GC-MS and HPLC analysis of phenolic acids extracted from propolis and from Populus nigra bud exudate

Fractions in which 37 organic compounds were identified by means of GC-MS method were isolated using extraction of four propolis samples and bud exudate from Populus nigra. Six of them were identified in propolis for the first time. They are: 4-hydroxybutyric acid (4-hydroxybutanoic acid), 3-hydroxybutyric acid (3-hydroxybutanoic acid), phthalic acid, 4-hydroxyhydrocinnamic acid (phenyllactic acid), imidazole and phenetole. The main components ofpropolis fraction are acids: benzoic,cis- and trans-p-coumaric, ferulic, caffeic and cinnamic. The compounds were determined by HPLC technique (according to analysis conditions estimated with Dry-Lab software) applying calibration curve calculation for the standards of those acids. Propolis ethanolic extracts consisted of 3. 5-8. 8% of dry residue and 2.9% bud exudate extract from Populus nigra. The percentage of acids in the isolated samples was determined in the range of 30% to 78%. The content of the compounds varied in different samples which confirms the fact that propolis composition is not constant. The determination of phenolic acids by HPLC technique in optimal conditions may be essential useful for propolis standardization.