One of the best anti-malarial drugs is extracted from a species of wormwood. A new study shows that it may be better to use the whole plant and save the cost of purifying it.
The best anti-malarial drug known is artemisinin, made from the wormwood plant Artemisia annua. The study, by researchers at the University of Massachusetts Amherst and Worcester Polytechnic Institute, found that dried leaves from the Artemisia annua plant may be a lot more effective than purified artemisinin, delivering 40 times more of the drug to the blood and reducing the level of parasitic infection more completely in mice.
Malaria kills and incapacitates millions of people every year. It's caused by parasites of the genus Plasmodium, transmitted by mosquitoes when they bite. There are several species and five of them infect people.
All of them operate in a similar way: a mosquito bites an infected person and transmits the parasites to the blood. The Plasmodia travel to the liver, where they invade the cells and mature and multiply. After that they burst out of the liver cells and go back to the bloodstream, infecting red blood cells and multiplying again. The repeated fevers that people with malaria get are the result of the blood cells getting destroyed.
The deadliest form of malaria is Plasmodium falciparum, which mostly occurs in Africa. Doctors treat it with a combination of artemisinin and drugs such as doxycycline and chloroquine. Wormwood plants don't yield much of the drug, though, so there are perpetual shortages. That makes the combination therapy expensive, especially for people in the developing world, where malaria is common.
There's also another problem, which makes health workers everywhere nervous: malaria has developed resistance to a host of drugs developed to kill it. That's why combination therapies are used.
The plant has a lot of other chemicals in it besides artemisinin that might help defeat the parasite. Wormwood has flavonoids, for example, which have some antimalarial properties. But flavonoids are just one set of hundreds of chemicals in wormwood, a good part of which aren't aren't known yet. The complexity of the compunds in the plant can also make it tougher for the malaria parasite to evolve resistance.
Whether the findings can be translated to humans isn't clear yet. In the mice, the whole plant treatment reduced the number of parasites in the blood more than the purified drug, but the effect fell off after 72 hours. Odds are that if such a therapy were applied to humans it would require multiple doses. Even if that were the case, though, the fact that the plants can be grown locally and used as-is means the costs of treatment would come down significantly.
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