scholarly journals Analytical Investigation of the Possible Chemical Interaction of Methyldopa with Some Reducing Carbohydrates Used as Pharmaceutical Excipients

2018 ◽  
Vol 8 (4) ◽  
pp. 657-666 ◽  
Author(s):  
Mohammad Reaz Siahi ◽  
Soma Rahimi ◽  
Farnaz Monajjemzadeh
Keyword(s):  
Binary Mixtures ◽  
Mass Spectra ◽  
Chemical Interaction ◽  
Analytical Investigation ◽  
Mass Ratio ◽  
Pharmaceutical Dosage Forms ◽  
Melting Endotherm ◽  
Physicochemical Methods ◽  
Dsc Curves ◽  
Reducing Carbohydrates

Purpose: Assessment of drug substance and excipients compatibility is an important issue during pre-formulation studies as well as the quality control of pharmaceutical dosage forms. In this study, potential incompatibility between methyldopa and reducing excipients was evaluated using physicochemical methods. Methods: Dextrose and lactose (anhydrous & monohydrate) were selected as reducing carbohydrates. The initial incompatibility was studied with DSC and FTIR on binary mixtures with 1:1 mass ratio. Results were confirmed using HPLC studies coupled with mass spectrometry. Results: The DSC curves indicated the elimination of the melting endotherm of methyldopa in the binary mixtures. A new peak at 1719 cm-1 was observed in the FTIR spectra that can be attributed to the loss of type one amine functionality. The m/z of the proposed compound was observed in the mass spectra. Conclusion: The potential incompatibility of Methyldopa with reducing carbohydrates was established using physicochemical methods.

scholarly journals Viscosity sinergism of hydrozypropmethyl and carboxy methyl cellulose

2008 ◽  
Vol 62 (1) ◽  
pp. 31-36 ◽  
Author(s):  
Jaroslav Katona ◽  
Verica Sovilj ◽  
Lidija Petrovic
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Binary Mixtures ◽  
Methyl Cellulose ◽  
Mass Ratio ◽  
Positive Deviation ◽  
Flow Properties ◽  
Concentration Changes ◽  
Overlap Concentration ◽  
Carboxy Methyl

Rheology modifiers are common constituents of food, cosmetic and pharmaceutic products. Often, by using two or more of them, better control of the product rheological properties can be achieved. In this work, rheological properties of hydroxypropymethyl cellulose (HPMC) and sodium carboxymethyl cellulose (NaCMC) solutions of different concentrations were investigated and compared to the flow properties of 1% HPMC/NaCMC binary mixtures at various HPMC/NaCMC mass ratios. Solutions of HPMC and NaCMC were found to be pseudoplastic, where pseudoplasticity increases with increase in the macromolecules concentration. Changes of the degree of pseudoplasticity, n as well as the coefficient of consistency, K with the concentration are more pronounced in HPMC solutions when compared to the NaCMC ones. This is mostly due to the ability of HPMC molecules to associate with each other at concentrations above critical overlap concentration, c , and greater flexibility of macromolecular chains. Binary mixtures of HPMC/NaCMC were also found to be pseudoplastic. Experimentally obtained viscosities of the mixture were proved to be larger than theoretically expected ones, indicating viscosity synergism as a consequence of HPMC-NaCMC interaction. Maximum in synergy was observed when HPMC/NaCMC mass ratio was 0.4/0.6, no matter of the shear rate applied. On the other hand, it was found that relative positive deviation, RPD decreases when shear rate is increased.

Eine Auswertmethode für DSC-Kurven binärer Gemische sowie die Phasendiagramme einige rMethylchlorsilane mit Lutidin / A New Evaluation of DSC-curves of Binary Mixtures and the Phase Diagrams of Some Methylchlorosilanes with Lutidine

1989 ◽  
Vol 44 (12) ◽  
pp. 1172-1176
Author(s):  
Karl Hensen ◽  
Michael Dräbing
Keyword(s):  
Phase Diagrams ◽  
Binary Mixtures ◽  
Melting Compound ◽  
Congruently Melting ◽  
Dsc Curves

Abstract A new evaluation of DSC-curves of binary mixtures is given. By analyzing the phase diagrams of methyltrichlorosilane and dimethyldichlorosilane with some lutidines the existence of the incongruently melting addition compounds MeSiCl3 · (2.3-Lutidine)-,, MeSiCl3 · 2.3-Lutidine, (MeSiCl3)2 · 3.4-Lutidine, Me,SiCl2 · (2.3-Lutidine)2, Me2SiCl2 · (2.5-Lutidine),, Me2SiCl2 · 2.5-Lutidine, Me2SiCl2 · (2.6-Lutidine)2, Me2SiCl2 · 2.6-Lutidine, Me2SiCl2 · (3.4-Lutidine)2, Me,SiCl2 · 3.4-Lutidine, (Me2SiCl2)2 · 3.4-Lutidine, Me2SiCl2 · (3.5-Lutidine)2, Me2SiCl2 · 3.5-Lutidine, and the congruently melting compound MeSiCl3 ·(3.4-Lutidine)2 was proven.

scholarly journals New iodine derivatives of flavonol and isoflavone

2009 ◽  
Vol 81 (1) ◽  
pp. 21-28 ◽  
Author(s):  
Mário G. de Carvalho ◽  
Virginia C. da Silva ◽  
Tânia M.S. da Silva ◽  
Celso A. Camara ◽  
Raimundo Braz-Filho
Keyword(s):  
Mass Spectra ◽  
Chemical Interaction ◽  
2D Nmr ◽  
Racemic Mixture ◽  
Reactive Site ◽  
Reaction Conditions ◽  
Unsaturated Ketones ◽  
Significant Difference ◽  
Stereo Selectivity ◽  
Derivatives Of

The reaction of the flavonol 3,7,3', 4'-tetra-O-methylquercetin (1) and of the isoflavone 7,4'-di-O-methylgenistein (2) with alkaline iodine in methanol afforded four new iodine derivatives: 8-iodo-5-hydroxy-3,7,3', 4'-tetramethoxy- flavone (1a) and 6-iodo-5-hydroxy-3,7,3', 4'-tetramethoxyflavone (1b) from 1; 2 afforded a mixture of two compounds, identified as a racemic mixture of (±)-trans-5-hydroxy-2,3,7,4'-tetramethoxy-8-iodo-isoflavanone (2a) and (±)-trans-5-hydroxy-2,3,7,4'-tetramethoxy-6,8-diiodo-isoflavanone (2b). The formation of these different products reveals a significant difference involving the chemical interaction between the reactive site of α, β-unsaturated ketones of flavonol and isoflavone under the tested reaction conditions (using I2/KOH/MeOH). Furthermore, the trans stereo selectivity is noteworthy in the nucleophylic addition of methanol at the isoflavone α, β-unsaturated system. The structures were identified on the basis of spectral data, mainly 1D and 2D NMR and mass spectra.

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