Identification of minor acylglycerols less polar than triricinolein in castor oil by mass spectrometry.

摘要

Acylglycerols in castor oil less polar than triricinolein were identified by electrospray ionization-mass spectrometry using the lithium adducts of the acylglycerols in the HPLC fractions of castor oil. Thirty four new molecular species of acylglycerols containing hydroxy fatty acids in castor oil were identified by MS. The chain lengths of fatty acid substituents were C16, C18, C20, C22 and C23. The numbers of double bonds of the fatty acids were from zero to three. The numbers of hydroxyl groups on the fatty acid chains were from zero to three as previously reported. The structure of fatty acid, OH18:2, was proposed as 12-hydroxy-9,13-octadecadienoic acid. An unusual odd-numbered long-chain fatty acid, 23:0 (tricosanoic acid), was identified. Some new estolides and tetraacylglycerols, were identified as (12-ricinoleoylricinoleoyl)-ricinoleoyl-linoleoyl-glycerol (RRRL), (12-ricinoleoylricinoleoyl)-ricinoleoyl-oleoyl-glycerol (RRRO), (12-ricinoleoylricinoleoyl)-ricinoleoyl-palmitoyl-glycerol (RRRP), (12-ricinoleoylricinoleoyl)-ricinoleoyl-stearoyl-glycerol (RRRS) and (12-ricinoleoylricinoleoyl)-ricinoleoyl-linolenoyl-glycerol (RRRLn). The normal fatty acid (non-hydroxylated) of these tetraacylglycerols were directly attached to the glycerol backbone. The biosynthetic pathway of castor oil is proposed