The Simon Flavell Research Laboratory in Southampton used a compound from the common gypsophila plant to break down the membrane of the leukaemia cells.
This allows antibodies with toxins to penetrate and kill the cells.
But the team admits it is unclear what effect the treatment may have on humans and any drug would take at least three years and cost millions to develop.
But the researchers at the charity-funded laboratory say there has already been interest from pharmaceutical companies.
The team collaborated with scientists in Berlin who had been using the gypsophila plant in tests to treat breast cancer.
A compound from the plant, called saponin, creates holes in the cells after being absorbed.
Special anti-bodies with toxins attached can then be introduced which penetrate the leukaemia cells and kill them much faster.
In the first experiment, the team say 99.9% of the cells died within hours.
The scientists said the first results were so surprising they thought their equipment had broken.
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