Chemical conversions of salvianolic acid B by decoction in aqueous solution

Salvianolic acid B (Sal B) is the most abundant phenolic compound in Salvia miltiorrhiza, which has been widely used for the treatment of cardiovascular diseases in Oriental medicine. To elucidate structure of the converted compounds of Sal B by decoction in aqueous solution, Sal B (200 mg) was decocted in an aqueous solution (200 mL) at pH 4.9 and the decocted solution was purified by Sephadex LH-20 column chromatography and preparative HPLC. The 13 converted compounds were isolated and the chemical structures were determined by NMR and MS. In addition to the 4 compounds previously reported as conversion products of Sal B by decoction, 9 compounds were first reported with the complete structure of compounds isolated from decocted Sal B solution and three of the compounds were determined to be novel compounds. In addition, a conversion mechanism of compounds converted by decoction was proposed on the basis of kinetics studies, which reasonably supported the conversion mechanism of Sal B. The 13 compounds seemed to be produced by the hydrolysis of an ester bond, decarboxylation, retro oxa-Michael reaction, hydration, and radical reaction during decoction in aqueous solution.