(E)-10-hydroxydec-2-enoic acid

Abstract

The lipidome of royal jelly (RJ) consists of medium-chained (8–12 carbon atoms) free fatty acids. We present herein a liquid chromatography-high resolution mass spectrometry (HRMS) method that permits the determination of RJ fatty acids and at the same time the detection of suspect fatty acids. The method allows for the direct quantification of seven free fatty acids of RJ, avoiding any derivatization step. It was validated and applied in seven RJ samples, where the major RJ fatty acid trans-10-hydroxy-2-decenoic acid (10-HDA) was found to vary from 0.771 ± 0.08 to 0.928 ± 0.04 g/100 g fresh RJ. Four additional suspect fatty acids were simultaneously detected taking advantage of the HRMS detection.

2.4. Analysis of RJ Samples

Seven different RJ samples, which were purchased from the local market, were analyzed. The extracted ion chromatograms (EICs) of the analytes in a standard solution (A), as well as in a representative RJ sample (B) are presented in . The isobaric 10-hydroxydecanoic acid and 3-hydroxydecanoic acid are well separated and are eluted at 2.37 and 3.25 min, respectively.

2.4. Analysis of RJ Samples

The concentrations of the seven analytes in seven RJ extracts (in triplicate) are summarized in . represents the multi sample analysis data. The contents of free fatty acids are expressed as g of fatty acid per 100 g of fresh RJ. 10-HDA was found to be the most abundant, as expected, and its content ranged from 0.771 ± 0.08 to 0.928 ± 0.04 g/100 g fresh RJ. These results are in accordance with literature taking into account that the content of 10-HDA depends on the origin of the jelly and the characteristics of the bee. The levels of 10-HDA have been found to vary from 0.75 to 2.54 by Genc and Aslan using column liquid chromatography [], and from 0.8 to 3.2 by Ferioli et al. using either CZE or HPLC [].