Molecular Species of Acylglycerols Incorporating Radiolabeled Fatty Acids from Castor (Ricinus communis L.) Microsomal Incubations

Sixty-one molecular species of triacylglycerols (TAG) and diacylglycerols produced from castor microsomal incubations incorporating six different 14C-labeled fatty acids have been identified and quantified. The preference for incorporation into TAG was in the order ricinoleate > oleate > linoleate > linolenate > stearate > palmitate. Ricinoleate was the major fatty acid incorporated, whereas stearate, linolenate, and palmitate were incorporated at low levels. Twenty-one molecular species of acylglycerols (HPLC peaks) in castor oil have also been assigned. The levels of TAG in castor oil are RRR (triricinolein) ≫ RR-TAG ≫ R-TAG > no R-TAG. The levels of the molecular species within the groups of RR-TAG, RL-TAG, and LL-TAG individually are ricinoleate > linoleate > oleate > linolenate, stearate, and palmitate. The results of the labeled fatty acid incorporation are consistent with ricinoleate being preferentially driven into TAG and oleate being converted to ricinoleate in castor oil biosynthesis. Keywords: Molecular species; triacylglycerol; diacylglycerol; castor oil; biosynthesis; HPLC; relative retention times; Ricinus communis L.