Two new sucrose cinnamates(1 and 2) along with nine known compounds(3-11) were isolated from ethanol extract of Polygonum lapathifolium var. salicifolium by silica gel column chromatography, ODS column chromatography and semi-preparative HPLC. Their structures were elucidated by extensive spectroscopic methods including 1 D-and 2 D-NMR experiments, as well as HR-ESI-MS analysis. Eleven compounds(7 sucrose cinnamates, 3 phenylpropanoids and 1 lactone) were obtained and their structures were identified as(1,3-O-di-p-coumaroyl)-β-D-fructofuranosyl-(2→1)-α-D-glucopyranoside(1),(1,3-O-di-p-coumaroyl)-β-D-fructofuranosyl-(2→1)-(6-O-acetyl)-α-D-glucopyranoside(2),(3-O-feruloyl)-β-D-fructofuranosyl-(2→1)-(6-O-p-coumaroyl)-α-D-glucopyranoside(3), hydropiperoside(4), vanicoside C(5),(1,3-O-di-p-coumaroyl)-β-D-fructofuranosyl-(2→1)-(6-O-feruloyl)-α-D-glucopyranoside(6), vanicoside B(7),trans-p-hydroxycinnamic acid methyl ester(8), trans-p-hydroxycinnamic acid ethyl ester(9), methyl ferulate(10) and dimethoxydimethylphthalide(11), respectively. Compounds 1 and 2 were two new sucrose cinnamates, and compounds 1-11 were isolated from this plant for the first time. The antioxidant activities of the isolated compounds 1-9 were investigated by an oxygen radical absorbance capacity(ORAC) assay, and all nine compounds were found to show strong antioxidant activities. Among them, compound 6(10 μmol·L~(-1)) was the supreme one in antioxidant activities, with its ORAC value equivalent to(1.60±0.05) times of 50 μmol·L~(-1) Trolox.
Keywords: Polygonum lapathifolium var.salicifolium; antioxidant activity; chemical constituent; sucrose cinnamates.