Abstract
Simple SummaryThe purpose of this study was to investigate the bioavailability and metabolic path of thymol, a major constituent of Thymus vulgaris L., in the rabbit organism. Oral bioavailability is a key parameter affecting the efficacy of substances, but it is not surprising that it does not correlate satisfactorily with efficacy. The main limitation factors are rate of absorption, metabolism, and excretion processes. In this work, the thymol metabolic path in the rabbit organism was determined for the first time after its sustained oral administration. We confirm intensive absorption of thymol from the gastrointestinal tract; our results point to metabolism and accumulation in kidney tissue and intensive metabolic and excretion processes in the liver. Some metabolic processes were present also after thymol withdrawal. Thymol as a lipophilic substance was found only in trace amounts in fat and muscle tissue as a consequence of its conversion into hydrophilic metabolite and greater elimination in the rabbit organism. This paper highlights the insufficient knowledge of modes of action of plant compounds in animal organisms.The objective of this study was the detection of thymol in rabbit plasma, tissues, large intestinal content, and faeces. Forty-eight rabbits were divided into control and experimental groups (thymol 250 mg/kg feed). Thymol was administered for 21 days and then withdrawn for 7 days. Concentration of thymol in the intestinal wall (IW) was significantly higher than in plasma (p < 0.05) and liver (p < 0.05); in the kidneys it was significantly higher than in plasma (p < 0.05) and liver (p < 0.05) during thymol addition. Thymol in IW was significantly higher than in plasma also after withdrawal (p < 0.01). Significant correlation (rs = −1.000, p < 0.01) between IW and plasma points to the intensive absorption of thymol from the intestine, while the correlation between plasma and liver (rs = 0.786, p < 0.05) indicates intensive biotransformation and excretion processes in liver. Significant correlation between liver and kidney (rs = 0.738, p < 0.05) confirms the intensive metabolism of thymol in the kidney. During the withdrawal period, thymol was detected above trace amounts only in faeces, and was significantly higher than in the colon during both periods (p < 0.01). Results show intensive biotransformation of thymol in the rabbit organism.
Highlights
In recent years, natural products have assumed great importance as antibiotic replacement additives and as growth promoting agents in food animals
After weaning at 35 days of age, 48 rabbits of both sexes were randomly divided into a control group (CG) fed a standard diet and an experimental group (EG) fed a standard diet into which 250 mg/kg of thymol was incorporated in powder form
Significant correlation was established between thymol concentration in plasma and intestinal wall, plasma and liver and liver and kidney
Summary
Natural products have assumed great importance as antibiotic replacement additives and as growth promoting agents in food animals. There is large pressure on the animal production industry to improve animal treatment as well as production performance, and to ensure the safety of products for human consumption while minimizing economic losses [1]. The benefits of herbal additives depend on the biological activities of their compounds and their pharmacokinetics, their precise mode of action at the molecular level has not yet been fully elucidated [2,3]. No information is available about absorption, distribution, and deposition of natural compounds at target sites in the rabbit organism. The efficiency of the rabbit’s digestion depends in large part on the production and ingestion of caecotrophes, which must be considered as an integral part of the rabbits digestion system. The process of caecotrophy may be considered as “pseudorumination” which improves feed utilization [8,9]
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