Propolis, a product from honeybees, is a resinous material composed of beeswax and resin obtained from plant secondary metabolites. It has been used as a folk remedy by humans since ancient times for treatment of many ailments such as wounds, inflammation and peptic ulcer disease. This study investigated the parasiticidal and metabolomic effects of propolis on Trypanosoma brucei, the etiologic agent for sleeping sickness which is an endemic parasitosis in sub-Saharan Africa as well as anti-mycobacterial effects. Propolis samples (n=91) which were mainly from Africa were extracted and profiled by high resolution LC-MS. The active samples which were available in high abundance were subjected to a series of chromatographic separations (open column, MPLC and HPLC) and screening techniques including HR-LCMS and NMR (1D & 2D) in order to separate and identify biologically active compounds present in the extracts. Fractionation was carried out on four samples as follows: S95 (Nigeria), S87 (Ghana), P1 (Tanzania) and KSA1 (Saudi Arabian) which possessed high potency against trypanosomes. Metabolomic effects were also investigated on blood stream form trypanosomes for a compound isolated from S87. Two new anti-trypanosomal prenylated stilbenes [(E)-5-(2-(8-hydroxy-2-methyl-2-(4-methylpent-3-en-1-yl)-2H-chromen-6-yl)vinyl)-2-(3-methylbut-2-en-1-yl) benzene-1,3-diol (F9) and 5-((E)-3,5-dihydroxystyryl)-3-((E)-3,7-dimethylocta-2,6-dien-1-yl) benzene-1,2-diol] (F13-11) were isolated from ethyl acetate extracts of the Ghanian sample (S87). Both compounds exhibited moderate activity against T. brucei with MICs of 6.73 and 16.45 μM, respectively. A new diterpene propsiadin [(ent)-2-oxo-kaur-16-en-6,18-diol] (4) along with three known flavonoids 3,4-dihydro-2-(3,4-dihydroxyphenyl)-2H-chromene-3,7-diol (1), psiadiarabin (2), psiadiarabin (5) and a known diterpene psiadin (3) were isolated from the Saudi Arabian sample. Compound 1 was inactive at the intial concentration tested against T. brucei and M.marinum while compounds 2-4 had MICs at 30.9, 78.1, and 78.1 μM against T. brucei and 312.1, 312.1 and 69.1 μM against M. marinum, respectively. Psiadiarabin (5) showed considerable activity (0.6 % of control) during the initial screening at 20 μg/ml concentration. A new stilbene compound (F13-11) exhibited more interesting biological activity and was isolated in higher quantities than F9-1, another stilbene, which made the former a suitable candidate for metabolomic profiling on T. brucei. Treatment of T. brucei with F13-11 revealed significant metabolomic changes including alterations in levels of some of the essential amino acids, elevation of some of the sugars, particularly sedoheptulose, and minor increments in lipids. Overall, this work has revealed new propolis constituents with significant activity against T. brucei and has confirmed the presence of some potential therapeutic compounds in propolis which could be employed as leads in new drug discovery.
|Date of Award||10 Sep 2015|
- University Of Strathclyde
|Supervisor||David Watson (Supervisor) & Ruangelie Edrada-Ebel (Supervisor)|