Subcritical water extraction and determination of nifedipine in pharmaceutical formulations

A rapid and simple continuous method for the extraction of nifedipine from tablets was developed by using pressurized hot water at 150 degrees C. This is the first time that subcritical water was applied to the extraction of low-polarity compounds in pharmaceutical analysis. The method is based on the increment in solubility of nifedipine in subcritical water. Extraction temperature and static and dynamic extraction time were optimized in order to reach quantitative extraction of the drug from the tablets. After extraction, the drug was determined by spectrophotometry by measuring absorbance at 338 nm. Accuracy and precision of the method were determined by analysis of 10 synthetic samples of pharmaceutical formulations prepared with common tablet excipients. Recovery was found to be 99.2% with a relative standard deviation of 1.9%, which indicates that the excipients of the formulation do not interfere in the determination. The method was applied to the determination of the drug content uniformity in tablets.     

Aplysinopsin-type alkaloids from Dendrophyllia sp., a scleractinian coral of the family dendrophylliidae of the philippines,facile photochemical (Z/E) photoisomerization and thermal reversal

The dendrophylliid Dendrophyllia sp. of Palawan contains the indole alkaloids 2′-demethylaplysinopsin ( 4 ) and 2′-demethyl-3′-N-methylaplysinopsin ( 6 ) and their 6-bromo analogues in H (Z/E) ratio larger than 95:5; these mixtures undergo facile photoisomerization to give mixtures richer in the (E) stereoisomer which undergo thermal isomerization to give back the original mixtures.     

Complexation of diazaperylene and bisisoquinoline with transition metal ions in the gas phase studied by electrospray ionization mass spectrometry

The complex formation of the ligands 1,12-diazaperylene (dap), 1,1'-bisisoquinoline (bis), 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen) with transition metal ions (M = Fe, Co, Ni, Cu, Zn, Ru, Os, Re, Pd, Pt, Ag and Cd) in the gas phase has been studied by electrospray ionization mass spectrometry. With the exception of Ru, Os, Fe, Ni and Cu, singly charged complexes [MLn](+) (n = 1,2) were observed. The complexes of dap and bis with Ru, Os, Fe and Ni ions, and the mixed ligand complexes with bpy and phen, are preferably of the doubly charged type [ML3]2+. In addition, collision-induced dissociation (CID) measurements were employed to evaluate the relative stabilities of these complexes. The CID experiments of mixed-ligand complexes which contain both dap and phen or dap and bpy exhibit preferential elimination of bpy, indicating that bpy is a weaker ligand than phen and dap.     

New examples of indefinite hyper-Kähler symmetric spaces

Following the approach to pseudo-Riemannian symmetric spaces developed in [I. Kath, M. Olbrich, On the structure of pseudo-Riemannian symmetric spaces, arXiv:math.DG/0408249, 2004] we exhibit examples of indefinite hyper-Kähler symmetric spaces with non-abelian holonomy. Moreover, we classify indecomposable hyper-Kähler symmetric spaces whose metric has signature (4,4n)$(4,4n)$. Such spaces exist if and only if n∈{0,1,3}$n\in \{0,1,3\}$.     

Viscosity studies of solutions of water inn-aliphatic alcohols at various temperatures

Viscosity measurements have been made at 25°C on solutions of water inn-propanol, and at 15, 25, 35, and 45°C on solutions of water inn-butanol,n-pentanol, andn-hexanol over the respective solubility ranges. For most of the systems, water decreases the viscosity of the dry alcohols, while for the lower members of the series literature data report an increase in viscosity on addition of water. These results are rationalized in terms of two kinds of interaction between water molecules and alcohols: participation of water molecules in chain formation for the lower alcohols and formation of water-centered complexes for butanol and higher alcohols.     

Adriadysiolide,the First Monoterpenoid Isolated from a Marine Sponge

Spectra and chemical transformations allow to establish the gross structure 6,7-epoxy-4,7-dimethyl-l-oxa-spiro[4.4]non-3-en-2-one for adriadysiolide ( 1 ), the first monoterpenoid isolated from a marine sponge, a Dysidea sp. of the Adriatic Sea. Its configuration 5R*, 6S*, 7S* as given in 1a is derived from diastereoselective total syntheses of both 1a and its diastereoisomer 1b via stereochemically predictable peracid epoxidations of olefinic precursors. Thus, OH assistance in allylic alcohol 8 leads to oxirane 13 which is subjected to methyl cuprate conjugate addition to give epiadriadysiolide ( 1b ), whilst electronic deactivation by a neighboring heterocyclic O-atom in intermediate 5 , derived from 8 mainly leads to adriadysiolide ( 1a ). Comparative ¹H-NMR shift-reagent effects with 1a and 1b , evaluated with the aid of molecular-mechanics calculations, support these conclusions.