Identification, characterization and HPLC quantification of formulation-related impurities of honokiol, an antitumor natural drug candidate in clinical trials

Abstract Natural products and their derivatives have historically been invaluable as a source of therapeutic agents. Honokiol, as a well-known natural product in Chinese herbal medicine Houpu, is finally being studied in a Phase I clinical trial (CTR20170822) in patients with Advanced Non-Small Cell Lung Cancer (NSCLS) in China this year. During the honokiol liposome formulation process, five major impurities were present in the range of 0.05–0.1% based on the HPLC analysis. These five major impurities were obtained from the forced degradation product of honokiol through countercurrent chromatography and prep-HPLC. The structure were elucidated with 1 H NMR, 13 C NMR, 2D NMR and MS spectral data. The proposed HPLC method was validated for specificity, linearity (concentration range 0.01–1.62, 0.003–0.96, 0.05–7.98, 0.04–6.52, 0.03–5.18 μg/ml for impurities I–V respectively, R2 > 0.9988), accuracy (99.11–100.67%), precision (CV