Glandular trichomes, histochemical localization of secretion, and essential oil composition in Plectranthus grandidentatus growing in Portugal

Abstract

Glandular trichomes and essential oils of Plectranthus grandidentatus grown in Portugal were studied for the first time. Trichome types and their distribution pattern were investigated by light and scanning electron microscopy. Three distinct types of glandular trichomes were described on the vegetative organs. Peltate trichomes, confined to the leaf abaxial surface, showed an orange–brownish characteristic colour and never developed a large subcuticular space. Digitiform and capitate trichomes were distributed on both leaf surfaces, the last being divided in two subtypes according to the dimension of the head, length of stalk and secretion process. In addition to these trichome types, flowers also exhibit uncommon conoidal glandular trichomes. Histochemical characterization of secretion revealed the presence of terpenoids and flavonoids as main constituents. Essential oils, isolated by hydrodistillation of aerial organs, harvested at the four calendar‐based seasons, were analysed by gas chromatography and gas chromatography–mass spectrometry. The oils with a dark–orange colour and agreeable odour were obtained in yields that ranged from 0.2 to 0.5% (v/d.w.). Sesquiterpenes constituted the dominant fraction (69–79%), β‐caryophyllene (9–13%) and δ‐cadinene (5–7%) being the most abundant hydrocarbons in all oils and β‐caryophyllene oxide (4–8%) and 14‐hydroxy‐9‐epi‐(E)‐caryophyllene (4–6%) the major oxygen‐containing compounds. The monoterpene fraction did not exceed 13%, oxygen‐containing diterpenes attained lower percentages (1–9%), and phenylpropanoids were only present in trace amounts. The essential oils isolated from plants collected during the vegetative phase (winter and spring) showed a similar chemical profile, while that isolated from plants harvested in summer, resembled the one obtained from plants in the flowering phase collected in autumn. Copyright © 2013 John Wiley & Sons, Ltd.

Volatile‐Oils Composition, and Bioactivity of the Essential Oils of Plectranthus barbatus, P. neochilus, and P. ornatus Grown in Portugal

“…The essential oils isolated from P. barbatus collected in Rwanda (Central Africa) were richer in sesquiterpenes than in monoterpenes, and contained mainly aromadendrene (8 -24%), a-copaene (4 -8%), caryophyllene oxide (3 -4%), and g-cadin-2-ene (2 -4%) [27]. Moreover, in these samples, an unidentified compound (77; UIA) was also detected ( Table 1), which, although perceived neither in P. neochilus nor in P. ornatus volatiles, was previously detected in P. grandidentatus essential oils [30]. However, in these Brazilian samples, a-pinene (22%) and b-phellandrene (26%) were the most abundant constituents from the leaf and stem essential oils, respectively, whereas in the Portuguese samples, with leaves and stems together, a-pinene (3; 12 -28%), oct-1-en-3-ol (6; traces -28%), and b-pinene (7; 26%) were the volatiles major constituents.…”

Supercritical CO2 Extracts and Volatile Oil of Basil (Ocimum basilicum L.) Comparison with Conventional Methods

“…For component identification, a gas chromatograph coupled to mass spectrometry (GC-MS) was used, consisting of a Perkin Elmer Autosystem XL gas chromatograph interfaced with a Perkin-Elmer Turbomass mass spectrometer (software version 4.1; Perkin Elmer, Shelton, CT, USA). The components were identified based on their comparative retention times relative to C 9 -C 27 n-alkane indices and GC-MS spectra from a lab-made library constructed based on the analyses of reference oils, laboratory-synthesized components, and commercially-available standards [34].…”

Morphology and histochemistry of glandular trichomes in Hyptis villosa Pohl ex Benth. (Lamiaceae) and differential labeling of cytoskeletal elements

“…The morphology of the glandular trichomes is highly variable within the family. In almost all studied species, capitate and peltate trichomes are present (Ascensão & Pais 1998), being common the occurrence of different versions of them (Ascensão et al 1995;Ascensão & Pais 1998;Ascensão et al 1999;Corsi & Bottega 1999;Martins 2002;Maggi et al 2010;Baran et al 2010;Mota et al 2013). Peculiarities on the distribution, arrangement and function of the different glandular morphotypes have been observed in Lamiaceae (Corsi & Bottega 1999) and a correlation between the gland morphology and the composition of secretion has been proposed (Werker 1993;Ascensão & Pais 1998;Corsi & Bottega 1999).…”