Identification of higenamine in Radix AconitiLateralis Preparataas a beta2-adrenergic receptor agonist1

Abstract

To screen beta2-adrenergic receptor (beta2-AR) agonists from Radix Aconiti Lateralis Preparata (RALP) as potential drug leads for asthma using a sensitive cell-based agonist assay. The beta2-AR gene was stably expressed by Chinese hamster ovary (CHO) cells also stably expressing a cyclic adenosine monophosphate (AMP) response element-linked enhanced green fluorescent protein reporter gene. The cells were used to screen agonists from high-performance liquid chromatographic fractions of an extract of RALP. The fraction with the highest activity was selected for further compound isolation and the study of the structure-activity relationship. Its active compound was further identified by chromatography and mass spectrometry. Bioactivity-directed fractionation of the crude extract of RALP led to the isolation and characterization of the effective compound, namely hignamine. It could dose-dependently relax the isolated guinea pig trachea strip precontraction with acetylcholine with EC(50) value of (2.60+/-0.36)x10(-5) mol/L. Further in vivo studies also displayed that hignamine could protect experimental asthma model induced by histamine in guinea pigs to prolong the latent periods of asthma. Hignamine, as a beta2-AR agonist existing in the extract of RALP, is the key compound contributing to the successful relief of the bronchoconstriction.