Libyan Propolis : a comprehensive chemical, in vitro biological investigation and metabolomic profiling of antiprotozoal activity

  • Weam Fathi Siheri

Student thesis: Doctoral Thesis

Abstract

Propolis (bee-glue) is collected by bees from plants as a defensive substance in response to environmental pressures which include a range of microorganisms and parasites. These parasites are known to include the protozoal species Crithidia. Since it is collected by bees for the specific purpose of providing chemotherapeutic protection this increases the likelihood of finding active compounds in propolis compared with random screening of plants.Twelve samples of Libyan propolis (P1-P12) were collected from different geographic zones of Libya. Ethanolic extracts of the twelve propolis samples were prepared and these were profiled initially by NMR which gave some general indication of the type of compounds which might be found in them providing signals typical of diterpene aldehydes and cycloartane triterpenoids depending on the origin of the sample.There were limited signals in the aromatic region between 6 and 8 ppm in contrast to Northern European samples where many signals from flavonoid compounds would be expected. The extracts were profiled by high resolution LC-MS and the LC-MS data was extracted and modelled by SIMCA-P software using PCA with HCA, which separated the samples into five main groups based on their chemical composition.The groups were according to Geographic origin which the samples from North East, North West, South East and Southwest Libya grouping together. The sample extracts were tested against a wide range of microorganisms including T. brucei, L. donovani, P. falciparum, C. fasiculata, M. marinum, S. aureus, K. pneumoniae and T. spiralis. In addition, cell based assays for cytotoxicity and anti-inflammatory activities were carried out.Eighteen isolated compounds were isolated including: eight diterpenes (1) 13-epi-torulosal, (2) 13-O- acetyl epi-cupressic acid, (3) 13-epicupressic acid, (4) 13-epitorulosol, (15) acetylisocuppressic acid, (16) Agathadiol, (17) Isocupressic acid and, (18) isoagatholal, three lignans; (5) sesamin, (6) Demethylpiperitol, (7) 5’, methoxy piperitol, (8) the flavonoid flavanone taxifolin-3-acetate-4’-methyl ether and five triterpenes of the cyclo artane type; (9) cycloartanol, (10) mangiferolic acid, (11) mangiferonic acid, (12) ambolic acid, (13) 27-hydroxymangeferonic acid and the resorcinol (14) cardol.Both the crude extracts and isolated compounds exhibited activity against the range of microorganisms were tested such as T. brucei, L. donovani, P. falciparum, C. fasiculata, M. marinum, S. aureus, K. pneumoniae and T. spiralis.
Date of Award1 Dec 2015
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SupervisorDavid Watson (Supervisor) & (Supervisor)

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