Maranz, Steven .
Evidence for an alternative evolutionary and ethnopharmacological role for anti-malarial plants in Sub-Saharan Africa.
Africa's human populations have numerous genetic adaptations linked to resistance to malaria. In addition to Duffy negative blood groups that confer almost complete resistance to Plasmodium vivax and hemoglobinopathies that reduce P. falciparum pathogenicity, there is a relatively higher threshold for bitter taste detection that corresponds geographically to endemic malaria areas. Traditional African anti-malarial therapies feature some extremely bitter treatments, such as touloucouna ('bitter oil') from Carapa procera DC (Meliaceae). However, tolerance to bitter taste may exist in non-human primates as well and probably pre-dates the development of conscious ethnomedicine. This raises the intriguing possibility that dietary compounds may influence malaria. Experiments using a mouse model of malaria demonstrate that a high oral intake of dietary flavonoids significantly reduces parasite loads and enhances the acquisition of immune memory. However, in vitro assays show that flavonoids marginally inhibit P. falciparum at physiological concentrations. Most in vitro investigations of African anti-malarial plants have likewise found only weak anti-plasmodial activity. This discrepancy may be resolved by the higher active compound concentration required to directly kill the parasite compared to the levels needed to modify the host endothelial environment. If flavonoids and other treatment compounds act primarily on the host rather than the parasite, the key effects will not be detectable in vitro. Thus, the current system of relying on in vitro screening of African plant extracts for direct anti-plasmodial activity is misplaced. Indeed, the epidemiological record of the past century shows that compounds with anti-plasmodial potency at nanomolar doses invariably select for drug resistant parasites. If indigenous equivalents to chloroquine or artemisinin had emerged in Africa's past, they would in all likelihood have failed as well. Given Africa's long exposure to malaria and extensive ethnobotanical experimentation with both diet and therapies, it is more likely that host-acting compounds that are not easily overcome by Plasmodium parasites would have been preferentially retained in the indigenous food ways and pharmacopeia.
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1 - Cornell University, Weill Medical College, Microbiology & Immunology, 1300 York Av, New York, NY, 10021, USA
TAS2R bitter taste genes
Presentation Type: Oral Paper:Papers for Sections
Location: Waterman Room/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 2:45 PM