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1.
Several natural neo-clerodane diterpenoids isolated from Linaria saxatilis and some semisynthetic derivatives were tested against several insect species with different feeding adaptations. The antifeedant tests showed that the oliphagous Leptinotarsa decemlineata was the most sensitive insect, followed by the aphid Myzus persicae. The polyphagous Spodoptera littoralis was not deterred by these diterpenoids; however, following oral administration, some of these compounds did have postingestive antifeedant effects on this insect. In general terms, the antifeedant effects of these compounds were species-dependent and more selective than their toxic/postingestive effects. The study of their structure-activity relationships showed that both the decalin moiety and the chain at C-9 determined their bioactivity. Furthermore, the presence of a 4,18-epoxy/diol moiety was an important feature for both the antifeedant and the toxic/postingestive effects.  相似文献   

2.
The antifungal activity on Botrytis cinerea of the diterpenoids 3beta-hydroxy-kaurenoic acid and kaurenoic acid, obtained from the resinous exudates of Pseudognaphalium vira vira, was determined. 3beta-Hydroxy-kaurenoic acid reduced the mycelial growth of B. cinerea in solid and liquid media. Additionally, the damage produced by the fungus on the surface of tomato leaves in the presence of the diterpenoids was evaluated. A higher protective effect was observed in the presence of the hydroxylated diterpene. On the other hand, the effect of the diterpenoids on the production of enzymes that participate in the plant infection by B. cinerea was analyzed. p-Nitrophenylbutyrate esterase production was induced by both diterpenoids, whereas laccase production was only induced by the hydroxylated diterpene. In the study of the mechanism of action of these compounds, it was determined that 3beta-hydroxy-kaurenoic acid would produce permeabilization of the cell membrane of B. cinerea.  相似文献   

3.
A structure-antifeedant activity relationship (SAR) study of clerodane diterpenoids was carried out. Attention was focused on the feeding-deterrent activities exhibited toward Tenebrio molitor by clerodane diterpenoids and withanolides. Azadirachtin was chosen as a reference compound. SAR studies on the clerodane compounds indicate that the stereoelectronic factors are more important than the hydrophobic aspects as determinants of antifeedant activity. A furan ring in the side chain and a carbonyl alpha,beta-unsaturated (or spiro-epoxide) group appear to be indispensable for the biological response. A conformational study indicate that the optimum interatomic distance between these moieties is a range between 9.5 and 10.5 A. In addition, a similar stereoelectronic response was found among withanolides and azadirachtin. On the basis of these results it is reasonable to imagine a closely related chemical mechanism for these compounds.  相似文献   

4.
Many Fusarium species produce trichothecenes, sesquiterpene epoxides that differ in patterns of oxygenation and esterification at carbon positions C-3, C-4, C-7, C-8, and C-15. For the first comprehensive and quantitative comparison of the effects of oxygenation and esterification on trichothecene phytotoxicity, we tested 24 precursors, intermediates, and end products of the trichothecene biosynthetic pathway in an Arabidopsis thaliana detached leaf assay. At 100 microM, the highest concentration tested, only the trichothecene precursor trichodiene was nontoxic. Among trichothecenes, toxicity varied more than 200-fold. Oxygenation at C-4, C-8, C-7/8, or C-15 was, on average, as likely to decrease as to increase toxicity. Esterification at C-4, C-8, or C-15 generally increased toxicity. Esterification at C-3 increased toxicity in one case and decreased toxicity in three of eight cases tested. Thus, the increase in structural complexity along the trichothecene biosynthetic pathway in Fusarium is not necessarily associated with an increase in phytotoxicity.  相似文献   

5.
Maillard model systems consisting of labeled D-[(13)C]glucoses, L-[(15)N]methionine, and L-[methyl-(13)C]methionine, have been utilized to identify the amino acid and carbohydrate fragmentation pathways occurring in the model system through Py-GC/MS analysis. The label incorporation analyses have indicated that the carbohydrate moiety produces 1-deoxy- and 3-deoxyglucosones and undergoes C(2)/C(4) and C(3)/C(3) cleavages to produce glycolaldehyde, tetrose, and C(3)-reactive sugar derivatives such as acetol, glyceraldehyde, and pyruvaldehyde. Glycolaldehyde was found to incorporate C-1, C-2 (70%) and C-5, C-6 (30%) glucose carbon fragments, whereas the tetrose moiety incorporates only C-3, C-4, C-5, C-6 glucose carbon atoms. In addition, the major source of reactive C(3) fragments was found to contain C-4, C-5, C-6 sugar moiety. On the other hand, methionine alone also generated Strecker aldehyde as detected by its condensation product with 3-(methylthio)propylamine. Plausible mechanisms were proposed for the formation of the interaction products between sugar and amino acid degradation products on the basis of the label incorporation patterns.  相似文献   

6.
奥利亚罗非鱼3种C型溶菌酶基因的克隆及其序列分析   总被引：1，自引：0，他引：1  
本研究结合RT-PCR和RACE法获得了奥利亚罗非鱼(Oreochromis aureus)三种C型溶菌酶基因C-1,-2和C-3的全长cDNA.3个基因的cDNA分别为581 bp、662 bp和695 bp,各编码143、156和143个氨基酸(GenBank accession No:EU913095,EU913094和EU836689),相互间氨基酸序列的同源性在63.9%~67.8%之间.3个基因均具有与其它物种C型溶菌酶相同的8个保守半胱氨酸残基和2个活性位点Glu~(35)和Asp~(52),可认为它们均为C型溶菌酶基因.在系统进化树中这3个基因首先与同属高等真骨鱼类的聚类,最后再与低等真骨鱼类的聚类,系统进化关系与传统鱼类分类地位相吻合,显示真骨鱼类C型溶菌酶的进化速度与物种的进化速度基本一致.蛋白分析软件分析显示这3个基因均具有C型溶菌酶的典型结构、相似的蛋白二、三级结构,推测应具有与C型溶菌酶相似的生理功能.但3个基因氨基酸序列间存在一定差异,其中C-1的等电点较低且碱性氨基酸较少,因此3种溶菌酶可能具有生理功能上的差异与分工.  相似文献   

7.
Pyrolysis was used as a microscale sample preparation tool to generate glucose/alanine reaction products to minimize the use of expensive labeled precursors in isotope labeling studies. The residue remaining after the pyrolysis at 250 °C was analyzed by electrospray time-of-flight mass spectrometry (ESI-TOF-MS). It was observed that a peak at m/z 199.1445 in the ESI-TOF-MS spectrum appeared only when the model system contained at least 2-fold excess alanine. The accurate mass determination indeed indicated the presence of two nitrogen atoms in the molecular formula (C(10)H(18)N(2)O(2)). To verify the origin of the carbon atoms in this unknown compound, model studies with [(13)U(6)]glucose, [(13)C-1]alanine, [(13)C-2]alanine, [(13)C-3]alanine, and [(15)N]alanine were also performed. Glucose furnished six carbon atoms, and alanine provides four carbon (2 × C-2 and 2 × C-3) and two nitrogen atoms. When commercially available fructosylalanine (N-attached to C-1) was reacted with only 1 mol of alanine, a peak at m/z 199.1445 was once again observed. In addition, when 3-deoxyglucosone (3-DG) was reacted with a 2-fold excess of alanine, a peak at m/z 199.1433 was also generated, confirming the points of attachment of the two amino acids at C-1 and C-2 atoms of 3-DG. These studies have indicated that amino acids can undergo multiple addition reactions with 1,2-dicarbonyl compounds such as 3-deoxyglucosone and eventually form a tetrahydropyrazine moiety.  相似文献   

8.
Three new diterpenoids belonging to the clerodane (2-3) and halimane (4) structural types have been isolated from the bark of Croton eluteria Bennet, commonly known as cascarilla. Their structures have been fully characterized by spectroscopic means. Cascarilla extract and its major component, cascarillin, were found to significantly increase histamine-induced gastric acid secretion in the mouse stomach. These preliminary results provide the first rationale for the use of cascarilla in bitter preparations aimed at improving digestion.  相似文献   

9.
Novel antiallergic catechin derivatives isolated from oolong tea.   总被引：5，自引：0，他引：5  
Two catechin derivatives (C-1 and C-2) with potent antiallergic activity were isolated from Taiwanese oolong tea by HPLC techniques. From NMR and FAB-MS analyses, the structures of C-1 and C-2 were elucidated as (-)-epigallocatechin 3-O-(3-O-methyl)gallate and (-)-epigallocatechin 3-O-(4-O-methyl)gallate, respectively. The oolong tea leaves contained 0.34% (dry weight) C-1 and 0.20% C-2. Traces of C-2 were detected in only 1 of 15 varieties of green tea tested. C-1 was detected in 13 of 15 green tea varieties; C-1 was most concentrated in tea cultivars classified as Assam hybrids (0. 50-0.82% of dry weight). Quantitative analyses of green tea, oolong tea, and black tea manufactured from same batches of tea leaves showed that neither catechin derivative was produced during the fermentation process. Oral doses of C-1 and C-2 (5-50 mg/kg) significantly inhibited type I allergic (anaphylactic) reactions in mice sensitized with ovalbumin and Freund's incomplete adjuvant. These inhibitory effects exceeded that of the major tea catechin, (-)-epigallocatechin 3-O-gallate, which has known antiallergic properties.  相似文献   

10.
Fusarium culmorum produces two major trichothecenes, 3-acetyldeoxynivalenol and sambucinol, and some minor apotrichothecenes. It was desired to investigate if during their biosynthesis a C-11-keto intermediate was involved. To verify this postulate, trichodiene, a known precursor to trichothecenes, was synthesized with two deuteriums at C-11 and one at C-15. It was then fed to F. culmorum cultures, and the derived metabolites were purified and analyzed. The results ruled out the involvement of an 11-keto intermediate but revealed two novel apotrichothecenes. The characterization of their structures suggested that one of the 2-hydroxy-11alpha-apotrichothecene stereoisomers (2alpha or 2beta) could be converted to sambucinol. These apotrichothecenes were therefore synthesized labeled specifically with two deuteriums at C-4 and C-15 and fed to F. culmorum cultures. Indeed, the result established for the first time that 2alpha-hydroxy-11alpha-apotrichothecene was a precursor to sambucinol. A biosynthetic scheme for the production of trichothecenes and apotrichothecenes is described.  相似文献   

11.
Antioxidant and antiradical activities of flavonoids.   总被引：24，自引：0，他引：24  
The relationship between the structure of 42 flavonoids and their antioxidant and antiradical activities was elucidated by heat-induced oxidation in a beta-carotene and linoleic acid system and by the 1,1-diphenyl-2-picrylhydrazyl decoloration test. From seven structurally divergent groups of flavonoids, only flavonols with a free hydroxyl group at the C-3 position of the flavonoid skeleton showed high inhibitory activity to beta-carotene oxidation. Antiradical activity depended on the presence of a flavonol structure or free hydroxyl group at the C-4' position. The effect of the 4'-hydroxyl was strongly modified by other structural features, such as the presence of free hydroxyls at C-3 and/or C-3' and a C2-C3 double bond.  相似文献   

12.
Two known neo-clerodane diterpenoids, scutecyprol A (1) and scutalbin C (2), have been isolated from the acetone extract of the aerial parts of Scutellaria sieberi. The antifeedant activity of scutecyprol A (1), of its 15-oxo derivative (3), and of several halohydrins (4-9), synthesized starting from compounds 1 and 3, against Spodoptera littoralis have been determined and structure-antifeedant relationships are discussed.  相似文献   

13.
Thermophilic ammonia-oxidizing bacteria (AOB) have the potential to reduce ammonium emissions from commercial-scale animal waste composting operations. Two new media have been designed to culture and enumerate thermophilic AOB species. C-1 medium was designed to reflect compost composition. C-2 medium and CQ-2 medium were modified synthetic organic wastewater for the cultivation and enumeration of AOB, respectively. These new media have several advantages over the conventional medium. C-2 medium is effective for nitrification at 50°C, and C-1 and C-2 media support reasonable growth of thermophilic AOB. Furthermore, C-1 and CQ-2 media allow enumeration of thermophilic AOB during the composting process. This is the first report of the successful cultivation and enumeration of thermophilic AOB in compost. These results suggest the possibility of isolation and manipulation of novel thermophilic AOB species for environmental bioremediation.  相似文献   

14.
A novel approach for the quantification of the degree of condensation at the C(5) position of etherified and phenolic phenylpropane (C-9) units of in situ lignin is described. This is achieved by degrading unmethylated and methylated wood by thioacidolysis and analyzing the resultant product mixtures by quantitative (31)P NMR spectroscopy. Applying this new method to compression wood and normal wood from Pinus radiata showed that, whereas 41-47% of etherified guaiacyl C-9 units are condensed at the C(5) position, almost all phenolic guaiacyl C-9 units exist as uncondensed moieties. Analysis of milled wood lignin (MWL) isolated from the same wood by (31)P NMR spectroscopy before and after thioacidolysis showed that the phenolic guaiacyl C-9 units were more condensed than those in the in situ lignin. This is likely due to partial cleavage of the more condensed etherified linkages during the lignin isolation, leading to a relative increase in condensed phenolic guaiacyl C-9 units.  相似文献   

15.
The formation of acetic acid was elucidated based on volatile reaction products and related nonvolatile key intermediates. The origin and yield of acetic acid were determined under well-controlled conditions (90-120 degrees C, pH 6-8). Experiments with various 13C-labeled glucose isotopomers in the presence of glycine revealed all six carbon atoms being incorporated into acetic acid: C-1/C-2 ( approximately 70%), C-3/C-4 ( approximately 10%), and C-5/C-6 (approximately 20%). Acetic acid is a good marker of the 2,3-enolization pathway since it is almost exclusively formed from 1-deoxy-2,3-diulose intermediates. Depending on the pH, the acetic acid conversion yield reached 85 mol % when using 1-deoxy-2,3-hexodiulose (1) as a precursor. Hydrolytic beta-dicarbonyl cleavage of 1-deoxy-2,4-hexodiuloses was shown to be the major pathway leading to acetic acid from glucose without the intermediacy of any oxidizing agents. The presence of key intermediates was corroborated for the first time, i.e., tetroses and 2-hydroxy-3-oxobutanal, a tautomer of 1-hydroxy-2,3-butanedione, also referred to as 1-deoxy-2,3-tetrodiulose. The hydrolytic beta-dicarbonyl cleavage represents a general pathway to organic acids, which corresponds to an acyloin cleavage or a retro-Claisen type reaction. Although alternative mechanisms must exist, the frequently reported hydrolytic alpha-dicarbonyl cleavage of 1 can be ruled out as a pathway forming carboxylic acids.  相似文献   

16.
用相转移催化法标记合成了植物生长延缓剂1-对氯苯基-2-[(5-(14)~C)-1,2,4-三唑-1-基]4,4-二甲戊-3-醇((14)~C-多效唑)。其步骤包括在相转移催化剂PEG800的存在下,(5-(14)~C)-1,2,4-三唑与一氯片呐酮在乙酸乙酯溶液中反应,生成(5-(14)~C)-α-三唑基片呐酮,后者在苯溶液中再与对氯氯苄反应,生成(14)~C-三唑酮,最后在甲醇溶液中用硼氢化钠还原得到(14)~C-多效唑。其总放化收率为20.9％(以(14)~C-三唑计),放化纯度大于99％。  相似文献   

17.
1) CO2 compensation points of the plants tested correlate well with the leaf anatomy. Low CO2 compensation plants had well-developed VBS containing large and specialized chloroplasts but no plant with a high CO2 compensation point possessed chloroplasts in the VBS.

2) CO2 Compensation Points Closely Correlated With The Major Carboxylation Pathway In Photosynthesis. Low Compensation Plants Fixed CO2 Via The C-4 Pathway (C-4 Plants) While High Compensation Plants Carried Out CO2 Fixation By The Calvin Cycle (C-3 Plants).

3) Close correlations could be established for the CO2 compensation point, the major carboxylation pathway, and glycolate oxidase activity. Glycolate oxidase activity was much higher in C-3 plants than in C-4 plants. On the other hand, dark respiration in C-4 plants was higher than that in C-3 plants.

4) TCA cycle activity in detached leaves was not inhibited to any large extent by illumination.

In C-3 plants, the release of 14CO2 from alanine-1-14C increased with an increase in the ambient O2 concentration; whereas, radioactivity in the sugar fraction was quite small at all O2 concentrations. In C-4 plants the release of 14CO2 was little affected by the ambient O2 concentration while sugar formation was stimulated at high O2 concentrations. This indicates that in C-3 plants CO2 fixation is blocked at a high O2 concentration, therefore, internal 14CO2 is released from the leaf without being refixed, but in C-4 plants internal 14CO2 can be efficiently refixed and metabolized to sugar by a combination of active PEP carboxylase and the ‘Kranz type’ of leaf anatomy.  相似文献   

18.
The butenolide, 3-methyl-2H-furo[2,3-c]pyran-2-one (1), has recently been identified as the germination stimulant present in smoke that promotes the germination of seeds from a wide range of plant species. In this paper, we describe the preparation of a number of analogues of 1 and compare their efficacy in promoting seed germination of three highly smoke-responsive plant species, Lactuca sativa L. cv. Grand Rapids (Asteraceae), Emmenanthe penduliflora Benth. (Hydrophyllaceae), and Solanum orbiculatum Poir. (Solanaceae). The results show that the methyl substituent at C-3 in 1 is important for germination-promoting activity while substitution at C-7 reduces activity. In contrast, bioactivity is mostly retained with analogues substituted at C-4 or C-5.  相似文献   

19.
Humic materials from the O-horizon of a Ferric Podzol and from the H-horizon of a Sapric Histosol were fractionated by dialysis into a low and a high molecular weight fraction. Each fraction was characterized by quantitative solution C-13-NMR. The low molecular weight fractions showed remarkably well resolved C-13 spectra, due to carbohydrates and their decomposition products.  相似文献   

20.
In continuation of a program aimed at the discovery and development of natural products-based insecticidal agents, two series of novel fraxinellone-based esters were synthesized by modification at the C-4 or C-10 position of fraxinellone and evaluated for their insecticidal activity against the pre-third-instar larvae of Mythimna separata in vivo. An efficient method for the stereoselective synthesis of 4α-hydroxyfraxinellone from fraxinellonone was developed, and the steric configuration of 6h was unambiguously confirmed by X-ray crystallography. Among 37 compounds, some derivatives displayed potent insecticidal activity; especially compounds 6h, 6q, 6t, and 7q showed more promising insecticidal activity than toosendanin, a commercial botanical insecticide derived from Melia azedarach . This suggested that introduction of the fluorine atom on the phenyl ring could lead to a more potent compound than one possessing chlorine or bromine. Meanwhile, introduction of the heterocyclic fragments at the C-4 or C-10 position of fraxinellone was essential for their insecticidal activity. This will pave the way for further design, structural modification, and development of fraxinellone as an insecticidal agent.  相似文献   

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