Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/2/2005
Publication Date: 7/1/2005
Citation: Lin, J.T., Wani, S., Nguyen, T.T., Mckeon, T.A. 2005. Incorporation of laurate into phosphatidylcholines and acylglycerols in castor microsomes. Journal of the American Oil Chemists' Society. 82: 495-499. Interpretive Summary: The presence of a hydroxyl group on ricinoleate (12-hydroxyoleate, 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. We have recently studied the incorporation of six endogenous long-chain FA into castor oil in castor microsomes. Ricinoleate was incorporated into castor oil most effectively among the six FA. Since the position of the hydroxyl group on ricinoleate (C18) is the same as 12-hydroxylaurate (C12), castor microsomal incorporation of radiolabelled laurate (La), 11-hydroxylaurate and 12-hydroxylaurate into PC and AG was of interest to determine the flexibility of castor in producing other hydroxyl FA. Laurate can be incorporate into castor oil at much slower rate than ricinoleate, while 11-hydroxylauric acid and 12-hydroxylauric acid cannot be incorporated.
Technical Abstract: Because castor produces oil with a high content of hydroxyl fatty acid (90% ricinoleate), we were interested in determining the flexibility of castor seed microsomes in incorporating other hydroxyl fatty acids. To this end, we incubated the [14C]-labelled 12:0 fatty acids (FA), laurate (La), 11-hydroxylaurate and 12-hydroxylaurate with castor microsomes that are capable of synthesizing castor oil. The molecular species of phosphatidylcholines (PC) and acylglycerols (AG) incorporating these non-endogenous FA of castor were identified by the reversed-phase C8 and C18 HPLC respectively. [14C]Laurate was incorporated into the molecular species of PC and AG at levels of 10% and 4% respectively, comparing to incorporation of [14C]ricinoleate. Similar to those from the incorporation of the six [14C]FA, ricinoleate (R), oleate (O), linoleate (L), linolenate (Ln), stearate (S) and palmitate (P) reported, the molecular species of PC incorporating [14C]laureate were LLa-PC > PLa-PC > OLa-PC > LnLa-PC > SLa-PC > RLa-PC. the molecular species of AG incorporating [14C]laurate were RRLa > LaLa > RLa > RLLa > ROLa > LOLa > LLLa > LLa > LLnLa > RSLa > OOLa. The retention times for lipids incorporating laurate are similar to those of lipids incorporating linolenate, because the equivalent carbon numbers of laurate and linolenate are the same. Relative retention times of the molecular species of PC and AG containing laurate are also reported here. The incorporation of 11-hydroxylaurate and 12-hydroxylaurate into PC and AG was not detected.