← The ApothecaryCombretaceaestem wood and bark (source of combretastatins), leaves (screened in ethnoveterinary research)Fact-checked 24 October 2026

Significant riskCombretastatins are potent antimitotic (anti-tubulin) agents active at nanomolar concentrations. In trials the main limits of fosbretabulin were cardiovascular toxicity and limited specificity. No safety data were found for the plant itself; it is not a herbal remedy.In an emergency, call your local emergency number or poison centre.

Cape bushwillow

Combretum caffrum

Also calledEastern Cape bushwillow

In older monographsCombretum salicifolium, Dodonaea caffra

A South African tree, the Eastern Cape bushwillow, whose stem wood yielded the combretastatins, a family of compounds that bind tubulin and shut down blood flow inside tumours. The phosphate prodrug of combretastatin A-4 (fosbretabulin) went through more than 20 clinical trials and holds FDA orphan-drug designations, but has not been approved; it is a research drug, not a herbal remedy.

What it is used for

Cancer: drugs and supportive care
Limited
Combretastatin A-4 phosphate (fosbretabulin) and A-1 phosphate produced objective and stable responses in many tumour types across more than 20 trials, with confirmed cures reported in some patients with anaplastic thyroid cancer, but a phase II/III trial in anaplastic thyroid cancer was terminated and the drug has not succeeded in phase III; cardiovascular toxicity limits its use. The plant itself is not used as a cancer treatment.^1,2

Safety

Pregnancy: Contraindicated
Breastfeeding: Contraindicated
Children: Not for any home use.

Do not use if

Any home or self-treatment use; combretastatins are given only in oncology trials

Side effects

Cardiovascular toxicity, mostly acute haemodynamic changes shortly after infusion (fosbretabulin)
Severe but reversible cardiac toxicity when combined with pazopanib

In the healing traditions

African traditional medicine
Cape bushwillow
Listed among plants used by South African livestock keepers in ethnoveterinary medicine for cattle diseases; its leaf extracts have been screened in the lab for antibacterial and antifungal activity.
Modern pharmacology
Combretastatins (fosbretabulin, CA4P)
Bioassay-guided study of the tree gave six series of combretastatins (A–D). The cis-stilbenes combretastatin A-4 and A-1 bind the colchicine site of tubulin, block microtubule assembly and collapse the cytoskeleton of tumour blood-vessel cells, causing vascular shutdown and necrosis (vascular-disrupting agents).

Active compounds

combretastatin A-4: cis-stilbene from the stem wood; inhibits tubulin polymerisation (IC50 2–3 µM) and is cytotoxic to cancer cell lines at nanomolar concentrations; given clinically as the phosphate prodrug fosbretabulin (CA4P)
combretastatin A-1: given as the phosphate prodrug CA1P (OXi4503) in phase I/II trials
combretastatins B and D series: other combretastatins from the stem wood (D-1 contains a lactone ring); less potent than A-4 and A-1

History

Bioassay-guided work on extracts of the South African tree led to the 1989 isolation of combretastatin A-4, a powerful inhibitor of tubulin and cancer-cell growth whose structure was confirmed by synthesis. Its water-soluble phosphate prodrug became the lead vascular-disrupting agent, entering phase I trials in 1998 and later phase II/III trials in thyroid and lung cancer.

Sources

Reference, not prescription. Nothing here is medical advice. Herbs can interact with medicines and be dangerous in pregnancy; tell your doctor or pharmacist about anything you take.