Artemisinin- the antimalarial

By Ifeyinwa Ugo-Amadi
Artemisinin is a powerful medicine isolated from the plant- Artemisua annua, sweet wormwood. It drastically reduces the number of Plasmodium parasites in the blood of patients with malaria. The world health organization discourages the use of artemisinin as a single malarial treatment drug but recommends artemisinin-based combination therapies (ACTs) as first line treatment for uncomplicated malaria. Artemisinin is expected to reduce the main parasite load while the partner drug eliminates the parasite completely. When used alone, there can be a return of malaria; making the parasite more resistant. Due to the poor bioavailability of artemisinin, derivatives have been developed, they are:
·         Artesunate
·         Artemether
·         Dihydroartemisinin
·         Artelinic acid
·         Artemotil
Central to the reproduction and survival of the Plasmodium parasite is the infection and destruction of the red blood cells. The parasite feeds on the haemoglobin of the host red blood cell as a source for amino acid and this generates oxidative stress. Plasmodium digests the globin protein in its lysosome resulting in the generation of free haem.
Though the mechanism of action of artemisinin is not fully understood, it is believed to be linked to its unusual peroxide bridge. However, various theories abound. Upon intake of artemisinin, the iron of the haem from the digested haemoglobin reduces the peroxide bond in artemisinin. This generates a high-valent-iron-oxo species, resulting in reactions that produce reactive oxygen radicals that damages the parasite, leading to its death. Another theory is that artemisinin gets activated by iron present in the parasite’s food vacuole; this closes phosphorylation, nucleotide binding and actuator domains by inhibiting a P-type energy enzyme involved in calcium transport. This leads to the parasite’s death. A more recent one describes how artemisinin disrupts cellular redox cycling.
Artemisinin is also effective in Cancer treatment and against schistosomes, the second-most prevalent infection after malaria.
Taking any drug that contains trace elements such as Fe2+, Cu2+ and Zn alongside artemisinin has been advised against because it reduces the efficacy of artemisinin. It mops up the free radicals generated by the peroxide bridge in the artemisinin structure. It does this by catalysing the physiological breakdown of the peroxide bridge through auto induced hydrolytic cleavage. Iron polymaltose III does not mop up the peroxide bridge of artemisinin yet promotes appetite, quick recovery.
References
http://en.wikipedia.org/wiki/Artemisinin
www.who.int/malaria/media/artemisinin.../en
http://www.britannica.com/EBchecked/topic/1126694/artemisinin
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