Effects of boiling-water extracts and 80% (v/v) ethanol extracts from Chinese medicinal herbs on the antiproliferation and differentiation
of human leukemic U937 cells were examined. Conditioned medium from peripheral blood monocytes (MNC-CM) stimulated with various levels (200-800 μg/mL) and types of herb extracts (MNC-CM mode) were used to screen the effective herbs. Results showed that among the herbs tested, MNC-CM from boiling-water extracts of Huang Gi (HG), Gan Cao (GC), Lian Zi (LZ), Da Zao (DZ), and Tang Shen (TS) showed remarkable (> 40%) growth inhibition on the U937 cells at high dosage, whereas mixtures of9 boiling-water extracts of tested herbs with culturing medium displayed insignificant results. Meanwhile, inferior inhibition on cell proliferation was observed when U937 cells were treated with ethanol extracts with MNC CM or conventional mode. Assays for cytoplasmic superoxide production (NBT reducing ability) by U937 cells induced by ethanol precipitates of boiling-water extracts (100-400 μg/mL) from LZ indicated a dose-dependent positive percentage (31-49%), revealing the apparent differentiation-inducing effect of MNC-CM on U937 cells.