New depsides from the roots of Salvia miltiorrhiza and their radical-scavenging capacity and protective effects against H2O2-induced H9c2 cells.

Phytochemical investigation of the roots of Salvia miltiorrhiza led to isolations of two new depsides (1-2), along with thirteen known compounds (3-15). Their structures and relative stereochemistry were elucidated by NMR spectral ((1)H and (13)C NMR, HSQC, HMBC), CD and HR-ESIMS data analyses. The absolute configuration of 1 was determined by comparison of the experimental and calculated ECD spectra. All the depsides (1-10) were found to exhibit stronger free radical scavenging capacity (ranging from 2.62 to 22.05μM) than diterpenoids (11-15, IC50>100μM), among which Salvianolic acid A and Salvianolic acid B were the most potent compounds. Additionally, most of depsides (1, 3, 5, 7, 8, 9, 10) possessed significant protective effects against H2O2-induced H9c2 apoptosis in low concentrations. The negative mode collision-induced dissociations of compound 1 and 2 were featured by the α-cleavage and β-cleavage to lose danshensu (198Da) and caffeic acid (180Da), respectively, while α,β-dihydroxybenzenes depsides (8-hydroxy) showed characteristic neutral elimination of H2O.