Metabolic profiling and pharmacokinetic studies of alkamides, a pair of cis-trans isomers N-isobutyl-2E,4E,8Z,10E/Z-dodecatetraenamide, from Asari Radix et Rhizoma by UHPLC-Q/TOF-MS and UHPLC-MS/MS.

ABSTRACT

Cis-trans isomers of N-isobutyl-2E,4E,8Z,10E-dodecatetraenamide (DDA-E) and N-isobutyl-2E,4E,8Z,10Z-dodecatetraenamide (DDA-Z) are representative alkamides with numbness of tongue, anti-inflammatory and analgesic activities of Asari Radix et Rhizoma. However, their respective metabolic pathways and pharmacokinetic behaviors are still unknown. This study aim to investigate the metabolism of the two alkamides in vitro and in vivo using ultra-high-performance liquid chromatography-quadruple-time-of-flight mass spectrometry. Furthermore, a rapid, sensitive, and selective ultra-high-performance liquid chromatography-tandem mass spectrometry method was developed to quantify DDA-E/Z in rat plasma. Results indicated that DDA-E and DDA-Z showed significant differences in metabolism and pharmacokinetics. Across all samples, 24 metabolites of DDA-E and 21 metabolites of DDA-Z were detected. A variety of pathways were involved in the production of these metabolites, mainly hydroxylation and oxidation. The linear range of DDA-E/Z was 1-2500 ng/mL (R2 = 0.9984), and the lowest quantification limit was 1 ng/mL. Precision, accuracy, extraction recovery, matrix effect, and stability of DDA-E/Z were within acceptable limits. Pharmacokinetic research was conducted using male Sprague-Dawley rats receiving intravenous (1 mg/kg) or intragastric (40 mg/kg) administration of DDA-E or DDA-Z solution. There was a calculated absolute bioavailability of 15.67 % for DDA-E and 4.83 % for DDA-Z when consumed orally. The apparent volume of distribution of intravenous and intragastric administrations were 4.44 ± 0.41 L/kg and 5.18 ± 0.67 L/kg for DDA-E, and 1.56 ± 1.66 L/kg and 2.35 ± 0.42 L/kg for DDA-Z. The maximal plasma concentrations of DDA-E and DDA-Z were 599.84 ± 149.92 nM and 422.09 ± 69.17 nM, and the time to maximum peak were 4.33 ± 3.51 h and 0.70 ± 1.12 h, respectively. In conclusion, in subsequent pharmacodynamics and safety evaluation studies, great attention should be paid to the metabolic characteristics and pharmacokinetic differences between DDA-E and DDA-Z.