Metabolomics analysis reveals elevation of 3-indoxyl sulfate in plasma and brain during chemically-induced acute kidney injury in mice: investigation of nicotinic acid receptor agonists.

An investigative renal toxicity study using metabolomics was conducted with a potent nicotinic acid receptor (NAR) agonist, SCH 900424. Liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) techniques were used to identify small molecule biomarkers of acute kidney injury (AKI) that could aid in a better mechanistic understanding of SCH 900424-induced AKI in mice. The metabolomics study revealed 3-indoxyl sulfate (3IS) as a more sensitive marker of SCH 900424-induced renal toxicity than creatinine or urea. An LC-MS assay for quantitative determination of 3IS in mouse matrices was also developed. Following treatment with SCH 900424, 3IS levels were markedly increased in murine plasma and brain, thereby potentially contributing to renal- and central nervous system (CNS)-related rapid onset of toxicities. Furthermore, significant decrease in urinary excretion of 3IS in those animals due to compromised renal function may be associated with the elevation of 3IS in plasma and brain. These data suggest that 3IS has a potential to be a marker of renal and CNS toxicities during chemically-induced AKI in mice. In addition, based on the metabolomic analysis other statistically significant plasma markers including p-cresol-sulfate and tryptophan catabolites (kynurenate, kynurenine, 3-indole-lactate) might be of toxicological importance but have not been studied in detail. This comprehensive approach that includes untargeted metabolomic and targeted bioanalytical sample analyses could be used to investigate toxicity of other compounds that pose preclinical or clinical development challenges in a pharmaceutical discovery and development.

Quantitative determination of hippuric and benzoic acids in urine by LC-MS/MS using surrogate standards.

An LC-MS/MS method for simultaneous determination of hippuric acid (HA) and benzoic acid (BA) in monkey urine after direct injection was developed. Since HA and BA are endogenous compounds in urine, surrogate standards ((13)C(6)-hippuric and (13)C(6)-benzoic acid) were employed to generate calibration curves. l-Phenylalanine-ring-D5 served as an internal standard. Multiple reaction monitoring in the negative ionization mode with an APCI source was used for detection of all components in the assay. The developed method is intended for determination of HA and BA in the range of 0.25-250 and 0.1-100microg/ml, respectively. Weighted (1/x) quadratic regression (r(2)>0.99) was used to generate calibration curves. Precision and accuracy of the method were assessed by analyzing 3 quality control samples (concentrations at low, medium, and high range of calibration curve) prepared in monkey urine. Stability for 48h at room temperature and after 3 freeze-thaw cycles was also evaluated. The proposed method was successfully utilized for analysis of urine samples from female monkeys following the administration of everninomicin alone and in combination with gentamicin. The concentrations of endogenous HA and BA were calculated based on the peak area ratio of the analyte to the internal standard using a regression equation for corresponding surrogate standard.

Antimicrobial resveratrol tetramers from the stem bark of Vatica oblongifoliassp. oblongifolia.

Two new resveratrol tetramers, hopeaphenol A (1) and isohopeaphenol A (2), along with the known vaticaphenol A (3), were isolated from the stem bark of Vatica oblongifolia ssp. oblongifolia through bioassay-guided fractionation. The structures and their relative stereochemistry were determined by spectroscopic techniques. Compounds 1 and 3 demonstrated moderate activity against methicillin-resistant Staphylococcus aureus and Mycobacterium smegmatis.