Chemical characterisation of Maltese propolis in relation to botanical sources

Abstract

Propolis (bee glue) is a bee product produced from resinous plant materials and beeswax. The chemical composition of propolis depends on the botanical sources available to the honeybees. Propolis was collected from different apiaries around the Maltese Islands, 14 samples from Malta and 3 samples from Gozo. A vegetational survey was compiled by observing the floral sources in the area surrounding the beehives. Thin layer chromatography (TLC) analysis was carried out to compare Maltese propolis with propolis samples from Greece (Crete) and Iran. Marker bands on the TLC of Maltese propolis were also identified which were then used to compare with the TLC analysis of resins from possible botanical sources. The compounds in Maltese propolis were analysed by gas chromatography-mass spectrometry (GC-MS). 25 compounds were identified, out of which seven compounds (neoabietic acid, 13-epi-cupressic acid, totarolone, junicedric acid, 13, 14-dehydrojunicedric acid, ferruginolon and sitosterol) were so far unreported in propolis in the published literature. 19 other compounds were observed in Maltese propolis samples but remained unidentified. The major compounds of Maltese propolis are terpene compounds specifically diterpenic acids. Possible major and minor botanical sources of Maltese propolis were discussed in view of the compounds identified. Plants from the families Cupressaceae and Pinaceae were identified as important botanical sources for Maltese propolis production. Tetraclinis articulata (V ahl) Masters is a possible botanical source of Maltese propolis and Ferula species are recognised as possible minor sources of Maltese propolis. Preliminary DPPH• free radical scavenging activity tests were carried out to study the antioxidative activity of Maltese propolis. Low antiradical scavenging activity was reported.