an ecuadorian specimen of ophryosporus peruvianus produced an essential oil with a yield of 0.4% of the weight of the fresh plant material. a total of thirty-two compounds were detected and quantified. the chemical composition showed the predominance of monoterpene hydrocarbons, with sabinene (22.5%), -pinene (15.1%), limonene (8.3%), -phellandrene (29.7%), -elemene (2.1%), and epi--cadinol (2.7%) being the main components, expressed as mean values on two stationary phases of different polarity. this composition was very different from that reported in the literature for the essential oil of a peruvian specimen, which was dominated by sesquiterpene hydrocarbons. these results indicate the existence of different chemotypes of o. peruvianus. moreover, an enantioselective analysis of the major chiral constituents was performed, which revealed (r)-(-)--phellandrene, (r)-(-)--phellandrene and (1r,9r,e)-(-)--caryophylleneas enantiomerically pure compounds. on the other hand, -thujene, -pinene, -pinene, sabinene, limonene, and terpinen-4-ol were scalemic mixtures. finally, a preliminary screening of enzymatic inhibitory activity was performedin vitro, showing modest but interesting inhibition of both butyrylcholinesterase and lipase.