Yam starch from Dioscorea cayenensis‐rotundata complex was isolated and characterized by scanning electron microscopy (SEM), particle size analysis, X‐ray diffraction, differential scanning calorimetry (DSC), compaction and rheology, and compared to maize (Zea mays) and potato (Solanum tuberosum) starches. Yam starch exhibited a log‐normal distribution of flattened ovoid shaped granules with a mean particle size of 25 µm. X‐ray diffraction showed a C‐type crystalline pattern with the degree of relative crystallinity estimated to be 34%. DSC analysis suggests that the crystalline regions in yam starch are thermally and structurally more stable as in maize and potato. Irrespective of the relative humidity (39, 67, 78% R.H.) yam starch exhibited higher moisture uptakes than maize starch and lower than potato. Intermediate values of swelling power and amylose leaching were obtained for yam as compared to maize and potato. Compaction properties of yam and potato starches were similar. However, compacts from yam presented a relatively lower tensile strength. Aqueous starch systems (4%) of yam and maize starches showed analogous shear‐thinning (pseudo‐plastic) behavior suitably described by the power‐law model. These results support the potential use of yam starch as excipient comparable to potato starch in pharmaceutical solid forms and as thickening agent similar to maize in pharmaceutical applications.
Amphotericin B (AmB) is a broad spectrum of antifungal drug used to treat antifungal diseases. However, due to the high toxicity of AmB, treated patients may suffer the risk of side effects, such as renal failure. Nanoencapsulation strategies have been reported to elicit low toxicity, albeit most of them possess low encapsulation efficiency. The aim of this research is to develop micellar delivery systems for AmB with reduced toxicity while maintaining its affectivity by employing retinol (RET)-conjugated amphiphilic block copolymers (ABCs) as precursors. Copolymers composed of poly(ε-caprolactone) (A) and polyethylenglycol (B) of types AB and ABA were synthesized by ring opening polymerization and subsequently conjugated with RET by Steglich esterification. 1H-NMR spectroscopy was used to corroborate the structure of copolymers and their conjugates and determine their molecular weights. Analysis by gel permeation chromatography also found that the materials have narrow distributions. The resulting copolymers were used as precursors for delivery systems of AmB, thus reducing its aggregation and consequently causing a low haemolytic effect. Upon conjugation with RET, the encapsulation capacity was enhanced from approximately 2 wt % for AB and ABA copolymers to 10 wt %. AmB encapsulated in polymer micelles presented improved antifungal efficiency against Candida albicans and Candida auris strains compared with Fungizone®, as deduced from the low minimum inhibitory concentration.
This paper reports the in vitro characterization of the interaction between the phosphate groups of DNA and the protonated species of drugs with basic groups through the determination of the affinity constants, the reversibility of the interaction, and the effect on the secondary structure of the macromolecule. Affinity constants of the counterionic condensation DNA–drug were in the order of 106. The negative electrokinetic potential of DNA decreased with the increase of the proportion of loading drugs. The drugs were slowly released from the DNA–drug complexes and had release kinetics consistent with the high degree of counterionic condensation. The circular dichroism profile of DNA was not modified by complexation with atenolol, lidocaine, or timolol, but was significantly altered by the more lipophilic drugs benzydamine and propranolol, revealing modifications in the secondary structure of the DNA. The in vitro characterization of such interactions provides a physicochemical basis that would contribute to identify the effects of this kind of drugs in cellular cultures, as well as side effects observed under their clinical use. Moreover, this methodology could also be projected to the fields of intracellular DNA transfection and the use of DNA as a carrier of active drugs.
6-Methylcoumarin (6MC) is a semisynthetic coumarin with important in vitro and in vivo antiinflammatory activity. In order to continue the pre-clinical characterization of this molecule, in vitro intestinal permeability, plasma profile and tissue distribution after oral administration in rats were studied. The permeability of 6MC was evaluated by the Caco-2 cellular model in both the apical-basal (A-B) and basal-apical (B-A) directions. The pharmacokinetics and biodistribution were evaluated in rats after oral and intraperitoneal administration at doses of 200 mg/kg. Transport experiments with Caco-2 cells showed that 6MC presented high permeability at all concentrations evaluated. This finding suggested that 6MC could be transported across the gut wall by passive diffusion. The plasma concentration-time curve showed that the maximum concentration (Cmax) was 17.13 ± 2.90 µg/mL at maximum time (Tmax) of 30 min for the oral route and Cmax 26.18 ± 2.47 µg/mL at 6.0 min for the intraperitoneal administration, with elimination constant of (K e ) 0.0070 min -1 and a short life half time of (T
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