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The Study of Drug Metabolism Using Radiotracers
Published in Graham Lappin, Simon Temple, Radiotracers in Drug Development, 2006
False positives are sometimes seen resulting from the facile hydrolysis of a metabolite that is not a glucuronide or sulfate conjugate, but which simply occurs under the incubation conditions. Such false positives can be identified by conducting an incubation in the presence of D-saccharic acid 1,4-lactone, an inhibitor of β-glucuronidase. β-glucuronidase is incubated with the sample and the phenolphthalein glucuronic acid control, both with and without the inhibitor. The phenolphthalein glucuronic acid without the inhibitor should give a pink color on the addition of base, showing that the enzyme is active. The phenolphthalein glucuronic acid with the inhibitor should not produce any color change on the addition of base, showing the conditions for inhibition were appropriate. If the suspect conjugate is a glucu-ronide (and susceptible to enzyme hydrolysis), then the sample without inhibitor should show hydrolysis of the putative conjugate and the sample with the inhibitor should show no change. If the latter does hydrolyze, then this does not rule out the presence of a glucuronide; it only means that it is labile and the result is ambiguous. D-saccharic acid 1,4-lactone is a competitive inhibitor, and therefore excess is required to fully inhibit enzyme hydrolysis, typically 10-fold the amount of substrate.
Thiazolidin-2-cyanamides derivatives as novel potent Escherichia coli β-glucuronidase inhibitors and their structure–inhibitory activity relationships
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2020
Tao-Shun Zhou, Bin Wei, Min He, Ya-Sheng Li, Ya-Kun Wang, Si-Jia Wang, Jian-Wei Chen, Hua-Wei Zhang, Zi-Ning Cui, Hong Wang
Thirteen thiazolidin-2-cyanamide derivatives containing 5-phenyl-2-furan moiety were provided by Prof. Zi-Ning Cui from South China Agricultural University (Guangzhou, China). p-Nitrophenyl-β-d-glucuronide acid (PNPG), d-saccharic acid-1,4-lactone (DSL), and dimethyl sulfoxide (DMSO) were supplied by Sigma-Aldrich (St. Louis, MO, USA). Dulbecco’s phosphate-buffered saline (PBS) was provided by Life Technologies (Carlsbad, CA, USA). Imidazole, kanamycin, and isopropyl β-d-1-thiogalactopyranoside (IPTG) were supplied by Biosharp (Hefei, China). Recombinant E. coli BL21 (DE3) harbouring pET28a-EcGUS was generously provided by Prof. Ru Yan from the University of Macau (Macau, China). Deionised water was purified by a Milli-Q purification system (Millipore, Bedford, MA, USA). Purities were all >98%.
A review on charred traditional Chinese herbs: carbonization to yield a haemostatic effect
Published in Pharmaceutical Biology, 2019
Zhi Chen, Si-Yong Ye, Ying Yang, Zhong-Yuan Li
It is believed that carbonizing causes change of chemical components relating to haemostasis. During carbonizing, a high temperature can damage volatile oil with effects of promoting blood circulation and anticoagulating in drugs. In addition, it can generate or increase of anticoagulant components. For example, during carbonizing of Sophora japonica, the content of rutin reduces constantly, but quercetin increases. The haemostatic effect of quercetin is closely related to change of active constituents in the process of carbonizing (Zhu and Li 2018). In a study on contents of saccharic acid in cockscombs before and after carbonizing, it was found that contents of saccharic acid in 10 groups of carbonizd cockscombs were higher. However, no saccharic acid was detected before carbonizing. Hence, the glucoside was generated by transformation caused by high heat (Bao et al. 2011). Ginger is an important TCM with the reported efficacy of arthritis, rheumatism, sprains, muscular aches, pains, sore throats, cramps, constipation, indigestion, vomiting, hypertension, dementia, fever, infectious diseases and helminthiasis (Aktan et al. 2006; Al-Amin et al. 2006; Amin and Hamza 2006). Different processing methods can produce different processed gingers with dissimilar chemical constituents and pharmacological activities (Ali et al. 2008; Marx et al. 2013).
Metabolism of metofluthrin in rats: II. Excretion, distribution and amount of metabolites
Published in Xenobiotica, 2018
Jun Abe, Yoshitaka Tomigahara, Hirokazu Tarui, Hirohisa Nagahori, Motohiro Kurosawa, Kenji Sugimoto, Naohiko Isobe
In the excretion study, since more than 95% of the excreted 14 C was contained in the samples by 48 h after administration, urine, bile and faecal homogenate samples collected by 48 hr were analysed for metabolites in all groups. In the tissue distribution study, samples of plasma and homogenates of liver and kidney (in 5-fold weight of water) at the last sampling point (i.e. 168 h) were also analysed for metabolites. The samples of the animals in each dose group were combined, and then applied to the further extraction and/or analysis. Urine and bile were directly applied to TLC plates. However, before TLC analysis, plasma was extracted three times with methanol and then concentrated, and faecal, liver, and kidney homogenates were extracted three times with methanol, three times with methanol/water (1:1, v/v) and then concentrated. To confirm that they were glucuronides, some polar metabolites were isolated and incubated with β-glucuronidase (from bovine liver, Type B-1, Sigma Aldrich, St. Louis, MO) in 0.2 M acetate buffer (pH 5.0) or in 0.2 M phosphate buffer (pH 7.4, to inhibit the sulfatase activity) at 37°C for approximately 16 h with or without D-saccharic acid 1,4-lactone (β-glucuronidase inhibitor, Sigma Aldrich) before being applied to TLC plates.