首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Unusual fatty acids with 24, 26, and 28 carbon atoms were found in triacylglycerols (TAGs) isolated from fat body tissue of bumblebee Bombus pratorum. The most abundant one was (Z,Z)-9,19-hexacosadienoic acid. Its structure was determined by mass spectrometry after derivatization with dimethyl disulfide and by infrared spectroscopy. ECL (equivalent chain length) values of its methyl ester were determined on both DB-1 and DB-WAX capillary columns. (Z,Z)-9,19-Hexacosadienoic acid is quite rare in nature. So far it has been identified only in marine sponges, and this work is the first evidence of its occurrence in a terrestrial organism. HPLC/MS analysis of the bumblebee TAGs showed that (Z,Z)-9,19-hexacosadienoic acid is present in one third of all TAG molecular species. As it was found in all sn-TAG positions, it is likely that (Z,Z)-9,19-hexacosadienoic acid is transported to tissues. Interestingly, labial gland secretion of B. pratorum was found to contain (Z,Z)-7,17-pentacosadiene, a hydrocarbon with markedly similar double bond positions and geometry. Possible biosynthetic relationships between these two compounds are discussed.  相似文献   

2.
Seed oils from Acer species are a potential source of the nutraceutical fatty acids, nervonic acid (cis‐15‐tetracosenoic acid, NA), and γ‐linolenic acid (cis‐6,9,12‐octadecatrienoic acid, GLA). To further characterize the genus, seed fatty acid content and composition were determined for 20 species of Acer. Fatty acid content ranged from 8.2% for Acer macrophyllum to over 36% for A. mono and A. negundo. The presence of very‐long‐chain fatty acids (VLCFA), with chain length of 20‐carbons or greater, and GLA were characteristic features of the seed oils. In all species, erucic acid (cis‐13‐docosenoic acid, EA) was the predominant VLCFA with the highest level of NA being only 8.6% in A. olivianum. Regioselective lipase digestion demonstrated that VLCFA are largely absent from the sn‐2 position of seed triacylglycerol, whereas GLA is primarily located at this position. Five Acer species contained low levels (<2%) of cis‐12‐octadecenoic acid and cis‐14‐eicosenoic acid, uncommon n‐6 fatty acids not previously reported from Acer.  相似文献   

3.
Why Phenolic Acids Are Unlikely Primary Allelochemicals in Rice   总被引:21,自引:0,他引:21  
Allelopathy in rice (Oryza sativa, L.) effective against weeds has been found in about 3.5% of tested rice germplasm in both laboratory and field experimentation. However, the allelochemicals responsible for growth inhibition of rice-associated weeds have not yet been identified. In the literature, phenolic acids are often mentioned as putative allelochemicals. If phenolic acids commonly reach growth inhibitory concentrations in rice ecosystems, it must be expected that the degree of tolerance to phenolic acids will vary among traditional rice cultivars or plant species adapted to rice environments having inherently different phenolic acid concentrations. Phenolic acids concentrations are normally greater in submerged than in aerobic soils. A dose–response study, however, showed that seedlings of rice cultivars adapted to submerged anaerobic soils did not have higher level of tolerance against p-hydroxybenzoic acid than did seedlings of varieties adapted to aerobic upland soils. Moreover, traditional rice cultivars had no greater tolerance than did improved cultivars that were recently bred for traits other than tolerance of phenolic acids. Similarly, there were no differences in tolerance of p-hydroxybenzoic acid between two Echinochloa weed species adapted to either anaerobic or aerobic growth conditions. Thus, neither the rice cultivars nor weed species had evolved different tolerance levels against the phenolic acid. However, all rice cultivars had significantly greater tolerance of p-hydroxybenzoic acid than did either weed species. In a second experiment, the rates at which rice plants released phenolic acids into solution cultures were measured for at least one month, the time period of greatest allelopathic activity following planting under field conditions. The maximum release rate of phenolic acids during the first month of growth was approximately 10 g/plant/day. At a conventional plant density, the release rate of phenolic acids would be approximately 1 mg/m2day. This order of release rate cannot provide concentrations remotely close to phytotoxic levels determined for these rice cultivars and weed species. The results presented in this paper do not preclude the possibility that phenolic acids might be one component in a mixture of chemicals that, when present simultaneously, are allelopathic.  相似文献   

4.
In order to identify new structures, the free fatty acids from an extract of a glass sponge Aulosaccus sp. (from the north‐west Pacific) belonging to one of the least chemically investigated classes (Hexactinellida), were fractionated by RP‐HPLC and analyzed by NMR spectroscopy and GC–MS of their pyrrolidine derivatives, methyl(ethyl) esters and their dimethyl disulfide adducts. One hundred and twenty‐three C12–C31 acids (including nine new compounds) were detected, one hundred and ten of these compounds have not been found previously in glass sponges. The levels of common methylene‐interrupted polyenes, monoenes of the (n–7) family and less common branched‐chain components proved to be high. New acids were shown to be 5,13‐dimethyl‐tetradec‐4‐enoic, cis‐10,11‐methylene‐heptadecanoic, 10,12‐dimethyl‐octadecanoic, cis‐12,13‐methylene‐nonadecanoic, (14E)‐13‐methyl‐eicos‐14‐enoic, 19‐methyl‐eicos‐13‐enoic, cis‐20,21‐methylene‐heptacosanoic, 27‐methyl‐octacos‐21‐enoic and (22Z)‐nonacos‐22‐enoic. Some important mass spectrometric characteristics of pyrrolidides of homologous cyclopropane fatty acids are reported and discussed.  相似文献   

5.
The fatty acid composition of the edible seeds from Pinus cembroides edulis (a nut pine), that might have been a commercial source of Δ5-olefinic acids in the United States, has been established. The dehulled seeds are rich in oil (64% by weight) and are characterized by high levels of both oleic and linoleic acids (ca. 47 and 41%, respectively), with only 10% of saturated acids. Δ5-Olefinic acids, which were not reported previously in this species, are exceptionally low as compared to most other conifer species: 5,9-18:2 acid, 0.1%; 5,9,12-18:3 acid, 0.4%; 5, 11, 14-20:3 acid, 0.3%. In this respect, P. cembroides edulis seed oil closely resembles that of P. pinea (a circum-Mediterranean species), which emphasizes the morphological and taxonomic relationship between the sections to which the two species belong (Parryana and Pinea, respectively).  相似文献   

6.
The phospholipid fatty acid composition of the North-East Atlantic sponge Polymastia penicillus (South Brittany, France) was investigated. Sixty fatty acids (FA) were identified as methyl esters (FAME) and N-acyl pyrrolidides (NAP) by gas chromatography–mass spectrometry (GC/MS), including eight Δ5,9 unsaturated FA and three long-chain 2-hydroxylated FA. The major phospholipid FA were palmitic (14.3% of the total FA mixture), vaccenic (12.7%), 15(Z)-docosenoic (13.4%) and 5(Z),9(Z)-hexacosadienoic (13.3%) acids. In addition to the iso- and anteiso-branched saturated FA, several unusual short-chain branched saturated FA were identified. In addition to the known Δ5,9 FA, and interestingly regarding their identification by GC–MS as N-acyl pyrrolidides, was the co-occurrence of unusual FA possessing a Δ3, Δ4 and Δ5 double bond such as iso-4-pentadecenoic, iso-5-heptadecenoic, anteiso-5-heptadecenoic and two new compounds, not hitherto found in nature, namely 17-methyl-13-octadecenoic (0.8%) and 3,16-docosadienoic (1.1%) acids.  相似文献   

7.
Difficulties in isolating and purifying antibiotic fatty acids from culture filtrates of Pseudozyma flocculosa, a biocontrol agent against powdery mildew, have been limiting factors in studying the properties and understanding the mode of action of the biocontrol agent. We report a new protocol for synthesizing (Z)-9-heptadecenoic and for the first time synthesis of (Z)-6-methyl-9-heptadecenoic acids, two antibiotic fatty acids produced by P. flocculosa. This allowed reproducible and quantifiable means of assaying biological activity of the molecules. In these bioassays, both molecules exhibited antifungal activity corresponding to their expected potency. These new developments should facilitate further studies aimed at deciphering the ecological properties of P. flocculosa.  相似文献   

8.
Biotransformation of long‐chain fatty acids into medium‐chain α,ω‐dicarboxylic acids or ω‐aminocarboxylic acids could be achieved with biocatalysts. This study presents the production of α,ω‐dicarboxylic acids (e.g., C9, C11, C12, C13) and ω‐aminocarboxylic acids (e.g., C11, C12, C13) directly from fatty acids (e.g., oleic acid, ricinoleic acid, lesquerolic acid) using recombinant Escherichia coli‐based biocatalysts. ω‐Hydroxycarboxylic acids, which were produced from oxidative cleavage of fatty acids via enzymatic reactions involving a fatty acid double bond hydratase, an alcohol dehydrogenase, a Baeyer–Villiger monooxygenase and an esterase, were then oxidized to α,ω‐dicarboxylic acids by alcohol dehydrogenase (ADH, AlkJ) from Pseudomonas putida GPo1 or converted into ω‐aminocarboxylic acids by a serial combination of ADH from P. putida GPo1 and an ω‐transaminase of Silicibacter pomeroyi. The double bonds present in the fatty acids such as ricinoleic acid and lesquerolic acid were reduced by E. coli‐native enzymes during the biotransformations. This study demonstrates that the industrially relevant building blocks (C9 to C13 saturated α,ω‐dicarboxylic acids and ω‐aminocarboxylic acids) can be produced from renewable fatty acids using biocatalysis.

  相似文献   


9.
The cyclopropane fatty acids 17-methyl-trans-4,5-methyleneoctadecanoic acid, 18-methyl-trans-4,5-methylenenonadecanoic acid, and 17-methyl-trans-4,5-methylenenonadecanoic acid were characterized for the first time in nature in the phospholipids (mainly PE, PG and PS) of the hermit-crab sponge Pseudospongosorites suberitoides. Pyrrolidine derivatization was the key in identifying the position of the cyclopropyl and methyl groups in the acyl chains and 1H NMR was used to determine the trans stereochemistry of the cyclopropane ring. The phospholipids from the sponge also contained an interesting series of iso-anteiso Δ5,9 fatty acids with chain-lengths between 17 and 21 carbons, with the fatty acids (5Z,9Z)-18-methyl-5,9-nonadecadienoic acid and the (5Z,9Z)-17-methyl-5,9-nonadecadienoic acid being described for the first time in sponges. The anteiso α-methoxylated fatty acid 2-methoxy-12-methyltetradecanoic acid was also identified for the first time in nature in the phospholipids of this interesting marine sponge. The novel cyclopropyl fatty acids could have originated from the phospholipids of a cyanobacterium living in symbiosis with the sponge.  相似文献   

10.
The pipevine swallowtail, Battus philenor, feeds exclusively on plants in the genus Aristolochia, many of which are known to contain the toxic alkaloids collectively known as aristolochic acids. Pipevine swallowtails sequester these compounds and use them for their own defense against predators. Numerous palatable butterflies are involved in Batesian mimicry complexes with B. philenor over its range. The California subspecies of the pipevine swallowtail, B. philenor hirsuta, has no mimics. Analysis of the butterfly and its only host plant, Aristolochia californica, indicate that both contain aristolochic acid. Aristolochic acid (I) and (II) are the primary aristolochic acids found in A. californica. The highest concentration of aristolochic acids was found in the flowers, which bloom before B. philenor emerges. Concentrations of aristolochic acids decreased in the leaves but not in stem tissue over the course of the season. Butterflies contained primarily aristolochic acid (I). Aristolochic acid content of individuals from Arizona, which are involved in mimicry complexes, did not differ from California populations. Thus, lack of California mimics cannot be attributed to low aristolochic acid content of the model.  相似文献   

11.
Free phenolic (FP), conjugated phenolic (CP), and insoluble-bound phenolic (IBP) acids were extracted from the seeds of seven species of oil-tea camellia and their antioxidant activities were evaluated. The results indicated that Camellia vietnamensis has the highest total phenolic content (TPC) (31.84 ± 0.11 g of gallic acid equivalent [GAE] kg−1) and that Camellia polyodontia has the lowest TPC (12.34 ± 0.22 g GAE kg−1) in the kernel. The average TPC among the species is similar in both the kernels and in the shells, and the content order of the three forms of phenolic compounds is FP > IBP > CP. HPLC-MS analysis showed the presence of 9–11 phenolic compounds in the FP, CP, or IBP extracts of the seven species of oil-tea camellia seed. Among the phenolics identified, ferulic acid, catechin, and epicatechin were the major contributors of antioxidant activity. Hierarchical cluster analysis conducted based on the phenolic properties showed that C. vietnamensis and Camellia semiserrata belong to the group characterized by high antioxidant capacities (FRAP, ferric-ion-reducing antioxidant power; ABTS assay), and Camellia chekiangoleosa and Camellia oleifera are arranged in a group with moderate phenolic properties. The other species constitute the third cluster with low phenolic content and antioxidant activity. The study demonstrated that oil-tea camellia seed contains significant amounts of phenolic acids. In addition, extracts from various parts of the seed could be interesting novel sources of natural antioxidants.  相似文献   

12.
2‐Hydroxy fatty acids can be found in several different organisms, including bacteria. In this study, we have studied the biosynthesis of 2‐hydroxy fatty acids in the myxobacteria Myxococcus xanthus and Stigmatella aurantiaca, resulting in the identification of a family of stereospecific fatty acid α‐hydroxylases. Although the stereospecificities of the hydroxylases differ between these two species, they share a common function in supporting fatty acid α‐oxidation; that is, the oxidative shortening of fatty acids. Whereas in S. aurantiaca this process takes place during normal vegetative growth, in M. xanthus it takes place only under developmental conditions. We were also able to identify serine palmitoyltransferase encoding genes involved in sphingolipid biosynthesis as well as sphingolipids themselves in both types of myxobacteria, and were able to show that the α‐hydroxylation reaction is in fact dependent on the presence of fatty acids bound to sphingolipids.  相似文献   

13.
The Cistus ladanifer L. shrub is a widespread species of the Mediterranean region that is available as a feed source for ruminants all the year round, constituting a source of energy and nutrients when most of the vegetation is dry. However, there is no trustworthy information about the fatty acid composition of C. ladanifer, as well as no information about the seasonal and age related changes in their fatty acid composition. Thus, we collected the aerial parts of C. ladanifer plants of two age groups [young vs. older ones (2–6 years old)] during four consecutive seasons to characterize their fatty acid composition. The fatty acid composition of C. ladanifer is dominated by saturated fatty acids including the occurrence of two methyl branched chain fatty acids (BCFA), the iso‐19:0 and iso‐21:0, which as far as we know were detected for the first time in shrubs. Also, we demonstrated that several labdane type compounds might interfere with the fatty acid analysis of C. ladanifer. Marked seasonal changes in BCFA and polyunsaturated fatty acids (PUFA) were found, suggesting that BCFA can replace PUFA in plant lipids at high environmental temperatures.  相似文献   

14.
Polyhydroxy Fatty Acids Derived from Sophorolipids   总被引:1,自引:1,他引:0  
Starting from 17-hydroxyoleic acid, which is readily available from acid alcoholysis of sophorolipids, several new polyhydroxy fatty acids have been synthesized. These compounds contain from 2 to 4 hydroxy groups, in some instances combined with other functional groups. The added hydroxy groups can be incorporated in the C18 chain in a variety of geometries, for example spaced widely throughout the chain at C1, C8, and C17. This regiochemical control will be of use in structure/function studies involving materials constructed from these hydroxy fatty acids. A further benefit is that the hydroxy groups can be present in protected or free states. The principal reactions used to introduce extra hydroxy groups are selenium oxide-mediated allylic hydroxylation, osmium-catalyzed dihydroxylation, and borohydride reduction of a carboxylic ester. These new compounds are expected to be of use in a number of areas, but particularly as building blocks for polymers or components of lubricant formulations. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture.  相似文献   

15.
两种开封产黄菊花脂肪酸成分研究   总被引:1,自引:1,他引:1  
用索氏提取法提取脂溶性成分,GC-MS联用法结合计算机检索首次对开封产两个黄色菊花品种(春日剑山和麦浪)的脂肪酸成分进行了分析鉴定。结果从春日剑山和麦浪中分别鉴定出了45和35种化合物,其中脂肪酸成分为21和11种,用气相色谱峰面积归一法测定了各组分的相对质量分数,鉴定成分各占其色谱总馏分出峰面积的93.99%和94.00%。两者主要脂肪酸为肉豆蔻酸、棕榈酸、亚麻酸、棕榈油酸、顺-9-顺-12-亚油酸和月桂酸。还检测到具有活性的α-香树脂醇(8.57%)、β-香树脂醇(7.47%)和(3β,5α,24S)-7-豆甾烯-3-醇(19.48%)仅存在于麦浪中,是与春日剑山有明显差别的药效成分。该文报告工作的新颖性已为河南大学图书馆2008年8月14日出具的第CX2008005号《科技查新报告》所证实。  相似文献   

16.
The banded sunflower moth (BSFM), Cochylis hospes Walshingham (Lepidoptera: Cochylidae) is a specialist insect, the larvae of which feed on sunflowers, Helianthus spp., and a few other species of Compositae. It is one of the most important pests of sunflower in the USA. Previous work on H. annuus, the cultivated sunflower, revealed two diterpenoids that function as oviposition stimulants for female BSFM, and that other, more polar compounds also stimulated oviposition. Using a bioassay-guided approach, we isolated three additional diterpenoids, grandifloric acid (1), 15β-hydroxy-ent-trachyloban-19-oic acid (2), and 17-hydroxy-16α-ent-kauran-19-oic acid (3), from polar fractions of pre-bloom sunflower head extracts. In laboratory bioassays, purified natural samples of each of these compounds stimulated oviposition by female BSFM. Structure–activity relationships of the five diterpenoids known to stimulate oviposition by female BSFM are discussed.  相似文献   

17.
Seeds from different collections of cultivatedSesamum indicum Linn. and three related wild species [specifically,S. alatum Thonn.,S. radiatum Schum and Thonn. andS. angustifolium (Oliv.) Engl.] were studied for their oil content and fatty acid composition of the total lipids. The wild seeds contained less oil (ca. 30%) than the cultivated seeds (ca. 50%). Lipids from all four species were comparable in their total fatty acid composition, with palmitic (8.2–12.7%), stearic (5.6–9.1%), oleic (33.4–46.9%) and linoleic acid (33.2–48.4%) as the major acids. The total lipids from selected samples were fractionated by thin-layer chromatography into five fractions: triacylglycerols (TAG; 80.3–88.9%), diacylglycerols (DAG; 6.5–10.4%), free fatty acids (FFA; 1.2–5.1%), polar lipids (PL; 2.3–3.5%) and steryl esters (SE; 0.3–0.6%). Compared to the TAG, the four other fractions (viz, DAG, FFA, PL and SE) were generally characterized by higher percentages of saturated acids, notably palmitic and stearic acids, and lower percentages of linoleic and oleic acids in all species. Slightly higher percentages of long-chain fatty acids (20∶0, 20∶1, 22∶0 and 24∶0) were observed for lipid classes other than TAG in all four species. Based on the fatty acid composition of the total lipids and of the different acyl lipid classes, it seems thatS. radiatum andS. angustifolium are more related to each other than they are to the other two species.  相似文献   

18.
Members of the genusLesquerella, native to North America, have oils containing large amounts of hydroxy fatty acids and are under investigation as potential new crops. The triglyceride structure of oils from twenty-fiveLesquerella species in the seed collection at our research center has been examined after being hydrolysis-catalyzed by reverse micellar-encapsulated lipase and alcoholysis-catalyzed by immobilized lipase. These reactions, when coupled with supercritical-fluid chromatographic analysis, provide a powerful, labor-saving method for oil triglyceride analysis. A comprehensive analysis of overall fatty acid composition of these oils has been conducted as well.Lesquerella oils (along with oils from two other Brassicaceae:Physaria floribunda andHeliophilia amplexicaulis) have been grouped into five categories: densipolic acid-rich (Class I); auricolic acid-rich (Class II); lesquerolic acid-rich (Class III); an oil containing a mixture of hydroxy acids (Class IV); and lesquerolic and erucic acid-rich (Class V). The majority of Class I and II triglycerides contain one or two monoestolides at the 1- and 3-glycerol positions and a C18 polyunsaturated acyl group at the 2-position. Most Class III and IV oil triglycerides contain one or two hydroxy acids at the 1- and 3-positions and C18 unsaturated acid at the 2-position. A few of the Class III oils have trace amounts of estolides. The Class V oil triglycerides are mostly pentaacyl triglycerides and contain monestolide and small amounts of diestolide. Our triglyceride structure assignments were supported by1H nuclear magnetic resonance data and mass balances.  相似文献   

19.
Bile acids constitute a group of structurally closely related molecules and represent the most abundant constituents of human bile. Investigations of bile acids have garnered increased interest owing to their recently discovered additional biological functions including their role as signaling molecules that govern glucose, fat and energy metabolism. Recent NMR methodological developments have enabled single-step analysis of several highly abundant and common glycine- and taurine- conjugated bile acids, such as glycocholic acid, glycodeoxycholic acid, glycochenodeoxycholic acid, taurocholic acid, taurodeoxycholic acid, and taurochenodeoxycholic acid. Investigation of these conjugated bile acids in human bile employing high field (800 MHz) 1H-NMR spectroscopy reveals that the ratios between two glycine-conjugated bile acids and their taurine counterparts correlate positively (R 2 = 0.83–0.97; p = 0.001 × 10−2–0.006 × 10−7) as do the ratios between a glycine-conjugated bile acid and its taurine counterpart (R 2 = 0.92–0.95; p = 0.004 × 10−3–0.002 × 10−10). Using such correlations, concentration of individual bile acids in each sample could be predicted in good agreement with the experimentally determined values. These insights into the pattern of bile acid conjugation in human bile between glycine and taurine promise useful clues to the mechanism of bile acids’ biosynthesis, conjugation and enterohepatic circulation, and may improve our understanding of the role of individual conjugated bile acids in health and disease. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

20.
The fatty acid compositions of the seeds from four Cephalotaxus species or varieties (plum yews; Cephalotaxaceae) and two Podocarpus species (podocarps; Podocarpaceae) have been established. These compositions were compared with those previously published for some Taxaceae species (Taxus and Torreya). Cephalotaxaceae, Podocarpaceae, and Taxaceae belong to the Taxares suborder. Δ5-Olefinic acids are present in the seed lipids from all species analyzed. In Cephalotaxus, Podocarpus, and Torreya, the prominent Δ5-olefinic acid that occurs is the trienoic acid 5,11,14–20:3 (sciadonic) acid, comprising from 6.7 to 26.4% of total fatty acids. In these species, the Δ5,11 structure is largely favored over the Δ5,9 structure: the 5,9–18:2 (taxoleic) and 5,9,12–18:3 (pinolenic) acids are at the limit of detection, in contrast to Taxus and most Pinaceae species, where these two Δ5-olefinic acids generally predominate. 14-Methylhexadecanoic acid, an habitual though minor component of Pinaceae and Ginkgo biloba seed lipids, could not be detected in Cephalotaxus species studied here and was tentatively identified in trace amounts only in one Podocarpus species. In addition to sciadonic acid, Cephalotaxus and Podocarpus seeds are characterized by unusually high amounts of 11,14–20:2 acid, in the range of 3.1–12.0%. This contrasts with most of the 170 species of conifers analyzed so far (from the families Pinaceae, Cupressaceae, Taxodiaceae, Taxaceae, and Sciadopityaceae, which belong to the Pinares suborder), where this acid is generally ≤2%. A close resemblance between Torreya grandis and three of the Cephalotaxus species analyzed might be indicative of some phyletic relationship between the families Cephalotaxaceae and Taxaceae. 13C nuclear magnetic resonance spectroscopy of the seed oils from C. drupaceae and P. andinus has shown that Δ5-olefinic acids are apparently excluded from the internal position of triacylglycerols, which is a characteristic common to all Coniferales species analyzed so far, and consequently of great antiquity.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号