The search for polyprenols in dendroflora of Vietnam

The occurrence of polyprenols in leaves of over 340 species of dendroflora in natural habitats in the regions of Hanoi and Hue in Vietnam was studied. Plant material was collected in the late autumn (October/November) during the end of a vegetation season. Leaves of about 200 plant species did not contain detectable amounts of polyprenols in contrast to few systematic families, e.g. Moraceae, Euphorbiaceae, where polyprenols were highly abundant and their pattern could be used as a chemotaxonomic criterion. Most often dominating polyprenols were prenol-11 and prenol-12. In several angiosperm species prenol-13 and detectable amounts of prenol-14 were also found. The incidence of prenol-13 and -14 was not restricted to a specific taxonomic group since species exhibiting domination of such longer chain polyprenols belonged to various systematic families. In some plants (e.g. Ceiba pentandra) alpha-cis polyprenols were accompanied by alpha-trans counterparts. This report describes several new plant species that may serve as natural sources of long chain polyprenols.     

Long-chain polyprenols in gymnosperm plants

Over 100 species of gymnosperm plants were checked for the presence of long chain polyprenols. Poly-cis long chain prenols, mainly as acetates, were found in green needles of about 60 species. In Cycadopsida either prenol-18 or prenol-20 were the main components of the natural polyprenol mixture. In Coniferopsida either a single polyprenol family was present like in all species of Pinaceae, or polyprenols consisted of two families differing in the size of polyprenol molecules: one family in which prenol-17 was the dominating component, and the other family of prenol-23. These complex mixtures of polyprenols were present in Araucariaceae, Cupressaceae, Taxodiaceae and also in Taxopsida. Seasonal variations were observed in the polyprenol content in green leaves.     

The occurrence of long chain polyprenols in leaves of plants of Rosaceae family and their isolation by time-extended liquid chromatography.

The long chain polyprenols composed of 30 and more isoprene units from leaves of plants belonging to the genera Potentilla and Rosa have been described. They occur in the form of fatty acid esters. The composition of polyprenol mixture was species dependent and its content reached ca. 0.5% wet weight. Large scale preparation of individual polyprenols from a natural polyprenol mixture was performed using time-extended liquid chromatography on the hydrophobic gel Lipidex-5000.     

Light conditions alter accumulation of long chain polyprenols in leaves of trees and shrubs throughout the vegetation season

In many plants belonging to angiosperms and gymnosperms the accumulation in leaves of long chain polyprenols and polyprenyl esters during growth in natural habitats depends on the light intensity. The amount of polyprenols in leaves is also positively correlated with the thickness of the leaf blade (SLA, specific leaf area). The polyprenol content of leaves shows seasonal changes with a maximum in autumn and a minimum in early summer with the difference between poorly and well illuminated plants persisting throughout the vegetation season.     

银杏叶聚戊烯醇抗肿瘤的生物活性研究

目的 :从银杏叶中分离聚戊烯醇新的有效部位 ,研究聚戊烯醇抗肿瘤的药效。方法 :通过提取、分离、精制 75 %以上银杏叶聚戊烯醇 ,以氟脲嘧啶 (5 Fu)为对照 ,选择肝癌 (Heps)实体型、肉瘤 (S180 )、艾氏癌 (EC)实体型等瘤谱 ,用不同剂量的聚戊烯醇进行小鼠移植性抗肿瘤药效实验。结果 :银杏叶聚戊烯醇对Heps、S180 和EC等移植性瘤谱的最高抑瘤率分别为 4 9 2 9%、6 0 89%和 5 2 4 7% (p <0 .0 0 5 )。结论 :银杏叶聚戊烯醇具有明显的抑制肿瘤的生物活性。     

The occurrence of unique, long-chain polyprenols in the leaves of Potentilla species

Polyprenols are accumulated in the leaves of Potentilla anserina at concentration up to 0.3% fresh weight. They constitute a mixture of poly-cis fully unsaturated analogues of up to 29 isoprene units long. In this and other species of Potentilla the polyprenol mixture is composed of two families, one grouping the medium chain-length polyprenols (built up of about 20 isoprene units), and the second one, composed mainly of very long prenolgues from 24 to approx. 28 isoprene units. This is a first report on the occurrence of polyprenyl alcohols of this chain length in plant material and the first one on the presence of multiple polyprenol mixture in angiosperms. A useful modification of polyprenols preparation from plant material, based on solid phase extraction with hydrophobic gel Lipidex-5000 is described.     

Long-chain betulaprenol-type polyprenols from the leaves of Ginkgo biloba.

A long-chain betulaprenol-type polyprenol mixture was isolated from the leaves of Ginkgo biloba mainly as acetate. The structure was determined by mass spectroscopy, 1H-n.m.r. spectroscopy and 13C-n.m.r. spectroscopy. The mixture contained polyprenols-14-22, predominantly polyprenols-17, -18 and -19, and consisted of the dimethylallyl terminal unit (omega-terminal), two trans-isoprene residues, a sequence of 11-19 cis-isoprene residues and a terminal hydroxylated isoprene unit (alpha-terminal) aligned in that order. The concentration of these polyprenols in leaves increased from 0.04 to 2.0% of dry wt. with maturing of the leaves, though the content of total lipids was constant. The distribution of chain length in these polyprenols showed little variation throughout the whole life of the leaves.     

The occurrence and seasonal distribution of C50-C60-polyprenols and of C100-and similar long-chain polyprenols in leaves of plants

Large amounts of fully unsaturated, mainly-cis, higher isoprenoid alcohols consisting of 17-30 isoprene units were found in several plants of the Rosaceae family. They occur as mixtures of several prenologues with either C85 - or C100 - prenol dominating in the form of acetates. The highest level of these polyprenols (0.5-1.0% of wet weight) were found in Crataegus crus- galli , Cotonoaster lucida, Prunus serotina and Sorbus suecica (intermedia). Their content increased with increasing age of the leaves. The dynamics of this rise is different from that observed in the case of accumulation of free C50- C60 - prenols (up to 0.5% of wet weight) in leaves of various plant species.     

Uptake and metabolism of polyprenols by animal cells cultured in vitro

Several mammalian, chicken, and mosquito cells grown in vitro take up tritiated dolichol supplied to the incubation medium. The extent of labelling varied markedly between different cell cultures. After 20 h incubation most of the dolichol taken up was unchanged and the major product of metabolism of dolichol was identified as its fatty acid esters. Green-monkey kidney cells were tested with 8 fully unsaturated and 6 alpha-saturated polyprenols ranging from C35 to C105. In general the uptake of alpha-saturated polyprenols (dolichol type, was higher. Considerable differences were found between the uptake of polyprenols of differing chain lengths. Less than 1% of the polyprenols taken up was converted into more polar product, mainly polyprenyl phosphates and polyprenyl phosphate sugars. The short-chain polyprenols, from C35 to C65, were metabolized more rapidly than the long-chain polyprenols, as judged from the amount of polar products and fatty acid esters of polyprenols.     

Acyl esters of polyprenols: specificity of microsomal transacylase for polyprenols of different chain length and saturation

Transfer of fatty acids from phospholipids to polyprenols, catalysed by the transacylase from rat liver microsomes, was investigated. The specificity of the enzyme for polyprenols of different chain length and different degree of saturation was studied using individual isoprenologues, the preparation of which in highly tritiated form is described. It was found that short-chain polyprenols are better substrates for the enzyme than long-chain polyprenols, and alpha-saturated better than unsaturated or multiply saturated polyprenols. Short-chain, alpha-saturated single isoprenologues were several-fold more active as acyl acceptors than natural dolichol.     

The occurrence of polyprenols in seeds and leaves of woody plants

The contents of the heterogenous group of polyisoprenoids was found about two orders of magnitude lower in seeds than the amount of polyprenols and/or their carboxylic esters accumulated during vegetation season in leaves. In contrast to leaves, no seeds were found containing more than 0.5 mg of these lipids per gram of dry tissue. Almost 50% had less than 0.01 mg/g - the amount which is the limit of detection by the procedure used in this work. In gymnosperms (10 representatives of Cupressaceae, Pinaceae and Taxaceae) the polyprenol spectra in seeds and in needles were similar. In angiosperms (25 representatives of 13 botanical families) the polyisoprenoid mixture in seeds resembled the minor, additional subfamily found in leaves.     

银杏叶中聚戊烯醇类化合物的研究进展

本文对银杏叶中聚戊烯醇类化合物的研究作了综述,主要包括它们的化学结 构、提取分离方法、光谱特征、分析方法、作用,以及多萜醇的合成等。并对其研究前景进 行了展望。     

Subcellular fractionation of polyprenyl diphosphate synthase activities responsible for the syntheses of polyprenols and dolichols in spinach leaves

Polyisoprenoid alcohols occurring in spinach leaves were analyzed by a two-plate TLC method. Z,E-mixed polyprenols (C(55-60)), glycinoprenols (C(50-55)), and solanesol (C(45)) were mainly found in chloroplasts, whereas dolichols (C(70-80)) were mainly found in microsomes. Analysis of enzymatic products derived from [1-(14)C]isopentenyl diphosphate and farnesyl diphosphate (FPP) with subcellular fractions revealed that chloroplasts and microsomes had the ability to synthesize Z,E-mixed polyprenyl (C(50-65)) and all E-polyprenyl (C(45-50)) diphosphates, and Z,E-mixed polyprenyl (C(70-85)) diphosphates, respectively. FPP and geranylgeranyl diphosphate (GGPP) were both accepted for these enzymatic reactions, the former being a better substrate than the latter. NMR analysis of naturally occurring spinach Z,E-mixed polyprenol (C(55)) and dolichol (C(75)) revealed that the number of internal trans isoprene residues in the former was three in comparison with two internal trans residues found for the latter. These results indicate that two kinds of polyprenyl diphosphate synthases occur in spinach: One is the chloroplast enzyme involved in the synthesis of the shorter-chain (C(50-65)) Z,E-mixed polyprenols and the other is the microsomal enzyme involved in the synthesis of longer-chain (C(70-85)) Z,E-mixed polyprenols, which is converted to dolichols.     

Dolichols of the fern Matteucia struthiopteris

Dolichols isolated from leaves of the fern Matteucia struthiopteris were present as a mixture of prenologues composed of 14 up to 20 isoprene units with Dol-16 dominating. They comprised approximately 0.004% of the fresh weight of fresh plant tissue and were accompanied by traces of polyprenols (Pren-14 up to Pren-17, Pren-16 dominating). Their structure was confirmed by electropray ionization mass spectrometry (ESI-MS). This is the first time that dolichols have been reported as dominating polyisoprenoid alcohols in plant photosynthetic tissue.     

The uptake of dietary polyprenols and their modification to active dolichols by the rat liver

The uptake of dietary polyprenols was studied by administering, through a gastric tube, labeled alpha-saturated and alpha-unsaturated polyprenols, with 11 and 19 isoprene residues. The lipids appeared in all organs but mostly in the liver after 16 h where those with 11 isoprenes were in much higher concentration than the prenols with 19 isoprene residues; the distribution in the liver was studied in detail. About 45% of the polyprenols taken up were esterified with fatty acids. A part of the radioactivity (6-30%) appeared in the supernatant but mostly in water-soluble form. Among subcellular fractions, the highest uptake was found in the outer mitochondrial membranes. After 16 h, both 11- and 19-residue alpha-unsaturated injected prenols were present to a large extent as alpha-saturated compounds in liver homogenates and subcellular fractions. About 10-15% of the lipids were phosphorylated. The results suggest that a part of the dolichol phosphate pool, participating in glycosylation reactions, may derive from dietary unsaturated polyprenols which after uptake can be reduced and phosphorylated.     

Alloprenols: novel alpha-trans-polyprenols of Allophylus caudatus

A novel type of polyprenols, alloprenols, with an α-trans-isoprenoid unit was found in the leaves of Allophylus caudatus (Sapindaceae) besides typical α-cis-polyprenols. The polyprenol family (Prenol-11-13, Prenol-12 dominating) was accompanied by traces of dolichols of the same chain-length. Prenol α-cis- and α-trans-isomers were chromatographically separated and their structure was analyzed by HPLC/ESI-MS, HR-ESI-MS and ¹H and ¹³C NMR spectroscopy. Model compounds, semi-synthetic α-isomers of all-trans-Pren-9 and mainly-cis-Pren-11, were obtained using an oxidation-reduction procedure. Comparison of their NMR spectra confirmed the structure of the newly identified polyprenols. The observed pattern of NMR signal shifts may be applied for elucidation of isoprenoid structure.     

Long chain polyisoprenoid alcohols in leaves of Capparis species.

Leaves of twelve species of the genus Capparis were examined for the presence of long chain polyisoprenoid alcohols. In a number of species the accumulation of polyisoprenoid alcohols was up to about 0.3% of dry weight of tissue. In all studied species polyisoprenoid alcohols composed of 12, 13, 14 or 15 isoprene residues formed the main polyprenol family. In the majority of the plants studied lower quantities of an additional polyprenol family were present, in which prenologues composed of 19, 20 or 21 isoprene units were dominating. In one species--Capparis coriacea also the presence of dolichol-like polyprenols with a hydrogenated OH-terminal isoprene unit was documented.     

Uptake and modification of dietary polyprenols and dolichols in rat liver

Short and long dolichols and polyprenols in free form or esterified with fatty acids were incorporated into liposomes and administered to rats through a gastric tube. The free alcohols were taken up by the liver to different extents. While uptake in other organs was less, it also involved the fatty acid esters. The use of systems other than liposomes did not increase the efficiency of uptake. Most of the administered lipids were recovered in the lysosomes. Exogenous dolichols and polyprenols were both partly esterified in the liver and, to some extent, also phosphorylated; a portion of the polyprenols was also alpha-saturated. These results indicate that various polyisoprenes are taken up, to a small extent, from the diet by tissues under normal conditions and in liver these dietary lipids undergo terminal modifications.     

Bioactive Components of Sea Buckthorn <Emphasis Type="Italic">Hippophae rhamnoides</Emphasis> L. Foliage

The composition of lipophilic components of sea buckthorn leafy shoots, a large tonnage waste in the production of sea buckthorn oil and during renewing the cultural plantings of sea buckthorn, was studied. Hexane was used as an extraction solvent for raw materials; it provides a high degree of lipophilic component extraction and is an analogue of extraction gasoline used in the food and perfume industries. The chemical composition of the hexane extract of sea buckthorn leafy shoots was studied by gas chromatography–mass spectrometry and high-performance liquid chromatography. Sixty-seven neutral and twenty-nine acidic components, including polyprenols, dolichols, triterpene alcohols and acids, sterols, were identified. β-Sitosterol was the main component of the sterol fraction. Its content was 6.9% of the extract mass, which is much higher than in the essential extracts of leaves and pulp of sea buckthorn fruit. It is mostly found in the free form in the extract. The acidic fraction contains highly active triterpene acids (up to 5% of the extract mass) along with the major aliphatic acids. Components with the chain length of 11 and 17 isoprene units predominate in the fraction of polyprenols and dolichols (up to 4.2%). The results allow us to consider sea buckthorn leafy shoots as a promising source of biologically active compounds.     

At the membrane frontier: a prospectus on the remarkable evolutionary conservation of polyprenols and polyprenyl-phosphates

Long-chain polyprenols and polyprenyl-phosphates are ubiquitous and essential components of cellular membranes throughout all domains of life. Polyprenyl-phosphates, which include undecaprenyl-phosphate in bacteria and the dolichyl-phosphates in archaea and eukaryotes, serve as specific membrane-bound carriers in glycan biosynthetic pathways responsible for the production of cellular structures such as N-linked protein glycans and bacterial peptidoglycan. Polyprenyl-phosphates are the only form of polyprenols with a biochemically-defined role; however, unmodified or esterified polyprenols often comprise significant percentages of the cellular polyprenol pool. The strong evolutionary conservation of unmodified polyprenols as membrane constituents and polyprenyl-phosphates as preferred glycan carriers in biosynthetic pathways is poorly understood. This review surveys the available research to explore why unmodified polyprenols have been conserved in evolution and why polyprenyl-phosphates are universally and specifically utilized for membrane-bound glycan assembly.