Phototoxic effect of curcumin supersaturated solutions toward pathogenic bacteria has already been demonstrated. However, to be useful in the clinical practice, a supersaturated solution needs to be physically and chemically stabile over the relevant time period. Poloxamer-based solid dispersions (SD) intended for ex tempore preparation of a supersaturated solution were designed to simultaneously facilitate dissolution and inhibit precipitation of curcumin in vitro. Due to the transformation of the crystalline compound to an amorphous form, as shown by X-ray powder diffraction, the desired concentration of curcumin could easily be achieved upon hydration of SDs. The efficiency of selected poloxamers (Pluronic® F-127, F-68 and P-123) as the precipitation inhibitors (PIs) and influence of an additional PI (polyethylene glycol 400, hydroxypropyl methylcellulose, and hyaluronic acid) on the physical stability of the solutions were examined by UV-Vis spectrophotometry. HPLC-PDA was employed to evaluate hydrolytic and photolytic stability of curcumin in the SD solutions. At sub-micellar concentrations, Pluronics® F-127 and P-123, but not F-68, delayed curcumin precipitation in aqueous media and protected the compound from hydrolytic degradation up to 24 h. Complete inactivation of Enterococcus faecalis was achieved after exposure to solutions of selected SDs at curcumin concentration ≥1 µM and the light dose of 9.4 J/cm.
The present study reports the new facile methodology for synthesis of
symmetrical and asymmetrical thioureas by an one-pot reaction of amine,
carbon disulfide and oxidants: hydrogen peroxide, ethylenediamine tetraacetic
acid (EDTA)/sodium percarbonate system or air. The structures of the
synthesized compounds were confirmed by IR, 1H and 13C NMR and MS methods.
Reaction mechanism has been proposed on the basis of reaction intermediate
isolation and their structure determination. The synthetic benefits of the
presented methods is reflected in the operational simplicity, mild reaction
conditions, short reaction times, recycling of solvent, high purity and yield
of products, absence of dangerous by-products and technological applicability
at industrial scale. Considering commercial importance of the thioureas, it
can be emphasized that implementation of the optimal synthesis of thiourea,
based on presented methods, at industrial level of production would provide
concurrent alternative to existing technologies in use. [Projekat
Ministarstva nauke Republike Srbije, br. 172013]
Curcumin (Cur) is known to bind to human serum albumin (HSA) which may lead to a reduced phototoxic effect of the compound in the presence of serum or saliva. The influence of excipients on the Cur-HSA binding was studied by HSA florescence quenching and Cur absorption and emission spectroscopy in the presence and absence of the selected excipients. Photostabilty of Cur in the presence of HSA was evaluated, as well as the effect of excipients on HSA bound Cur photodegradation. Cyclodextrins (CDs) (2-hydroxypropyl-β-cyclodextrin and 2-hydroxypropyl-γ-cyclodextrin) and polymers (polyethylene glycol 400, PEG 400 and Pluronic F-127, PF-127) were selected for the study. CDs and PF-127 seem to decrease Cur binding to HSA, probably through competitive binding. Cur was still bound to HSA in polyethylene glycol (PEG) solutions at the highest investigated concentration (5% w/v). However, high PEG concentration appears to have effect on the protein conformation, as shown by the fluorescence quenching study. Low Cur photostability in the presence of HSA could be improved by the addition of hydroxylpropyl-γ-cyclodextrin (HPγCD) to the samples, whereas PEG and PF-127 showed no effect.
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