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Tumor blood vessels are an important emerging target for anti-cancer therapy. The antimitotic agent combretastatin A-4 (CA- 4), a cis-stilbene natural product isolated from the South African tree Combretum caffrum Kuntze, is the lead compound of a new class of anti-cancer drugs that target tumor vasculature. CA-4 inhibits tubulin polymerization by interacting at the colchicine binding site on tubulin. This alters the morphology of endothelial cells and causes vascular shutdown and regression of tumor vasculature. Some tubulin-binding vascular-disrupting agents (VDAs) are currently in clinical trials for cancer therapy. As a consequence of the potential favorable applications of these compounds, several analogs projected to induce rapid and selective vascular shutdown in tumors have been synthesized during the last few years. Many of these molecules have already been tested for their effects on tubulin polymerization as well as for their antiproliferative activity and other biological properties, and possible mechanisms of action have been investigated. The aim of the present review is to offer an overview of most recently developed combretastatin derivatives, focusing on biological effects exerted by these compounds. The published data about new analogs are presented and compared, and a detailed investigation of structure-activity relationships is described.

We have studied the cytotoxic activity of extracts and jacaranone from Senecio leucanthemifoliusPoiret. Extracts from S. leucanthemifoliuswere able to inhibit the in‐vitro proliferation of a series of human tumour cell lines. The dichloromethane extract demonstrated effective cytotoxic activity with an IC50 of 20.1 μg mL−1on the large cell carcinoma cell line COR‐L23. The ethyl acetate extract showed an IC50 value of 5.0 μg mL−1and the butanol extract an IC50 value of 6.4 μg mL−1on the same cell line. A major active constituent of the dichloromethane extract was shown to be jacaranone, which was demonstrated to have a very strong activity against all of the tumour cell lines with IC50 values between 2.86 and 3.85 μg mL−1, although it did not account for all the activity observed. Constituents of S. leucanthemifoliusextracts were identified by GC/MS analysis and NMR.

The isolation of (−)-arctiin (1) , arctigenin (2) , onopordopicrin (3) , kaempferide, eriodictyol, luteolin and stigmasterol from the aerial parts of Carduus micropterus ssp. perspinosus , is reported.