A Search for Biologically Active Phytochemicals From Endemic Plants of the Southeastern United States.
Date of Award
Doctor of Philosophy (PhD)
Nikolaus H. Fischer
In an investigation of allelopathy in the Florida scrub, bioassays with terpenes were performed against: Lactuca sativa, Rudbeckia hirta, Leptochloa dubia and Schizachyrium scoparium. Cineole was phytotoxic against Rudbeckia at 17 ppm and Lactuca at 165 ppm. (S)-camphor was phytotoxic to Rudbeckia at 1 ppm, Lactuca at 28 ppm, and Leptochloa and Schizachyrium at 134 ppm. (R)-Camphor, myrtenol and myrtenal were phytotoxic against Rudbeckia at concentrations of 28, 25 and 15 ppm respectively. Farnesol stimulated the germination of Schizachyrium at concentrations up to 50 ppm and at 100 ppm it reduced the radicle length of all test species. Geraniol stimulated the germination of Schizachyrium at 10 ppm and reduced germination at concentrations greater than 25 ppm. Aqueous washes of Cladonia subtenuis, C. prostrata and C. leporina did not affect the germination or radicle growth of the test species used in bioassays. Atranorin, isolated from C. prostrata, did not demonstrate any biological activity against the test species; however, usnic acid inhibited germination of all four test species at 50 ppm. In a phytochemical investigation of Euthamia leptocephela and E. tenuifolia, the roots of both species provided the polyacetylenes cis- and trans-dehydromatricaria esters; the triterpenes, epifriedelinol, friedelin, $\beta$-amyrin, $\alpha$-amyrin; and the sesquiterpene curcuphenol. Both species were analyzed for their volatile constituents. Ten monoterpenes and 13 sesquiterpenes were identified with varying distributions in both species. The flowers of both species afforded the known flavanoid demethoxysudachitin and the known diterpene liminodilactone and its 6-$\beta$-hydroxyl derivative and acetate which are new compounds. The MIC values of the three liminodilactone diterpenes, friedelin, and epifriedelinol were $>$125 $\mu$g/ml against Mycobacterium tuberculosis H37Rv and M. avium. cis-Dehydromatricaria ester had a MIC value of 25 $\mu$g/ml against both M. tuberculosis H37Rv and M. avium. The MIC of usnic acid was 16 $\mu$g/ml against M. tuberculosis H37Rv and $>$125 against M. avium. Curcuphenol had a MIC of 16 against M. tuberculosis H37Rv. Liminodilactone, 6-$\beta$-hydroxyliminodilactone and 6-$\beta$-acetoxyliminodilactone did not display any significant inhibition against Spodoptera litura larvae at 100 ppm.
Robbs, Steven Lynn, "A Search for Biologically Active Phytochemicals From Endemic Plants of the Southeastern United States." (1997). LSU Historical Dissertations and Theses. 6402.