Quantification of diterpene acids in copaiba oleoresin by UHPLC-ELSD and heteronuclear two-dimensional qNMR

The oleoresin of selected Copaifera species, commonly known as copaiba oil, is a traditional Brazilian remedy for the treatment of various ailments, such as urinary tract infections, respiratory diseases, wound healing, rheumatism, herpes and tumors [1],[2]. Due to its wide application in folk medicine, the oleoresin has been subject of various studies examining its chemical composition and the correlation with its health benefits.

As both, the diterpene acids and the biological activities vary between the different Copaifera species [2], the aim of the present study was the development of analytical methods for the quantification of diterpene acids.

The first method is an UHPLC assay using reversed-phase material and evaporative light scattering detection. With this method precise (RSD values below 4%), accurate (mean recovery rates of 91-105%) and sensitive quantification (LOQs of 10 and 20 µg/mL) was achieved. For the second assay, quantitative heteronuclear single quantum correlation spectroscopy (qHSQC) was applied. Here, calibration curves of eight different NMR cross-peaks were established and normalized with dimethyl terephthalate, which served as internal standard. This approach allowed the direct quantification of four major and one minor diterpene, whereas he contents of the remaining minor compounds were obtained with simple calculation procedures.

Comparison with the UHPLC assay showed good agreement for seven of out of eight diterpenoids. In terms of precision, the qHSQC method was advantageous for the quantification of the three major compounds, whereas UHPLC was superior in the determination of the minor components.

• References

• 1 Veiga Junior VF, Pinto AC. O genero Copaifera L. Quim Nova 2002; 25: 273-286.
• 2 Leandro LM, de Sousa Vargas F, Souza Barbosa PC. et al. Chemistry and biological activities of terpenoids from copaiba (Copaifera spp. Oleoresins Mol 2012; 17: 3866