Flavour Fragr. J. 2010, 25, 63–70 Copyright © 2009 John Wiley & Sons, Ltd. Research Article Received: 26 June 2009; Revised: 30 September 2009; Accepted: 5 November 2009; Published online in Wiley InterScience: 2 December 2009 (www.interscience.wiley.com) DOI 10.1002/j.1962 Histochemical localization of secretion and composition of the essential oil in Melittis melissophyllum L. subsp. melissophyllum from Central Italy Filippo Maggi, a * Fabrizio Papa, b Gloria Cristalli, b Gianni Sagratini, b Sauro Vittori b and Claudia Giuliani c ABSTRACT: The distribution and morphology of the secretory structures in Melittis melissophyllum L. subsp. melissophyllum (Lamiaceae) were studied for the irst time by light and scanning electron microscopy. The indumentum of the vegetative and reproductive organs includes non-glandular hairs and peltate (type A) and capitate (types B and C) glandular trichomes. Histochemical techniques enabled speciic location of the site of essential oil accumulation in the type A peltate hairs. In order to conirm the occurrence of the 1-octen-3-ol chemotype in central Italy, six populations growing in diferent places were analysed for the essential oil composition by GC–FID and GC–MS. In all populations, 1-octen-3-ol was detected as the major volatile component, representing 56.3–70.6% of the total oils. To date, these percentages are the highest detected in a plant essential oil. Copyright © 2009 John Wiley & Sons, Ltd. Keywords: Melittis melissophyllum subsp. melissophyllum; Lamiaceae; glandular trichomes; histochemistry; essential oil; 1-octen- 3-ol; GC–FID; GC–MS * Correspondence to: F. Maggi, Department of Environmental Sciences, Section of Botany and Ecology, University of Camerino, via Pontoni 5, 62032 Camerino, Italy. E-mail: ilippo.maggi@unicam.it a Department of Environmental Sciences, Section of Botany and Ecology, University of Camerino, Via Pontoni 5, 62032 Camerino, Italy b Department of Chemical Sciences, University of Camerino, Via Sant’Agostino 1, 62032 Camerino, Italy c Department of Plant Biology, University of Florence, Via La Pira 4, 50121 Florence, Italy Introduction Melittis melissophyllum L. subsp. melissophyllum (Lamiaceae), known as bastard balm, is a perennial herb found in thermophi- lous broadleaf woodlands, mainly composed of oaks and horn- beams. In Italy it is common in the north-western and central regions. [1] The stem is quadrangular and covered by abundant protecting trichomes, whereas glandular trichomes seem to be missing or very scant in the whole plant. [2] The plant has petiolate to subsessile, decussate, ovate to cordate and dentate leaves that, when rubbed, emanate a coumarin scent. The lowers, of white, pink or purple colour, are the biggest in the family Lamiaceae. [3] In the folk medicine of central Italy, this plant, called ‘Erba Lupa’, was used as an antispasmodic and against insomnia and eye inlammations. [4] So far, phytochemical studies of this taxon have involved only the essential oil composition of plants from Greece and Spain. [5,6] Recently we investigated plants from central Italy, whose essential oil contained extremely high amounts (43.6–54.2%) of the mush- room-like aroma component 1-octen-3-ol. [7] To our knowledge, these percentages are the highest detected in an essential oil up to now. On the other hand, this aromatic alcohol occurred only in very small amounts or was lacking in the essential oils of plants from Greece and Spain. [5,6] 1-Octen-3-ol is the most important C8 mushroom aromatic compound produced by many species of edible fungi [8] and, because of its low volatile lavour threshold, is an aroma component in several food products and beverages. [9–13] Since this compound has high economic importance in the food industry, [14] in this study we extended the analysis of the essential oil to numerous other populations, representatives of central Italy, in order to prove the existence of a particular che- motype, characterized by an essential oil rich in 1-octen-3-ol. For a more complete characterization of these plants, we report for the irst time the distribution, micromorphology and histo- chemistry of the glandular trichomes, sites of the synthesis and storage of the essential oil and other secondary metabolites. Experimental Plant Material Aerial parts of M. melissophyllum subsp. melissophyllum were collected at lowering in May 2008 in six woody places sited in Marche (central Italy; Table 1). These samples were used for both chemical analysis and mor- phological studies on the vegetative and the reproductive organs. Voucher specimens were identiied by Dr Maggi using the available lit- erature [2] and deposited in the Herbarium Camerinensis (included in the online edition of Index Herbariorum: http://sweetgum.nybg.org/ih/) [15] of the Department of Environmental Sciences, Section of Botany and Ecology, University of Camerino, Italy. They are also available at the following website: htpp://erbariitaliani.unipg.it. 63