Bush Willow / River Bushwillow

Combretum caffrum from the South African bushveld is the source of combretastatins — a family of stilbenoid compounds that act as vascular-disrupting agents (VDAs). Combretastatin A-4 phosphate (CA4P / fosbretabulin) is in Phase II and III clinical trials for anaplastic thyroid cancer, ovarian cancer, and solid tumours. VDAs work differently from anti-angiogenic drugs — rather than preventing new blood vessel growth, they rapidly destroy existing tumour vasculature, cutting off blood supply and causing central tumour necrosis. Combretastatins also bind tubulin at the colchicine site, inducing cancer cell apoptosis independently.