In our investigation of a cell proliferation-based screening assay using human ligand-dependent cell lines for medicinal herbal extracts, the acetone extract of the whole plants of Euphorbia lunulata (EL) was observed for its proliferation activity for insulin- and interleukin-10 (IL-10)-dependent cell lines. Fractionation of the active extract led to the isolation of one new flavonoid galactoside, quercetin 3-O-(2'',3''-digalloyl)-beta-D-galactopyranoside (1), and four known ones, quercetin 3-O-(2''-galloyl)-beta-D-galactopyranoside (2), hyperin (3), quercetin (4), and gallic acid (5). Compounds 1 and 2 showed insulin-like activity. Compounds 4 and 5 showed IL-10-like activity. This is the first report of these activities of EL, and 1 and 2 will become the seed compounds for the development of a nonpeptidyl insulin substitutional medicine. Compounds 4 and 5 support the pharmacological use of EL, which has been employed as an herbal medicine for the treatment of bronchial asthma.