The chemical characterization of Nigerian propolis samples and their activity against Trypanosoma brucei

Omar, Ruwida and Igoli, John O. and Zhang, Tong and Gray, Alexander I. and Ebiloma, Godwin Unekwuojo and Clements, Carol J. and Fearnley, James and Edrada Ebel, RuAngelie and Paget, Tim and de Koning, Harry P. and Watson, David G. (2017) The chemical characterization of Nigerian propolis samples and their activity against Trypanosoma brucei. Scientific Reports, 7 (1). 01038. ISSN 2045-2322 (https://doi.org/10.1038/s41598-017-01038-2)

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Abstract

Profiling of extracts from twelve propolis samples collected from eight regions in Nigeria was carried out using high performance liquid chromatography (LC) coupled with evaporative light scattering (ELSD), ultraviolet detection (UV) and mass spectrometry (MS), gas chromatography mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy (NMR). Principal component analysis (PCA) of the processed LC-MS data demonstrated the varying chemical composition of the samples. Most of the samples were active against Trypanosoma b. brucei with the highest activity being in the samples from Southern Nigeria. The more active samples were fractionated in order to isolate the component(s) responsible for their activity using medium pressure liquid chromatography (MPLC). Three xanthones, 1,3,7-trihydroxy-2,8-di-(3-methylbut-2-enyl)xanthone, 1,3,7-trihydroxy-4,8-di-(3-methylbut-2-enyl)xanthone a previously undescribed xanthone and three triterpenes: Ambonic acid, mangiferonic acid and a mixture of α-amyrin with mangiferonic acid (1:3) were isolated and characterised by NMR and LC-MS. These compounds all displayed strong inhibitory activity against T.b. brucei but none of them had higher activity than the crude extracts. Partial least squares (PLS) modelling of the anti-trypanosomal activity of the sample extracts using the LC-MS data indicated that high activity in the extracts, as judged from LCMS2 data, could be correlated to denticulatain isomers in the extracts.

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