The n-hexane extract that has shown activity in the tracheospasmolytic bioassay was fractionated by solvent extraction and from the major active fraction two compounds were isolated and identified as viteosin-A and vitexicarpin. These compounds blocked spontaneous contraction of isolated male guinea pig trachea induced by histamine; however only vitexicarpin was active in a model using sensitized guinea pig trachea stimulated by ovalbumin up to minimum dose of 1.3 x 10(-5) M. The result suggests that vitexicarpin is able to block effects of histamine released from sensitized mast cells possibly by stabilizing the mast cells membrane function.