Rapid determination of six kavalactones in kava root and rhizome samples using Fourier transform infrared spectroscopy and multivariate analysis in comparison with gas chromatography

Abstract

Kava has been used as a folk medicine and well-known traditional beverage. This study focused on quantitative analyses of kavalactones in kava samples using Fourier transform infrared spectroscopy (FTIR) integrated with an attenuated total reflectance (ATR) accessory and multivariate calibration analysis. The calibration set consisted of 50 standard mixtures which were made up of six major kavalactones. Derivative transformations (1st and 2nd), mathematical enhancements such as mean centering and variance scaling, and multivariate regression by partial least square (PLS) were implemented to develop and enhance the calibration model. Distinct peaks associated with the six kavalactones varied in the range between 1100 and 1800 cm⁻¹. The PLS-2nd derivative calibration model based on the 50 standard mixtures with mean centering data processing showed standard errors of calibration (SEC) of 0.72–1.73, standard errors of prediction (SEP) of 0.98–3.52 and correlation coefficients (R²) of 0.81–0.98 for model validation. This model was used for the analysis of these kavalactones in kava samples and then compared with gas chromatography (GC). Results showed that the FTIR-predicted values were similar to GC-determined values (R², 0.75–0.98), indicating that the FTIR method is suitable for determination of the contents of the six kavalactones in kava samples and thereby the chemotypes.