ACETYLENIC ACID BIOSYNTHESIS IN CREPIS RUBRA

Time studies of crepenynic acid synthesis in Crepis rubra show that this acid is not present in the seed for several days after, flowering commences but builds up rapidly between the 14th and 28th days to become the major fatty acid of the seed oil. Radioactive tracer studies clearly demonstrate that the acetylenic bond is introduced into the carbon chain of a preformed long-chain fatty acid rather than built in during formation of the carbon chain. The nearest precursor found is oleic acid. There is no conversion to crepenynic acid by seed preparations of cis, cis-linoleic acid, cis,trans (trans,cis)-linoleic acid, or cis-12,13-epoxy-oleic acid. Possible biosynthetic pathways to explain these results are suggested. The crepenynic acid is chiefly, but not entirely, in triglycerides in the seed oil, and it has been shown to be esterified in the 2- and 3- positions of the triglyceride. © 1968 American Oil Chemists' Society.