The Makerere University at Kampala has been able to demonstrate over the recent years that the regular consumption of Artemisia annua tea may lead to a strong preventive effect against malaria. ( PE Ogwang et al., Trop J Pharmac Res, 2012,13:3, 445-453; PE Ogwang et al., Brit J Pharmac Res 201, 1 :4, 124.132). This research effort sponsored by government of Uganda and Carnegie corporation USA, has led to the development of drug called Artavol® which is now available in pharmacies in Uganda. This product contains ingredients from three medicinal herbs.
In fact major research efforts are now devoted to the study the prophylactic effect of other plants or herbs. For example in India ( B Prakash et al., JEthnopharmacology, 146, 2013, 768.772) or Burkina Faso (RS Yerbanga et al., J Etnopharmacology 140, 2012, 255-260). In all these papers Neem (Azadirachta indica) is often the most active constituent.
The flavonoid quercetin is one of the major constituents of Neem and interferes with the cytochrome P-450 reductase ( MM Iwu et al ; Pharmacol Res Commun. 18:1, 1986, 81-91). Quercetin is a common and strong antioxidant usually present in glycolisated forms, such as quercitrin or rutin. The latter releases quercitin to perform its anti-inflammatory effect (M Comalada, Eur J Immunol 2005, 35:2, 584-92). It has a protective effect against chloroquine hepatotoxic effects ( SK Mishra et al. Hindawi Publishing Corporation, Malaria Research and Treatment, 2010, ID141734) A study from Luxembourg showed that Neem leaf extract induced apoptosis in leukemia cancer cells and that the important constituent quercetine probably played a key role ( M Schumacher et al., Genes Nutr 211, 6:2, 149-160).
Quercetin also is a strong inhibitor of the growth of the intraerythrocytic malaria parasite with an IC50 of 15 µM. (A Lehane, BMC Research Notes, 2008, 1:26). This was confirmed by a more recent study (D Ganesh et al., Parasitol Res 2012, 11:6, 2289). Among 8 flavonoids the quercetin analogue rutin was the most active antiplasmodial substance. In a study from Indonesia the extract of neem leaves had an IC50 of 3,8 µg/ml on Plasmodium falciparum.(Y Hanifah et al., Conf Proc Syla Kuala, 2011).
But the prophylactic effect of Neem extracts like the effect of Artemisia extracts is only effective progressively and in the long term. In a study by M Barlow-Benschop in Tanzania on 152 patients showed a decrease of malaria episodes from 57% at 3 months to 81% after 6 months of treatment. The treatment probably triggers an increase of the monocyte and/or T-cell count.
Very surprising and interesting results are delivered by a study from Nigeria ( C Mghemena et al., J Amer Sc. 2010, 6:8, 503-506). The authors investigated the effect of methanol, ethanol and aqueous extracts of neem and lemon grass against plasmodium development. After treatment with these 6 different extracts the albino mice were left for eight days and then infected with P.berghei. The aqueous extract of Neem had by far the highest suppression (76.1%) 8 days after infection.
This rather short range prophylaxis could be interesting for travelers. Neem tea has no side effects unlike other chemical prophylactic drugs.
Pierre Lutgen & Patrick Ogwang Engeu
Étiquettes : neem prophylaxie malaria quercetin