BIODIVERSITY STUDIES ON PORTUGUESE THYMBRA CAPITATA

Thymbra capitata is a characteristic species of the Lamiaceae family, growing wild in the Mediterranean basin. Endemic in SW Iberian Peninsula it is now in regression in Portugal. Thymbra capitata essential oil has been used since ancient times in pharmaceutical, food flavouring, cosmetic and perfumery, being one of the most expensive among the origanum oils. The micromorphology, distribution and density of Thymbra capitata trichomes were studied, using light and scanning electron microscopy. Peltate and capitate trichomes are present in vegetative organs. These glandular trichomes are similar to those found in other Lamiaceae, although a few morphological differences are seen, namely in the broad head cell number: 8-12-celled head. Peltate trichome density is higher in leaves’ lower surface. The composition of the essential oils isolated from the populations collected was determined by GC and GC-MS. Carvacrol (51-77%) was the major compound, followed by thymol (9-21%), p-cymene (5-11%) and y-terpinene (2-9%). Our results point to a similar essential oil composition, in plants collected at the same development stage, growing on different localities with distinct ecological and edaphically features.