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Isolation, Characterization, and Synthesis of Bioactive Natural Products from Rainforest Flora
Berger, John Michael
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As part of our ongoing investigations for anticancer drugs from rainforestflora, five plant extracts were determined to contain interesting bioactivity. These extracts were subjected to various separation techniques, affording a number of bioactive compounds that were then characterized by spectral and degradative methods. A methanol extract of Cestrum latifolium Lam. yielded the known compound parissaponin Pb. Hydrolysis afforded its aglycone, the known spirostanol diosgenin. GCMS analysis characterized the derivatized, hydrolyzed sugars. Previous investigations of Albizia subdimidiata provided two saponins including the new compound albiziatrioside A. The sugar moieties of these two compounds required further characterization. They were characterized by spectral analysis of the partially hydrolyzed products and by GCMS analysis of the hydrolyzed sugars. Pittoviridoside, a saponin from Pittosporum viridiflorum, was isolated in a previous investigation. Further investigation was required to characterize the stereochemical environment of the sugar moiety. The stereochemistries of the pentose sugars were determined by conversion into thiazolidine acetates of known stereochemistries and analysis with standards by GCMS. Two new diterpenes were isolated from Hymenaea courbaril, which in an earlier investigation provided a new diterpene. The absolute configurations of these diterpenes were assigned on the basis of anisotropic NMR studies, X-ray crystallography, circular dichroism analysis and previously reported literature. A previous investigation of Miconia lepidota isolated two benzoquinones, primin and its n-heptyl analog. Fifteen analogs were synthesized for structure-activity relationship determination. It was found that benzoquinones with moderate-length alkyl side chains displayed the strongest activity in our yeast and cancer cell lines.
- Doctoral Dissertations