A new caryophyllene, 4,5-epoxy-13-hydroxy-b-caryophyllene, has been isolated from Pterocaulon serrulatum using a bioassay guided fractionation procedure. Several known compounds were also identi®ed in the extracts, including 14-hydroxy-bcaryophyllene, three simple coumarins and a ¯avanone. # 1998 Published by Elsevier Science Ltd. All rights reserved.