinated with n‐Bu₄N[¹⁸F] to produce 12 and 13 , which by acid hydrolysis yielded 14 and 15 , respectively. The crude products were purified by HPLC to obtain [¹⁸F]‐FBT and [¹⁸F]‐FPT. The radiochemical yields were 58–65% decay corrected (d.c.) for 14 and 46–57% (d.c.) for 15 with an average of 56% in three runs per compound. Radiochemical purity was >99% and specific activity was >74 GBq/µmol at the end of synthesis (EOS). The synthesis time was 65–75 min from the end of bombardment (EOB). Copyright © 2006 John Wiley & Sons, Ltd.     

FLT3 Antibody‐based therapy for leukemia

Technological advances in antibody generation and production have facilitated recent clinical and commercial success with antibody‐based cancer therapeutics. The class III receptor tyrosine kinase FLT3 is highly expressed on the blast cells in most cases of acute myelogenous leukemia (AML) and B‐cell acute lymphoblastic leukemia (ALL). Activating mutations of FLT3 are detected in approximately 37% AML patients. FLT3 expression in normal tissue is limited to myeloid and B‐cell precursor cells. Therefore, over‐expressed or mutated FLT3 is an attractive target for therapeutic intervention using monoclonal antibodies. This review will discuss recent progress in the development of anti‐FLT3 antibodies as well as their therapeutic potentials in the treatment of AML and other hematological malignancies. Drug Dev. Res. 67:495–500, 2006. © 2006 Wiley‐Liss, Inc.     

组合生物合成研究进展

组合生物合成是在抗生素产生菌的次级代谢产物合成途径中涉及到的一些酶的编码基因之间的互换,从而产生许多新的“非天然的天然化合物”。本文综述了近二年来组合生物合成的研究所取得的进展,着重介绍了I类PKS的研究结果,并对Ⅱ类PKS、NRPS及DOS也作了简单介绍。     

Radiosynthesis of microtubule‐targeted theranostic methyl N‐[5‐(3’‐radiohalobenzoyl)‐1H‐benzimidazol‐2‐yl]carbamates

Microtubules are a target for a broad spectrum of drugs used as chemotherapeutics to treat hematological malignancies and solid tumors. Most of these drugs have significant dose‐limiting toxicities including peripheral neuropathies that can be debilitating and permanent. In an ongoing effort to develop safer and more effective drugs, benzimidazole‐based compounds are being developed as replacement for vincristine and similar agents. In this report, we describe radiosyntheses of novel microtubule‐targeting methyl N‐[5‐(3’‐radiohalobenzoyl)‐1H‐benzimidazol‐2‐yl]carbamates 4 that are intended as potential imaging agents and molecular radiotherapeutics. ¹²⁵I‐ and ¹³¹I‐radiolabeled derivatives were prepared either by direct radioiodination of methyl N‐(6‐benzoyl‐1H‐benzimidazol‐2‐yl)carbamate 1 or radioiododestannylation of the corresponding stannane precursor 3 . The direct radioiodination was conducted in a solution of 1 in triflic acid and produced after ~1 hour at elevated temperatures and HPLC purification on average 62% of the no‐carrier added products ¹²⁵I‐ 4 and ¹³¹I‐ 4 . Radioiododestannylation of 3’‐trimethylstannane 3 proceeded with ease at room temperature in the presence of H₂O₂ as the oxidant and produced no‐carrier‐added ¹²⁵I‐ 4 and ¹³¹I‐ 4 in high isolated yields, on average 85%. The radiohalodestannylation protocol is universal and can be applied to other radiohalides including ¹²⁴I to produce ¹²⁴I‐ 4 , a positron emission tomography agent, and ²¹¹At to produce ²¹¹At‐ 4 , an α‐particle emitting radiotherapeutic.     

1,3‐Disubstituted‐4‐Aminopyrazolo [3, 4‐d] Pyrimidines,a New Class of Potent Inhibitors for Phospholipase D

Phospholipase D enzymes cleave lipid substrates to produce phosphatidic acid, an important precursor for many essential cellular molecules. Phospholipase D is a target to modulate cancer‐cell invasiveness. This study reports synthesis of a new class of phospholipase D inhibitors based on 1,3‐disubstituted‐4‐amino‐pyrazolopyrimidine core structure. These molecules were synthesized and used to perform initial screening for the inhibition of purified bacterial phospholipase D, which is highly homologous to the human PLD₁. Initially tested with the bacterial phospholipase D enzyme, then confirmed with the recombinant human PLD₁ and PLD₂ enzymes, the molecules presented here exhibited inhibition of phospholipase D activity (IC₅₀) in the low‐nanomolar to low‐micromolar range with both monomeric substrate diC₄PC and phospholipid vesicles and micelles. The data strongly indicate that these inhibitory molecules directly block enzyme/vesicle substrate binding. Preliminary activity studies using recombinant human phospholipase Ds in in vivo cell assays measuring both transphosphatidylation and head‐group cleavage indicate inhibition in the mid‐ to low‐nanomolar range for these potent inhibitory novel molecules in a physiological environment.     

Biological activities of 3,4,5‐trihydroxypiperidines and their N‐ and O‐derivatives

3,4,5‐Trihydroxypiperidines belong to the family of 1,5‐dideoxy‐1,5‐iminosugar natural products and are structural analogues of pentose monosaccharides in the pyranose form. The biological activities of these apparently structurally simple molecules and their N‐ and O‐alkylated and ‐arylated derivatives are no less remarkable than their C‐6 hydroxymethyl counterparts of the hexoses (such as 1‐deoxynojirimycin, DNJ). Their biological profiles indicate that the hydroxymethyl branch is crucial to neither potency nor selectivity, with O‐alkylation demonstrated to produce exquisite selectivity extending beyond glycosidase inhibition, to immunosuppressant and antibacterial activities.     

Citral inhibits N‐nitrosodiethylamine‐induced hepatocellular carcinoma via modulation of antioxidants and xenobiotic‐metabolizing enzymes

Hepatocellular carcinoma (HCC) ranks the sixth position among various cancers worldwide. Recent research shows that natural and dietary compounds possess many therapeutic effects. Citral is a monoterpene aldehyde that contains geranial and neral. The present study was considered to study the role of citral against N‐nitrosodiethylamine (NDEA)‐induced HCC via modulation of antioxidants and xenobiotic‐metabolizing enzymes in vivo. NDEA‐alone‐administered group II animals profoundly showed increased tumor incidence, reactive oxygen species, liver marker enzyme levels, serum bilirubin levels, tumor markers of carcinoembryonic antigen, α‐fetoprotein, proliferative markers of argyrophilic nucleolar organizing regions, proliferating cell nuclear antigen (PCNA) expressions, phase I xenobiotic‐metabolic enzymes and simultaneously decreased antioxidants, and phase II enzymes levels. Citral (100 mg/kg b.w.) treatment significantly reverted the levels in group III cancer‐bearing animals when compared to group II cancer‐bearing animals. In group IV animals, citral‐alone administration did not produce any adverse effect during the experimental condition. Based on the results, citral significantly inhibits the hepatocellular carcinogenesis through restoring the antioxidants and phase II xenobiotic‐enzyme levels; thereby, it strongly proves as an antiproliferative agent against rat HCC.     

Biosynthesis of hybrid peptide-polyketide natural products

The structural and catalytic similarities between non-ribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) support the idea of combining individual NRPS and PKS modules for combinatorial biosynthesis. Recent advances in cloning and characterization of biosynthetic gene clusters for naturally occurring hybrid polyketide-peptide metabolites have provided direct evidence for the existence of hybrid NRPS-PKS systems, thus setting the stage to investigate the molecular basis for intermodular communication between NRPS and PKS modules. Reviewed in this article are biosynthetic data pertinent to hybrid peptide-polyketide biosynthesis published up to late 2000. Hybrid peptide-polyketide natural products can be divided into two classes: (i) those whose biosyntheses do not involve functional interaction between NRPS and PKS modules; and (ii) those whose biosyntheses are catalyzed by hybrid NRPS-PKS systems involving direct interactions between NRPS and PKS modules. It is the latter systems that are most likely amenable to combinatorial biosynthesis. The same catalytic sites appear to be conserved in both hybrid NRPS-PKS and normal NRPS or PKS systems, with the exception of the ketoacyl synthase domains in hybrid NRPS-PKS systems which are unique. Specific linkers may play a critical role in communication, facilitating the transfer of the growing intermediates between the interacting NRPS and/or PKS modules. In addition, phosphopantetheinyl transferases with broad carrier protein specificity are essential for the production of functional hybrid NRPS-PKS megasynthetases. These findings should now be taken into consideration in engineered biosynthesis of hybrid peptide-polyketide natural products for drug discovery and development.     

Phylogenetic Study of Polyketide Synthases and Nonribosomal Peptide Synthetases Involved in the Biosynthesis of Mycotoxins

Polyketide synthase (PKSs) and nonribosomal peptide synthetase (NRPSs) are large multimodular enzymes involved in biosynthesis of polyketide and peptide toxins produced by fungi. Furthermore, hybrid enzymes, in which a reducing PKS region is fused to a single NRPS module, are also responsible of the synthesis of peptide-polyketide metabolites in fungi. The genes encoding for PKSs and NRPSs have been exposed to complex evolutionary mechanisms, which have determined the great number and diversity of metabolites. In this study, we considered the most important polyketide and peptide mycotoxins and, for the first time, a phylogenetic analysis of both PKSs and NRPSs involved in their biosynthesis was assessed using two domains for each enzyme: β-ketosynthase (KS) and acyl-transferase (AT) for PKSs; adenylation (A) and condensation (C) for NRPSs. The analysis of both KS and AT domains confirmed the differentiation of the three classes of highly, partially and non-reducing PKSs. Hybrid PKS-NRPSs involved in mycotoxins biosynthesis grouped together in the phylogenetic trees of all the domains analyzed. For most mycotoxins, the corresponding biosynthetic enzymes from distinct fungal species grouped together, except for PKS and NRPS involved in ochratoxin A biosynthesis, for which an unlike process of evolution could be hypothesized in different species.     

Evaluation of nicotine in tobacco‐free‐nicotine commercial products

Recently, a variety of new tobacco‐free‐nicotine, TFN, products have been commercialized as e‐liquids. Tobacco‐derived nicotine contains predominantly (S)‐(−)‐nicotine, whereas TFN products may not. The TFN products are said to be cleaner, purer substances, devoid of toxic components that come from the tobacco extraction process. A variety of commercial tobacco and TFN products were analyzed to identify the presence and composition of each nicotine enantiomer. A rapid and effective enantiomeric separation of nicotine has been developed using a modified macrocyclic glycopeptide bonded to superficially porous particles. The enantiomeric assay can be completed in <2 min with high resolution and accuracy using high performance liquid chromatography with electrospray ionization mass spectrometry. The results of this study suggest the need for pharmacological studies of (R)‐(+)‐nicotine, which is present in much greater quantities in commercial TFN products compared to commercial tobacco‐derived products. Such studies are required by the FDA for new enantiomeric pharmacological products. Copyright © 2016 John Wiley & Sons, Ltd.     

DNA Adduct Levels and Intestinal Lesions in Congenic Rapid and Slow Acetylator Syrian Hamsters Administered the Food Mutagens 2‐Amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) or 2‐Amino‐3‐methylimidazo[4,5‐f]quinoline (IQ

Epidemiological studies indicate that rapid acetylators with a high intake of well‐done red meat have an increased risk of colorectal cancer. Arylamine N‐acetyltransferase enzymes (E.C. 2.3.1.5) activate carcinogenic heterocyclic amines found in the crust of fried meat via O‐acetylation of their N‐hydroxylamines to reactive intermediates that bind covalently to DNA and produce mutations. Syrian hamsters as well as humans express two N‐acetyltransferase isozymes (NAT1 and NAT2) which differ in substrate specificity and genetic control. Nucleic acid substitutions in the NAT2 gene segregate individuals into rapid, intermediate and slow acetylator phenotypes. In the present paper, we examined the role of the polymorphic NAT2 acetylator genotype in carcinogenesis induced by the food mutagens 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) or 2‐amino‐3‐methylimidazo[4,5‐f]quinoline (IQ) by comparing Syrian hamster lines congenic at the NAT2 locus. No differences were found between rapid and slow acetylator congenic hamsters in levels of intestinal PhIP‐DNA adducts. In contrast to previous studies in rats, no carcinogen‐related induction of the preneoplastic lesions aberrant crypt foci or tumors was found in the intestines of rapid and slow acetylator congenic Syrian hamsters administered PhIP or IQ.     

Cytochrome P450‐mediated metabolism of the synthetic cannabinoids UR‐144 and XLR‐11

In recent years, synthetic cannabinoids have emerged in the illicit drug market, in particular via the Internet, leading to abuse of these drugs. There is currently limited knowledge about the specific enzymes involved in the metabolism of these drugs. In this study, we investigated the cytochrome P450 (CYP) enzymes involved in the metabolism of the two synthetic cannabinoids (1‐pentyl‐1H‐indol‐3‐yl)‐(2,2,3,3‐tetramethylcyclopropyl)methanone (UR‐144) and [1‐(5‐fluoropentyl)‐1H‐indol‐3‐yl)](2,2,3,3‐tetramethylcyclopropyl)methanone (XLR‐11). This study extends previous studies by identifying the specific CYP enzymes involved in the metabolism of UR‐144 and XLR‐11 utilizing a panel of nine recombinant enzymes (CYP1A2, 2B6, 2C8, 2C9, 2C18, 2C19, 2D6, 3A4, and 2E1). This is followed by an investigation of the effect of specific inhibitors targeted against CYP1A2, 2B6, 2C9, 2C19, 2D6 and 3A4 in human liver microsomes (HLM). Incubations of UR‐144 and XLR‐11 with recombinant CYP enzymes revealed that UR‐144 and XLR‐11 are extensively metabolized by CYP3A4 at the tetramethylcyclopropyl (TMCP) moiety, but also CYP1A2 and CYP2C19 showed activity. Inhibition of CYP3A4 in HLM attenuated the metabolism of UR‐144 and XLR‐11, while inhibition of the other CYP enzymes in HLM had only minor effects. Thus, CYP3A4 is the major contributor to the CYP mediated metabolism of UR‐144 and XLR‐11 with minor contributions from CYP1A2. Users of UR‐144 and XLR‐11 are thus subject to the influence of potential drug‐drug interactions, if they are concomitantly medicated with CYP3A4 inducers (e.g. some antiepileptics) or inhibitors (e.g. some antifungal drugs). Copyright © 2015 John Wiley & Sons, Ltd.     

An efficient laboratory synthesis of α‐deuteriated profens

An efficient and practical laboratory synthesis of a series of 2‐deuterio‐2‐arylpropionic acids (α‐deuterioprofens) is described. The levels of deuterium incorporation are high and the products are synthetically useful. Copyright © 2006 John Wiley & Sons, Ltd.     

Protective Effects of d‐Limonene on Lipid Peroxidation and Antioxidant Enzymes in Streptozotocin‐Induced Diabetic Rats

The aim of this study was to evaluate the protective effects of d ‐limonene on the levels of lipid peroxidation by‐products and antioxidant defence systems in the plasma and tissues of normal and streptozotocin (STZ)‐induced diabetes rats. The experimental diabetes was induced in rats by a single dose of STZ (40 mg/kg i.p.) injection, and treatment with d ‐limonene was continued for 45 days. After the treatment period, oxidative stress parameters such as lipid peroxidation by‐products; enzymatic antioxidants such as superoxide dismutase, catalase, glutathione peroxidase and glutathione‐S‐transferase; non‐enzymic antioxidants including reduced glutathione, Vitamins C and E were measured in the plasma and tissues of experimental rats. An increase in the levels of lipid peroxidation by‐products and significant decrease in antioxidant enzymes were observed in untreated diabetic rats. Administration of d ‐limonene to diabetic rats for 45 days caused a significant reduction in the levels of lipid peroxidation by‐products and an increase in the activities of antioxidant enzymes, when compared with the untreated diabetic group. There was no significant difference in normal treated groups, when compared with normal rats. Biochemical observations were substantiated with the help of histopathological examinations through its antioxidant properties and thereby conferred protection against STZ‐induced diabetic rats. The result of this study indicates that d ‐limonene has antioxidant potential in addition to its antidiabetic effect in experimental diabetes.     

Anti‐Clastogenic Effect of Berberine against DMBA‐Induced Clastogenesis

Abstract: Our aim was to evaluate the protective effect of berberine on 7,12‐dimethylbenz[a]anthracene (DMBA)‐induced chromosomal aberrations and micro‐nucleated polychromatic erythrocytes (MnPCEs) frequency in bone marrow cells of golden Syrian hamsters. The anti‐clastogenic effect of berberine (50 mg/kg b.w. p.o.) was also assessed by measuring the status of phase II detoxification enzymes and oxidative stress, as biochemical endpoints, during DMBA (30 mg/kg b.w. i.p.) induced clastogenesis. Marked chromosomal aberrations, increased MnPCEs frequency and enhanced status of lipid peroxidation, antioxidants and phase I and II detoxification enzymes were noticed in hamsters treated with DMBA alone. Oral pre‐treatment with berberine for 5 days to DMBA‐treated hamsters significantly reduced the frequency of MnPCEs and chromosomal abnormalities as well as reversed the status of lipid peroxidation, antioxidants and phase I and II detoxification enzymes. The present study thus suggests that berberine has potent anti‐clastogenic potential against DMBA‐induced clastogenesis, which is probably due to its anti‐lipid peroxidative potential and effect on modulation of phase I and II detoxification cascade.     

Identification of pyrolysis products of the new psychoactive substance 2‐amino‐1‐(4‐bromo‐2,5‐dimethoxyphenyl)ethanone hydrochloride (bk‐2C‐B) and its iodo analogue bk‐2C‐I

2‐Amino‐1‐(4‐bromo‐2,5‐dimethoxyphenyl)ethanone hydrochloride (bk‐2C‐B) has recently emerged as a new psychoactive substance (NPS). It is most commonly consumed orally, although there are indications that it might also be ingested by inhalation or ‘smoking’. Information about the stability of bk‐2C‐B when exposed to heat is unavailable and the potential for pyrolytic degradation and formation of unknown substances available for inhalation prompted an investigation using a simulated ‘meth pipe’ scenario. Twelve products following pyrolysis of bk‐2C‐B were detected and verified by organic synthesis of the corresponding standards. In addition, 2‐amino‐1‐(4‐iodo‐2,5‐dimethoxyphenyl)ethanone hydrochloride (bk‐2C‐I) was characterized for the first time and subjected to pyrolysis as well. Similar products were formed, which indicated that the replacement of the bromo with the iodo substituent did not affect the pyrolysis pattern under the conditions used. Two additional products were detected in the bk‐2C‐I pyrolates, namely 1‐(2,5‐dimethoxyphenyl)‐ethanone and 1‐iodo‐4‐ethenyl‐5‐methoxyphenol. The potential ingestion of pyrolysis products with unknown toxicity adds an element of concern. Copyright © 2017 John Wiley & Sons, Ltd.     

5‐Trideuteromethyl‐α‐tocotrienol and 5‐14CH3‐α‐tocotrienol as biological tracers of tocotrienols

The tocotrienols have attracted increased attention recently as evidence has accrued that their biological activities are significantly different from tocopherols. The biokinetics and metabolic fate of tocopherols have long been studied using deuteromethylated forms of α‐tocopherol prepared by a stannous chloride catalysed paraformaldehyde methylation of γ‐ and δ‐tocopherols. We show here that his methodology is not an efficient route to deuterated α‐tocotrienol because of low yields and extensive exchange of allylic hydrogens under the prolonged acidic conditions of the deuteromethylation. Instead, we have prepared deuteromethylated and ¹⁴C‐radiolabelled α‐tocotrienol by aminomethylation at C‐5 of γ‐tocotrienol (available from palm oil), followed by reduction with NaCNBD₃ in refluxing iso‐butanol. The deuteromethylation procedure is amenable to multi‐gram scale reactions. Copyright © 2006 John Wiley & Sons, Ltd.     

Facile preparation of disulfide‐bridged peptides using the polymer‐supported oxidant CLEAR‐OXTM*

Abstract: Formation of disulfide bonds in synthetic peptides is one of the more challenging transformations to achieve in peptide chemistry, in view of the possible formation of oligomeric by‐products and other side reactions, as well as occasional solubility problems in aqueous oxidizing media. It was shown previously that 5,5′‐dithiobis(2‐nitrobenzoic acid) (DTNB ≡ Ellman's reagent), when attached to polyethylene glycol‐polystyrene (PEG‐PS^TM), controlled‐pore glass (CPG), or modified Sephadex supports, was an effective oxidizing agent that promoted disulfide formation under mild conditions. More recently, this work was extended to Cross‐Linked Ethoxylate Acrylate Resin (CLEAR) supports, because of their compatibility with both organic and aqueous solvent mixtures. The resultant new tool, termed CLEAR‐OX^TM, was used to conveniently produce several model cyclic disulfides with improved purities and yields, when compared with solution oxidations. A particularly striking example was the gram‐scale oxidation of a urotensin II antagonist peptide containing a hindered penicillamine unit.