Unique metabolic pathway of [(14)C]lenvatinib after oral administration to male cynomolgus monkey.

Lenvatinib, a potent inhibitor of multiple tyrosine kinases, including vascular endothelial growth factor receptors 2 and 3, generated unique metabolites after oral administration of [(14)C]lenvatinib (30 mg/kg) to a male cynomolgus monkey. Lenvatinib was found to be transformed to a GSH conjugate, through displacement of an O-aryl moiety, at the quinoline part of the molecule in the liver and kidneys. The GSH conjugate underwent further hydrolysis by γ-glutamyltranspeptidase and dipeptidases, followed by intramolecular rearrangement, to form N-cysteinyl quinoline derivatives, which were dimerized to form disulfide dimers and also formed an N,S-cysteinyl diquinoline derivative. In urine, a thioacetic acid conjugate of the quinoline was also observed as one of the major metabolites of lenvatinib. Lenvatinib is a 4-O-aryl quinoline derivative, and such compounds have been known to undergo conjugation with GSH, accompanied by release of the O-aryl moiety. Because of intramolecular rearrangement in the case of lenvatinib, hydrolysis of the GSH conjugate yielded N-cysteinylglycine and N-cysteine conjugates instead of the corresponding S-conjugates. Because the N-substituted derivatives possess free sulfhydryl groups, dimerization through disulfide bonds and another nucleophilic substitution reaction with lenvatinib resulted in the formation of disulfanyl dimers and an N,S-cysteinyl diquinoline derivative, respectively. Characteristic product ions at m/z 235 and m/z 244, which were associated with thioquinoline and N-ethylquinoline derivatives, respectively, were used to differentiate S- and N-derivatives in this study. On the basis of accurate mass and NMR measurements, a unique metabolic pathway for lenvatinib in monkey and the proposed formation mechanism have been elucidated.

Identification of urinary biomarkers useful for distinguishing a difference in mechanism of toxicity in rat model of cholestasis.

This (1)H nuclear magnetic resonance metabonomics study was aimed to determine urinary biomarkers of cholestasis resulting from inhibition of biliary secretion of bile or obstruction of bile flow. To inhibit biliary secretion of bile, cyclosporine A was administered to male Sprague-Dawley rats. Obstruction of bile flow was induced by administration of 4,4'-methylene dianiline, alpha-naphthylisothiocyanate or bile duct ligation. Clinical pathological and histopathological examinations were performed to confirm cholestatic injury and (1)H nuclear magnetic resonance spectral data for urine samples were analysed to determine similarities and differences in profiles of metabolites using the Spotfire. In cyclosporine A-treated groups, serum total bilirubin and bile acid were significantly increased but no remarkable hepatic histopathological-changes were observed. In 4,4'-methylene dianiline-, alpha-naphthylisothiocyanate- and bile duct ligation-treated groups, serum alkaline phosphatase, gamma-glutamyltranspeptidase and total bilirubin levels increased significantly, and hepatic histopathological-changes were observed. On urinary (1)H nuclear magnetic resonance spectral analysis, area intensities derived from 0.66 to 1.90 ppm were decreased by cyclosporine A, whereas they were increased by other treatments. These metabolites were identified using the NMR suite as bile acids, branched-chain amino acids, n-butyrate, propionate, methyl malonate and valerate. These metabolites were further investigated by K-means clustering analysis. The cluster of these metabolites is considered to be altered by cholestasis. We conclude that bile acids, valine and methyl malonate have a possibility to be urinary cholestatic biomarkers, which distinguish a difference in mechanism of toxicity. (1)H nuclear magnetic resonance metabonomics thus appears to be useful for determining the mechanisms of toxicity and can be front-loaded in drug safety evaluation and biomarker discovery.

Synthesis and pharmacological profile of serofendic acids A and B.

We present efficient syntheses of serofendic acids A and B (SA-A and SA-B), novel neuroprotective substances isolated from fetal calf serum. Biological and pharmacological evaluation showed that SA-A and SA-B have potent protective action against glutamate-induced neurotoxicity, but do not interact directly with glutamate receptors. A pharmacokinetic study showed that they have good oral bioavailability in rats. The results indicate that SA-A and SA-B are potential lead compounds for candidate drugs to treat various neurological disorders.

Stereochemistry of pladienolide B.

Pladienolide B is a 12-membered macrolide isolated from Streptomyces platensis Mer-11107. It showed potent in vitro and in vivo antitumor activities and is a potential lead for novel antitumor agents. The absolute configurations at ten chiral centers were determined on the basis of spectral data of pladienolide B and its chemical transformation products.

Stereochemistry of pteriatoxins A, B, and C.

The C34 and C2' stereochemistry of pteriatoxins A-C has been established. The availability of all the stereoisomers via total synthesis has played an indispensable role.

Pladienolides, new substances from culture of Streptomyces platensis Mer-11107. II. Physico-chemical properties and structure elucidation.

In the course of our screening using fermented broth from soil microorganisms, novel metabolites (pladienolides), possessing inhibitory activity against vascular endothelial growth factor (VEGF) expression and cancer cell proliferation, were isolated from Streptomyces platensis Mer-11107. Pladienolides A (1), B (2), C (3), D (4), E (5), F (6), and G (7) were found to be novel 12-membered macrolides by spectroscopic studies including 1H, 13C NMR, HMQC, HMBC, and NOE experiments. Pladienolides are unusual 12-membered macrolides having a long side chain at the carbon that bears a lactone oxygen.

Enhanced detection of malignant glioma xenograft by fluorescein-human serum albumin conjugate.

OBJECT: During the surgical resection of malignant gliomas, it is important to make clear the border zone between the tumor tissue and normal brain tissue. For this purpose, we conjugated fluorescein and human serum albumin (FLS-HSA) and compared its effectiveness against that of fluorescein-sodium (FLS-Na) alone in detecting human glioma xenografts in SCID mice through a fluorescence microscope. METHODS: We made FLS-HSA conjugate using carbodiimide as a linking reagent. SCID mice, with U251MG cells transplanted subcutaneously, were prepared as tumor models. The animals were sacrificed 15, 30, 60, 180, 360, or 720 min after the intravenous administration of either the FLS-HSA conjugate or FLS-Na alone (n = 3). Fluorescence images were taken with a digital camera, and the brightness of the tumor and that of the peripheral tissue in each image were quantified. In the group of tumor-bearing mice that received FLS-Na, the fluorescence of tumor tissue disappeared 60 min after the reagent was administered, and there was no significant difference in brightness between the tumor and peripheral tissue at any time point. On the other hand, injection of FLS-HSA revealed relative tumor-selective brightness and sufficient contrast between the tumor and surrounding tissue 60 and 360 min after administration. CONCLUSION: FLS-HSA has the advantages of specificity and persistence of fluorescence over FLS-Na for the purpose of identifying glioma nodules in xenogenic subcutaneous tumor transplantation models.

Isolation of a diterpenoid substance with potent neuroprotective activity from fetal calf serum.

Excess activation of glutamate receptors and production of free radicals including nitric oxide may result in severe and irreversible damage to the mammalian central nervous system (CNS), but endogenous defense systems that protect neurons from these insults are poorly understood. Here, we purified and isolated a neuroprotective substance, which has been named "serofendic acid," from a lipophilic fraction of FCS based on the ability to protect rat primary cortical neurons against nitric oxide cytotoxicity. Mass spectrometry and NMR spectroscopy revealed the chemical structure of serofendic acid (15-hydroxy-17-methylsulfinylatisan-19-oic acid) as a sulfur-containing atisane-type diterpenoid, which is unique among known endogenous substances. Synthetic serofendic acid exhibited potent protective actions on cortical neurons against cytotoxicity of a nitric oxide donor as well as of glutamate, although it did not show appreciable influences on glutamate receptor-mediated responses in these neurons. Electron spin resonance analysis demonstrated that serofendic acid had no direct scavenging activity on nitric oxide radicals but was capable of inhibiting the generation of hydroxyl radical, a presumed "executor" radical in the nitric oxide-mediated neurotoxic cascade. These findings suggest that serofendic acid is a low-molecular-weight bioactive factor that promotes survival of CNS neurons, probably through the attenuation of free radical-mediated insults.