This work describes two distinct
annulations between ynamides and
1,2-benzisoxazoles with chemoselectivity controlled by ligands. With
IPrAuCl/AgNTf2, aryl-substituted ynamides undergo [5+2]-annulation
reactions, whereas P(t-Bu)2(o-biphenyl)AuCl/AgNTf2 alters the chemoselectivity of the
same ynamides to implement [5+1]-annulation reactions. 13C-Labeling experiments confirm
that a 1,2-sulfonamide shift is involved in the [5+1]-annulation process.
A plausible mechanism is postulated to rationalize the mechanisms
of the two annulations.
Novel RES-carrying piperine loaded mixed micelles (RES-P-MM) composed of Poloxamer 407 and d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) were developed to enhance the solubility, oral bioavailability and anticancer potency of RES.
Objective: The aim of the present study was to design novel drug delivery system containing ramipril microemulsion. Ramipril is an antihypertensive drug having very low aqueous solubility and bioavailability. Ramipril microemulsion could be used as a possible alternative to the traditional oral formulation to improve dissolution rate and hence its bioavailability with avoidance of the first-pass metabolism.Methods: The microemulsion existence region was determined by constructing pseudoternary phase diagram and prepared by using four components orange oil, tween 80 as a surfactant, propylene glycol as co-surfactant and distilled water as the aqueous phase. The water titration method was employed for its determination. All formulated microemulsion were subjected for visual inspection, centrifugation and stability test. The all stable formulations were selected for further study.The optimized microemulsion formulation B-9 was subjected for various evaluation parameters such as, visual inspection, stability studies, pH, viscosity measurements, electrical conductivity, content uniformity and dye solubility test.Results: Results revealed that construction of phase diagram and use of phase titration method was a suitable technique for the preparation of microemulsion as most of the formulations were transparent. It was found that the best microemulsion result was found for ratio 2:1. The results of stress tests conclude that the optimized formulation was both physically and chemically stable for 8 mo. Also, The Fourier transform infrared (FTIR) radiation measurement and Differential scanning calorimetry (DSC) of optimized formulation indicate the compatibility of ramipril with orange oil, surfactant-tween 80 and cosurfactant-propylene glycol. From electrical conductivity 0.283 σ and staining test the prepared optimized formulation B-9 was found to be o/w type of microemulsion. The optimized B-9 formulation showed good viscosity 13.52±0.01cps and pH 3.21±0.02 with highest drug content uniformity was found to be 84.98±0.02 %.Conclusion: In the present study a satisfactory attempt was made to formulate a novel o/w microemulsion of ramipril which improves the gastrointestinal absorption by raising its water solubility and hence oral bioavailability is also enhanced.
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