Development of a new chromatographic method for the determination of bakuchiol in cosmetic products

The aim of this study was to develop and validate a simple, fast, and universal reversed-phase high-performance liquid chromatography method with fluorescence detection for the quantitation and evaluation of the stability of bakuchiol in cosmetic products. The analyte was extracted by tetrahydrofuran and separated on a Zorbax Eclipse Plus C18 analytical column (100 × 4.6 mm, 3.5 μm particle size) by a gradient elution program with the mobile phase consisting of water and acetonitrile and a flow rate of 1.0 mL min^-1. The column temperature was held at 25 °C and fluorescence detection was performed at excitation and emission wavelengths of 264 and 338 nm, respectively. The stability studies of bakuchiol in cosmetic products were conducted under various conditions, including thermal and photolytic degradation, according to International Conference on Harmonization Guidelines. The calibration curve was linear in the range of 0.5-50.0 μg g^-1 with a correlation coefficient greater than 0.9999. The limits of detection and quantification of the method were 0.1 and 0.5 μg g^-1, respectively. Recovery values were in the range of 93.37-106.39 μg g^-1, with relative standard deviations less than 6%. The method has been successfully applied to analyze different types of cosmetic products and proved to be reliable.