, Volume 72, Issue 9, pp 1037-1042

The structure of the triacylglycerols, containing punicic acid, in the seed oil ofTrichosanthes kirilowii

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Abstract

Triacylglycerols of the seed oil ofTrichosanthes kirilowii have been resolved by high-performance liquid chromatography (HPLC) in the silver-ion and reverse-phase modes. The fatty acids were identified by gas chromatography/mass spectrometry as the picolinyl esters. The main components arecis,cis-C18:2n-6 (38.2 mole%), C18:39c,11t,13c (punicic acid, 38.0 mole%), andcis-C18:1n-9 (11.8 mole%). Small amounts of C18:39c,11t,13t (α-eleostearic acid) and C18:39t,11t,13c (catalpic acid) were detected. Silver-ion HPLC exhibited excellent resolution in which fractions were resolved on the basis of the number and configuration of double-bonds. In this instance, the strength of interaction of a conjugated trienoic double-bond system with silver ions seemed to be between that of dienoic and monoenoic double bond systems. The triacylglycerols were also separated into 20 fractions by reverse-phase HPLC, and the fractionation was achieved according to the partition number in which a conjugated trienoic double bond was not equivalent to three monoenoic double bonds in a molecule with a given chainlength. The principal triacylglycerol species are (C18:2n-6) (C18:39c,11t,13c )2 (28.3 mol% of total), (C18:1n-9)(C18:2n-6) (C18: 39c,11t,13c ) (19.0 mol%), and (C18:2n-6)2(C18:39c,11t,13c ) (16.2 mol%), while simple triacylglycerols such as (C18:39c11t,13c )3 and (C18:2n-6)3 were present as minor components only (<1.0 mol%). Species esterified with conjugated trienoic acids comprise more than 96% of the total.

Stereospecific analysis gave rise to insurmountable difficulties, but it is evident that there is some asymmetry in the distribution of fatty acids in the molecules.