A possible covalent xanthine oxidase inhibitor TS10: Inhibition mechanism, metabolites identification and PDPK assessment.

Xanthine oxidase (XO) inhibitors are widely used in the control of serum uric acid levels in the clinical management of gout. Our continuous efforts in searching novel amide-based XO inhibitors culminated in the identification of N-(4-((3-cyanobenzyl)oxy)-3-(1H-tetrazol-1-yl)phenyl)isonicotinamide (TS10), which exhibited comparable in vitro inhibition to that of topiroxostat (TS10, IC50 = 0.031 µM; topiroxostat, IC50 = 0.020 µM). According to the molecular modeling, we speculated that, as well as topiroxostat, TS10 would be biotransformed by XO to yield TS10-2-OH. In this work, TS10-2-OH was successfully identified in XO targeted metabolism study, demonstrated that TS10 underwent a covalent binding with XO via a TS10-O-Mo intermediate after anchoring in the XO molybdenum cofactor pocket. Furthermore, TS10-2-OH is a weak active metabolite, and its potency was explained by the molecular docking. In metabolites identification, TS10 could be oxidized by CYP2C9, CYP3A4 and CYP3A5 to generate two mono-hydroxylated metabolites (not TS10-2-OH); and could occur degradation in plasma to mainly generate a hydrolytic metabolite (TS10-hydrolysate). In pharmacokinetic assessment, the low oral system exposure was observed (Cmax = 14.73 ± 2.66 ng/mL and AUClast = 9.17 ± 1.42 h⋅ng/mL), which could be explained by the poor oral absorption property found in excretion studies. Nonetheless, in pharmacodynamic evaluation, TS10 exhibited significant uric acid-lowering effect after oral administration in a dose-dependent manner. Briefly, in addition to allopurinol and topiroxostat, TS10 is possibly another explicitly mechanism-based XO inhibitor with powerful covalent inhibition.

Comparative pharmacokinetics study of leonurine and stachydrine in normal rats and rats with cold-stagnation and blood-stasis primary dysmenorrhoea after the administration of Leonurus japonicus houtt electuary.

Leonurus japonicus houtt, a well-known herb of traditional Chinese medicine, is widely used to treat gynaecological diseases. In this study, a rapid and sensitive liquid chromatography with tandem mass spectrometry method for simultaneously quantifying leonurine and stachydrine, the two main bioactive components in Leonurus japonicus houtt, was developed and validated. Plasma samples were prepared by protein precipitation with acetonitrile and separation by a Hewlett Packard XDB-C8 column (150 × 4.6 mm, id, 5 µm) equipped with a gradient elution system containing methanol-water and 0.1% formic acid at a flow-rate of 0.4 mL/min. Components were then detected by a mass spectrometer in positive electrospray ionization mode. This method showed good linearity, precision, accuracy, recovery, stability, and negligible matrix effects, which were within acceptable ranges. The method was successfully applied to compare the pharmacokinetics in normal rats and rats with cold-stagnation and blood-stasis primary dysmenorrhoea treated with Leonurus japonicus houtt electuary. The result showed significant differences (p < 0.05) in the pharmacokinetic parameters between the primary dysmenorrhoea and normal groups. This result implied that Leonurus japonicus houtt electuary remained longer and was absorbed slower in rats with primary dysmenorrhoea and exhibited higher bioavailability and peak concentration.

Ultra-Liquid Chromatography Tandem Mass Spectrometry (UPLC-MS/MS)-Based Pharmacokinetics and Tissue Distribution Study of Koumine and the Detoxification Mechanism of Glycyrrhiza uralensis Fisch on Gelsemium elegans Benth.

Gelsemium elegans Benth. (G. elegans), which is a famous Chinese folk medicine, has been commonly used to treat certain types of skin ulcers and alleviate inflammation, headaches, and cancer pain. However, the extensive clinical use of G. elegans has been greatly hampered by its toxicity. As one of the most widely used herbal medicines, Glycyrrhiza uralensis Fisch, has a unique effect on detoxification of G. elegans. In the present study, a rapid and sensitive method using ultra-liquid chromatography tandem mass spectrometry (UPLC-MS/MS) was established and validated for determination of koumine, the most abundant molecule among the alkaloids of G. elegans, in rat plasma, tissue, and liver microsome. The developed method was successfully applied to the pharmacokinetics, tissue distribution, and in vitro metabolism study in rat with or without pre-treated Glycyrrhiza uralensis Fisch extract. Meanwhile, the expression level of CYP3A1 mRNA was analyzed to explain the detoxification mechanism of Glycyrrhiza uralensis Fisch on G. elegans. As a result, our work demonstrated that Glycyrrhiza uralensis Fisch could significantly affect the pharmacokinetics and tissue distribution of koumine in rats. The detoxification mechanism of Glycyrrhiza uralensis Fisch on G. elegans may be its cytochrome enzyme up-regulation effect.

Two new species of Dugesia (Platyhelminthes, Tricladida, Dugesiidae) from the subtropical monsoon region in Southern China, with a discussion on reproductive modalities.

BACKGROUND: Freshwater planarians of the genus Dugesia (Platyhelminthes, Tricladida, Dugesiidae) are distributed in a major part of the Old World and Australia, although until recently only very few species were known from China. RESULTS: Two new species of Dugesia from Southern China are described on the basis of an integrative taxonomic approach. BI and ML phylogenetic trees based on the independent genes and on the concatenated dataset had similar topologies, only differing in some nodes that were weakly supported. Phylogenetic trees based on the concatenated dataset revealed that D. adunca Chen & Sluys, sp. nov. and D. tumida Chen & Sluys, sp. nov. are not closely related and belong to different clades. The two new species occupy separate long branches with high support values and, thus, are well-differentiated from their congeners. Separate species status of D. adunca and D. tumida is supported also by the genetic distances between the species included in our analysis, albeit that COI distances varied greatly among species. Dugesia adunca from Guangxi Province is characterized by the following features: living mature animals rather small; asymmetrical openings of the oviducts into the bursal canal; penis papilla with shape of an aquiline bill, albeit with a blunt tip; asymmetrical penis papilla, with a large antero-dorsal lip and a much smaller ventro-posterior lip; very large seminal vesicle, provided with trabeculae; small diaphragm; mixoploid karyotype with diploid complements of 2n = 2x = 16 and triploid complements of 2n = 3x = 24, with all chromosomes being metacentric. Dugesia tumida from Guangdong Province is characterized by a penis papilla provided with a large, symmetrical penial valve from the middle of which arises the small, distal section of the papilla; a duct intercalated between the seminal vesicle and the small diaphragm; ventrally displaced ejaculatory duct curving upwards before opening to the exterior; penis papilla highly asymmetrical, having a slim and long ventral portion and a short and stubby dorsal part; vasa deferentia separately opening into antero-dorsal portion of seminal vesicle; oviducts openings symmetrically into ventral portion of the bursal canal, near its opening into the atrium; mixoploid karyotype, with diploid chromosome portraits of 2n = 2x = 16, and triploid complements of 2n = 3x = 24, with all chromosomes being metacentric. In the context of the various kinds of mixoploidy and the sexualization of specimens, reproductive modalities within the genus Dugesia are shortly discussed. CONCLUSION: Molecular, morphological, and karyological markers show that the two populations examined represent members of the genus Dugesia and constitute two new, distinct species.

[Lidamycin metabolism in vitro].

This paper is to report the study of the metabolism of lidamycin in vitro including in plasma and microsomes to guide clinical therapy. Lidamycin was quantified by detecting its active ingredient using HPLC-MS/MS. The metabolic stability of lidamycin in rat, Beagle dog, monkey and human plasma and liver microsomes, and its inhibition to cytochrome P450 isoforms in human liver microsomes were studied. Results showed that lidamycin was metabolized in the four species of plasma, and the sequence of metabolic rates in plasma were in rat > in dog > in human > in monkey. But among the four species of liver microsomes, lidamycin was metabolized only in monkey liver microsomes. There was almost no inhibition to cytochrome P450 isoforms at the concentrations of between 0.0005 and 10 ng x mL(-1). Therefore, the property of lidamycin metabolism in human is similar with that in dog, and metabolism of other drugs would not be decreased by cytochrome P450 as used along with lidamycin in clinic.

Tetra-aqua-diazido-cobalt(II) 3,3'-dicarb-oxy-l-ato-1,1'-ethyl-enedipyridinium.

The asymmetric unit of the title compound, [Co(N(3))(2)(H(2)O)(4)]·C(14)H(12)N(2)O(4), comprises half of the cobalt(II) complex mol-ecule and a half of the 3,3'-dicarboxyl-ato-1,1'-ethyl-enedipyridinium mol-ecule. The Co(II) atom is located on an inversion centre and hence the complex mol-ecule adopts a centrosymmetric trans-octa-hedral geometry. The zwitterionic organic mol-ecule is also centrosymmetric with the centre of the C-C bond of the ethyl-ene moiety coinciding with an inversion centre. The adduct of metal complex and organic mol-ecule is associated into a three-dimenional network through O-H⋯O hydrogen bonds.

Structures and magnetism of azide- and carboxylate-bridged metal(II) systems derived from 1,2-bis(N-carboxymethyl-4-pyridinio)ethane.

Four coordination polymers of different transition metal ions with azide and the zwitterionic dicarboxylate ligand 1,2-bis(N-carboxymethyl-4-pyridinio)ethane (bcpe) were synthesized, and structurally and magnetically characterized. They are formulated as [M(2)(bcpe)(N(3))(4)].H(2)O (M = Mn, 1; Co, 2; and Ni, 3) and [Cu(3)(bcpe)(N(3))(6)].(H(2)O)(2) (4). In the isomorphous compounds , octahedral metal ions are linked by the mixed (micro(2)-syn,syn-COO)(mu(2)-EO-N(3))(2) triple bridges (EO = end-on) to give anionic uniform chains, which are cross-linked by the cationic bis(pyridinium) spacers to produce two-dimensional coordination layers. Magnetic studies demonstrated that the magnetic coupling through the mixed triple bridge is antiferromagnetic in the Mn(ii) compound (1) but ferromagnetic in the Co(ii) and Ni(ii) species (2 and 3). Compound 4 also consists of two-dimensional coordination layers in which Cu(ii) chains are interlinked by the organic spacers, but the chain has mixed mu(2)-EO-azide, mu(3)-EO-azide and mu(2)-O(carboxylate) bridges and features tetranuclear dicubane-based units sharing Cu ions or alternatively linear trinuclear units connected by long axial Cu-N/O bonds. Magnetic studies suggested that the Cu(ii) ions linked by the double azide bridges in the equatorial-equatorial fashion are strongly coupled to give a ferromagnetic S = 3/2 ground state for the trinuclear units, with very weak antiferromagnetic interactions through the equatorial-axial bridges between the units.