Weichao Ren

Rapid identification of primary constituents in parotoid gland secretions of the Australian cane toad using HPLC/MS‐Q‐TOF

Toad parotoid gland secretion or toad venom has in recent years been increasingly shown to possess potentially beneficial pharmacological effects; this speculation has drawn much interest centred on elucidating the chemical basis of its multimodal effects. For this purpose, we explored the use of a rapid and accurate analysis method for systemic investigation of the parotoid gland chemistry, when extracted from Australian cane toads. Full-scan data of cane toad venom extract was acquired using high-performance liquid chromatography coupled with a hybrid quadrupole-time of flight mass spectrometry system (HPLC/MS-Q-TOF), with multiple ionization sources (ESI and APCI) in positive and negative mixed modes. By measuring the exact mass differences between the theoretical and measured mass of each assumed compound, we confirmed the presence of 12 key constituents. The present results demonstrate that the use of HPLC/MS-Q-TOF with multiple ionization sources delivers exemplary selectivity and sensitivity, allowing for the rapid and accurate identification of constituents within cane toad venom. This paves the way for this technique to be used in future routine screening of components within the genus Bufo and for key analytes too, then reliably assessed for any purported beneficial (clinic) properties.

Determination of Glycyrrhizin in Dog Plasma by Liquid Chromatography—Mass Spectrometry and its Application in Pharmacokinetic Studies

A sensitive liquid chromatography–electrospray ionization–mass spectrometry (LC-ESI-MS) method was established and validated for the determination of glycyrrhizin in dog plasma. After treatment with methanol to precipitate proteins, plasma samples were analyzed on a reversed-phase C18 (ODS) column with a mobile phase of methanol:1% formic acid solution (75:25, v/v). MS determination was performed using negative electrospray ionization (negative ESI) in the selected ion monitoring mode. Glycyrrhizin was monitored at the m/z 821 channel and the internal standard (gliquidone) at the m/z 526 channel. The calibration curve was linear over the range from 0.05 μg mL−1 to 10 μg mL−1 with a correlation coefficient above 0.99. This method was successfully applied to the pharmacokinetic studies in beagle dogs. The absolute bioavailability of glycyrrhizin in beagle dogs was 3.24%.

The Potential Drug–Drug Interactions of Ginkgolide B Mediated by Renal Transporters

Ginkgolide B (GB) is a selective and strong antagonist of platelet‐activating factor with great benefits in CNS diseases treatment. The renal excretion constitutes the predominant secretory pathway of GB. Here, we investigated the potential role of renal drug transporters in GB urinary excretion. The intravenous administration of GB was conducted at 10 min post‐administration of probenecid (potential inhibitor of organic anion transporters/organic anion transporting polypeptides) or bromosulfophthalein (traditional inhibitor of multi‐drug resistance proteins) in rats. Pretreated with probenecid, the systemic exposure of GB was significantly elevated from 8.319 ± 1.646 to 14.75 ± 1.328 µg · mL−1∙h but with reduced total clearance from 1.17 ± 0.331 to 0.596 ± 0.0573 L · h−1∙kg−1 accompanying no changes in plasma elimination half‐lives compared with control group. With no pronounced effect on metabolic elimination, the decreased total clearance was closely pertained to the reduced renal excretion, indicating the potential effect of organic anion transporters and/or organic anion transporting polypeptides in renal secretory of GB from blood to urine. However, the possible effect of bromosulfophthalein was restricted within a minor extent, suggesting the mild role of multi‐drug resistance protein in GB renal excretion. Copyright

Biliary excretion of glycyrrhetinic acid: glucuronide-conjugate determination following a pharmacokinetic study of rat bile

Liquorice is a commonly prescribed herb in traditional Chinese medicine with the primary constituent, glycyrrhetinic acid (GA) responsible for the toxic effects arising from its chronic consumption. Hepatic transformation and biliary excretion of GA are significant and well‐documented pharmacokinetic pathways in humans, while glucuronide conjugates are the major identified metabolites. Here we report the role of bile in GA bioconversion in rats; this being achieved following intravenous administration of GA to Sprague–Dawley rats at a dose of 2 mg/kg with bile fluid analyzed for 3 h post‐injection using HPLC. The maximum concentration of glucuronides was detected about 30 min post‐administration, while the cumulative biliary excretion of glucuronides after 3 h was found to be 63.6 ± 6.4%. Our findings indicate a relatively high rate of biliary excretion for GA via the formation of glucuronide conjugates, and as a result of these findings, glucuronidation can be firmly regarded as a primary detoxification pathway for GA in rats. Copyright