Antiplasmodial and phytochemical investigation of traditionally used antimalarial plants of the United States

Malaria is a devastating parasitic disease that causes over 200 million infections and 600,000 human deaths a year. Increased drug resistance to currently used antimalarial therapies signifies a need to discover and develop novel treatments. Although not a present day issue, malaria was once a major concern in the United States and people often utilized local plant species to treat the disease. Since the eradication of malaria from the U.S. in the 1950’s, many herbal remedies have been forgotten and survive only in written records. Such historically reported plants may hold potentially potent and novel antimalarial compounds. This research project was designed to 1) Identify promising plant species of the United States that have been used to treat malaria; 2) Collect, extract and test the in vitro antiplasmodial activity of the selected species; 3) Isolate, identify and characterize the phytochemicals within those plants that are responsible for the observed activity. This work resulted in the in vitro antiplasmodial screening of 243 extracts from 46 plant species representing 28 angiosperm families. Six species were selected for bioassay guided fractionation to isolate the bioactive constituents (of which four are described in detail here). Forty two chemical compounds displaying antiplasmodial activity were isolated in pure form, of which 9 novel compounds were newly described. The IC50 values of the compounds ranged from 0.11 µM to over 100 µM. All isolated compounds were also tested for cytotoxicity and several for their in vitro ability to inhibit Leishmania tarentolae as a proxy for antileishmanial activity. This work provides pharmacological and phytochemical support for the ethnobotanical use of plant species traditionally used to treat malaria in the United States. It also adds to the number and diversity of plant derived antiplasmodial compounds. The rich ethnobotanical history of the United States has been overshadowed as reliance on modern medicine has become the standard. However, as evidenced by this dissertation, traditional remedies, even those that are no longer used, continue to serve as a potentially important source lead for modern drug discovery.Ph. D.Includes bibliographical referencesby Rocky Thomas Grazios