Date of Award

1990

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Nikolaus H. Fischer

Abstract

As part of the investigation of the allelopathic interactions of members of the Florida scrub community, the chemical constituents of Solidago pauciflosculosa (Asteraceae) and Calamintha ashei (Lamiaceae) were studied. Aqueous and organic extracts of fresh leaves of S. pauciflosculosa provided large amounts of diterpene acids. The two major diterpenes isolated, 17-oxygrindelic acid and 17-oxogrindelic acid, showed significant inhibitory effects on germination and radicle growth of two Florida sandhill grasses, Schizachyrium scoparium and Leptochloa dubia. The organic extracts of S. pauciflosculosa were very rich in sesquiterpenes, the three major sesquiterpenes being (+)-epicurlone, (+)-episesquiphellandrene ($-$)-a-trans-bergamotene. These three compounds did not show any significant effects on the germination and radicle growth of test species. Fresh leaves of C. ashei were very rich in menthofuran monoterpenes and flavonoids. The two major monoterpenes, epievodone and desacetylcalaminthone exhibited strong inhibitory effects on the germination and root growth of test species at concentrations of 106 and 92 ppm, respectively, whereas the flavonoids showed no effects. Investigation of the chemical constituents of the root of S. pauciflosculosa, S. canadensis and S. sempervirens provided acetylenic compounds and diterpene acids. cis,cis- and cis,trans-Matricaria esters from S. pauciflosculosa as well as cis-dehydromatricaria ester from S. canadensis showed strong inhibitory effects on the germination of test species. cis,cis-Matricaria ester completely inhibited germination of Florida sandhill grasses at 106 and 53 ppm. Biosynthetic studies of chemical constitutents of hairy root cultures of Tagetes patula (Asteraceae), using $\sp{13}$C-labeled acetates, established the biosynthetic pathway of two bithiophenes and the sesquiterpene b-farnesene. The bithiophenes are formed by linear combination of acetate followed by loss of the two terminal carbon units to give the 12 carbon skeleton of the bithiophenes. b-Farnesene also followed the predicted pathway via the mevalonic acid route. Further investigation of the chemical constituents of hairy root cultures of Tagetes patula provided, besides the above three compounds, two known bithiophenes and four benzofurans.

Pages

289

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