Identification by Gas Chromatography-Mass Spectrometry of 150 Compounds in Propolis

Propolis is the substance used by bees as a draught excluder and general purpose sealer for their hives. It usually consists of a mixture of pop­ lar bud exudate and beeswax [1]. Propolis balsam (a 70% alcohol extract of propolis which contains the bud exudate components) is a popular herbal medicine [2-4] containing a number of phenolic constituents with antimicrobial activity [4-6], Bees appear to prefer to collect bud exudate from poplars of the Section Aigeiros, such as Populus nigra L., the European black poplar [1,7, 8], We have previously identified by gas chromato­ graphy-mass spectrometry (GC-MS) 104 com­ ponents in propolis balsam originating from P. x euramericana (Dode) Guinier, an intrasec­ tional hybrid between P. nigra and P. deltoides Marsh, the eastern cottonwood of North America [9], That sample of propolis contained compounds typical of Section Aigeiros poplars and essentially lacked compounds typical of poplars of other sec­ tions. We here describe the detailed analysis by GC-MS of both the headspace volatiles and other less volatile components of a propolis sample which contains, in quantity, series of compounds, such as dihydrochalcones and sesquiterpenols, which are typical of Section Tacamahaca poplars [10, 11], together with pinocembrin (3,5,7-trihydroxyflavanone) and pinocembrin derivatives which are typical of Section Aigeiros poplars [1214], The sample of propolis described here (for ori­ gin and availability see Methods) is therefore un-