The nature of the association between sorbed water and two high‐barrier hydrophilic polymers used in oxygen‐sensitive food packaging, and exhibiting opposite oxygen barrier behavior in the presence of moisture, has been studied by FT‐Raman and FT‐Infrared spectroscopy. The polymers considered in this work were an ethylene‐vinyl alcohol copolymer with superior oxygen barrier properties (32 mol‐% of ethylene EVOH) and an amorphous polyamide (aPA). The results revealed that for the latter glassy amorphous polymer, water molecules associate with the C?O and N? H groups of the ca. 10% “free” amide moieties, being the excess sorbed water self‐associated in clusters; thus, moisture sorption does not appear to disrupt the originally present hydrogen‐bonded amide groups. This “unusual” behavior leads to an overall increase in the extension of the hydrogen‐bonding, which may help explain the lower oxygen permeability displayed by the aPA with increasing relative humidity on the basis of the known free‐volume competing mechanism. Differently, water sorption appears to progressively disrupt the strong polymer self‐association present in the very efficient high‐barrier semicrystalline EVOH material by hydrogen‐bonding to hydroxyl groups, hence leading to the well‐known highly plasticized rubbery structure with much lower intermolecular cohesion and oxygen barrier.
FT‐IR spectra of severely dried, dry (dotted), and water‐equilibrated (thicker line) aPA in the range 2 600–3 800 cm?1. 相似文献
The clinical application of cisplatin (CP), one of the most extensively used antineoplastic drug, is restricted by its numerous side effects. CP's antitumor potential resides in the free generation of reactive oxygen species leading to oxidative stress. This stress is a source of the side effects associated with its use. Ellagic acid (EA), a polyphenol is known to possess multiple health benefits owing to its antioxidant properties. EA is largely metabolized by the colon microbiota of different mammals and therefore was a polyphenol of choice in the present study. The present study was thus carried out to explore the protective potential of EA on CP induced hepatotoxicity in colon tumor bearing mice. The administration of EA (10 mg/kg bwt po daily for 6 weeks) significantly ameliorated the toxicity caused by CP (5 mg/kg bwt ip once a week for 4 weeks). Activities of liver marker enzymes and lactate dehydrogenase were brought back to normal. EA cotreatment also led to a marked reduction in the extent of peroxidative damage to liver tissue as was evident from the improvement in the histopathological changes observed and FT‐IR analysis. The present study, therefore, suggests that the administration of EA reduces the CP‐induced hepatotoxicity, thereby emerging out as a potential candidate for chemopreventive action. 相似文献
The aim of this investigation was to find the effect of the ethanol–water solvent system and the ethanolic solution of carvone on the permeation of nimodipine across rat abdominal skin in order to select a suitable solvent system and optimal concentration of carvone for the development of membrane‐moderated transdermal therapeutic system of nimodipine. The solubility of nimodipine in water, ethanol, and ethanol–water cosolvent systems, or the selected concentration of carvone [2% (w/w) to 12% (w/w)] in 60:40 (v/v) ethanol–water were determined. The effect of these solvents or cosolvent systems on the transdermal permeation of nimodipine was also studied using in vitro permeability studies across the rat abdominal skin. The cosolvent system containing 60:40 (v/v) of ethanol–water showed highest permeability across the rat abdominal skin. Further, the effect of ethanolic solution [60% (v/v) ethanol–water] of carvone [2% (w/w) to 12% (w/w)] on the in vitro permeation of nimodipine across the rat abdominal skin from 2% (w/w) hydroxypropyl methylcellulose (HPMC) gel was also investigated. The transdermal permeability of nimodipine across rat abdominal skin was enhanced further by the addition of carvone to HPMC gel prepared with 60% (v/v) of ethanol. There was a steady effect on the flux of nimodipine (161.02 ± 4.14 µg/cm2/hr) with an enhancement ratio of 4.56 when carvone was incorporated at a concentration of 10% (w/w) in HPMC gels prepared with 60% (v/v) ethanol. The Fourier transform infrared data indicated that ethanolic solution of carvone increased the transdermal permeability of nimodipine across the rat abdominal skin by partial extraction of lipids in the stratum corneum. The results suggest that 10% (w/w) of carvone in 60% (v/v) ethanol–water, along with HPMC as antinucleating agent may be useful for enhancing the skin permeability of nimodipine from the membrane‐moderated transdermal therapeutic system. 相似文献
