排序方式: 共有73条查询结果,搜索用时 134 毫秒
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Michael D. Jones Bharathi Avula Yan-Hong Wang Lu Lu Jianping Zhao Cristina Avonto Giorgis Isaac Larry Meeker Kate Yu Cristina Legido-Quigley Norman Smith Ikhlas A. Khan 《Analytica chimica acta》2014
Roman and German chamomile are widely used throughout the world. Chamomiles contain a wide variety of active constituents including sesquiterpene lactones. Various extraction techniques were performed on these two types of chamomile. A packed-column supercritical fluid chromatography–mass spectrometry method was designed for the identification of sesquiterpenes and other constituents from chamomile extracts with no derivatization step prior to analysis. Mass spectrometry detection was achieved by using electrospray ionization. All of the compounds of interest were separated within 15 min. The chamomile extracts were analyzed and compared for similarities and distinct differences. Multivariate statistical analysis including principal component analysis and orthogonal partial least squares-discriminant analysis (OPLS-DA) were used to differentiate between the chamomile samples. German chamomile samples confirmed the presence of cis- and trans-tonghaosu, chrysosplenols, apigenin diglucoside whereas Roman chamomile samples confirmed the presence of apigenin, nobilin, 1,10-epioxynobilin, and hydroxyisonobilin. 相似文献
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Sriramoju Shamili Kavitha Siddoju Avula Srinivas Sd. Ishrath Farheen 《Journal of heterocyclic chemistry》2023,60(1):116-122
Pyran was formed by reacting methyl 3-methoxyacrylate (1) with 2-benzylidenemalanonitrile to form compound 2 . The pyrano derivatives 3–6 were obtained by reacting the second molecule with 2-benzylidenemalanonitrile, carbon disulfide, formamide, and benzylidene cyclohexanone. Compound (2) interacted with ethyl chloroacetate to form compound 8 , which then cyclized in the presence of sodium ethoxide to form compound 9 . Compound 7 was formed when compound (2) was treated with acetic acid in the presence of sulfuric acid and reacted with ethylchloroacetate to form compound 10 and then was converted to compound 11 by the addition of sodium ethoxide. Analytical and spectral data have been used to determine the structures of the newly synthesized substances and they were then tested for their antibacterial and antioxidant activities. In terms of antioxidant activity, compounds 2 and 8 were found to have the greatest and lowest levels, respectively, against Enterobacter aerogenes. 相似文献
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Balakrishna A Reddy MV Nayak SK Manjunath M Reddy CD Reddy CS 《Chemical & pharmaceutical bulletin》2008,56(10):1486-1489
4-Amino-5-phenyl-4H-1,2,4-triazole-3-thiol (1) underwent facile condensation with various phosphorus dichlorides (2a-j) in the presence of triethylamine in dry tetrahydrofuran at 60-65 degrees C and afforded corresponding thiadiazaphosphol-2-ones (3a-j). Their chemical structures were characterized using IR, (1)H-, (13)C-, (31)P-NMR and Mass spectral studies. All the title compounds were screened for antioxidant properties by radical scavenging methods such as 1,1-diphenyl-2-picryl hydrazyl (DPPH), hydroxyl and lipid peroxidation. They exhibited potent in vitro antioxidant activity dose dependently. Their bioassay showed them to possess significant antibacterial activity. 相似文献
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Chidananda Swamy Rumalla Bharathi Avula Yatin J. Shukla Yan‐Hong Wang Rahul S. Pawar Troy J. Smillie Ikhlas A. Khan 《Journal of separation science》2008,31(22):3959-3964
A HPTLC method was developed for simple and rapid chemical fingerprint analysis of four Hoodia species, dietary supplements that claim to contain Hoodia gordonii, and plants from genera related to Hoodia. HPTLC was performed on precoated silica 60F254 plates with dichloromethane/methanol/water 75:17:2.2 by volume, as mobile phase. Evaluation of the HPTLC plates was done by using the CAMAG DigiStore2 digital system with winCATS software. The authentication of H. gordonii was achieved by comparing the band colors and Rf values for TLC fingerprints with those of 11 standard compounds including P57. The developed method was successfully applied for the identification of the 11 pregnane glycosides for four different species of Hoodia, 24 related genera and 13 dietary supplements that claim to contain H. gordonii. Different sample matrices were successfully analyzed, providing a wide range of applicability for this method, including gels, capsules, tablets, sprays, teas, snack bars, powders, and juices. The developed method was validated for specificity, stability, repeatability, and robustness. The results of HPTLC method were verified by LC‐UV‐MS method. 相似文献
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Avula Prashant Gazaula DavidKrupadanam Roberto R. Gil Lee-Juian Lin Geoffrey A. Cordell 《合成通讯》2013,43(24):4655-4663
Reaction of 7,8-dihydroxy-2H-1-benzopyran-2-one, and its 4-methyl derivative, with α-haloketones affords α-pyrano-1,5-benzodioxapines, while 3-chloro-4-methyl-7,8-dihydroxy-2H-1-benzopyran-2-one gives α-pyrano-1,4-benzodioxane. The structures of the compounds were deduced using a combination of 1H nmr, 13C nmr (BB, DEPT), HETCOR, NOESY, and selective INEPT techniques and molecular modeling. 相似文献
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Satya Girish Avula Kenneth Alexander Alan Riga 《Journal of Thermal Analysis and Calorimetry》2010,99(2):655-658
A eutectic is formed from a mixture of two or more solids and has a melting point lower than that of each of its constituents.
It is generally represented by a phase diagram where the liquid and solid phases impact upon each other with a value known
as the eutectic point. In pharmaceuticals, poor water solubility is a major obstacle for releasing new dosage forms into the
market. Eutectic formation overcomes these problems. Preparation of a phase diagram by Differential Scanning Calorimetry can
determine eutectic properties, but it is tedious. A modified Van’t Hoff (VH) equation was used in this study. Devalina Law developed a dimensionless index for the VH equation. The difference in melting points of an excipient polymer and drug are
divided by the slope of the VH equation. In previous studies, five excipient–drug compositions were evaluated. The final index
relationship was in good agreement except for the salt, quinine sulfate. In order to test the validity of the VH index, further
studies of PEG with acetylsalicylic acid, acetaminophen, diflunisal, dimenhydrinate, ketoconazole, and mefenamic acid were
performed. 相似文献
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Amin E Wang YH Avula B El-Hawary SS Fathy MM Mohammed R Khan IA 《Journal of AOAC International》2012,95(3):757-762
Triterpenoid saponins are a class of glycosides with a wide range of bioactivities, which make them interesting research candidates. Zygophyllum coccineum is an Egyptian desert plant rich in triterpenoid saponins. Reviewing the relevant literature, no data concerning the HPLC or ultra-performance LC (UPLC) analysis of Zygophyllum content were found. This paper presents two methods, HPLC-UV and UPLC-UV-evaporative light scattering detector (ELSD)/MS, for the simultaneous determination of 10 compounds in the alcohol extract of Z. coccineum. The HPLC method uses a C18 column and water-acetonitrile (both containing 0.1% trifluoroacetic acid) gradient system. The separation was achieved within 32 min. The developed UPLC method simultaneously detects and quantifies the 10 compounds using an Acquity UPLC BEH Shield RP18 column and reagent alcohol-acetonitrile (80/20, v/v) and water (both containing 0.5% formic acid) gradient system within 14 min with UV, ELS, and MS detectors. The methods were used to analyze another species, Z. simplex, and results revealed a great variation between the secondary metabolite pattern of both species. 相似文献
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An analytical method was developed for the simultaneous quantitative analysis of 6 amines and 20 flavonoids in fruits and extracts of 30 Citrus species, including C. aurantium, near-Citrus relatives, and dietary supplements by liquid chromatography with photodiode array detection. The separation was achieved with a Phenomenex Synergi Hydro reversed-phase column using gradient mobile phase of sodium acetate buffer (pH 5.5) and acetonitrile. Elution was run at a flow rate of 1.0 mL/min and UV at 254, 280, and 330 nm. Among the amines analyzed, synephrine, the main component, was present in the levels from 0.11 to 2.0 mg/g dry weight in 21 Citrus species and 0.07 to 18.62% in dietary supplements claiming to contain C. aurantium. The flavanones and flavones were analyzed in the same Citrus samples and were species-specific. The levels of flavones were very low compared with those of flavanones. The method facilitated the simultaneous quantification of 6 amines and 20 flavonoids in various Citrus species, the distinction between the different Citrus species, and the analysis of dietary supplements containing C. aurantium. 相似文献