Optimization of headspace solid-phase microextraction for analysis of β-caryophyllene in a nanoemulsion dosage form prepared with copaiba (Copaifera multijuga Hayne) oil

Recent studies have shown the anti-inflammatory activity of Copaiba oils may be addressed to the high content of β-caryophyllene, the most common sesquiterpene detected, especially in the Copaifera multijuga Hayne species. In the present study, nanoemulsions were proposed as a delivery system for copaiba oil in view to treat locally inflamed skin. This article describes the optimization and validation of a stability-indicating SPME-GC method, for β-caryophyllene analysis in the nanoemulsions produced by high pressure homogenization. SPME methods are performed with PDMS (polydimethylsiloxane) fiber (100 μm). Three SPME parameters were evaluated by a three-level-three-factor Box–Behnken factorial design as potentially affecting the technique efficiency. According to the results obtained, the best conditions to extract β-caryophyllene were: (i) sampling temperature of 45 °C, (ii) sampling time of 20 min and (iii) no NaCl addition. Results coming from the forced degradation tests showed a reduction of β-caryophyllene peak area when both caryophyllene methanolic solution and nanoemulsions were exposed to acid hydrolysis, UV-A irradiation, oxidative (H2O2) and thermolitic (60 °C) conditions. Such reduction occurred in lower extent in the nanoemulsions, suggesting a protective effect of the formulation to β-caryophyllene content. Since no degradation products were detected in the same retention time of β-caryophyllene, the specificity of the method was demonstrated. The method was linear in the range of 0.14–0.68 μg mL−1 of β-caryophyllene (r2 > 0.999), and was also validated for precision (R.S.D. ≤ 5.0%), accuracy (97.85–101.87%) and robustness. Finally, the method was applied to quantification of β-caryophyllene content in the developed formulations.

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► A SPME-CG method is proposed for β-caryophyllene assay in nanoemulsions containing copaiba oil.
► SPME parameters were optimized for efficient β-caryophyllene extraction.
► The stability-indicating capability and specificity of the method were satisfied.
► Nanoemulsions partially protected β-caryophyllene under stressing conditions.
► The proposed method presents linearity, lows LOD and LOQ, good precision, accuracy and robustness.