FEATURES OF SAMPLE PREPARATION FOR ANALYSIS OF SEED OIL WITH CONJUGATE FATTY ACIDS: MOMORDICA COCHINCHINENSIS SEED OIL

A method of gac (Momordica cochinchinensis) seed oil sample preparation is proposed with allowance for high chemical lability of the compounds containing conjugated C=C-bonds. The method includes extraction at room temperature and purification by solid-phase extraction (SPE), n-hexane being a convenient solvent for oil extraction from seeds and the extract can be directly purified by oil sorption on the syringe (packed)cartridges filled with silica gel. However, before cleaning, it is necessary to verify the absence of catalytic activity of the sorbent towards chemically labile conjugated trienoic compounds. It has been shown that some commercial grades of silica gel can quickly disintegrate the oil. Using the developed method we obtained transparent seed oil with a refractive index of 1.503 typical for highly unsaturated oils, the oil content of seeds being 53%. Data of reversed-phase HPLC revealed the same set of triacylglycerols (TAG) characteristic of another Momordica species bitter melon (M. charantia) and contains di-α-eleostearate-stearate as a main component (47.9 ± 0.5 mol. %), each of triacylglycerol set has isomers wherein the radical of α-eleostearic acid is replaced by radical of α-eleoctearic acid. Fatty acid composition of the oil, calculated from TAG composition contains: 62.1 ± 0.3% eleostearic acids, 11.2 ± 0.3% linoleic, 5.5 ± 0.2% oleic, 1.5 ± 0.2% palmitic and 19.7 ± 0.4% stearic acids.

sample preparation, solid phase extraction, vegetable oil, Momordica cochinchinensis, acids with conjugated double bonds, HPLC

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