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Zebrafish (Danio rerio) water tank (ZWT) approach was investigated as an alternative model for metabolism studies based on six different experiments with four model compounds. Sibutramine was applied for the multivariate optimization of ZWT conditions, also for the comparison of the metabolism among ZWT, humans and mice, beyond for the role of CYP2B6 in ZWT. After the optimization, 18 fish and 168 hours of experiments is the minimum requirement for a relevant panel of biotransformation products. A comparison among the species resulted in the observation of the same hydroxylated metabolites, with differences in metabolites concentration ratio. However, the ZWT allowed tuning of the conditions to obtain a specific metabolic profile, depending on the need. In addition, by utilizing CYP2B6 inhibition, a relevant ZWT pathway for the demethylation of drugs was determined. The stereospecificity of the ZWT metabolism was investigated using selegiline and no racemization or inversion transformations were observed. Moreover, the investigation of metabolism of cannabimimetics was performed using JWH-073 and the metabolites observed are the same described for humans, except for the hydroxylation at the indol group, which was explained by the absence of CYP2C9 orthologs in zebrafish. Finally, hexarelin was used as a model to evaluate studies by ZWT for drugs with low stability.As a result, hexarelin displays a very fast metabolization in ZWT conditions and all the metabolites described for human were observed in ZWT. Therefore, the appropriate conditions, merits, and relevant limitations to conduct ZWT experiments for the investigation of drug metabolism are described.

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Dietary supplements in many countries such as the USA do not require registration prior to commercialization. The Agência Nacional de Vigilância Sanitária (ANVISA) registers substances with functional properties as foods. Lutein is a carotenoid with antioxidant activity available on the market. However, no regulatory mandates exist to govern the design of quality control tests, which are necessary to ensure formulation effectiveness. Therefore, in the present study, tablet and dosage formulations from different manufacturers were tested following general methods outlined in the Brazilian and American Pharmacopeias. The averageweight, disintegration, content and dose uniformity assays were performed for all tablets and capsules, whereas hardness assays were only performed on tablets. None of the 10 formulations studied were found to be of satisfactory quality. Of all tablets tested, two had no-significant available lutein content, which may indicate adulteration. The capsules displayed adequate amounts of lutein, however had alarmingly negative disintegration and dissolution test results, which may contribute to non-bioavailability of lutein. All formulations analyzed are currently being marketed in the Brazilian and American markets. The low physicochemical performance in these formulations can be explained by the lack of specific regulations, which are necessary to ensure the quality of lutein-containing products on the market.

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