首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   19篇
  免费   5篇
  2023年   1篇
  2019年   1篇
  2018年   2篇
  2017年   1篇
  2016年   2篇
  2015年   2篇
  2014年   1篇
  2013年   2篇
  2011年   1篇
  2009年   1篇
  2008年   1篇
  2007年   1篇
  2004年   2篇
  2003年   1篇
  2002年   1篇
  1994年   2篇
  1987年   1篇
  1983年   1篇
排序方式: 共有24条查询结果,搜索用时 31 毫秒
1.
Six bioactive compounds were isolated from the seeds extract of Piper nigrum Linn. following a larvicidal activity guided isolation against 4th instar larvae of Aedes aegypti L., a Dengue vector mosquito and a carrier of yellow fever. Their structures were elucidated using spectroscopic methods including HR-EI-MS, FAB-MS, 1H and 13C NMR (Broad Bond Decoupled, & DEPT), and 2D-NMR techniques (1H–1H COSY, NOESY, HMQC, HMBC, & 2D-J-resolved). These include three new constituents namely pipilyasine (1), pipzubedine (2) and pipyaqubine (3), and three known constituents pellitorine (4), pipericine (5) and piperine (6). The larvicidal activity was determined by WHO method.  相似文献   
2.
The hexose monophosphate (HMP) shunt acts as an essential component of cellular metabolism in maintaining carbon homeostasis. The HMP shunt comprises two phases viz. oxidative and nonoxidative, which provide different intermediates for the synthesis of biomolecules like nucleotides, DNA, RNA, amino acids, and so forth; reducing molecules for anabolism and detoxifying the reactive oxygen species during oxidative stress. The HMP shunt is significantly important in the liver, adipose tissue, erythrocytes, adrenal glands, lactating mammary glands and testes. We have researched the articles related to the HMP pathway, its metabolites and disorders related to its metabolic abnormalities. The literature for this paper was taken typically from a personal database, the Cochrane database of systemic reviews, PubMed publications, biochemistry textbooks, and electronic journals uptil date on the hexose monophosphate shunt. The HMP shunt is a tightly controlled metabolic pathway, which is also interconnected with other metabolic pathways in the body like glycolysis, gluconeogenesis, and glucuronic acid depending upon the metabolic needs of the body and depending upon the biochemical demand. The HMP shunt plays a significant role in NADPH2 formation and in pentose sugars that are biosynthetic precursors of nucleic acids and amino acids. Cells can be protected from highly reactive oxygen species by NADPH 2. Deficiency in the hexose monophosphate pathway is linked to numerous disorders. Furthermore, it was also reported that this metabolic pathway could act as a therapeutic target to treat different types of cancers, so treatments at the molecular level could be planned by limiting the synthesis of biomolecules required for proliferating cells provided by the HMP shunt, hence, more experiments still could be carried out to find additional discoveries.  相似文献   
3.
Compounds containing nitrogen and sulfur atoms can be widely used in various fields, including industry, medicine, biotechnology, and chemical technology. Among them, amides of acids and heterocyclic compounds have an important place. These amides and thiazolidine‐4‐ones showed good inhibitory action against butyrylcholinesterase (BChE), acetylcholinesterase (AChE), and human carbonic anhydrase isoforms. AChE exists at high concentrations in the brain and red blood cells. BChE is an important enzyme that is plentiful in the liver, and it is released into the blood in a soluble form. They were demonstrated to have effective inhibition profiles with Ki values of 23.76–102.75 nM against hCA I, 58.92–136.64 nM against hCA II, 1.40–12.86 nM against AChE, and 9.82–52.77 nM against BChE. On the other hand, acetazolamide showed Ki value of 482.63 ± 56.20 nM against hCA I, and 1019.60 ± 163.70 nM against hCA II. Additionally, Tacrine inhibited AChE and BChE, showing Ki values of 397.03 ± 31.66 and 210.21 ± 15.98 nM, respectively.  相似文献   
4.
Two new natural triterpenes, lantaninilic acid and lantoic acid, along with the known triterpenes lantadene A, and oleanolic, ursolic, betulinic, lantanolic, and camaric acid, were obtained from the aerial parts of Lantana camara through bioassay‐guided isolation, monitoring the in vitro antileishmanial activity against promastigotes of Leishmania major. Oleanolic acid ( 3 ), ursolic acid ( 4 ), lantadene A ( 5 ), and lantanilic acid ( 7 ) showed significant leishmanicidal activities with IC50 values of 53.0, 12.4, 20.4, and 21.3 μM , respectively. The IC50 value of ursolic acid ( 4 ; 12.4 μM ) was found to be comparable with that of the standard drugs, pentamidine (IC50 15.0 μM ) and amphotericin B (IC50 0.31 μM ). The in vitro activities of L. camara and its constituents against promastigotes of Leishmania major are reported here for the first time.  相似文献   
5.
Gliadins, seed storage proteins, are popular markers effectively employed for the analysis of common wheat. Gliadin electrophoretic patterns are genotype-specific, reproducible, not dependent on growing conditions and are suitable for germplasm identification complementary to molecular markers. Gliadins have been identified and used in wheat from various countries, but prior to this study little was known about gliadin polymorphism in wheat from Kazakhstan. In this study, 48 alleles of six gliadin-coding loci were identified in 43 cultivars of spring wheat from Northern Kazakhstan. The alleles Gli-A1 f , Gli-B1 e , Gli-D1 a , Gli-A2 p , Gli-B2 d and Gli-D2 e had maximal frequencies in each of the six loci. Identified Gli alleles in the loci formed ‘Gliadin Genetic Formula’ unique for each studied variety, and these were compared to the published data from previously analyzed wheat varieties. Pedigree analysis of 43 varieties studied for gliadin polymorphisms indicated that some Gli alleles were conserved and inherited from the progenitor cultivar Akmolinka 1. In contrast, other Gli alleles were replaced by those from modern germplasms. It is assumed that a higher frequency of gliadin alleles can be associated with the selection of genotypes with improved traits for yield and seed quality in the studied wheat cultivars from Northern Kazakhstan.  相似文献   
6.
The thiolation reaction was carried out in a benzene solution at 80°C and p‐substituted ketones and mercaptoacetic acid in a molar ratio (1:4) of in the presence of a catalytic amount of toluene sulfonic acids. The enzyme inhibition activities of the novel amides of 1,1‐bis‐(carboxymethylthio)‐1‐arylethanes derivatives were investigated. These novel amides of 1,1‐bis‐(carboxymethylthio)‐1‐arylethanes derivatives showed good inhibitory action against acetylcholinesterase (AChE) butyrylcholinesterase (BChE), and human carbonic anhydrase I and II isoforms (hCA I and II). AChE inhibitors, interacting with the enzyme as their primary target, are applied as relevant drugs and toxins. Many clinically established drugs are carbonic anhydrase inhibitors, and it is highly anticipated that many more will eventually find their way into the market. The novel synthesized compounds inhibited AChE and BChE with Ki values in the range of 0.64–1.47 nM and 9.11–48.12 nM, respectively. On the other hand, hCA I and II were effectively inhibited by these compounds, with Ki values between 63.27–132.34 and of 29.63–127.31 nM, respectively.  相似文献   
7.
Siddiqui BS  Ilyas F  Rasheed M  Begum S 《Phytochemistry》2004,65(14):2077-2084
The continued studies on the constituents of the fresh leaves and stem bark of Plumeria obtusa Linn. have led to the isolation and characterization of four new triterpenoids, dammara-12,20(22)Z-dien-3-one (1), dammara-12,20(22)Z-dien-3beta-ol (2), olean-12-en-3beta,27-diol (3), and 27-hydroxyolean-12-en-3-one (4) and 12 known compounds, which included eight triterpenoids; dammara-3beta,20(S),25-triol (5), urs-12-en-3beta-hydroxy-27-Z-feruloyloxy-28-oic acid (6), 3beta-hydroxyolean-12-en-28-oic acid (7), 3beta,27-dihydroxylupan-29-ene (8), 3beta-hydroxylupan-29-en-28-oic acid (9), 3beta-hydroxyursan-12-en-28-oic acid (11), 3beta-hydroxy-27-p-coumaroyloxy-olea-12-en-28-oic acid (12) and urs-12-en-3-one (15); an iridoid 1alpha-plumieride (10); a cardenolide 3alpha,14beta-dihydroxy-17beta-card-20(22)-enolide (13); a fatty acid ester methyl n-octadecanoate (14) and a steroid 3beta-hydroxy-delta5-stigmastane (16). The new constituents were characterized through spectroscopic studies including 1D (1H and 31C NMR) and 2D (COSY-45, NOESY, J-resolved, HMQC and HMBC) NMR and chemical transformations. This is the first report on the isolation of dammarane triterpenoids from P. obtusa. Compounds 5 and 6 are hitherto unreported from P. obtusa. The known compounds were identified by comparison of their spectral data with those reported in the literature.  相似文献   
8.
Cobra snakeNaja naja naja hemoglobin shows four bands on Triton electrophoresis. We present the primary structure of oneα and oneβ chain. The separation of polypeptide chains was achieved by ion exchange chromatography on carboxymethyl cellulose column. The amino acid sequence was established by automatic Edman degradation of the native chains and tryptic and hydrolytic peptides in a gas-phase sequencer. The structural data are compared with those of human and other reptile hemoglobins and reveal not only large variations from human but within reptiles. The amino acid exchanges involve several subunit contacts and heme binding sites. This is the first study on the hemoglobin of a land snake. There are only two amino acid sequences of sea snake hemoglobin (Microcephalophis gracilis gracilis andLiophis miliaris) reported in the literature.  相似文献   
9.
Following nematicidal activity‐guided isolation studies on the fruits, bark, and leaves of Cordia latifolia, two new constituents, cordinoic acid (=11‐oxours‐12‐ene‐23,28‐dioic acid; 1 ) and cordicilin (=2‐{[(E)‐3‐(3,4‐dihydroxyphenyl)prop‐2‐enoyl]oxy}‐3‐[4‐hydroxy‐3‐(stearoyloxy)phenyl]propanoic acid; 2 ) were isolated from the stem and leaves, respectively, together with nine known compounds, namely cordioic and cordifolic acid from the stem bark, latifolicin A–D and rosmarinic acid from the fruits, and cordinol and cordicinol from the leaves. Their structures were determined by means of spectroscopic analyses including 1D‐ and 2D‐NMR techniques. The nematicidal activities of these constituents were determined against the root‐knot nematode Meloidogyne incognita. Hundred percent mortality was caused by all of these after 72 h at a 0.125% concentration. Compound 1 and cordioic acid were most active and caused 100% mortality after 24 h at a 0.50% concentration. Furthermore, compound 2 , the ester of rosemarinic acid, was found to be more active than the free acid.  相似文献   
10.
Two new olean-12-ene triterpenoids, camarolic acid (1) and lantrigloylic acid (2), have been isolated from the aerial parts of Lantana camara, along with ten known triterpenes, namely, camaric acid, lantanolic acid, lantanilic acid, pomolic acid, camarinic acid, lantoic acid, camarin, lantacin, camarinin, and ursolic acid. The new compounds have been characterized as 3,25-epoxy-3alpha-hydroxy-22beta-{[(S)-3-hydroxy-2-methylidenebutanoyl]oxy}olean-12-en-28-oic acid (1) and 3,25-epoxy-3alpha-hydroxy-22beta-[(3-methylbut-2-enoyl)oxy]olea-9(11),12-dien-28-oic acid (2) through spectroscopic studies and a chemical transformation. Seven of the constituents, namely pomolic acid, lantanolic acid, lantoic acid, camarin, lantacin, camarinin, and ursolic acid, were tested for nematicidal activity against root-knot nematode Meloidogyne incognita. Pomolic acid, lantanolic acid, and lantoic acid showed 100% mortality at 1 mg/ml concentration after 24 h, while camarin, lantacin, camarinin, and ursolic acid exhibited 100% mortality at this concentration after 48 h. These results are comparable to those obtained with the conventional nematicide furadan (100% mortality at 1 mg/ml concentration after 24 h).  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