Revisiting <i>Securidaca longipedunculata</i> Seed Oil: Applying <scp>NMR</scp> and Mass Spectroscopy to Confirm the Presence of 2‐Acetyl‐1,3‐Diacyl– <i>sn</i> ‐Glycerols and Conjugated Hydroxydienoic Fatty Acids

ABSTRACT Based on a previous report of unusual conjugated hydroxydienoic fatty acids and triacyglycerols esterified with acetate groups, a re‐evaluation of the seed oil from the violet tree ( Securidaca longipedunculata Fres.) was conducted. Using a combination of GC‐FID and GC–MS analysis of FAMEs generated from the oil of mature seeds, the presence of coriolic acid (13‐hydroxy‐ cis ‐9, trans ‐11‐octadecadienoic acid) and two, related, shorter chain fatty acids (11‐hydroxy‐ cis ‐7, trans ‐9‐hexadecadienoic acid and 9‐hydroxy‐ cis ‐5, trans ‐7‐tetradecadienoic acid) was confirmed. Hydroxy fatty acids (HFA) accounted for 58% of the esterified fatty acids of the seed oil. Coriolic acid was not accompanied by the isomer 9‐hydroxy‐ trans ‐10, cis ‐12‐octadecadienoic acid as observed in the seed oil of Tagetes species, suggesting that the pathway of HFA biosynthesis in these species may be different. Optical activity was observed for S. longipedunculata seed oil, but in contrast to the oils of castor bean and Physaria fendleri which are rich in HFA and have positive specific rotation, S. longipedunculata oil has a strong negative specific rotation which can he attributed to the HFA components of the oil. Analysis of the oil by TLC, together with NMR, revealed the presence of sn ‐2 acetyl‐triacylglycerol and triacylglycerol without acetate, but not sn ‐3 acetyl‐triacylglycerol. The HFAs are components of the seed triacylglycerol but do not appear to be present in significant amounts at the sn ‐2 position. S. longipedunculata is a plant of considerable interest due to its novel HFA and oil structure and would be an excellent model for further study of the biosynthesis of unusual seed lipids.