Validation of a gas chromatographic method to quantify sesquiterpenes in copaiba oils

Copaifera species (Leguminoseae) are popularly known as "copaiba" or "copaíva". The oleoresins obtained from the trunk of these species have been extensively used in folk medicine and are commercialized in Brazil as crude oil and in several pharmaceutical and cosmetic products. This work reports a complete validated method for the quantification of β-caryophyllene, α-copaene, and α-humulene in distinct copaiba oleoresins available commercially. Thus, essential oil samples (100μL) were dissolved in 20mL of hexanes containing internal standard (1,2,4,5-tetramethylbenzene, 3.0mM) in a 25mL glass flask. A 1μL aliquot was injected into the GC-FID system. A fused-silica capillary column HP-5, coated with 5% phenyl-methylsiloxane was used for this study. The developed method gave a good detection response with linearity in the range of 0.10-18.74mM. Limits of detection and quantitation variety ranged between 0.003 and 0.091mM. β-Caryophyllene, α-copaene, and α-humulene were recovered in a range from 74.71% to 88.31%, displaying RSD lower than 10% and relative errors between -11.69% and -25.30%. Therefore, this method could be considered as an analytical tool for the quality control of different Copaifera oil samples and its products in both cosmetic and pharmaceutical companies.