ABSTRACT
<p><b>OBJECTIVE</b>To study the chemical changes of salvianolic acid B and lithospermic acid of Salvia miltiorrhiza under the conditions of high temperature and high pressure and explore the reaction mechanism.</p><p><b>METHOD</b>S. miltiorrhiza extracts, salvianolic acid B and lithospermic acid were put in the reactor under the conditions of high temperature and high pressure (120 degrees C, 0.2 MPa), and the chemical changes and stability was studied.</p><p><b>RESULT</b>Salvianolic acid A was the primary product in salvianolic acid B and lithospermic acid's conversion process, and lithospermic acid was an intermediate in the conversion process of salvianolic acid B. Compared with salvianolic acid B, lithospermic acid could convert into more salvianolic acid A and fewer other products in the same conditions. Salvianolic acid A was not stable under the conditions of high temperature and high pressure, and could sequentially convert into other small molecules.</p><p><b>CONCLUSION</b>Referring to the chemical conversion of salvianolic acid B and lithospermic acid, a method of large-scale preparation of salvianolic acid A can be developed.</p>