336 T. ANTUNES ET AL. Copyright © 2004 John Wiley & Sons, Ltd. Flavour Fragr. J. 2004; 19: 336–340 FLAVOUR AND FRAGRANCE JOURNAL Flavour Fragr. J. 2004; 19: 336–340 Published online 10 March 2004 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/ffj.1310 Micromorphology of trichomes and composition of essential oil of Teucrium capitatum Teresa Antunes, 1 Isabel Sevinate-Pinto, 1 José G. Barroso, 2 Carlos Cavaleiro 3 and Lígia R. Salgueiro 3 * 1 Centro de Biologia Ambiental, Departamento de Biologia Vegetal, Faculdade de Ciências de Lisboa, C2 Campo Grande 1749- 016, Lisboa, Portugal 2 Centro de Biotecnologia Vegetal, Departamento de Biologia Vegetal, Faculdade de Ciências de Lisboa, C2 Campo Grande 1749-016, Lisboa, Portugal 3 Laboratório de Farmacognosia/CEF, Faculdade de Farmácia, Universidade de Coimbra, Rua do Norte, 3000-295 Coimbra, Portugal Received 22 October 2002; Revised 10 April 2003; Accepted 21 April 2003 ABSTRACT: The morphology and distribution of the glandular trichomes of Teucrium capitatum L., as well as the chemical composition of the essential oils, were studied. Important differences were found with regard to the major con- stituents of the essential oils of five populations of T. capitatum grown in Portugal. The oil isolated from one population was characterized by a high content of oxygenated monoterpenes (33.0%), isomenthone (7.7%) being the major con- stituent. Another oil from a population collected from the same region was dominated by monoterpene and sesquiterpene hydrocarbons (43.9% and 23.2%, respectively), α α α-pinene (7.7%), sabinene (11.2%) and β β β -pinene (10.3%) being the main compounds. The oils from the other three populations were characterized by a high content of both sesquiterpene hydro- carbons (23.0%, 32.2% and 33.2%) and oxygenated sesquiterpenes (39.7%, 23.4% and 20.4%). T-cadinol (24.1%) and α α α-cadinol (9.8%) were the major compounds in the oil from one population, whereas δ δ δ -cadinene (7.5% and 9.8%) and E-caryophyllene (5.4%) or α α α-muurolol (6.0%) were the major constituents in the other samples. The indumentum of the vegetative and reproductive ograns from the five populations of T. capitatum, observed under scanning electron microscopy, showed the same type and distribution of glandular and non-glandular trichomes. Since the ecological and edaphic features of the collecting sites were quite similar, the chemical polymorphism observed seems to be due to genetic factors. Copyright © 2004 John Wiley & Sons, Ltd. KEY WORDS: Teucrium capitatum; trichomes; histochemistry; essential oils; GC; GC–MS * Correspondence to: L. R. Salgueiro, Laboratório de Farmacognosia/CEF, Faculdade de Farmácia, Universidade de Coimbra, Rua do Norte, 3000-295 Coimbra, Portugal. E-mail: ligia@ff.uc.pt described. As far as we know, only one single study on the essential oil from T. polium mentions the subspecies (T. polium subsp. capitatum = T. capitatum). 7 Thus, continuing our research on the micromorphology of trichomes and on the composition of the essential oils of the Portuguese Teucrium taxa, we now report on the results obtained with Teucrium capitatum L. The purpose of this work is to investigate the composition and chemical polymorphism of the essential oil from this species, as well as the micromorphology and histochemistry of the trichomes occurring on the leaves and flowers. Materials and Methods Plant Material Aerial parts of the plants were collected at the flowering stage in June 1999 and 2000, in the centre of Portugal: Fonte Coberta; Serra do Sicó (sample 1); Rabaçal, Serra do Sicó (sample 2); Portunhos, Cantanhede (samples 3 and 4); and Covão do Feto, Serra D′Aire (sample 5). All Introduction The section Polium, which includes Teucrium capitatum L. [= T. polium L. ssp. capitatum (L.) Arcangeli], contains more than half of the Teucrium spp. and is the largest and most morphologically diverse section of the genus. 1,2 Teucrium capitatum, family Lamiaceae, is a Mediterra- nean dwarf shrub up to 45 cm tall, that grows wild in central and south-east Portugal. As in other Lamiaceae described in the literature, the aerial organs of Teucrium spp. are covered by an indumentum of glandular and non-glandular trichomes. Some work on the composition of the volatile oils of Teucrium polium s.l. (subspecies not referred) were reported in the literature, 3–6 and some chemical differ- ences, probably related to the different subspecies and/ or to the geographical origin of the plants, were also