Antitumor activity of xanthanolides from Xanthium italicum Moretti

The genus Xanthium (Asteraceae) is represented by limited number of species, which are distributed in all parts of the world. Some species were used in the traditional medicine for the treatment of basal cell carcinoma and different cancers and cold tumors.[1,2] In the course of our screening program for antiproliferative compounds in Asteraceae family found in Central and East Europe, extracts of X. italicum were evaluated. High cytotoxic activity was recorded for the lipophylic extract, thus this species was selected for bioassay-guided fractionation in order to identify the compounds responsible for the cytotoxic effect.

X. italicum, a widespread common wead in South and Central Europe, was collected in various stage of vegetation. Different parts of the dried plant (radix, flower, stem and leaf) were extracted with methanol. The extracts were concentrated in vacuo, and then subjected to liquid-liquid partition with n-hexane and chloroform. The cytotoxic effects of the extracts were investigated on HeLa (cervix epithelial adenocarcinoma), A431 (skin epidermoid carcinoma) and MCF7 (breast epithelial adenocarcinoma) cell lines using the MTT assay. The most active n-hexane fraction of the leaves was separated by VLC, preparative TLC, HPLC and CPC with guidance of cytotoxic assay affording five compounds. The structures were established by means of NMR spectroscopy (¹H-NMR, JMOD, ¹H,¹H-COSY, NOESY, HSQC and HMBC) as xanthanolide-type sesquiterpene lactones. The cytotoxic assay on the three human cell lines demonstrated that the isolated xanthanolides possess remarkable cell growth inhibitory activity comparable to that of the positive control cisplatin.

References: [1] Hartwell, J. (1968) J Nat Prod 31: 71–170. [2] Saxena, V.K., Mondal, S.K. (1994) Phytochemistry 35: 1080–1082