Profiling of propolis samples from UK, Indonesia and sub-Saharan Africa and isolation of some pure components

  • K Khaled Ahmed Asmeida Saleh

Student thesis: Doctoral Thesis

Abstract

Propolis is a resinous material collected by bees as part of the defensive system of the bee hive. It has a wide range of biological activities including anti-protozoal and [sic] and microbial activity. Samples of propolis from different parts of the UK, Africa and Indonesia were extracted and profiled by liquid chromatography-high resolution mass spectrometry. The data were aligned and features were extracted into 0.02 amu windows. In order to establish a platform for comparison of the samples the top features by peak intensity, after excluding abundant dimer peaks, were further characterized by MS2. Putative identities were deduced from accurate masses which were within 3 ppm deviations from the exact mass of the proposed elemental compositions. For the UK propolis samples, over 90% of the peaks could be assigned identities with some level of confidence. The compounds identified fell into the major categories: flavonoid esters and possibly some ethers, phenyl propanoid esters, glycerol esters, flavonoid glycosides and hydroxylated fatty acids. Pinobanksin was the most abundant compound in the samples. The flavonoids pinocembrin, pinobanksin, galangin and chrysin showed a relatively low degree of variation across the nine samples whereas flavonoid esters and glycerol esters were more variable in their response across the nine samples. The propolis samples from hives in three different areas of Scotland yielded hundreds of components, many of which were not identified. In the Aberdeenshire samples principal components analysis (PCA) followed by hierarchical cluster analysis (HCA) grouped nine samples into six groups according to the abundance of their components. The Aberdeenshire samples were abundant in glycerol esters. Five samples from Fort William could be divided into four groups. These samples had quite a different composition from the Aberdeenshire samples containing an abundance of compounds putatively identified as being sesquiterpene acids.Three samples from Dunblane were different again but had more similarity in composition to the Aberdeenshire samples than the Fort William samples. The propolis sample from Indonesia yielded predominantly phenolic compounds. Although standards were not available to determine the identities and actual amounts of the compounds in the samples, preparative chromatographic separation enabled the identification of some of the compounds by NMR spectroscopy (1D and 2D) and mass spectra as pinobanksin, apigenin, lupeol, gallic acid and quercetin. The role of propolis in warding off infections in the bee hive which is yet established was addressed in this study and the approach provides a potential method for correlating hive health with the composition of the propolis gathered by the bees. Thus this study also confirms local and regional variations in propolis composition over a relatively small areas and over wide geographical regions.
Date of Award1 Sep 2017
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorDavid Watson (Supervisor) & Ruangelie Edrada-Ebel (Supervisor)

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