Chemicals in the seeds of magnolia trees have been found to inhibit the growth of new blood vessels, cutting tumour growth in mice by half.
A team of scientists at Emory University School of Medicine in the US report that extracts from the plant could be developed for use as an angiogenesis inhibitor, of growing interest in cancer prevention. Other anti-angiogenic compounds found in plants include curcumin from the turmeric plant and derivatives from the South American mate tea.
The researchers tested fractions of the natural magnolia mixture for their ability to prevent the growth of an endothelial cell line (the cells that make up the walls of blood vessels) and found honokiol, a compound previously studied by Japanese researchers in herbal medicines, to be the active component of the magnolia extract.
Honokiol reduced the growth of endothelial cells by driving them into apoptosis or cell self-destruction, they report in the Journal of Biological Chemistry published online on 19 June. Importantly for the specificity of its anti-tumour activity, honokiol inhibited the growth of endothelial cells more than other kinds of cells, they said. In mice inoculated with tumour-promoting cells, honokiol reduced tumour growth by 50 per cent over a control group of mice.
The team is now working to more precisely determine the mechanism by which honokiol affects endothelial cell growth, finding the direct target in the cell. Honokiol may also act by activating a natural tumour defense, stimulating the production of a protein within the body that induces suicide by tumour cells.
Honokiol is the active ingredient in a Japanese herbal medicine, saiboku-to, and is traditionally consumed as a tea thought to have anti-anxiety effects.