Positional-Species Composition of Diacylglycerol Acetates from Mature Euonymus Seeds.

The positional-species composition (PSC) of 3-acetyl-1,2-diacyl-sn-glycerols (AcDAGs) from the seeds of mature fruits of 14 species of the genus Euonymus L. was established. The residues of six major fatty acids (FAs), palmitic (P), stearic (St), hexadecenoic (H), octadecenoic (O), linoleic (L), and linolenic (Ln), were present in the AcDAGs. Here, we demonstrated that the profile of PSC of AcDAGs could serve as chemotaxonomic factor to divide euonymus species studied here into groups which completely correlate with the present day systematic of the genus. In particular, the Euonymus section greatly exceeded other sections of the Euonymus subgenus as well as the Kalonymus one in the total levels of AcDAGs positional species having one and two O residues and was characterized by significantly lesser concentrations of species with one and two L residues. Moreover, in seed, AcDAGs of almost all Euonymus species EFL values were slightly higher than EFO ones, but all EFL and EFO values were higher than 1.0, and therefore, it can be concluded that both FAs mainly esterified sn-2-position of the glycerol moiety and saturated FAs residues were always virtually absent in the sn-2 position of Euonymus seed AcDAGs, as it is also the case in nearly all TAGs molecules of plant origin.

Dynamics of fatty-acid composition of neutral acylglycerols in maturing euonymus fruits.

The dynamics of the fatty-acid (FA) composition of neutral acylglycerols (NAGs) composed of 1,2,3-triacyl-sn-glycerols (TAGs) and 3-acetyl-1,2-diacyl-sn-glycerols (acDAGs) was determined in the fruit seeds and arils of three Euonymus L. species at three stages of their maturity. The NAG composition comprised 29 FAs, linoleic, oleic, palmitic, and α-linolenic acids being predominant. Noticeable amounts of other FAs, such as lauric, myristic, hexadec-9-enoic, stearic, (Z)-vaccenic, and arachidic acid, etc., could also be present. In the course of maturation, the qualitative composition of major FAs remained nearly unchanged, while the unsaturation index of FAs in seeds and in TAGs, as well as, but to a lesser extent, in arils and in acDAGs, respectively, always decreased. This decline was brought about by a sharp fall of the α-linolenate level, a decrease of the linoleate content, and a corresponding rise in the oleate content. It is suggested that, in both seeds and arils, both classes of NAGs were formed at the expense of the same FA pool; the quantitative composition of this pool was characteristic of a given fruit part and strongly changed during maturation. The accumulation of TAGs in E. europaeus fruits was accompanied by a conversion of hexadec-9-enoic acid into (Z)-vaccenic acid via the C2 -elongation reaction.

Occurrence of fatty acid short-chain-alkyl esters in fruits of Celastraceae plants.

Small amounts of a mixture of fatty acid short-chain-alkyl esters (FASCAEs) were obtained from the fruits of twelve plant species of Celastraceae family, and in five of them the FASCAEs were present not only in the arils but also in the seeds. These mixtures contained 32 individual FASCAE species, which formed four separate fractions, viz. FA methyl, ethyl, isopropyl, and butyl esters (FAMEs, FAEEs, FAIPEs, and FABEs, resp.). The FASCAE acyl components included the residues of 16 individual C14-C24 saturated, mono-, di-, and trienoic FAs. Linoleic, oleic, and palmitic acids, and, in some cases, also α-linolenic acid predominated in FAMEs and FAEEs, while myristic acid was predominant in FAIPEs. It can be suggested that, in the fruit arils of some plant species, FAMEs and FAEEs were formed at the expense of a same FA pool characteristic of a given species and were strongly different from FAIPEs and FABEs esters regarding the mechanism of their biosynthesis. However, as a whole, the qualitative and quantitative composition of various FASCAE fractions, as well as their FA composition, varied considerably depending on various factors. Therefore, separate FASCAE fractions seem to be synthesized from different FA pools other than those used for triacylglycerol formation.

Silver ion liquid-chromatographic mobility of plant diacylglycerols as a function of their composition and spatial arrangement.

Coordination complexes of unsaturated rac-1,2-diacylglycerols (DAGs) with silver ions were separated by adsorption and reversed-phase TLC (silver ion TLC and silver ion RP-TLC, respectively). During silver ion TLC, silver ion complexes are formed by an indeterminate number of coordination centers of various nature and only at the adsorbent surface; separation of the complexes proceeds according to an adsorption mechanism, and there is an inverse exponential relationship between DAG unsaturation and their mobility. With silver ion RP-TLC, the complexes are formed only with double bonds, only in solution, and at a 1:1 ratio; the complexes are fractionated by lipophilic partitioning between two liquid phases, and the relationship between the unsaturation of DAGs and their mobility is a direct linear one. Nevertheless, in spite of all these differences, the use of both methods demonstrated that DAG species characterized by a coiled acyl configuration always greatly exceeded in polarity those with the same unsaturation, but with the configuration close to an extended one; in the former group, this excess amounted to two- to three-fold and 30-40% for silver ion TLC and silver ion RP-TLC, respectively. In addition, for both versions of silver ion LC, these two groups of species differ from each other quantitatively, but not qualitatively, in the pattern of the relationship between the unsaturation and mobility of DAG complexes. Thus, under all conditions of silver ion LC studied here, the polarity of DAG complexes and, therefore, their mobility are conditional not only on the number of double bonds, but also on their configuration.