A Sensitive HPLC-MS/MS Analysis of Dencichine in Rat Plasma and Its Application to Pharmacokinetics

In order to quantitate dencichine in biological samples, a selective and sensitive method for the determination of dencichine in rat plasma based on high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed and validated. (l)-2-amino-3-(carboxymethylthio)propionic acid was used as the internal standard (I.S.). After a protein precipitation extraction with acetonitrile, dencichine and the I.S. were chromatographed on an Xterra MS-C18 column. The mobile phase was consisted of 20mmol/L ammonium acetate solution-acetonitrile (35:65, V/V) at a flow rate of 0.2 mL/min. The detection was performed on a triple quadrupole mass via electrospray ionization (ESI) source in the positive mode. The intra- and inter-day precision (relative standard deviation, R.S.D.) values of dencichine were below 6.7%. The extraction recoveries were up 85%. The lower limit of quantification was 20 ng/ml, which was sensitive enough to detect the analyte. The HPLC-MS/MS method was successfully applied to the pharmacokinetic study after an intravenous administration of dencichine in Sprague-Dawley (SD) rat.

An ultrasonic-ionic liquid process for the efficient acid catalyzed hydrolysis of feather keratin

A novel efficient method for hydrolyzing feather keratin using an ultrasonic-ionic liquid coupling process has been developed, with reaction conditions optimized using response surface analysis of data obtained from single factor optimization studies. Ultrasonic irradiation(225 W power) of feathers in 8.4 mol·L^(-1) hydrochloric acid containing 1-butyl-3-methylimidazolium chloride as a cosolvent at 80 °C for 1.4 h, followed by heating at 110 °C for 8.3 h, resulted in hydrolysis of their keratin component in an excellent 83.1% yield. Compared with previous methods, this new method employs reduced amounts of hydrochloric acid, shorter reaction time, and affords amino acid hydrolysis products in higher yield.

Synthesis of Vitamin E Succinate from Candida rugosa Lipase in Organic Medium

A screening of commercially available lipases for the synthesis of vitamin E succinate showed that lipase from Candida rugosa presented the highest yield. The synthesis of vitamin E succinate in organic solvents with dif- ferent lgP values ranging from -1.3 to 3.5 was investigated. Of particular interest was that dimethyl sulfoxide （DMSO） with the lowest lgP exhibited the highest yield among all the organic solvents used. It suggests that lgP is incapable of satisfactorily predicting the biocompatibility of organic solvents due to the complexity of enzymatic reaction with hydrophilic and hydrophobic substrates in organic solvent. Effects of different operating conditions, such as molar ratio of substrate, enzyme concentration, reaction temperature, mass transfer, and reaction time were also studied. Under the optimum conditions of 10 g/L enzyme, a stirring rate of 100 r/min, a substrate molar ratio of 5：1 at 55℃ for 18 h, a satisfactory yield（46.95%） was obtained. The developed method has a potential to be used for efficient enzymatic production of vitamin E succinate.