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691.
pH‐zone‐refining centrifugal partition chromatography was successively applied in the large‐scale separation of close Rf antipsychotic indole alkaloids directly from CHCl3 fraction of Rauwolfia tetraphylla leaves. Two experiments with increasing mass from 500 mg to 3 g of crude alkaloid extracts ( 1 C) of R. tetraphylla were carried out in normal‐displacement mode using a two‐phase solvent system composed of methyl tert‐butyl ether/ACN/water (4:1:5, v/v/v) where HCl (12 mM) was added to the lower aqueous stationary phase as a retainer and triethylamine (5 mM) to the organic mobile phase as an eluter. The two centrifugal partition chromatography separations afforded a total of 162.6 mg of 10‐methoxytetrahydroalstonine ( 1 ) and 296.5 mg of isoreserpiline ( 2 ) in 97% and 95.5% purity, respectively, along with a 400.9 mg mixture of α‐yohimbine and reserpiline ( 3 and 4 ). Further, this mixture was resolved over medium pressure LC using TLC grade silica gel H (average particle size 10 μm), which afforded 160.4 mg of α‐yohimbine ( 3) and 150.2 mg of reserpiline ( 4) in >95% purities. The purity of the isolated antipsychotic alkaloids was analyzed by high‐performance LC and their structures were characterized on the basis of their 1D, 2D NMR and electrospray ionization‐mass spectroscopic data. 相似文献
692.
Clawson C Ton L Aryal S Fu V Esener S Zhang L 《Langmuir : the ACS journal of surfaces and colloids》2011,27(17):10556-10561
Novel lipid-polymer hybrid nanoparticles are designed with a poly(ethylene glycol) (PEG) coating that is shed in response to a low pH trigger. This allows the nanoparticles to be stable during systemic circulation and at neutral pH, but destabilize and fuse with lipid membranes in acidic environments. The hybrid nanoparticles consist of a poly(lactic-co-glycolic acid) core with a lipid and lipid-PEG monolayer shell. To make the hybrid nanoparticles pH sensitive, a lipid-(succinate)-mPEG conjugate is synthesized to provide a hydrolyzable PEG stealth layer that is shed off the particle surface at low pH. The pH-sensitivity of the nanoparticles is tunable using the molar concentration of the lipid-(succinate)-mPEG incorporated in the lipid shell of the particles. Possible uses of these pH-sensitive nanoparticles include aggregating in acidic tumor microenvironments, escaping acidified endosomes, or aggregating in deep lung tissue for improved inhalation administration. 相似文献
693.
M. Koteswara ReddyK. Santosh Kumar P. SreenivasG.L. David Krupadanam K. Janardhan Reddy 《Tetrahedron letters》2011,52(49):6537-6540
New 1,4-disubstituted-1,2,3-triazole analogues of forskolin (5a-g, 6a-g) have been prepared by regioselective propargylation at 1-position followed by Cu(I) catalysed cycloaddition of different alkyl azides under the click reaction conditions. An interesting acyl shift in the base catalysed propargylation afforded a new series of 1,4-disubstituted-1,2,3-triazole analogues of forskolin (6a-g). These analogues have potential selective therapeutic applications as antihypertensive, antiglaucoma, antiasthma and antiobesity agents. 相似文献
694.
Optimization of ethanol production through addition of substratum and protein-lipid additives was studied. Oilseed meal extract
was used as protein lipid supplement, while rice husk was used as substratum. The effect of oil seed meal extract and rice
husk was observed at varying concentration of medium sugar from 8% to 20%. Of the three oil seed meal extracts used, viz.
groundnut, safflower, and sunflower, safflower was found to be most efficient. The use of oilseed meal extract at 4% was found
to enhance ethanol production by almost 50% and enhanced sugar tolerance from 8% to 16%. A further increase of almost 48%
ethanol was observed on addition of 2 g of rice husk per 100 ml of medium. An increase in cell mass with better sugar attenuation
was observed. Further optimization was sought through use of sugarcane juice as the sugar source. While 8.9% ethanol yield
with 75% sugar attenuation was observed at 20% sucrose concentration, it was found to increase to 12% (v/v) with almost complete utilization of medium sugar when sugarcane juice was used. Cell weight was also observed to increase
by 26%. 相似文献
695.
Turlington M Du Y Ostrum SG Santosh V Wren K Lin T Sabat M Pu L 《Journal of the American Chemical Society》2011,133(30):11780-11794
(S)-1,1'-Binaphth-2-ol (BINOL) in combination with ZnEt(2), Ti(O(i)Pr)(4), and biscyclohexylamine was found to catalyze the highly enantioselective (83-95% ee) addition of various 1,3-diynes to aldehydes of diverse structures. This method provides a convenient pathway to generate a number of optically active dienediynes as the acyclic precursors to polycyclic compounds. The chiral dienediynes undergo highly chemoselective Pauson-Khand (PK) cycloaddition in benzaldehyde by using [Rh(cod)Cl](2) as the catalyst in the presence of rac-BINAP. High diastereoselectivity (up to >20:1) has also been achieved with the chiral dienediyne substrates containing a bulky substituent adjacent to the chiral center. In the presence of the Grubbs II catalyst, ring-closing enyne metathesis of the PK cycloaddition products led to the formation of the desired 5,5,7- and 5,5,8-fused tricyclic compounds. Further highly diastereoselective Diels-Alder reaction of a 5,5,7-tricyclic compound with maleic anhydride produced a 5,5,7,6-polycyclic product. The asymmetric synthesis of polycyclic compounds from optically active dienediynes has established a novel and efficient synthetic route to the structural framework of many biologically significant molecules. 相似文献
696.
Pankaj Soni Santosh K. Sar Anand Kamavisdar Rajmani Patel 《Journal of Analytical Chemistry》2011,66(6):596-599
A new simple procedure for the spectrophotometric determination of tricyclic antidepressant drug imipramine is proposed. The
method is based on the enhancement of the colour intensity of the Fe(III)-SCN− complex due to the addition of the drug imipramine. The value of molar absorptivity of the Fe(III)-SCN− imipramine complex in terms of the drug lies in the range of (2.77–3.16) × 103 L/mol cm at the absorption maximum 460 nm. The detection limit of the method was 250 μg/L. The slope, intercept, and correlation
co-efficient for the present method were found to be 0.008, 0.005, and 0.998, respectively. The effect of analytical variables
on the determination of the drug and the composition of the complex are discussed. The method is applicable to the determination
of imipramine in the drug samples. 相似文献
697.
Ramhari V. Rote Deepak P. Shelar Sandeep R. Patil Santosh S. Shinde Raghunath B. Toche Madhukar N. Jachak 《Journal of fluorescence》2011,21(1):453-459
Novel pyrazolo-pyrrolo-pyrimidine (PPP) derivatives having remarkable photophysical properties are designed with the help of theoretical semiempirical calculations. These compounds then synthesized successfully and studied effect of substituents on its photophysical properties. Figure
698.
The dependence of geomagnetic activity on solar features and interplanetary (IP) parameters is investigated. Sixty-seven intense
(−200 nT ≤ Dst < −100 nT) and seventeen superintense (Dst < −200 nT) geomagnetic storms (GMSs) have been studied from January
1996 to April 2006. The number of intense and superintense GMSs show three distinct peaks during the 11-year period of 23rd
solar cycle. The largest number of high strength GMSs are observed during maximum phase of solar cycle. Halo and partial halo
CMEs are likely to be the major cause for these GMSs of high intensity. No relationship is observed between storm duration
and the number of CMEs involved in its occurrence. The intensity of the GMS is also independent of the number of CMEs causing
the occurrence of storm. These geoeffective CMEs show western and northern bias. Majority of the geoeffective CMEs are associated
with X-ray solar flares (SFs). Solar and IP parameters, e.g., V
CME, V
SW, B, B
z
(GSE and GSM coordinates) and their products, e.g., V
SW · B and V
SW · B
z
are observed and correlated to predict the occurrence of intense GMSs. V
CME does not seem to be the appropriate parameter with the correlation coefficient, r = −0.2 with Dst index, whereas the correlation coefficient, r = −0.57, −0.65, 0.75, −0.68 and 0.77 of the parameters V
SW, B, B
z
, V
SW · B and V
SW · B
z
respectively, with Dst indicating that V
SW · B
z
and B
z
may be treated as the significant contributors in determining the strength of GMSs.
相似文献
699.
We explore the signals of a charged Higgs arising in a two Higgs doublet model respecting SUL(2)×U(1)×Z2 symmetry with three singlet right-handed neutrinos, NR. The charged Higgs in this model has negligible coupling with quarks, and has unsuppressed coupling to leptons and neutrinos. This leads to novel signatures of the charged Higgs at the LHC, especially in the case of an inverted neutrino mass hierarchy, in the form of electrons and muons with missing energy. 相似文献
700.
We study the Kolmogorov-Johnson-Mehl-Avrami theory of phase conversion in finite volumes. For the conversion time we find the relationship tau(con)=tau(nu)[1+f(d)(q)]. Here d is the space dimension, tau(nu) the nucleation time in the volume V, and f(d)(q) a scaling function. Its dimensionless argument is q=tau(ex)/tau(nu), where tau(ex) is an expansion time, defined to be proportional to the diameter of the volume divided by expansion speed. We calculate f(d)(q) in one, two, and three dimensions. The often considered limits of phase conversion via either nucleation or spinodal decomposition are found to be volume-size dependent concepts, governed by simple power laws for f(d)(q). 相似文献