Uncaria tomentosa

Johannes Keplinger

[CURITIBA] An Amazonian plant could form the basis of a drug to combat dengue fever, according to Brazilian researchers.

A group of scientists at the Viral Immunology Laboratory of the Brazil-based Oswaldo Cruz Foundation has found that compounds of the plant 'cat's claw' (Uncaria tomentosa) — native to the Amazon rainforest — have both antiviral and immune system-regulating properties when they come into contact with infected cells in the laboratory.

Cat's claw is known in traditional medicine for its anti-inflammatory — immune system-regulating — effects, which prompted the scientists to investigate the plant.

Dengue infection causes fever, nausea, headache and abdominal pain. In extreme cases — known as dengue haemorraghic fever — the immune system overreacts causing low blood pressure, and bleeding from mucosal tissues and under the skin, which can lead to death.

"We reacted a solution containing substances extracted from cat's claw with immune cells and noticed that the product inhibited the production of cytokines, proteins necessary to react to the inflammatory effects of dengue," biologist Claire Kubelka, chief of the laboratory and one of the coordinators of the study, told SciDev.Net.

The researchers also found fewer dengue virus cells in immune cells that had been treated with the cat's claw preparation.

The tests were carried out in the laboratory, but, according to the researcher, if the effects are repeated in humans, a treatment derived from cat's claw could dampen the immune response to dengue infection and reduce the chance of death.

But years of testing remain until a medicine could be available, warns Kubelka.

Dengue fever is a disease caused by a virus of the genus Flavivirus, transmitted by Aedes aegypti mosquitoes. The WHO estimates there might be 50 million dengue infections worldwide every year. No effective medicine exists so the only recommended treatment is hydrating patients while they are recovering.

Kubelka says the group cannot patent the research because the solution of cat's claw used was patented in 1992 by Japanese researchers who imported the plant from Peru. Besides Uncaria tomentosa, the Brazilian group is currently looking for anti-dengue properties in solutions of approximately 15 other plants.

The research was published in International Immunopharmacology in December.

Link to abstract in International Immunopharmacology