Ruizao Yi

Comparative evaluation of the radical-scavenging activities of fucoxanthin and its stereoisomers.

Fucoxanthin (Fuco) is a characteristic carotenoid of brown seaweeds. In the present study, Fuco and its stereoisomers 9Z-Fuco, 13Z- and 13Z-Fuco were extracted from Laminaria japonica Aresch. They were isolated and purified by silica gel column chromatography, Sephadex LH-20, and reversed-phase HPLC. The radical-scavenging activities of the three stereoisomers were evaluated toward 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, 2-2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical, hydroxyl radical, and superoxide radical. The order of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity was 13Z- and 13Z-Fuco > (all-E)-Fuco > 9Z-Fuco. The order of 2-2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and hydroxyl radical-scavenging activities were 9Z-Fuco > (all-E)-Fuco > 13Z-and 13Z-Fuco. The order of superoxide radical-scavenging activity was 13Z- and 13Z-Fuco > (all-E)-Fuco > 9Z-Fuco. The scavenging activities of Fuco and its stereoisomers toward the four radical types were all dose-dependent. The ABTS, DPPH, and superoxide radical-scavenging activities were all weaker than that of tocopherol (VE), while their hydroxyl radical-scavenging activities were stronger than that of VE. The results confirmed that Fuco and its stereoisomers have potent antioxidant activities.

A Study of 11-[3H]-Tetrodotoxin Absorption, Distribution, Metabolism and Excretion (ADME) in Adult Sprague-Dawley Rats

Tetrodotoxin (TTX) is a powerful sodium channel blocker that in low doses can safely relieve severe pain. Studying the absorption, distribution, metabolism and excretion (ADME) of TTX is challenging given the extremely low lethal dose. We conducted radiolabeled ADME studies in Sprague-Dawley rats. After a single dose of 6 μg/(16 μCi/kg) 11-[3H]TTX, pharmacokinetics of plasma total radioactivity were similar in male and female rats. Maximum radioactivity (5.56 ng Eq./mL) was reached in 10 min. [3H]TTX was below detection in plasma after 24 h. The area under the curve from 0 to 8 h was 5.89 h·ng Eq./mL; mean residence time was 1.62 h and t½ was 2.31 h. Bile secretion accounted for 0.43% and approximately 51% of the dose was recovered in the urine, the predominant route of elimination. Approximately 69% was recovered, suggesting that hydrogen tritium exchange in rats produced tritiated water excreted in breath and saliva. Average total radioactivity in the stomach, lungs, kidney and intestines was higher than plasma concentrations. Metabolite analysis of plasma, urine and feces samples demonstrated oxidized TTX, the only identified metabolite. In conclusion, TTX was rapidly absorbed and excreted in rats, a standard preclinical model used to guide the design of clinical trials.

Simultaneous Determination of Fucoxanthin and Its Deacetylated Metabolite Fucoxanthinol in Rat Plasma by Liquid Chromatography-Tandem Mass Spectrometry

Fucoxanthin and its deacetylated metabolite fucoxanthinol are two major carotenoids that have been confirmed to possess various pharmacological properties. In the present study, fucoxanthinol was identified as the deacetylated metabolite of fucoxanthin, after intravenous (i.v.) and intragastric gavage (i.g.) administration to rats at doses of 2 and 65 mg/kg, respectively, by liquid chromatography-tandem mass spectrometric (LC-MS/MS) analysis. Next, an accurate and precise LC-MS/MS method was developed to quantitatively determine fucoxanthin and fucoxanthinol in rat plasma. Plasma samples were resolved by LC-MS/MS on a reverse-phase SB-C18 column that was equilibrated and eluted with acetonitrile (A)/aqueous 0.1% formic acid (B; 92/8, v/v) at a flow rate of 0.5 mL/min. Analytes were monitored by multiple-reaction monitoring (MRM) under positive electrospray ionization mode. The precursor/product transitions (m/z) were 659.3→109.0 for fucoxanthin, 617.2→109.0 for fucoxanthinol, and 429.4→313.2 for the internal standard (IS). Calibration curves for fucoxanthin and fucoxanthinol were linear over concentrations ranging from 1.53 to 720 and 1.17 to 600 ng/mL, respectively. The inter- and intraday accuracy and precision were within ±15%. The method was applied successfully in a pharmacokinetic study and the resulting oral fucoxanthin bioavailability calculated.

Rapid Determination of Tetrodotoxin in Human Plasma by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry

A sensitive analytical method was developed to determine tetrodotoxin(TTX) in human plasma samples using protein precipitation, followed by ultra performance liquid chromatography(UPLC) analysis coupled with tandem mass spectrometry(MS/MS) using 11-deoxytetrodotoxin(11-deoxyTTX) as an internal standard. The plasma samples were prepared using protein precipitation prior to being analyzed by UPLC-MS/MS to identify TTX over a zwitterionic-hydrophilic interaction liquid chromatography column. The retention time values of TTX and 11-deoxyTTX were 4.12 and 3.67 min, respectively. TTX and 11-deoxyTTX were monitored and quantitated on the basis of their ion transitions for their respective precursor ions to their product ions(i.e., m/z 320.0→162.1 for TTX and m/z 304.0→176.0 for 11-deoxyTTX) in the multiple reaction-monitoring mode. The lower limit of quantification of this method was determined to be 0.0199 ng/mL. This method showed good linearity for plasma samples that contained TTX concentrations in the range of 0.0199—1.99 ng/mL. The specificity, precision, accuracy, matrix effect, and stability characteristics of this method were also examined. The intra-assay precision and accuracy ranged from 1.89% to 6.00% and from 92.21% to 100.00%, whereas the inter-assay precision and accuracy ranged from 0.64% to 7.75% and from 99.38% to 101.26%, respectively. This new method therefore represents a rapid, accurate, reliable, and highly sensitive method for the qualitative and quantitative analyses of a trace amount of TTX in human plasma samples.

Determination of trehalose by ion chromatography and its application to a pharmacokinetic study in rats after intramuscular injection

An ion chromatography method was established for detecting trehalose in rat plasma. The samples were analyzed using a CPMA1 column (250u2009×u20094.0u2009mm, Thermo) with 120 mm NaOH as eluent at a flow rate of 0.7u2009mL/min. The standard curve was yu2009=u20091.4316xu2009-u20090.0654 (Ru2009=u20090.9992), and the linear range was 0.2-10u2009mg/L. The relative standard deviations of within-run and between-run precisions at low, medium and high concentrations were within 0.96-8.33%, and the accuracy was within 80.09-114.99%. The method was verified by rigorous methods, and applied to a pharmacokinetic study in rats after intramuscular injection (20 mg/kg, nu2009=u20096). The pharmacokinetic parameters, specifically AUC0-t , AUC0-∞ , t1/2 , CL and Vd , were 15.542u2009±u20093.122u2009mg h/L, 15.599u2009±u20093.141u2009mg h/L, 0.73u2009±u20090.347u2009h, 1.331u2009±u20090.293u2009L/h kg and 1.403u2009±u20090.735u2009L/kg, respectively. The developed ion chromatography method met the requirements of biological sample measurement, and will be helpful for future pharmacological studies of trehalose.

Diisopropyl [(4-meth­oxy­benzamido)(p-tol­yl)meth­yl]phospho­nate

The asymmetric unit of the title compound, C22H30NO5P, contains two independent molecules in which the dihedral angles between the benzene rings are 82.0u2005(2) and 78.4u2005(2)°. In the crystal, each molecule forms an inversion dimer via a pair of N—H⋯O(=P) hydrogen bonds.