The experimental study of Cortex Eucommiae on meridian tropsim: The distribution study of aucubin in rat tissues

Meridian tropism (MT) theory is a core principle of traditional Chinese medicine (TCM) theories and plays an essential role in instructing clinical pharmacy. The scientific explanation of MT theory will certainly further promote the reasonable, effective application of TCM. In view of the MT of Cortex Eucommiae (CE), aucubin (AU), the effective component of CE, was appointed and observed its distribution in rat tissues following a single intravenous (i.v.) dose. A simple, inexpensive and accurate high-performance liquid chromatographic (HPLC) method was developed and validated for the determination of AU in rat tissues. Acceptable intra-day and inter-day precision and accuracy at high, medium and low concentration ranged from 0.56% to 4.18% and 0.73% to 4.53%, respectively. Good assay and extraction recoveries were obtained with a single and relatively fast precipitation protein step. The mean assay recovery and extraction recovery of AU were 94.7% and 90.9%, respectively. All tissues reached maximum AU level at 5 min post-dose. Considerable AU was present in kidney and liver. AU concentration was highest in kidney and remained much higher than that in other tissues over the experiment course. Lung, heart, spleen and testis were also detected to contain AU. The results closely conformed to the MT of CE and clearly demonstrated that AU was one of the material bases of the MT of CE.