Caffeine in Chiang Rai tea infusions: Effects of tea variety,type, leaf form,and infusion conditions

Caffeine in Chiang Rai tea infusions was found to be dependent on infusion conditions (water temperature and infusion time), and leaf form (non-ground or ground) but independent of tea variety and type. For non-ground leaf samples, the higher the water temperature and the longer the infusion time, the higher the caffeine concentrations in tea infusions. After infusing for longer than 15 min, the dissolution rate of caffeine became slower and the concentration was essentially constant. For ground leaves, the caffeine content was not influenced by infusion time. Caffeine concentrations in tea infusions from Camellia sinensis var. sinensis (26.8 ± 0.81 and 22.3 ± 5.55 mg/100 ml for ground and non-ground samples, respectively) were not significantly different from that of Camellia sinensis var. assamica (24.4 ± 0.66 and 20.3 ± 5.07 mg/100 ml for ground and non-ground samples, respectively). The difference in caffeine concentration between green tea (28.1 ± 8.19 mg/100 ml) and oolong tea (20.3 ± 1.52 mg/100 ml) was not statistically significant.     

Effect of heat on characteristics of chitosan film coated on theophylline tablets

The effect of heat on the characteristics of chitosan film coated on theophylline tablets was studied. Chitosan of high viscosity grade with molecular weight in the range of 800,000-1,000,000, 80-85% degree of deacetylation was used as a film former by dissolving in 1% v/v acetic acid solution. The coated tablets had been cured at 40, 60, and 100°C for 6, 12, and 24 hr. The morphology of the film at the edge and surface of coated tablets was investigated using scanning electron microscopy. Film cracking was increased and clearly observed in the coated tablets cured at 100°C for 24 hr. As a result, more water could be absorbed into the tablets, followed by faster disintegration and faster drug release. The evidence of partial conversion of chitosonium acetate to chitin in the ¹³C nuclear magnetic resonance (NMR) spectra of chitosan films cured at 40, 60, and 100°C was observed, but it had no effect on drug release behavior. Theophylline tablets coated with chitosan films gave sustained release behavior in various media, i.e., distilled water, 0.1 N hydrochloric acid, pH 4.5 acetate buffer, and pH 6.8 phosphate buffer. In addition, the film coating temperature at 55-60°C and curing process at 40 and 60°C had no effect on the drug release from theophylline tablets coated with chitosan polymer. Finally, it might be concluded that both the physical and chemical properties of chitosan films were affected by heat.     

Fabrication of thermally stabilized shellac through solid state reaction with phthalic anhydride

Shellac has been regarded as an obsolete polymer due to its poor thermal stability. The purpose of the study was to solve the problem by solid-state synthesis of shellac phthalate (SHL-PHT). Shellac was ground with phthalic anhydride and then thermally activated at various conditions. The solid-state esterification of shellac was clearly observed after annealing. As indicated by an increase of acid value, the esterification was more pronounced after the increase of annealing temperature and time. The formation of SHL-PHT was confirmed by FTIR spectra and other characterization techniques. The SHL-PHT demonstrated to improve the thermal stability as compared to native shellac. After aging at high temperature, percent insoluble solid and acid value of the native shellac dramatically changed while those of SHL-PHT were relatively the same as initial value, especially for the more esterified SHL-PHT. The protection of hydroxyl groups of shellac by phthalate moieties might be a possible explanation for the improved stability. In conclusion, the study may give an eco-friendly way to synthesize the shellac derivatives for future applications.