Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: January 28, 2005
Publication Date: November 1, 2006
Citation: Lin, J.T. 2006. Identification and Quantifications of the Molecular Species of [14c]Acylglycerols Incorporating Various [14c]Fatty Acids in Plant Microsomes and Non-Labeled Acylglycerols in Castor Oil by HPLC, in Triglycerides and Cholesterol Research (Welson, L. T., ed), Nova Science Publishers, Hauppauge, NY, 127-157. (book chapter). Interpretive Summary: This is a review of the author's accomplishments in triglycerides invited by the publisher to be published in a monograph. High-performance liquid chromatography (HPLC) method for the separation of the molecular species of triglycerides has been developed and used for the identification and quantification. The examples of the identification and quantification of the radiolabelled molecular species of triglycerides incorporated from various radiolabelled fatty acids in castor microsomes are given as well as those of the non-radiolabelled castor oil. The presence of a hydroxyl group on ricinoleate (12-hydroxyl, C18 long-chain fatty acid) underlies many industrial uses such as the manufacture of lithium grease, plastics, coatings and cosmetics. Castor oil contains 90% of its fatty acids (FA) as ricinoleate and is the only commercial source of ricinoleate. The HPLC methods were used to establish the biosynthetic pathway of castor oil and were used to determine the control steps on the pathway driving ricinoleate into castor oil. Castor plant is toxic. The control steps on the pathway can be the targets of the genetic engineering for the new oil seed plant to produce castor oil substitute.
Technical Abstract: High-performance liquid chromatography (HPLC) can be used for the identification and quantification of the molecular species of acylglycerols (AG) using a C18 column and linear gradient from methanol to isopropanol. The molecular species of [14C]AG incorporated from six radiolabelled fatty acids (FA) in castor microsomes were identified by HPLC with a flow scintillation analyzer. The six [14C]FA used were stearate (S), oleate (O), linoleate (L), linolenate (Ln), ricinoleate (R) and palmitate (P). Sixty-one radiolabelled molecular species of triacylglycerols (TAG) and diacylglycerols (DAG) incorporated were identified by co-chromatography with the standards and by the elution characteristics of the molecular species when the standards were not available. Ricinoleate was the major FA incorporated into TAG, whereas stearate, linolenate and palmitate were incorporated at low levels. Sixteen molecular species of AG in castor oil were identified and quantified by HPLC with an evaporative light scattering detector. RRR constituted about 71% of castor oil. The results of [14C]FA incorporation are consistent with ricinoleate being preferentially driven into TAG and oleate being converted to ricinoleate in castor oil biosynthesis. The incorporation of [14C]ricinoleate into TAG in soybean microsomes was slightly better than that of [14C]oleate and indicated that soybean was capable of incorporating ricinoleate into TAG when ricinoleate can be produced endogenously in a transgenic soybean. The incorporation of FA into TAG in soybean microsomes was much slower than those in castor microsomes.