A high performance liquid chromatographic (HPLC) method is described for the determination of conjugated linoleic acids (CLA) and conjugated linolenic acids (CLN). Methyl esters prepared from purified lipid fractions of soybean oil were analyzed using HPLC system equipped with photodiode-array detector to detect peaks having maximum absorption around 233 nm and 275 nm. These peaks were concentrated by AgNO 3 -silicic acid column chromatography and reversed-phase HPLC.The structural analysis, of dimethyloxazoline (DMOX) derivatized methyl esters, using GC-MS showed the occurrence of 9,11-and 10,12-conjugated linoleic acids (CLA) and 8,10,13-, 8,10,12-and 9,11,13-conjugated linolenic acids (CLN). The comparison of these conjugated fatty acids with authentic isomers by HPLC revealed the presence of isomeric mixtures of CLA (cis(c),trans(t) or t,c and t,t) and CLN (c,t,t or t,t,c and t,t,t).Traces of 9,11-and 10,12-CLA (c,t or t,c) was found in crude oil. CLN isomers (8,10,12-18:3 and 9,11,13-18:3) were found to be forming during bleaching of soybean oil processing. 8,10,13-CLN and 9,11-and 10,12-CLA (t,t) were only found in soybean oil after deodrization step. CLN contents in commercial soybean oil varied from 387 mg/kg oil to 1316 mg/kg oil. Decreased level of bleaching earth and temperature resulted in reduced CLN content. Possibly, CLN would be derived from linoleate hydroperoxides formed during processing and storage of soybean oil.KEY WORDS: HPLC, CLA, CLN, soybean oil, lipid oxidation. 2Conjugated fatty acids have evoked increased interest due to the beneficial effects they afford in terms of human health. Among them, conjugated linoleic acid (CLA) has been researched and reviewed extensively in relation to its occurrence (1), metabolism and physiological effects (1-4). On the other hand, several researchers have reported the occurrence of various conjugated fatty acids including trienes, tetraenes and pentaenes in different plant resources from both terrestrial and aquatic enviroments.Conjugated linolenic acids (CLN) have been reported to occur in terrestrial plant lipids, especially seed oils. Important CLN from plant sources include α-eleostearic acid (9cis(c),11trans(t),13t-18:3), catalpic acid (9t,11t,13c-18:3), punicic acid (9c,11t,13c-18:3), calendic acid (8t,10t,12c-18:3) and jacaric acid (8c,10t,12c-18:3) (5).On another hand, Yurawecz et al. (6) only could find traces (up to 0.2%) of CLN in vegetable oils in their study of 27 oils for CLN content by UV measurement. The isomers were identified as α-eleostearic acid (9c,11t,13t-18:3), β-eleostearic acid (9t,11t,13t-18:3), and 8t,10t,12t-18:3. The possible mechanism for the formation of these CLN isomers involves linoleate oxidation, reduction of hydroperoxide to hydroxide, and dehydration (7,8). CLN exhibits less oxidative stability as reported by our previous study (9), indicating that CLN may influence oxidative deterioration of vegetable oils, in spite of being present in trace.Crude oil is refined by a series of processes to remove impu...

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The presence of conjugated trienoic acids were found in the purified fish oil from the Japanese sardine by an analysis of high performance liquid chromatography equipped with a photodiode-array detector. Gas chromatography-mass spectrometry indicated that main conjugated trienoic acids were those of 16:3, 20:5, and 22:6. Conjugated trienoic acid of 16:3 was identified as a cyclopropanoid acid with conjugated triene by NMR analysis. All conjugated trienoic acids were formed by heat treatment during the deodorization of fish oil, but not found after de-gumming, alkaline refining, and bleaching. Conjugated trienoic acids of 16:3, 20:5, and 22:6 originated from 16:4n-1, 20:5n-3 (EPA), and 22:6n-3 (DHA) in the fish oil during the heat treatment for deodorization.