Submitted to: Meeting Abstract
Publication Type: Abstract only
Publication Acceptance Date: 12/5/2006
Publication Date: 5/13/2007
Citation: Lin, J.T., Arcinas, A.J. 2007. Identification of Regiospecific Isomers of Diricinoleoyl-acyl-glycerols containing one non-ricinoleoyl chain in Castor Oil by ESI-MS. Meeting Abstract. Interpretive Summary: Ricinoleate, an industrially useful hydroxy fatty acid occurs abundantly as triglycerides in castor bean, in addition to the toxin, ricin. We have used mass spectrometry to show the location of the non-ricinoleoyl chain on the molecules of triglycerides in castor oil. The determination of the location of the non-ricinoleoyl fatty acid on molecules of triglycerides identifies the enzymatic step driving non-ricinoleoyl fatty acids into castor oil. This information can be used to block the incorporation of the non-ricinoleoyl fatty acid into seed oils in transgenic plants to increase the ricinoleate content in transgenic seed oil.
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 at sn-2 position. The content of 1,3-diricinoleoyl-2-oleoyl-sn-glycerols (ROR) in the three stereospecific isomers, RRO, ROR and ORR, combined is about 88%. The contents of other 1,3-diricinoleoyl-2-acyl-glycerols in the three stereospecific isomers combined are 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, 100%; 1,3-diricinoleoyl-2-palmitoyl-sn-glycerol, 78%; and 1,3-diricinoleoyl-2-lesqueroloyl-sn-glycerol, 31%. These non-hydroxyl fatty acids are mostly at the sn-2 position of triacylglycerols in castor oil. On the biosynthetic pathway of castor oil, the phospholipase A2 hydrolysis of PC containing non-hydroxyl fatty acid at the sn-2 position is either blocked or partially blocked in vivo. 1,3-Diricinoleoyl-2-lesqueroloyl-glycerol is about one third of the three isomers combined. 2-Lesqueroloyl-PC can be hydrolyzed by castor phospholipase A2 as well as 2-ricinoleoyl-PC.