Scientists have examined over 2,000 plants

In addition to anti-malarials, plants may contain a cure for HIV, an antidote to diabetes or even protection against cancer.

Kew gets plants sent from the Americas and Africa for testing, and also grows many of its own potentially useful species.

Plants from across the world

Plectranthus, a plant from Brazil is one of many which has been used by traditional healers in South America.

Professor Monique Simmonds is overseeing the first scientific tests of the plant.

It will be distilled and the chemicals extracted to see if it has anti malarial properties.

She told the BBC: "We're really going back, and reinventing the wheel, looking again at some of the techniques we possibly dismissed a little while ago.

"In the last 20 - 30 years we were looking for a vaccine for malaria. But natural products from plants might come to the fore in the search for antimalarials."

Poisonous plants database

Many of the plants being looked at for their anti-malarial properties also have the ability to repel mosquitoes.

Prof Simmonds is to visit Colombia next week to tell the scientific community there what she's found.

Professor Simmonds is leading the work

Kew's other work includes taking visitors' suggestions on other plants which might have health benefits.

The experts at Kew were recently asked by doctors to design a CD Rom of poisonous plants after a child nearly died a from eating one which no one could identify.

No major pharmaceutical companies have expressed an interest in the anti malarial work being done at Kew.

But the researchers say their hope simply is to help countries hit by malaria get rid of the disease using their own, inexpensive methods.