Lipase-Catalyzed Synthesis of Fatty Acid Pyridylcarbinol Ester for the Analysis of Seed Lipids

Numerous derivatives of fatty acids (FA), including esters of methanol/3‐hydroxymethylpyridine or dimethyloxazoline, are used for the analysis of FAs in biological specimens. Picolinyl derivatives are frequently prepared for structural determination by gas chromatography–mass spectrometry (GC‐MS) since they provide characteristic fragments. The ester can be prepared by chemical methods‐multistep methodologies or basic transesterification. Microbial lipases catalyze a number of transesterification reactions, and their catalytic activities are often stable at extreme conditions. Although these characteristic features may be useful in the application of typical FA structure analysis by picolinyl ester, detailed studies have not been reported. To address the problems, a simple and quantitative methodology for the synthesis of picolinyl esters from lipids has been developed. It involves the transesterification with Novozym 435 (Novozymes Biopharma US Inc., Franklinton, USA), resin‐immobilized lipase from Candida antartica in toluene. Mild reaction conditions allow for complete derivatization of perilla seed oil in 30 min at 50 °C. The procedure was further studied with various TAGs and fatty wax from 17 plants. The optimized procedure was as follows; 1 mg lipid and 20 mg catalyst in 2 mL toluene at 50 °C for 1 h. Quantitative analysis of marker FAs was performed with the proposed method. The results coincided well with those from potassium t‐butoxide‐catalyzed reaction. The optimized method, however, was not applicable for the determination of some epoxy FAs, fatty wax, and parinaric acid.