An LC-MS/MS method for the determination of salidroside and its metabolite p-tyrosol in rat liver tissues

Salidroside and its metabolite p-tyrosol are two major phenols in the genus Rhodiola L. (Crassulaceae). They have been confirmed to possess various pharmacological properties and are used for the prophylaxis and therapeutics of many diseases. Several analytical methods have been developed for the determination of the two compounds in plant materials and biological plasma matrices. However, these methods are not optimal for biological samples containing complex organic interferences, such as liver and brain tissues.

This study aimed to further develop and validate a simple and specific LC-MS/MS method for the determination of salidroside and its metabolite p-tyrosol in rat liver tissues using paracetamol as the internal standard (IS).

Salidroside and p-tyrosol with the IS paracetamol and liver tissues were used as model compounds and biological samples. Samples were processed by protein precipitation (PP) with methanol, the supernatant was dried under nitrogen and the residue was reconstituted in a mobile phase that consisted of a mixture of acetonitrile and water (1:9, v/v). Salidroside and p-tyrosol were detected in negative mode under multiple reaction monitoring (MRM) by a triple quadrupole tandem mass spectrometer coupled with electrospray ionization.

Standard curves were linear over the concentration range of 50-2000 ng/mL with correlation coefficients of 0.995 or better for both salidroside and p-tyrosol. The intra- and inter-day accuracy for salidroside ranged between 104.90 and 112.73% with a precision of 3.51-14.27%. For p-tyrosol, the intra- and inter-day accuracy was between 92.38 and 100.59%, and the precision was 8.54% or less. The stability data showed that no significant degradation occurred under the experimental conditions. The recoveries were 111.44, 108.10, and 102.00% for salidroside at concentrations of 50, 500 and 2000 ng/mL, respectively, and were 105.44, 105.50, and 113.04% for tyrosol at concentrations of 50, 500 and 2000 ng/mL, respectively. The matrix effects were 83.85-92.45% for salidroside and 85.61-92.49% for p-tyrosol at three QC levels. This method was successfully applied to a liver tissue distribution study of salidroside and its metabolite p-tyrosol in rats.

This newly established method is validated as simple, reliable and accurate. It can be used as a valid analytical method for the intrinsic quality control of biological matrices, especially tissue samples.