Quantification of isoflavone glycosides and aglycones in rat plasma by LC-MS/MS: Troubleshooting of interference from food and its application to pharmacokinetic study of Semen Sojae Praeparatum extract

The isoflavones widely exist in the daily diets and interferences are usually inevitable in the determination of the in vivo level of the same analytes. A new strategy to eliminate the dietary interference was established to evaluate the exposure of isoflavones including daidzin, glycitin, genistin, daidzein, glycitein, and genistein in rats fed with Semen Sojae Praeparatum (SSP) extract. Plasma samples were pretreated by liquid-liquid extraction with ethyl acetate using quercetin as the internal standard (IS). The chromatographic separation was achieved on a Symmetry C18 column (100 mm × 3.0 mm) using a gradient mobile phase consisting of acetonitril and water (containing 0.1% formic acid) with a run time of 13.0 min at a flow rate of 0.4ml/min. The detection was carried out by a triple-quadrupole tandem mass spectrometer in multiple reaction monitoring (MRM) mode via polarity switching between negative (for and positive (for daidzin glycitin) ionization mode. All calibration curves exhibited good linearity (r> 0.99) over a wide concentration range for all components. The lower limit of quantitation (LLOQ) was in the range of 0.1-0.4 ng/ml. The intra-day and inter-day precisions (RSD) at three different levels were both less than 14.9% and the accuracies (RE) ranged from -9.3% to 14.5%. The extraction recoveries of the analytes and the IS ranged from 85.7% to 100.2%. The validated method was first successfully applied to pharmacokinetic study of the six isoflavones in rat plasma after oral administration of SSP extract. The dynamic baseline levels of six isoflavones in blank plasma from rats consuming food containing dietary isoflavones were measured for the correction of the plasma concentrations. The principle pharmacokinetic parameters were calculated from rats with or without regular commercial food, and found to be altered by the dietary food containing some isoflavones.

Evidence supporting the conceptual framework of cancer chemoprevention in canines

As with human beings, dogs suffer from the consequences of cancer. We investigated the potential of a formulation comprised of resveratrol, ellagic acid, genistein, curcumin and quercetin to modulate biomarkers indicative of disease prevention. Dog biscuits were evaluated for palatability and ability to deliver the chemopreventive agents. The extent of endogenous DNA damage in peripheral blood lymphocytes from dogs given the dietary supplement or placebo showed no change. However, H₂O₂-inducible DNA damage was significantly decreased after consumption of the supplement. The expression of 11 of 84 genes related to oxidative stress was altered. Hematological parameters remained in the reference range. The concept of chemoprevention for the explicit benefit of the canine is compelling since dogs are an important part of our culture. Our results establish a proof-of-principle and provide a framework for improving the health and well-being of “man’s best friend”.

Sample preparation for liquid chromatographic analysis of phytochemicals in biological fluids

INTRODUCTION

Natural products have been used traditionally for the treatment and prevention of diseases for thousands of years and are nowadays consumed as dietary supplements and herbal medicine. To ensure the safe and effective use of these herbal products, information about bioavailability of active compounds in plasma or target tissues should be provided via validated analytical methods combined with appropriate sampling methods.

OBJECTIVE

To provide comprehensive and abridged information about sample preparation methods for the quantification of phytochemicals in biological samples using liquid chromatography analysis.

METHODS

Sample pre-treatment procedures used in analytical methods for in vivo pharmacokinetic studies of natural compounds or herbal medicines were reviewed. These were categorised according to the biological matrices (plasma, bile, urine, faeces and tissues) and sample clean-up processes (protein precipitation, liquid-liquid extraction and solid-phase extraction).

RESULTS

Although various kinds of sample pre-treatment methods have been developed, liquid-liquid extraction is still widely used and solid-phase extraction is becoming increasingly popular because of its efficiency for extensive clean up of complex matrix samples. However, protein precipitation is still favoured due to its simplicity.

CONCLUSION

Sample treatment for phytochemical analysis in biological fluids is an indispensable and critical step to obtain high quality results. This step could dominate the overall analytical process because both the duration of the process as well as the reliability of the data depend in large part on its efficiency. Thus, special attention should be given to the choice of a proper sample treatment method that targets analytes and their biomatrix.