The aerial parts of D. assadii Alava. were collected in the wild from Lalehzar (Kerman Province, in southern Iran) at the flowering stage, in July 2007. The material was dried at room temperature and used for distillation. Distillation: A direct-fired field distillation unit containing a distillation tank (capacity: 1,000 L), a condensation column and receiver, all made of stainless steel, and which can process 30-50 kg of dried aerial parts from the plants/batch, was installed at an altitude of 2600 m (boiling point: 87 ℃). Dried aerial parts from the plants (40 kg) were charged into the distillation unit along with 500 L fresh water and the unit was heated by steam. The system was kept open to atmospheric pressure until the temperature reached to 70 ℃, when the air present in the unit was replaced by the vapor. After complete removal of air from the unit, the air vent was closed and the whole unit was operated as a closed system under pressure to distill the oil. The pressure, temperature and rate of distillation were controlled manually. The process was completed after the collection of 500 L of water distillate. The oil collected in the receiver and dried over anhydrous Na₂SO₄. Extraction of Ducrosia Second Oil From Ducrosia Water by Redistillation: The seprated distillate water collected in the receiver was redistilled in a 1,000 L still to yield more Doucrosia oil (this oil is known as secondary essential oil, second oil, cooked oil or indirect oil).

Fifty components were identified in a second oil of D. assadii from Lalehzar with decanal (35.2%), nonadecane (12%) and citronellyl acetate (11.6%) as the main constituents. The oil from Dehbakrii also contained decanal (36.4%) as the main component of an oil recovered from the distillate water. The results showed that the amount of decanal is remarkably high in the oils of D. assadii.

Plants were collected in the Inner plain, the Sharon plain and the kava valley.

The major constituent of all three oils was found to be 1,8-cineole (26.4-34.5%) followed by menthone (10.0-16.7%), pulegone (7.0-7.5%), and isomenthone (4.7-7.8%). Despite some differences in the component proportions, the plants of all three populations clearly belong to the same chemotype.

Mentha rotundifolia leaves were collected in the second week of November 2004 in two localities of Algeria (Rouina: altitude 250 m, Miliana: altitude 780 m) within the region of Ain-Defla located in northern Algeria.

Thirty-nine compounds were identified in leaf oil of sample 1 (Rouina, Algeria), the main one being cis-piperitone oxide. Thirty-nine compounds were identified in leaf oil of sample 2 (Miliana, Algeria). The main one being piperitenone oxide.

The aerial parts of flowering Mentha spicata plants (cut at ground level) and individual M. spicata plants were collected in the summer (July, 2003) from three wild populations located in the Municipality of Laganas, Zakynthos, W. Greece. Location 1 (N 37° 39′ 39″, E 20° 48′ 44″; map datum WGS 84; altitude 160 m; 14/07/03) was near the village of Keri, Location 2 (N 37° 41′ 29″, E 20° 50′ 25″; altitude 3 m; 14/07/03) was close to Keri Beach (Limni Keriou) and Location 3 (N 37° 43′ 34″, E 20° 50′ 41″; altitude 35 m; 14/07/03) was near the village of Pandocratoras. The three locations are within the mainland limits of the protected area of the National Marine Park of Zakynthos (NATURA 2000 Network, site GR 2210002; 8).

The main oil constituents were trans-piperitone oxide, piperitenone oxide and 1,8-cineole. On a whole plant basis (aerial parts) the trans-piperitone oxide content ranged from 1.4 % location (Loc 1) to 32.5% (Loc 3) and appeared to have an inverse relationship with the 1,8-cineole content which ranged from 10.8 % (Loc 3) to 37.9 % (Loc 1). 1,8-cineole was the major oil constituent (37.9 %) of M. spicata plants from Loc 1. The major constituent of the inflorescence oils was piperitenone oxide which ranged from 32.4 % (Loc 3) to 46.3 % of the oil (Loc 1). The major constituent of the leaf oils was 1,8-cineole (40.5 %) in plants from Loc 1 and trans-piperitone oxide in plants from Loc 2 (19.8 %) and Loc 3 (33.5 %). This is the first report for wild populations in Greece of a M. spicata oil in which 1,8-cineole is the major constituent. The observed variation in essential oil composition between locations and plant organs in July would not appear to be directly related to the climatic conditions.

Aerial parts of P. dysenterica were collected during the flowering stage from two different locations in Greece in August 2002. Sample A: Katara (Perfecture Trikala). Sample B: Arahova (Perfecture Viotia).

Fifty-four components were identified representing 80.5% (sample A) and 72.6% (sample B) of the total oils. The main components in sample A were (Z)-nerolidol (11.2%), caryophyllene oxide (9.1%) and (E)-nerolidol (6.6%), while those of sample B were beta-caryophyllene (12.8%), caryophyllene oxide (12.8%) and (E)-nerolidol (6.9%).

Plant materials were collected from the following localities in north western Turkey. A = Trabzon: Caykara, Soganli dag on July 28, 1994; B = Bayburt: Caykara, Mohakambo yaylasi on July 25, 1994; C = Trabzon: Koprubasi, Vizara yaylasi on July 20, 1994.

One hundred and four compounds were identified representing 97.5-99.5% of the total components detected in thymol/carvacrol (50.14/10.67%), thymol/linalool (23.14/20.24%) and linalool/alpha-terpinyl acetate/geraniol (21.55/16.70/11.17%) rich oils.

Aerial parts of the plant were collected from four localities: A = Kirklareli: Karadere in May 1991; B = Kirklareli: Karahamza Village in May 1990; C = Kirklareli: Evciler Village on 13 June 1993; D = Kirklareli: Korukoy on 25 May 1994

The four oils obtained from plants collected in different localities of the same region gave quite different compositions as follows: A: thymol (10.5%), 1,8-cineole (9.96%), p-cymene (9.48%), carvacrol (5.28%); B: beta-caryophyllene (29.50%), carvacrol(20.59%); C: thymol (34.7%), beta-caryophyllene (12.74%), carvacrol (5.24%); D: beta-caryophyllene (56.48%), germacrene D (11.12%), carvacrol (4.85%). Since the identities of the plant materials were checked repeatedly, any misidentification is ruled out. Except for A and C, all the other materials showed beta-caryophyllene as the major constituent. Carvacrol (20.59%) was present in good amount in the oil of B. In A, however, high percentages of 1,8-cineole (10%) and p-cymene (9.5%) were significant. This oil contained only a trace amount of beta-caryophyllene. Four isomeric caryophyllene alcohols were detected in the oil B. The results clearly indicate that the oil of T. striatus var. interruptus has no consistency and we can safely suggest that there are at least three chemotypes, namely thymol/1,8-cineole/p-cymene-type; thymol/beta-caryophyllene-type; and beta-caryophyllene-type, of this species.