A rapid and simple analytical method based on liquid chromatography – ultraviolet detection has been developed and validated for the simultaneous determination of two high added-value cosmetic ingredients, honokiol and magnolol, in commercial cosmetic samples. These compounds from the Magnolia plant present demonstrated benefits for the skin, such as antioxidative and anti-inflammatory properties, besides of antimicrobial and antifungal capacity, which may lead to their possible use as alternative preservatives in cosmetic products. The proposed method has been successfully validated showing good linearity, limits of detection and quantification in the low µg mL−1 level (0.06 to 0.07 µg mL−1 and 0.19 to 0.24 µg mL−1, respectively) and good repeatability (relative standard deviation below 9%). The proposed method has been evaluated by analyzing a laboratory-made cosmetic sample containing known concentrations of the analytes, providing low relative errors (-6% for honokiol and −4% for magnolol) and quantitative recovery values (96 to 111%). Finally, the proposed analytical method has been applied to the determination of both analytes in eight commercial cosmetic samples with different properties, obtaining quantitative recovery values (93 to 115%) and thus showing that matrix effects are negligible. In summary, the results show that this firstly proposed method for honokiol and magnolol determination in cosmetic products is accurate and useful for the routinely quality control of these consumer products containing both ingredients.

Keywords:Alternative preservatives, cosmetic products, high-performance liquid chromatography (HPLC), honokiol, liquid chromatography, Magnolia plant extract, magnolol.

Full reference:
Rapid and Simple Determination of Honokiol and Magnolol in Cosmetic Products by Liquid Chromatography with Ultraviolet Detection, J.L. Benedé, E. Rodríguez, A. Chisvert, A. Salvador, Analytical Letters 54 (2021) 1510-1521