A new triterpene, 21-O-senecioyl-R1-barrigenol (1) and 13 known compounds were isolated from the ethanol extracts of the leaves and bark of Pittosporum brevicalyx (Oliv.) Gagnep. Their structures were elucidated based on spectral data. The antiarrhythmic action of one furofuran lignan, liriodendrin (2), was tested on a model of $CaCl_2$-induced arrhythmia and compared with the effect of verapamil. The prophylactic administration of liriodendrin (2) was effective in prolonging latency of arrhythmia and reducing the occurrence of ventricular fibrillation from 75% to 25%. The overall mortality rate was significantly reduced by the prophylactic administration of liriodendrin from 87.5% to 25%. The antiarrhythmic effect of liriodendrin (5.0 mg/kg) was similar to that of verapamil (1.05 mg/kg). Thus, liriodendrin may be a potent suppressor of $CaCl_2$-induced arrhythmias.