Ten different plants of wormwood were collected in March 1997 from each one of the following four wild populations in the Spanish Pyrenees: Tallo de Aulet (prov. Huesca) and Pont de Suert, Sort and Farga de Moles (prov. Lleida). In three of the four populations studied, there was another chemotype, with 25-65% of cis-epoxyocimene and 15-50% of chrysanthenyl acetate. This chemotype, called chemotype B, was less frequent in the Pyrenees than the chemotype A, appearing only in 17% of the samples (two samples in TallO de Aulet and in Pont de Suert and three samples in Farga de Moles).

Two chemotypes were detected; a cis-epoxyocimene type (with more than 50% of this compound) which was predominant in all the populations, and a cis-epoxyocimene + chrysanthenyl acetate type (with 25-65% of cis-epoxyocimene and 15-50% of chrysanthenyl acetate). The distribution of these chemotypes had no relation with the altitude of the samples.

Plant materials were collected from Chalous Road (north of Tehran province) both at the flowering stage in June and the seed stage in September 2003. The fresh plants were dried at room temperature. Dried stems/leaves (S/L) (collected during flowering stage), seeds (S) were hydrodistilled for 3 h in a Clevenger-type apparatus to produce the oils.

The major constituent in the stem/leaf oil was trans-alpha-bergamotene (77.1%), whereas the major constituent of the seed oil was pregeijerene (87.0%). Nonadecane (8.6%) were the other major constituents in the stem/leaf.