As part of an International Cooperative Biodiversity Group (ICBG) program and a collaborative research project with the Natural Products Discovery Institute, four plant extracts were investigated for their antiproliferative and antiplasmodial activities. With the guidance of bioassay guided fractionation, two known antiproliferative terpenoids (2.1 and 2.2) were isolated from Hypoestes sp. (Acanthaceae), four known antiplasmodial liminoids (3.1-3.4) were isolated from Carapa guianensis (Meliaceae), one inactive terpenoid (4.1) was isolated from Erica maesta (Ericaceae), and four cerebrosides (4.2-4.5) were obtained from Hohenbergia antillana (Bromeliaceae). The structures of these compounds were elucidated by using 1D (1H and 13C), 2D (HMBC, HSQC, COSY, NOESY) NMR spectroscopy and mass spectrometry. The structures of the compounds were also confirmed by comparing them with reported values from the literature. Compounds 2.1 and 2.2 showed moderate antiproliferative activity against the A2780 human ovarian cancer cell line with IC50 values of 6.9 uM and 3.4 uM, respectively. They also exhibited moderate antiplasmodial activity against chloroquine-resistant Plasmodium falciparum strain Dd2 with IC50 values of 9.9 ± 1.4 uM and 2.8 ± 0.7 uM, respectively. Compounds 3.1 to 3.4 had moderate antiplasmodial activity against Plasmodium falciparum Dd2 strain with IC50 values of 2.0 ± 0.3 uM, 2.1 ± 0.1 uM, 2.1 ± 0.2 uM and 2.8 ± 0.2 uM, respectively. Compounds 4.1 and 4.2 showed very weak antiplasmodial activity against Plasmodium falciparum Dd2 strain, with IC50 values between 5 and 10 ug/mL. / Master of Science

Malaria, caused by the parasite Plasmodium falciparum, has a long history as a global health threat. The vector-borne disease causes millions of deaths yearly, especially in developing countries with tropical climates that facilitate transmission. Compounding the problem is the emergence of drug-resistant strains due to overuse of outdated treatments. New compounds with antiplasmodial activity are needed to be developed as effective drugs against malaria. The hypothesis for this project is that marine microorganisms have a high likelihood of yielding novel antiplasmodial chemotypes because of their high diversity, which has not yet been explored for antimalarial development. In this project, microbes harvested and fermented by the Harbor Branch Oceanographic Institute in Fort Pierce, Florida were explored as sources for antiplasmodial natural products. Using a SYBR Green I fluorescence-based assay, 1,000 microbial extracts were screened for inhibition of the multidrug-resistant Plasmodium falciparum strain Dd2. Dose-response analysis was performed on 46 fractions from isolates whose extracts demonstrated greater-than or equal to] 70% inhibition of Dd2 at 1 micro]g/mL. To evaluate cytotoxicity, the MTS cell viability assay was used to calculate IC50 of extracts from active isolates in NIH/3T3 embryonic mouse fibroblasts. Several extracts demonstrated low IC50 in Dd2 and high IC50 in 3T3, suggesting that they contain potential lead antimalarial compounds. Extracts with high selectivity indices (potent plasmodial inhibition with low mammalian toxicity) have been prioritized for dereplication, with the goal of identifying novel active components that can be developed as antimalarial drugs.