Microdetermination of ergocalciferol (vitamin D2) in pharmaceutical preparations by differential spectroscopy using trifluoroacetic acid in the absence of vitamin A.
A differential spectroscopy method for the determination of microgram quantities of ergocalciferol, using trifluoroacetic acid and hydrogen peroxide, was applied to commercially available pharmaceutical preparations. Tablets were powdered and extracted with methanol after being made basic with diethylamine. The methanol was concentrated, chloroform was added, and the mixture was chromatographed on neutral alumina using chloroform as the eluent. Ergocalciferol was determined in an aliquot of the eluate by differential spectroscopy and was compared with a reference ergocalciferol standard treated similarly. The method applied to low potency formulations (2.5-6 mug/tablet) is simple and quantitative, needs less than 5 hr for completion, and has a precision of less than +/- 2%. A simple and accurate chromatographic method for the determination of ergocalciferol in stabilized powders and high potency tablets, which precludes the necessity of solvent-solvent extraction, was also developed. The results are comparable with those obtained by the rat bioassay and the USP XVIII chemical assay.
Studies on the isomerization of vitamin D and related compounds with acidic reagents. II. Mechanism of the isomerization of vitamin D2 and its isomers with boron trifluoride.
Kinetic experiments on the isomerization of vitamin D2, pre-D2, 5, 6-trans-D2 and T2 with BF3 were investigated by using the determination method as reported previously (1). The related components in the reaction mixtures were confirmed to be one of the starting compounds, iso-D2 and iso-T2 in all cases by applying the qualitative method using both TLC and GLC. Then, the components were individually determined by the proposed method according to lapse reaction times. The con-version rates of all the starting compounds followed apparent first-order kinetics and the rate constants of vitamin D2, pre-D2, 5, 6-trans-D2 and T2 were 0.277, 0.462, 0.693 and 0.330, respectively. When the yields of iso-D2 and iso-T2 to the concentrations of converted starting compounds were calculated on the basis of the corresponding reaction times, the initial rates of yields of iso-D2 and iso-T2 at zero conversions of the starting compounds were respectively 100 and 0% in all cases. The results induced the conclusions in all cases that iso-D2 was originated as the first reaction product directly from the starting compounds while iso-T2 was the second reaction product originated via iso-D2. The conclusions are summarized as follows: Vitamin D2, pre-D2, 5, 6-trans-D2 or T2 →BF3 iso-D2 →BF3 iso-T2 The reaction mechanism was discussed from the conclusions (Fig. 4).
Atomistic insight into novel co-delivery of doxorubicin and paclitaxel using fullerene modified by dimethyl acrylamide trimethyl chitosan: A computational study

 Background: The distribution of drugs could not be controlled in the conventional drug delivery system. This has led to the development of a smart nanoparticle-based drug delivery system, known as smart drug delivery systems. In cancer research, novel biocompatible nanocarriers have received much attention for various ranges of anticancer drugs.In the current study, the effect of a novel co-polymer "dimethyl acrylamide-trimethyl chitosan" was investigated on drug delivery of doxorubicin and paclitaxel utilizing modified fullerene nanocarrier. This study was performed via molecular dynamics simulation based on acidic pH sensitivity of the cancer microenvironment. Furthermore, hydrogen bonds, diffusion coefficient, gyration radius, and drug-carrier interaction energies were investigated here. Interestingly, a simultaneous pH and temperature-sensitive system was proposed for paclitaxel and doxorubicin for a co-polymer. A pH-sensitive and temperature-sensitive copolymer was used based on trimethyl chitosan and dimethyl acrylamide, respectively. In such a dualistic approach, co-polymer makes an excellent option to have two properties in one bio-polymer. Results: The results suggest the dramatic and indisputable role of the co-polymer in the release of doxorubicin and paclitaxel in cancerous tissues, as well as an increased biocompatibility and drug uptake in a neutral state. The validation test was performed by repeated simulations of a similar article. The results are very close to those of the reference paper .Conclusions: Overall, conjugated fullerene and dimethyl acrylamide-trimethyl chitosan (DMAA-TMC) as carriers can be a good proposition for loading, delivery, and release of anti-cancer drugs based on a pH/temperature-sensitive smart drug delivery system.