Malaria parasite defeated by garlic and onions

Thursday, November 15, 2001
By Environmental News Network

A group of compounds found in garlic and onions may be an effective treatment for malaria, researchers from the University of Toronto have discovered. And the mechanism by which they inhibit persistent malarial infections appears to be similar to the way they fight cancer cells.

The compounds, called disulfides, occur naturally in garlic and onions and are known to have antifungal, anticancer, and antibacterial properties. But this is the first research that indicates garlic and its cousins might be helpful in fighting malaria.

Ian Crandall, assistant professor of laboratory medicine and pathobiology at the University of Toronto, reported these findings Wednesday at the 50th Annual Meeting of the American Society of Tropical Medicine and Hygiene in Atlanta. "Does eating garlic influence the outcome of malaria? There is evidence that yes, it may," said Crandall.

At a minimum, between 700,000 and 2.7 million people die annually from malaria worldwide, more than 75 percent of them African children, according to the Multilateral Initiative on Malaria, an international alliance of research and public health agencies and African scientists. Malaria is transmitted by the bite of a mosquito carrying the malaria parasites in its saliva.

For years scientists have suspected that one of these compounds in garlic may be helpful against malaria and have proven it in animal models. Crandall and his colleagues were more interested in understanding how these disulfides worked against infection.

They tested 11 different synthetic disulfide compounds against malaria-infected cells. They also tested the effect of these compounds on cancer cells. While not all of the disulfides were effective against Plasmodium falciparum, the malaria parasite, those that were effective are the same compounds that were effective at killing the cancer cells.

"We looked at the active compounds to see what they had in common. Apparently P. falciparum-infected cells and these cancer cells seem to have the same susceptibility profile," said Crandall.

Crandall believes that the mechanism of action may be on the glutathione system within the cell. In this system, the glutathione is reduced by a process that is the the opposite of oxidation, and then it is stored in the cell like energy in a battery. This reduced glutathione can then be brought out of the cells when required to absorb damage caused by oxygen and other harmful particles.

The glutathione system is of particular importance in cells that rapidly reproduce, like cancer cells or malaria infected cells, because these harmful particles are natural by-products of metabolism.

Ajoene, the disulfide that naturally occurs in garlic, is a known inhibitor of glutathione reduction. "Normal cells recharge glutathione and therefore are able to deal with the oxidative stress that normal metabolism generates, but in the presence of an inhibitor they, cannot recharge and therefore are more prone damage and eventually death," said Crandall.

Garlic, a member of the onion family, is thought to have originated in the deserts of Central Asia. Among the oldest cultivated plants, garlic has been used throughout history to treat a host of illnesses, including typhus and dysentery during World War I. Epidemiological studies have found that, in areas of the world where people eat a lot of garlic and onions, there is decreased incidence of cancer.

Garlic has also been shown to reduce blood cholesterol. According to medical journalist Jean Carper, garlic prevents bad-type LDL cholesterol from oxidizing, a process that initiates plaque buildup on artery walls, which can lead to clogging, heart attack, and stroke.

Much research shows that garlic contains many chemicals that in laboratory animals block cancers of every type, including breast, liver, and colon, Carper said. A specific garlic compound suppressed the growth of prostate cancer cells in test tubes by about 25 percent, reports John Pinto of Memorial Sloan Kettering Cancer Center in New York.

Yet not all researchers agree on the effectiveness of garlic as a disease fighter. Dietary use of garlic may lower some types of cholesterol in the short term, but it does not appear to offer long-term protection against cardiovascular disease, according to a review and analysis of scientific evidence related to clinical studies of garlic in humans report released in October 2002 by the Agency for Healthcare Research and Quality.

Crandall hopes that one days compounds in garlic and onions may be used to treat not only malaria but some types of cancer as well. There is one drawback, though. "Does this stuff smell like garlic? Well, every time we open a vial of it in the lab everybody runs," he laughed.