Chemistry and Physics of Lipids, 23 (1979) 285-290 O Elsevier/North-Holland Scientific Publishers Ltd. IDENTIFICATION OF CYCLOPENTENYL FATTY ACIDS BY GAS LIQUID CHROMATOGRAPHY AND MASS SPECTROMETRY V.K.S. SHUKLA and E.M. ABDEL-MOETY Bundesanstalt fiir Fettforschung D-4400 Milnster (G.F,R.) E. LARSEN and H. EGSGAARD Chemistry Department, Risa National Laboratory DK-4000 Roskilde (Demark) Received October 2nd, 1978 accepted October 23rd, 1978 The straight chain fatty acids and the cyclopentenyl fatty acids present in the lipids of Hyclnocarpus wight~ana seeds were separated as their pyrrolidides by means of gas chromato- graphy. A gas chromatography-mass spectrometry system confirmed the complete separation and permitted the identification of the individual components in the sample. I. Introduction Cyclopentenyl fatty acids constitute up to 85% of the total fatty acids in the seed fats [ 1] ofHydnocarpus wightiana and other genera of Flacourtiaceae that have been used in the treatment of leprosy [2]. Small amounts of cyclopentenyl fatty acids have been traced in leaf lipids of Caloncoba echinata and Hydnocarpus anthelminthica [3] as well as in tissue cultures ofHydnocarpus anthelminthica [4]. The methyl esters of straight chain fatty acids and of cyclopentenyl fatty acids are not completely resolved in gas chromatographic analysis [1,5]. Vetter et al. [6] demonstrated the possibilities of using pyrrolidides in the mass spectrometric (MS) analysis of complicated alicyclic and aliphatic compounds. Shortly thereafter, Andersson et al. [7,8] studied the mass spectra of a range ofmonounsatu- rated and polyunsaturated fatty acid pyrrolidides and formulated a rule for the localization of double bonds in these compounds. Recently, we have analysed (V.K.S. Shukla et al., unpublished data) the total fatty acid pyrrolidides in tissue samples of arctic organisms. The present study reports the mass spectra ofpyrrolidide derivatives of cyclopentenyl fatty acids. Our data show that the straight chain fatty acids and cyclopentenyl fatty acids in a natural mixture can be unambiguously identified by combined gas liquid chromato- graphy (GLC) and mass spectrometry of their pyrrolidides. H. Materials and methods A. Materials and preparation of derivatives Reference compounds were purchased from Nu Check Prep, Elysian, MN, U.S.A. 285