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

Abstract

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 (1H and 13C 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.