Development of gastro-resistant microparticles containing tymol for veterinary application: preliminary study

Salmonellosis are the subject of control in developed countries to prevent the spread of bacterial epidemics transmitted from animals to humans through consumption of meat animals; the pig breeding is one of the main carriers of Salmonella Typhimurium. In recent years essential oils have attracted increasing interest as an alternative feeding strategy to replace antibiotic growth promoters. Apparently, one of the more effective essential oils against common harmful bacteria is Thymol (T). As salmonella is involved in causing diseases of the intestines, aim of this work is to target the T directly to the intestine by developing microparticles able to protect drug release in the stomach. T was first loaded in stearic acid (SA) by spray congealing (T-SA); then T and Beta-cyclodextrin (CD) in 1:1 molar ratio was prepared by sealing heating method and then sprayed with stearic acid (TCD-SA). Drug loading was determined by capillary electrophoresis analysis. Dissolutions tests were carried out under simulated gastro-intestinal fluids. The possible taste-masking effect of formulation was evaluated by head-space analysis in gas chromatography. The presence of CD is useful to reduce the loss of T during the spray congealing process. SA is a good excipient to prevent T release in simulated gastric fluid. However TCD-SA microparticles show higher release rate in enteric fluid compared to T-SA ones due to the T-CD complex, which improves drug solubilization rate. Unfortunately, both formulations show insufficient taste-masking effect.