Anatoly V. Zhukov

Occurrence of fatty acid lower-alkyl esters in euonymus fruits

Small amounts of a mixture of fatty acid lower-alkyl esters (FALAEs) were obtained from chloroform extracts of the fruit arils and seeds of four euonymus species (Euonymus sp., Celastraceae). The FALAEs were the products of biosyntheses in the cell rather than experimental artifacts. By using GC-MS, this mixture was shown to contain a total of 19 individual FALAE species comprising four separate fractions, viz. methyl (FAMEs), ethyl (FAEEs), n-propyl, and n-butyl FA esters. Fruit FALAEs included mainly FAEEs and, to a lesser extent, FAMEs, while the n-propyl and n-butyl FA esters, which occurred less frequently, were found here for the first time as the plant products. The FALAE acid components included C14-C18 saturated, mono-, di-, and trienoic FAs with the predominance of ubiquitous linoleic, oleic, palmitic, and, in some cases, also α-linolenic acid. The indices of qualitative and quantitative composition of separate FALAE fractions varied considerably depending on the plant species, fruit part (aril or seed), and the extent of fruit maturity. It can be supposed that, in some euonymus species, FAMEs and FAEEs are formed at the expense of the same FA pool characteristic for a given species. As a whole, euonymus FALAEs and triacylglycerols seem to be synthesized from different FA pools. Discussed is the physiological significance of FALAE biosynthesis in plant metabolism, possible pathways of this biosynthesis, as well as the perspectives of further investigations of FALAEs of plant origin.

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.

Accumulation of neutral acylglycerols during the formation of morphologo-anatomical structure of euonymus Fruits

At three stages of fruit ripening of three euonymus species (Euonymus sp.), growth parameters, the development of morphologo-anatomical structure, and the accumulation of neutral acylglycerols (NAG) of fatty acids were studied. It was established that, in all species studied, in the cells of endosperm and cotyledons, as well as in arillus cells, small oleosomes of similar size were formed, whereas in Euonymus europaeus and E. maximowiczianus large oleosomes differing in their sizes also appeared. Independently of fruit age, dry weight of seeds exceeded that of arils by several times. At the determination of separate NAG classes: TAG (1,2,3-triacyl-sn-glycerols) and acDAG (3-acetyl-1,2-diacyl-sn-glycerols), it was shown that the absolute content of acDAG in seeds was 1.5 orders of magnitude higher than that of TAG; in contrast, in arils TAG were much more abundant than acDAG. Euonymus species differed markedly in the growth pattern and NAG accumulation in seeds and arils.

Palmitic acid and its role in the structure and functions of plant cell membranes

The content of palmitic acid (PA) in the fractions of plant lipids of different polarity were investigated. The following relationship was revealed: when polarity of lipid fraction rose, the content of PA in total fatty acids of this fraction increased. It was shown that in a number of consecutive extracts of total lipids isolated from plant tissue with the same solvent each next extract containing more tightly bound lipids carries more PA. Predominance of this fatty acid within high-polar lipids that may be compared to annular lipids and are indispensable for operation of numerous enzymatic systems are discussed. A considerable quantity of PA was shown in wheat mitochondrial membranes; under cold stress, its level rose even higher. Among phospholipids, the greatest content of PA is usually associated with phosphatidyl inositols, while that among glycolipids is with sulfoquinovosyl diacylglycerols.

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.

Mild non-enzymatic hydrolysis of an ester bond between the orthophosphoric acid and ethanolamine residues in phosphatidylethanolamines

Abstract Acetylation of phosphatidylethanolamine (PE) yielding its N -acetamide (AcPE) brings about changes in the charge and conformation of the polar head group. As a result, the POC bond of AcPE can be hydrolysed, with the formation of ethanolamine (EA) N -acetamide (AcEA), under much more mild conditions than the respective bond in the original PE. Thus, introduction of an acyl substituent into the PE amino moiety exerts a profound effect on the course of hydrolysis of the PE POC bond separated from this moiety by two CH 2 segments.

Fatty Acid Composition of Lipids from Leaves and Strobila of Cycas Revoluta ( Cycas revoluta )

Fatty acid (FA) composition of lipids from leaves and differentiated fleshy strobila tissues and sporangia with spores of Cycas (Cycas revoluta Thumb.) after their step quantitative extraction from plant material was investigated. Quantitative content and qualitative composition of FAs of extractable and nonextractable leaf lipids were determined. It was established that flesh lipids of sporophylls are characterized by a high saturation level and contain a considerable proportion of saturated FAs with the usual chain length (C12–C18, 53–57%). At the same time, total amount of etherified FAs with a very long chain in lipids not extractable by the method of Zhukov and Vereshchagin exceeds several times that found in extractable lipids (~15 and ~4%, respectively). Neutral lipids of Cycas spores were represented by triacylglycerols, the lower-alkyl esters of FAs, free FAs, and sterol esters.