ARS | Publication request: Regiospecific Quantification of Triacylglycerols Containing Dihydroxy Fatty Acids in Castor Oil by Mass Spectrometry

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 15, 2009
Publication Date: November 18, 2009
Citation: Lin, J.T. 2009. Regiospecific Quantification of Triacylglycerols Containing Dihydroxy Fatty Acids in Castor Oil by Mass Spectrometry. International Sympoisijm of Biocatalysis and Biotechnology, November 18-20, 2009, Taichung, Taiwan.

Interpretive Summary: Ricinoleate, a monohydroxy fatty acid in castor oil, has many industrial uses. Dihydroxy fatty acids and triacylglycerols containing dihydroxy fatty acids have different physical properties, e.g., viscosity, pour point, melting point, from those of ricinoleate, and can be used in industry similar to those of ricinoleate with different physical properties. The regiospecific isomers of triacylglycerols also affect the physical properties of the oil. The quantification of regiospecific isomers of triacylglycerols containing dihydroxy fatty acids in castor oil will be presented in the meeting.

Technical Abstract: The triacylglycerols (TAG) containing dihydroxy fatty acids have been recently identified by mass spectrometry in castor oil. These new dihydroxy fatty acids were proposed earlier as 11,12-dihydroxy-9-octadecenoic acid (diOH18:1), 11,12-dihydroxy-9,13-octadecadienoic acid (diOH18:2) and 11,12-dihydroxyoctadecanoic acid (diOH18:0). The regioisomers of the TAG were quantified by fragment ions from the loss of fatty acids at the sn-2 position as a,ß-unsaturated fatty acids by electro spray ionization-mass spectrometry of the lithium adducts (MS3). The content of regio-isomeric diOH18:1-OH18:1-diOH18:1 (ABA, with two identical fatty acids) was about 92 % in the total of the three stereo-isomeric diOH18:1-OH18:1-diOH18:1, OH18:1-diOH18:1-diOH18:1 and diOH18:1- diOH18:1-OH18:1 combined. The approximate contents of regio-isomers of other TAG were as follows: diOH18:1-OH18:1-OH18:1 (92%), diOH18:1-diOH18:0-diOH18:1 (91%), diOH18:2-OH18:1-OH18:1 (80%) and diOH18:0-OH18:1-OH18:1 (96%). The regioisomers of the TAG with three different fatty acids (ABC) were quantified as about 7:1:2 (OH18:1 : diOH18:1 : diOH18:2 at the sn-2 position) in the total of the six stereo-isomeric TAG combined, and about 7:2:1 (OH18:1 : diOH18:0 : diOH18:1 at the sn-2 position) in the total of the six stereo-isomeric TAG combined. Ricinoleate (OH18:1) was predominately at the sn-2 position of TAG (AAB and ABC) containing dihydroxy fatty acids and ricinoleate. The dihydroxy fatty acids were mainly at the sn-1,3 positions of the TAG in castor oil.