Chemical polymorphism of the essential oils from populations of Thymus caespititius grown on the island S. Jorge (Azores)

The compositions of the essential oils obtained from ten populations of Tin,lna caespititus grown on S. Jorge (Azores) were studied by GC and GC MS. All the oils analysed were dominated by their monoterpene fraction (69-91%). The st 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 fr om 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%), calvacrol (31-52%), thymol (44-58%) and sabinene (41%). The essential oil from Til. caespititius showed a clear chemical polymorphism. that was particularly evident among four populations growing along a 200 m distance at Pico Verde. (C) 2000 Elsevier Science Ltd. All rights reserved.