Synthesis of six-membered cyclic siloxanes via enyne metathesis with a ruthenium catalyst generated in situ

The catalytic system in situ generated by combination of [RuCl₂(p-cymene)]₂ as a ruthenium source, 1,3-bis(mesityl)imidazolinium chloride (MesH₂ImCl) as a bulky electron-releasing carbene precursor and cesium carbonate as a base, is shown to be an efficient catalyst for the metathesis reaction of propargylic allylsilyl ethers R¹---CCCR₂---O---SiMe₂---CH₂CH=CH₂. The metathesis products, the cyclic siloxanes, were obtained after complete conversion of the enynes in 67–87% isolated yields. These six-membered ring compounds contain the 1,3-diene unit that is used in Diels–Alder reaction and give access to heterobicyclic derivatives. The resulting cyclic siloxanes are selectively opened under oxidative conditions with H₂O₂ to afford allylic diols, with fluoride to form conjugated triene and under hydrogenation conditions with Pd/C catalyst to give a tetrasubstituted alkene.     

Binding and Encapsulation of Doxorubicin on Smart Pectin Hydrogels for Oral Delivery

Pectins (Pec) of 33 to 74?% esterification degree were tested with doxorubicin (Dox), a very high toxic drug widely used in cancer therapies. Pec with 35 and 55?% DE were selected because of the Dox binding higher than Pec microspheres of 35 and 55?% obtained by ionotropic gelation with Ca⁺² have 88 and 66?% Dox loading capacity. Kinetic Dox release showed more than 80.0 and about 30.0?% free drug from 35?% and 55?% Pec formulations at pH 7.4, and 37?°C after 1-h incubation, respectively. Besides, Dox release decrease to 12?% in 55?% Pec microsphere formulation after 1-year storage at 4?°C. FTIR analysis of Pec?CDox complex showed hipsochromic shifts for the ??_C=O, ??_N-H and ??_C-C vibrational modes compared to Dox spectrum suggesting strong interaction between the drug cargo and the matrix. Rheological studies of Pec and Pec?CDox samples flow behavior exhibited a shear-thinning nature. Fifty-five percent of Pec showed higher viscosity than the viscosity for 35?% Pec in all range of temperatures analyzed, and decreased when the temperature is raised. Besides, Pec?CDox complexes have higher viscosity values than those of the corresponding Pec samples, and viscosity curves as function of shear rate for 35?% Pec?CDox are above the curves of 55?% Pec?CDox. In both cases, the results are confirming significant interaction between the cargo and the matrix, which also was established in viscoelastic dynamic analysis.     

New temperature-assisted ionic liquid-based dispersive liquid–liquid microextraction method for the determination of glyphosate and aminomethylphosphonic acid in water samples

A new analytical temperature-assisted ionic liquid-based dispersive liquid–liquid microextraction (TA-IL-DLLME) method was developed for glyphosate and aminomethylphosphonic acid determination in water samples. Extracted analytes were derivatized using 9-fluoroenylmethylchloroformate and quantified by liquid chromatography with fluorescence detection. For the TA-IL-DLLME method, two strategies for phase solubilization were evaluated; in approach 1, the ionic liquid and aqueous matrix sample were mixed and then heated, while in approach 2, the aqueous sample was first heated and then the ionic liquid was injected. For both approaches, optimization included parameters that significantly affect extraction efficiency: ionic liquid type and volume, solubilization temperature and time, cooling and centrifugation time. Among the evaluated ionic liquids, 1-decyl-3-methylimidazolium tetrafluoroborate showed the best performance for TA-IL-DLLME and was selected for the two solubilization approaches; with approach 2, slightly better results were obtained. Thus, sample analyses were performed using a procedure based on approach 2. An important matrix effect, attributed to the presence of salts and metals in real water samples was observed. Sample acidification before derivatization allowed this problem to diminish, with recoveries ranging from 75 and 99%, and enrichment factors between 57 and 76 for target analytes.     

Controlled Release of Sulfasalazine Release from “Smart” Pectin Gel Microspheres under Physiological Simulated Fluids

Sulfasalazine (SLZ) is a synthetic nonsteroidal anti-inflammatory drug used mainly for the treatment of an inflammatory bowel and other diseases. Two pectins with different methylation degrees were blended to synthesized gel microspheres by ionotropic gelation for SLZ encapsulation. The encapsulation efficiency was found to be around of 99% in all formulations tested. However, different SLZ release profiles related to the methylation degrees of pectin were observed. Mixture of low methylated (LM) and high methylated (HM) pectins in the presence of calcium(II) displayed the best microsphere morphologies among the formulations tested determined by optical and electronic microscopies. The percentage of drug release using a mixture of LM and HM pectins after 255?min in simulated gastric fluid (pH?=?1.2), simulated intestinal fluid (pH?=?6.8), and phosphate buffer (pH?=?7.4) were 15.0%, 47.0%, and 52.2%, respectively.