An ancient native American treatment for cancer has been shown to have a beneficial effect despite scepticism from the medical establishment.
The shrub chaparral dominates parts of south-western US
Chaparral, an evergreen desert shrub, has long been used by native Americans to treat cancer, colds, wounds, bronchitis, warts, and ringworm.
But experts dismissed its worth, and warned it could be dangerous.
Now researchers at the Medical University of South Carolina have shown an extract may shrink some tumours.
Chaparral tea was widely used in the US as an alternative anti-cancer agent from the late 1950s to the 1970s.
However, the American Cancer Society said there was no proof that it was an effective treatment for cancer - or any other disease.
And the US Food and Drug Administration warned against its use after research showed it could damage the liver and the kidneys.
However, initial results from the latest study show that an extract of the shrub appears not only to be safe, but to have a positive effect.
The researchers tested a refined extract taken from chaparral called M4N.
They injected it into the tumours of eight patients with advanced head and neck cancer that had not responded to other forms of treatment.
The trial was primarily designed to test whether the extract was safe. The results were encouraging - patients seemed to tolerate it well, and there was no evidence of the serious liver damage previously associated with chaparral use.
However, the study also produced some evidence that the extract had begun to shrink the tumours.
The researchers now plan a larger study aimed at showing whether the drug really does work.
Henry Scowcroft, science information officer at Cancer Research UK, said: "Chaparral does not have a good track record as an anti-cancer treatment, but this finding is interesting and suggests that the active ingredients of the plant should be investigated further.
"Plants are an extremely useful source of anticancer drugs. For example the drugs vinblastine and vincristine from the periwinkle plant are used to treat many different cancers.
"And Taxol, which is obtained from the bark of yew trees, is used to treat ovarian and breast cancer.
"It is extremely important to test plant extracts thoroughly before they are routinely used in people, to make sure they have no harmful side effects.
"This is why clinical trials of the M4N chaparral extract will be so important."
Head and neck cancer is usually treated with surgery and radiation, although a
few drugs have shown some promise.
But because patients usually do not realise they have cancer until it has spread, it is very hard to treat.
Results of the study were presented at an International Conference on Head and Neck Cancer in Washington.