Chemical analysis and antimicrobial activity of Greek propolis.

One new 2,3-dihydroflavone derivative, 7- O-prenylstrobopinin, and 25 known diterpenes and phenolic compounds were identified from the n-butanol extract of Greek propolis. This is the first time that diterpenes have been isolated from propolis of European origin, while six of the known compounds are reported as propolis constituents for the first time. The structures of the isolated compounds were determined by spectroscopic methods, mainly by the concerted application of 1D, 2D NMR techniques (HMQC, HMBC, NOESY) and mass spectrometry. The studied sample and the isolated compounds were tested for their antimicrobial activity against Gram (+/-) bacteria and fungi and five of them exhibited strong activities.