Effects of the aqueous extract of Salvia Miltiorrhiza (danshen) and its magnesium tanshinoate B-enriched form on blood pressure.

Danshen is the dried root and rhizome of the Chinese medicinal plant Salvia miltiorrhiza Bunge (Labiatae), which has been used to treat hypertension and myocardial infarction. One of its water-soluble active components is magnesium tanshinoate B (MTB). The present study examined and compared the cardiovascular effects of the water-soluble extract of danshen (SME) and its MTB-enriched form (containing 70% of MTB (MTB70)). Anaesthetized rats were infused intravenously with saline or phenylephrine to achieve a normal or elevated blood pressure, respectively. Different doses of SME, MTB70 or vehicle were then injected intravenously and their effect on blood pressure was monitored. The results indicate that SME and MTB70 reduce blood pressure dose-dependently. Independently of the initial blood pressure, SME caused a smaller reduction in blood pressure than MTB70. In rats infused with phenylephrine, MTB70 caused greater decreases in blood pressure than in rats infused with saline, while the responses to SME did not differ between the two groups. From these findings, it appears that MTB is one of the major components responsible for the cardiovascular effects of danshen, and that the beneficial cardiovascular effect of the extract is more prominent under conditions of elevated blood pressure.