New phenylethanoid glycosides and sugar esters from ku-ding-cha, a herbal tea produced from Ligustrum purpurascens

Ku-Ding-Cha is a kind of herbal tea used commonly in China for its effects on hypertension, fatness, inflammation, and diuresis. The chlorophyll removal fraction from 60% aqueous acetone extract of Ku-Ding-Cha produced from the leaves of Ligustrum purpurascens (Oleaceae) exhibited observable antioxidant activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay (SC50 = 45 microg/mL). Further detailed phytochemical investigation on this fraction led to the isolation of 2 new phenylethanoid glycosides, ligupurpurosides C-D (1 and 2), and 2 new sugar esters, ligupurpurosides E-F (3 and 4), together with 15 known compounds (5 to 19). All of them, except for 7, 8, 9, 11, and 12, were isolated from Ku-Ding-Cha and its original plants for the first time. The chemical structures were elucidated based on the analysis of spectroscopic data, including 1D, 2D NMR, and FABMS. In addition, the isolated compounds were evaluated for their antioxidant activities by DPPH assay.