Chemical characterisation of Maltese propolis in relation to botanical sources

Abstract

Propolis is a sticky dark-coloured resinous material produced by honeybees (Apis mellifera L.) from plant materials. The worker bees collect the lipophilic resins secreted from plant wounds or secreted during bud formation, mix it with wax and use it in construction and adaptation of the hive. Propolis is a multi-variant product. Its chemical constituents include waxes, resins, balsams, essential oils, amino acids, sugars and various secondary metabolites, the composition depending on the botanical sources available to the honeybees. Flavonoids and cinnamic acid derivatives, particularly the hydroxycinnamic acid caffeic acid, and its derivate caffeic acid phenyl ester, are commonly found in propolis samples. Over 40% of the main constituents of propolis from the temperate zones are polyphenolic acids and flavonic compounds. However tropical and sub-tropical (Mediterranean) samples do not contain such substances. Diterpenes and triterpenes have been identified in previous studies of propolis from the sub-tropical regions, specifically from Greece, Sicily and Turkey. The primary objectives of this study were to chemically characterise the compounds found in Maltese propolis by GC-MS analysis and identify possible botanical sources since such studies are totally lacking locally.