A validated ¹H NMR method for quantitative analysis of α-bisabolol in essential oils of Eremanthus erythropappus

α-Bisabolol is a natural terpene produced by Eremanthus erythropappus and is widely used in cosmetics and pharmaceuticals due to its anti-inflammatory, antibacterial and antimycotic properties. Due to these applications, a control of composition and authenticity of commercial oils rich in this terpene is required, resulting in a demand for new methodologies for quality control. In this work a rapid and efficient method for quantification of α-bisabolol in the essential oil of E. erythropappus (candeia) using ¹H NMR was developed, validated and compared to gas chromatography (GC) method. The quantification of α-bisabolol by ¹H NMR was successfully achieved for most of the essential oil samples of E. erythropappus evaluated, except for those with a more complex composition. To circumvent this limitation a 2D NMR COSY contour map was used. This method proved to be a fast and efficient alternative, providing results with standard deviations SD<0.3%. All evaluated parameters (selectivity, linearity, accuracy/precision, repeatability, robustness and stability of analyte and internal standard in solution) gave satisfactory results. Using the ¹H NMR signals at 5.36 and 5.13ppm, the limit of detection (LOD) and limit of quantification (LOQ) were 0.26 and 2.59mg, respectively. The results obtained by the ¹H NMR method presented SD=0.59%, smaller than the value found for GC (SD=1.18%). Tukey tests have shown that the results obtained by ¹H NMR and COSY methodology are similar to the obtained by the traditional GC-FID technique using external and internal standardization and normalization with 95% confidence.