Chemical investigations into the constituents of I, Rhodomyrtus macrocarpa (Myrtaceae) II, some British marine red algae.

  • Chike A. Igboechi

Student thesis: Doctoral ThesisPhD


The "Australian finger cherry", Rhodomyrtus macrocarpa, was re-examined resulting in the isolation and characterisation of two new isomers of the natural dibenzofuran derivative, rhodomyrtoxin, and smaller quantities of a third isomer, possibly psi-rhodomyrtoxin. A high performance liquid chromatographic method is described which offers a rapid and sensitive approach to both quantitative and qualitative analysis of the dibenzofuran derivatives from Rhodomyrtus macrocarpa. This could be used to investigate the possibility of geographical or seasonal variations, or variations linked with the stage of maturity, in the dibenzofuran constituents of the fruits. A pentacyclic triterpenoid acid was also isolated from Rhodomyrtus macrocarpa and this raises the possibility of the presence of pharmacologically active glycosides which may be responsible for the reported toxicity of the fruits. Five species of British marine algae were examined chemically. The known heterosides, floridoside and sodium mannopyranosylglycerate were isolated from Palmaria palmata and Polysiphonia lanosa respectively. Comprehensive spectroscopic data are given and the usefulness of spectroscopic techniques in determining the configuration at the anomeric carbon atom, and position of glycosidic linkage is highlighted. The known potassium sulphate ester salt, lanosol sulphate, was isolated from samples of Polysiphonia lanosa collected from two different geographical locations but the related ether-soluble brominated phenols were found only in a sample from Kimmeridge Bay and not in one from Berwick-on-Tweed. The possibility that they may be extraction artifacts was investigated. A fatty acid isolated from Corallina officinalis is shown to have an unusual arrangement of double bonds and the structure was in all probability limited to two possible isomers, 4,8,11,14, 17 - or 4,7,10,13,17 - eicosapentaenoic acid. An aliphatic aldehyde isolated from Laurencia pinnatifida was assigned a tentative structure by a combination of NMR, infrared, and mass spectral evidence as well as results obtained from oxidative cleavage and gas-liquid chromatographic analysis. Sterols, free fatty acids and amino acids were routinely isolated and analyzed.
Date of Award1983
Original languageEnglish
Awarding Institution
  • University of Bath

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