Gas chromatographic-mass spectrometric investigation of volatile and extractable compounds of crude royal jelly.

Using headspace solid-phase microextraction (HS-SPME) followed by diethyl ether and methanol extraction, it was possible to isolate as many as 185 organic compounds out of 17 samples of crude royal jelly (RJ). Of the above compound number, 169 compounds were positively identified by means of gas chromatography-mass spectrometry. The volatile fraction of RJ consists of 25 different compounds where approximately 47% of the total ion current (TIC) of volatile compound chromatograms were composed of substances characterized by bactericidal (phenols) and repelling (octanoic acid and 2-heptanone) activities. Preliminary investigations have shown that RJ stored for 10 months at -18°C and 4°C keeps its composition of volatile compounds unchanged, however, at the same time at room temperature RJ phenol contents is decreased twice, whereas the fraction of aliphatic acids is increased 2.8 times due to the presence of both acetic and butyric acids. The chromatogram of RJ ether extracts showed 85 different compounds, however about 88% of TIC consisted exclusively of 8 compounds, i.e. 10-hydroxy-2-decenoic, 10-hydroxydecanoic, 3,10-dihydroxydecanoic, 8-hydroxyoctanoic, 2-decene-1,10-dioc and (Z)-9-hydroxy-2-decenoic acids. Nine aliphatic acids, which were detected for the first time, are the homologues of hydroxy- and oxo-acids identified earlier in RJ. In the RJ methanol extracts 82 compounds were identified, mainly carbohydrates and their derivatives. Approximately 87% of TIC consisted of fructose, glucose and sucrose. Special attention was paid to discrepancies between obtained and literature data concerning the presence of free amino acids in RJ. It was suggested that these inconsistencies can be explained by the differences in the methods of RJ collection and/or sample preparation.