Magnesium tanshinoate B (MTB) inhibits low density lipoprotein oxidation

Danshen, a Chinese herbal medicine has been widely used for the treatment of cardiovascular diseases. Magnesium tanshinoate B (MTB) is an active compound purified from Danshen. The objective of this study was to investigate the effect of MTB on the susceptibility of low density lipoproteins (LDL) to oxidative modification as well as on the accumulation of lipids in THP-1 derived macrophages. Aliquots of LDL were incubated with copper sulfate in the absence or presence of MTB. The degrees of oxidative modification of LDL were assessed by examining the relative gel electrophoretic mobility, by measuring the amount of thiobarbituric acid reactive substances (TBARS), and by continuous monitoring of the formation of conjugated dienes upon the increase in absorbency at 234 nm. MTB at concentrations of 1-10 microM significantly inhibited oxidative modification of LDL. Such inhibitory effect resulted in a decrease in the uptake of LDL by THP-1 derived macrophages. Taken together, these results clearly demonstrate that MTB inhibits oxidative modification of LDL and hence prevents the uptake of LDL by cultured macrophages. Such effect may be therapeutically relevant in protecting cells from lipid peroxidation in vascular disorders.