In the course of searching for novel cytotoxic compounds which can be used in chemotherapy, several Traditional Chinese Medicines (TCM) have been screened by bioassay-guided fractionation and isolation.
METHODS AND RESULTS:
An extract of rhizomes of Iris tectorum Maxim., a TCM used to treat cancer, exhibited highest potency and led to the isolation of two flavonoids, 7-O-methylaromadendrin and tectorigenin, and four iridal-type triterpenes, iritectols A and B, Isoiridogermanal and iridobelamal A. The cytotoxicities of the isolated compounds against four human cancer cell lines were evaluated by the SRB assay. Iritectol B, Isoiridogermanal and iridobelamal A showed similar cytotoxicity with IG(50) around 11 microM and 23 microM against MCF-7 and C32 cell lines, respectively. Cell cycle-specific inhibition and apoptosis induced by the isolated compounds were determined using flow cytometry with two sets of co-labelling systems: annexin V-FITC/propidium iodide and fluorescein diacetate/propidium iodide. Iritectol B demonstrated dose-dependent apoptotic effect against COR-L23 cells with an apoptotic rate of 33% at 100 microM.
CONCLUSIONS:
Tectorigenin (an analogue of genistein) showed cell cycle specific inhibition and arrested cells at G(2)/M phase up to 400 microM, but did not demonstrate apoptotic effect against COR-L23 cells up to 1 mM. The overall activities of isolated compounds observed in the present study support the traditional use of Iris tectorum Maxim. in the treatment of cancer. |