The antinociceptive and anti-inflammatory potential and pharmacokinetic study of significant alkamides ingredients from Asarum Linn

Asari Radix et Rhizoma (ARR), including 3 major plants of genus Asarum Linn, A. heterotropoides Fr. Schmidt var. mandshuricum (Maxim.) Kitag., A. sieboldii Miq. f. sieboldii and A. sieboldii Miq f. seoulense (Nakai) C. Y. Cheng et C. S. Yang, is one of the most important traditional herbal medicine in Asia with tremendous pharmacological activities. For a long time, researchers focus attention on studing asarinin and essential oils, the indicating ingredients of ARR, but paid less attention to another characteristic component, alkamides. The role of alkamides in the major efficacy of ARR medication remains to be elucidated. This study aims to investigate the contribution of alkamides in the efficacy of ARR according to the evaluation of antinociceptive and anti-inflammatory effects and in vivo pharmacokinetics processes. For pharmacodynamic study, the analgesic and anti-inflammatory effects of alkamides-enriched fraction (ARRA) were comparatively evaluated by writhing test, hot plate test, and ear swelling test in mice after oral administration. For pharmacokinetic study, an UHPLC-MS/MS method was developed for the simultaneous determination of N-isobutyl-2E,4E,8Z,10Z/E-dodecatetraenamide (DDA) and other 6 major characteristic ingredients of ARR in rat plasma. The analytical method was validated and successfully applied to the pharmacokinetic study of ARR extract and DDA. Pharmacodynamic study show that the ARR and ARRA can significantly inhibit the writhing times of mice caused by acetic acid administration, increase the pain threshold of thermal stimulation, and inhibit xylene treated ear swelling degree by reduce PGE₂ and TNF-α levels in the inflamed tissue. For pharmacokinetic study, the pharmacokinetic parameters of Vd/F and CL/F after intravenous administration in rats of DDA are 63.94 ± 32.12 L/kg and 0.33 ± 0.06 L/min/kg, respectively. The plasma drug concentration declined with the T₁/₂ value of 2.25 ± 0.96 h, and the MRT₀₋∞ was 2.23 ± 1.02 h. The absolute bioavailability of DDA after oral administration was calculated as 10.73%. DDA, methyleugenol, and asarinin have relatively high AUC₀₋∞ values when the ethanol and water extract of ARR is orally administered. ARRA is a kind of active ingredients with potential analgesic and anti-inflammatory effects that played a significant role in the major efficacy of ARR. DDA, the major compound of ARRA, has a high level of exposure in vivo, which could be is suitable for the pharmacokinetic marker or new quality marker of ARR.