Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 4/1/2007
Publication Date: 11/28/2007
Citation: Lin, J.T. 2007. Biosynthesis of castor oil studied by the regiospecific analysis of castor triacylglycerols by ESI-MS. In: Hou, C.T, and Shaw, J.F., editors. Biocatalysis and Bioenergy for Functional Foods and Industrial Products. New York, NY:CRC Press. p. 449-461. Interpretive Summary: Castor oil contains high level of ricinoleate (hydroxyl fatty acid) for industrial uses. However castor also contains toxic substances. It is desirable to produce ricinoleate in other oil seed plants. It is important to know the biosynthetic pathway of castor oil to develop other plants to produce ricinoleate. Using mass spectrometry, regiospecific isomers of triacylglycerols in castor oil were identified and quantified. The results suggested an enzymatic step that could be targeted for inhibition to increase the ricinoleate content in other oil seed plants.
Technical Abstract: HPLC fractions of diricinoleoyl-acyl-glycerols containing one non-ricinoleoyl chain from castor oil were used to identify the regiospecific location of this non-ricinoleoyl chain on the glycerol backbone using electrospray ionization-MS3 of lithium adducts. The regiospecific ions used were from the loss of unsaturated fatty acid specific ally at the sn-2 position. The content of 1,3-diricinoleoyl-2-oleoyl-sn-glycerols (ROR) among the three stereospecific isomers, RRO, ROR and ORR, was about 91%. The contents of other 1,3-diricinoleoyl-2-acyl-glycerols among the three stereospecific isomers were as follows: 1,3-diricinoleoyl-2-linoleoyl-sn-glycerol, 95%; 1,3-diricinoleoyl-2-linolenoyl-sn-glycerol, 96%; 1,3-diricinoleoyl-2-stearoyl-sn-glycerol, 96%; 1,3-diricinoleoyl-2-palmitoyl-sn-glycerol, 78%; and 1,3-diricinoleoyl-2-lesqueroloyl-sn-glycerol, 31%. These non-hydroxyl fatty acids were mostly at the sn-2 position of triacylglycerols in castor oil. Inhibition of phospholipase C hydrolysis of phosphatidylcholine (PC) might be used to block the incorporation of non-hydroxyl fatty acids into triacylglycerols, thus increasing the content of ricinoleate in seed oil.