Aniba riparia (Nees) Mez. (Lauraceae) is popularly known as "louro", and is found in Amazonia and in the Guianas, its distribution extends to the Andes. Alkamide alkaloids were isolated from its green fruit; they were denominated riparin I (methyl ether of N-benzoyl tyramine), riparin II (methyl ether of N-2-hydroxy-benzoyl tyramine) and riparin III (methyl ether of N-2,6-dihydroxy-benzoyl tyramine) in tribute to the plant. When administered orally and intraperitoneally to mice, riparin I and III are anxiolytic, yet without any sedative or muscle relaxing effects. The present study shows that variables such as extraction solvent, centrifugation force, and centrifugation time, are important in the simultaneous liquid-liquid extraction of riparin I and III from male and female Wistar rat blood in HPLC-UV studies. The study confirms matrix influence on simultaneous recovery and detection of riparin I and III. The effect of rat blood matrix for riparin I was -13.86%, while for riparin III it was -10.94%. The recovery for riparin I was 82.14%, while for riparin III it was 87.42%. The efficiency of the process was 73.25% for riparin I and 77.81% for riparin III, demonstrating an optimal method for simultaneous recovery of riparins I and III from the blood of rats. The matrix effect for rat blood showed values of 10.25% for riparin I and -83.01% for riparin III. Recovery for riparin I was 113.11%, whereas for riparin III it was 13.65%. The process efficiency of this method for female rat blood was 125.88% for riparin I and 2.58% for riparin III. Simultaneous recovery of riparin I and III from the blood of male and female rats using acetonitrile as the precipitating solvent, while centrifuged at 10,000 × g for 10 min demonstrated the importance of the parameters chosen for the extraction/recovery process of different analytes.
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