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The essential oils, isolated by distillation-extraction (DE) and hydrodistillation (H) for different extraction periods, from the aerial parts of Origanum glandulosum collected at the flowering phase in Algeria, were analysed by GC and GC-MS. The oil yields determined by hydrodistillation attained 1.8% (v/w) and 2.7% (v/w) when extracted for 10 min and 3 h, respectively. The essential oils were dominated by the monoterpene fraction (DE 95-96% and H 86-97%), carvacrol being the main component of all oils (49-57 and 45-47% for DE and H oils, respectively). The other main components (> > > > >5%) were γ γ γ γ γ-terpinene (DE 17-13 and H 18-13%), p-cymene (DE 14-10 and H 17-11%) and thymol (DE 7 and H 5-7%). The composition of the glycosidic bound volatiles showed very little resemblance to the corresponding essential oil fraction. Thirteen components were detected in the glycosidic bound volatiles, only six of which were also present in the essential oil. The oxygen-containing monoterpenes were the dominant fraction (75-97%) of the glycosidic bound volatiles, but the main component was dependent on the extraction period and not on the isolation procedure. Carvacrol (71% for DE and 61% for H) dominated the 10 min distillation, whereas thymoquinone, which was not present on the essential oil, was the dominant component in the 3 h distillation (79% for DE and 59% for H).

The compositions of the essential oils obtained from ten populations of Thymus caespititius grown on S. Jorge (Azores) were studied by GC and GC-MS. All the oils analysed were dominated by their monoterpene fraction (69-9%). The sesquiterpene fraction was rather small (4-17%) and consisted mainly of oxygen-containing compounds (3-13%). Enantiomeric ratio of sabinene and alpha-terpineol was investigated in the oils from some populations. (+)-Sabinene was detected with high enatiomeric purity (96 99%). Although ( +)-alpha terpineol was the predominant enantiomer, its purity varied considerably (66-97%). Cluster analysis of all identified components grouped the oils into four main clusters that corresponded with their major components: alpha-terpineol (43-68%), carvacrol (32-52%), thymol (44-58%) and sabinene (41%). The essential oil from Th. caespititius showed a clear chemical polymorphism, that was particularly evident among four populations growing along a 200 m distance at Pico Verde.

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Aerial parts of Pittosporum undulatum were collected fortnightly for 1 year at the Parque de Saúde de Lisboa. Collective samples of two populations were investigated, i.e. from pruned and non-pruned trees, and in addition samples from one pruned and one non-pruned individual. An SEM study of the aerial parts showed the presence of nonglandular T-shaped trichomes, and capitate trichomes with an elongated stalk and two to four round-shaped cells on the top. Numerous canals were seen at the level of the capsule wall as well as in the leaves and stems. Essential oil samples were isolated from the (deep-frozen) aerial parts by hydrodistillation to estimate the oil yields, and by distillation-extraction to determine their percentage composition, and analysed by GC and GC-MS. Monoterpenes (59-97%) were dominant in all oils, sabinene (5-58%), limonene (2-37%) and terpinen-4-ol (4 -27%) being the major components, although in different relative amounts during the year of collection. Benzyl benzoate (8%) and benzyl salicylate (10%) attained high relative amounts in the oils from fully developed flowers, whereas in the oils from the other plant parts their relative amounts did not exceed 1%. The enantiomeric ratio of sabinene, limonene and terpinen-4-ol was investigated in the leaf, flower and capsule oils, showing dominance of the (+ + + + +)-forms and homogeneity between all the oil samples.