Insight into clinically effective herbal antimalarial products: Effects on drug metabolizing enzymes and p-glycoprotein

Malaria is a leading cause of morbidity and mortality in many developing tropical countries, particularly in children and pregnant women. With growing concerns about the development of resistance to current antimalarial drugs, herbal alternatives may provide significant and sustainable treatment options in affected regions. This review aimed at providing an updated overview of available data on Herbal Medicinal Products (HMPs) with reproducible evidence-based antimalarial efficacies. In addition, it identified the antiplasmodial phyto-constituents and discussed the potential of these products to modulate activities of drug metabolizing enzymes and drug transport systems. This is particularly important because the co-morbidity of malaria with other diseases, often prevalent in malaria endemic regions, is marked by a concurrent use of herbal antimalarial products with conventional drugs. An extensive literature search was undertaken and the information obtained were critically analysed. Enormous work has been reported on investigations of the antiplasmodial activity of herbs, and more than 1000 plants have been studied using in vitro and animal malaria infection models. However, only a few of these HMPs have been subjected to randomized clinical trials. Herb-drug interactions are of great concern since phytochemical compounds in HMPs are subject to the same pharmacokinetic processes that determine the fate of synthetic drugs in the human body. Thus, specific effects of these clinically effective antimalarial HMPs on drug metabolizing enzymes were reported with a view to documenting information for optimization of their therapeutic utility. Beneficial and adverse clinically significant interactions were also identified for close therapeutic attention.   Key words: Antimalarial herbal products, evidence-based efficacy, cytochrome P450, herb-drug interactions.