Determination and quantitation of five cucurbitane triterpenoids in Momordica charantia by reversed-phase high-performance liquid chromatography with evaporative light scattering detection

A simple and specific analytical method for the quantitative determination of five cucurbitane-type triterpenoids isolated from the fruit of Momordica charantia is developed. The triterpenoids present in the fruits of Momordica charantia are separated with an acetonitrile (0.1% acetic acid)-water (0.1% acetic acid)-methanol (0.1% acetic acid) gradient at a flow rate of 0.5 mL/min. The high-performance liquid chromatography separation was performed on a Phenomenex C18 reversed-phase column. By using an evaporative light scattering detector, the main triterpenoids of Momordica charantia could be detected at levels as low as 10 microg/mL. The method was validated for precision, repeatability, and accuracy. The relative standard deviation was between 0.6-4.4%. The method was sensitive, quick, and accurate for the determination of main triterpenes and saponins in Momordica charantia, and can be used for quality control of Momordica charantia and its related dietary supplements.     

A Simple and Convenient Strategy for the Synthesis of Novel Ten,Twelve, and Fourteen‐membered Phosphorus Macrocyclic Compounds

Synthesis of the title compounds 4(a – i) was accomplished through a two‐step process. The synthetic route involves the cyclization of equimolar quantities of 2,2′‐methylene(methyl)bis(4,6‐di‐tert‐butyl‐phenol) ( 1 ) with tris‐(2‐chloro‐ethyl) phosphite ( 2a ), tris‐(2‐bromo‐ethyl) phosphine ( 2b ), and tris‐bromo methyl phosphine ( 2c ) in the presence of sodium hydride in dry tetrahydrofuran at 45–50°C. They were further converted to the corresponding oxides, sulfides, and selenides under N₂ atmosphere by reacting them with hydrogen peroxide, sulfur, and selenium, respectively ( 4a – c , 4d – f, and 4g – i ). But the compounds 6a , b were prepared by the direct cyclocondensation of equimolar quantities of 1 with (2‐chloro‐ethyl)‐phosphonic acid dibromomethyl ester ( 5a ) and (2‐chloro‐ethyl)‐phosphonic acid bis(2‐bromo‐ethyl) ester ( 5b ) in the presence of sodium hydride in dry tetrahydrofuran at 45–50°C in moderate yields. All the newly synthesized compounds 4 ( a – i ) and 6 ( a – b ) exhibited moderate in vitro antibacterial and antifungal activities.     

Trifluoroborane catalyzed chemoselective synthesis of highly functionalized 1,3-thiazin-2-ylidenes

An efficient chemoselective synthesis of 1,3-thiazine-2-ylidenes was achieved via annulations of β-aroyl-thioacetamide with propargyl alcohols using BF₃ OEt₂ as Lewis acid catalyst. A broad spectrum of substrates was well tolerated under the mild reaction conditions producing desired thiazine heterocyclics in good yields.     

Investigating sub-2 μm particle stationary phase supercritical fluid chromatography coupled to mass spectrometry for chemical profiling of chamomile extracts

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.     

Bending of an incompressible aelotropic rectangular block into an elliptical shell

A solution for the problem of bending of an incompressible aelotropic rectangular block into an elliptical shell has been obtained The maximum value of η, (the ratio of the semi-dimension of the rectangular block in the deformed state, to the semi-axis of the elliptical shell) is so small that the higher power η can be neglected and thus reducing the problem to a simple differential equation, the solution is obtained in terms of the strain energy function Analytic expressions for the resultant normal force and moment of the resultant couple have been obtained. The solution of bending of an aelotropic incompressible rectangular block into a right circular cylindrical shell has been derived as a particular case of the present investigation. These results agree with those obtained by Green and Adkins.     

Synthesis and biological assessment of some fused Pyran derivatives

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.