Chem. Pharm. Bull. 53(3) 305—308 (2005)

east of China. It has long been used as a traditional crude drug for the treatment of bronchial asthma and chronic bronchitis. Previous investigations of the whole plants of E. lanulata have yielded kaempferol, quercetin, kaempferol 3-O-Lrhamnoside, quercetin 3-O-L-rhamnoside, 6,7-dihydroxycoumarin and maoyancaosu. More than 30 types of cytokines and growth factors have been identified as ligands to date. Recently, those genes were cloned one after another, yielding recombinant genes. However, only very few of the peptides and proteins made in this way are used as drugs. The reasons such peptides are hard to utilize as medicines are: metabolization, absorption, neutralization antibody, side effects, etc. Screening of low molecular compounds mimicking a ligand of protein is carried out to solve these problems. However, conventional screening methods derive from ligand competent cells and require tracking of the signal after ligands bind to receptors, but signal detection is not easy. We earlier developed a high-throughput, cell proliferationbased screening assay using the human granulocyte colony stimulating factor (G-CSF)-, erythropoietin (EPO)-, thrombopoietin (TPO)-, interleukin-10 (IL-10)and insulin-dependent cell lines (BAF/GCSFR, BAF/EPOR, BAF/TPOR, BAF/IL10R and BAF/InsR) to identify low molecular compounds that mimic human ligands. These cell lines were originally derived from a mouse interleukin-3 (mIL-3)-dependent cell line, BAF/B03. The BAF/GCSFR, BAF/EPOR, BAF/TPOR, BAF/IL10R and BAF/InsR cells proliferate in response to the corresponding ligand or rmIL-3, and undergo apoptosis when deprived of these growth factors. In the present study, we searched for compounds that mimic human ligands by using this screening method jointly with a process for purification of EL extract. We discovered that EL showed proliferation activity for BAF/InsR and BAF/IL10R. Therefore, analysis of EL was undertaken to identify the active compounds. Here we describe the isolation and structure elucidation of one new flavonoid galactoside, quercetin 3-O-(2 ,3 -digalloyl)-b-Dgalactopyranoside (1), and four known ones, quercetin 3-O(2 -galloyl)-b-D-galactopyranoside (2), hyperin (3), quercetin (4), and gallic acid (5) as well as their ligand-like activities.