A New Caffeoyl Phenylethanoid Glycoside from the Unripe Fruits of Forsythia suspensa

AimTo study the chemical constituents on the unripe fruits of Forsythia suspensa (Thunb.) Vahl in order to find new or biologically active components.MethodsCompounds were isolated by repeated silica gel column and reversed-phase preparative high performance liquid chromatography. The structures were elucidated by spectroscopic methods, including 2D NMR and HRESIMS spectrometry as well as by comparison with published data. All the isolated compounds were examined for antibacterial activity against eight bacterial strains (Staphylococcus aureus, Escherichia coli, Beta-hemolytic streptococci, Bacterium vulgare, Aeruginosus bacillus, Micrococcus pneumoniae, S. albus and B. dysenteriae) in vitro by plate method.ResultsFive compounds were isolated from the unripe fruits of Forsythia suspensa, their structures were identified as phillygenin (1), (+)-isolariciresinol (2), phillyrin (3), forsythiaside (4) and lianqiaoxinside A (5, 3, 4-dihydroxy-β-phenethyl-O-α-L-rhamnopyranosyl-(1→6)-3-O-caffeoyl-β-D-glucopyranoside).ConclusionLianqiaoxinside A (5) is a new caffeoyl phenylethanoid glycoside, and the pharmacological screens eight bacterial strains in vitro disclosed that the principal antibacterial constituents from F. suspense were caffeyol phenylethanoid glycosides.