Inhibition of Rat CYP1A2 and CYP2C11 by Honokiol, a Component of Traditional Chinese Medicine.

BACKGROUND AND OBJECTIVES: Honokiol, a major constituent isolated from Magnolia officinalis, is regarded as a phytochemical marker and bioactive substance present in many traditional Chinese medicines. However, the effect of honokiol on cytochrome P450 (CYP) has not been thoroughly investigated. The aim of this study was to investigate the effect of honokiol on CYP1A2 and CYP2C11 in vitro and in vivo. METHODS: The effect of honokiol on CYP1A2 and CYP2C11 was investigated with rat liver microsomes (RLMs) by measuring phenacetin and tolbutamide metabolism (probe drugs for CYP1A2 and CYP2C11, respectively), and then explored in vivo by measuring the effect of honokiol (2.5 and 5 mg/kg, intravenous injection) on the pharmacokinetics of theophylline and tolbutamide (probe drugs for CYP1A2 and CYP2C11, respectively) in rats in vivo. RESULTS: Honokiol inhibited the formation of acetaminophen from phenacetin and 4-hydroxytolbutamide from tolbutamide in RLMs, with inhibition constant (Ki) values of 1.6 µM and 16.5 µM, respectively. In vivo, honokiol (2.5 or 5.0 mg/kg) increased the half-life (t1/2) of theophylline by 40.9% and 119.9%, decreased the clearance (CL) by 23.8% and 42.9%, and increased the area under the curve (AUC) by 41.3% and 83.4%, respectively. Similarly, the t1/2 of tolbutamide increased by 25.5% and 33.8%, the CL decreased by 14.3% and 19.1%, and the AUC increased by 19.2% and 25.7%, respectively. CONCLUSION: The inhibition of CYP1A2 by honokiol is greater than the inhibition of CYP2C11. The changes in the pharmacokinetics of theophylline and tolbutamide in rats treated with honokiol are due to the inhibition of CYP1A2 and CYP2C11 activity in a dose-dependent manner.

Development and Validation of Quantitative (1)H NMR Spectroscopy for the Determination of Total Phytosterols in the Marine Seaweed Sargassum.

Knowledge of phytosterol (PS) contents in marine algae is currently lacking compared to those in terrestrial plants. The present studies developed a quantitative (1)H NMR method for the determination of the total PSs in Sargassum. The characteristic proton signal H-3α in PSs was used for quantification, and 2,3,4,5-tetrachloro-nitrobenzene was used as an internal standard. Seaweed samples could be recorded directly after total lipid extraction and saponification. The results showed that the PS contents in Sargassum fusiforme (788.89-2878.67 mg/kg) were significantly higher than those in Sargassum pallidum (585.33-1596.00 mg/kg). The variable contents in both species suggested that fixed raw materials are very important for future research and development. Orthogonal projection to latent structures discriminant analysis was carried out in the spectral region of δ 3.00-6.50 in the (1)H NMR spectrum. S. fusiforme and S. pallidum could be separated well, and the key sterol marker was fucosterol.