ABSTRACT
<p><b>OBJECTIVE</b>The traditional decoction method of Dachengqi Tang is that "First boiling Magnolia officinalis and Citrus aurantium with a pipeful of water, taking out five litres from the decoction, removing residues, adding rheum officinale, boiling again, taking out two litres from it, removing residues, adding mirabilite, boiling it with low fire". According to it, residues of M. officinalis and C. aurantium should be removed after decocting. This essay aims to study the content of anthraquinones, in order to proof whether the removal of residues of M. officinalis and C. aurantium is scientific.</p><p><b>METHOD</b>The traditional method was adopted to prepare Dachengqi Tang. Decoction A (original method) was obtained by removing residues of M. officinalis and C. aurantium, whereas decoction B was obtained without removing residues of M. officinalis and C. aurantium. The content of anthraquinones of both methods was determined with HPLC.</p><p><b>RESULT</b>The content of both combined and free anthraquinones in decoction A was higher than that of decoction B. The content of total anthraquinones in residues of decoction A was lower than that of residue B.</p><p><b>CONCLUSION</b>The traditional decoction method of removing residues of M. officinalis and C. aurantium from Dachengqi Tang is scientific, because it improves the dissolution rate of effective ingredients, which provides a theoretical basis for effective substances of the drug.</p>