Hyptis marrubioides were collected in March 2003 at the mature vegetative stage from their natural habitat; 20 randomised individual plants at the same age representing the local population were collected as homogenous samples from each locality: (A) Lavras (21° 14′ S/44° 59′ W), at an altitude of 919 m; (B) Tiradentes (21° 6′ S/44° 10 m W), 927 m.

The results were submitted to Principal Component and Cluster analysis which allowed three groups of oils to be distinguished with respect to sampling site and post-harvested process: cluster I (fresh leaves and fresh or dried stems from Lavras site) with high percentage of caryophylla-4(14),8(15)-dien-5beta-ol (16.7%) and eudesma-4(15),7-dien-1beta-ol (12.8%); cluster II (dried leaves and stems from Tiradentes site) with epi-longipinanol (16.2%) rich oil, and cluster III (dried leaves from Lavras) containing a high content of beta-caryophyllene (17.4%) and alpha-copaene (10.1%). Canonical discriminant analysis showed that is possible to accurately predict 100% well-classification in the original clusters using beta-caryophyllene, epi-longipinanol and caryophylla-4(14),8(15)-dien-5beta-ol as predictor variables. The whole or sliced plant materials resulted in similar chemical composition.

H. officinalis var. dectimbens was grown on Banon (Alpes de Haute-Provence, France). The fresh flowering tops were steam distilled at the beginning of October 1995. A sample of H. officinalis oil produced in Italy (Piedmont) by Agronatura was examined as a useful standard in accordance with the IS0 9841 Standard (1991 E).

The bicyclic monoterpene ketones, pinocamphone and isopinocamphone, were present in Piedmont, Italy (4.4% and 43.3%, respectively, in accordance with the ISO 9841 Standard, 1991 E), but their percentages were very low in Banon, France, where instead linalool (49.6%), 1,8-cineole (13.3%) and limonene (5.4%) were predominant.

The leaves of R. eriocalyx were harvested at random from two localities of the forest in the North and South ranges of Boutaleb in Algeria at different altitudes during the full flowering stage. Sample N3(Locality: Northern slope; Altitude (m): 850; Collection date: Mar 20,1993); Sample S3(Locality: Southern slope; Altitude (m): 850; Collection date: Mar 20,1993).

Concerning the alcohols, the highest amount of 1,8-cineole (11.4%) coincided with a very low amount of terpinen-4-ol(1.0%) in sample N3 as well as with a generally low concentration of hydrocarbons (apart from camphene and pinene) in all samples of R. eriocalyx.