New volatile constituents from leaves of Stemodia trifoliata (Link.) Reichb. (Schrophulariaceae)

the leaf essential oils of stemodia trifoliata (scrophulariaceae), collected at the same month of two different years (august 2005 and 2006), were analized by gc-ms and gc-fid. a total of 22 volatile components represented by sesquiterpenes and diterpenes was identified. β-caryophyllene (9.4-15.4%) and caryophyllene oxide (6.2-9.0%) were the major compounds identified in the sesquiterpene fraction, while the diterpenoids 6α-acetoxymanoyl oxide (13.9-23.2%) and 6α-hydroxymanoyl oxide (25.1-29.7%) were the main constituents of the diterpene fraction. the two novel manoyl oxide derivatives had their structures established by means of spectroscopic methods, particularly 1d and 2d nmr. this work describes for the first time the chemical investigation on the volatile composition of s. trifoliata.