Glandular Trichomes and Essential Oil Composition of Endemic Sideritis italica (Mill.) Greuter et Burdet from Central Italy

Abstract

Sideritis italica (Mill.) Greuter et Burdet belongs to the Lamiaceae family and is endemic to Italy. The glandular trichomes (morphology, distribution, histochemistry, and ultrastructure) of the plant were studied for the first time, along with the chemical composition of the essential oils. Abundant non-glandular hairs and peltate (type A) and capitate (types B, C(1), and C(x)) glandular trichomes were observed both on the vegetative and reproductive organs. The histochemical procedures and the ultrastructural investigation enabled specific location of the main site of essential oil production mainly in type-A peltate hairs. Particular emphasis is given to the release mechanism of the secreted material in all of the types of glands, and the potential taxonomic value of the indumentum in the Lamiaceae family is briefly discussed. Essential oils were hydrodistilled from flowering aerial parts of S. italica, and 136 compounds (112 in flowerheads, 79 in vegetative parts) were identified. The quantitative prevalence of diterpenoids (43.4% in flowerheads and 22.3% in vegetative parts) was the most significant characteristic of the essential oil of S. italica that could be classified as a diterpene-rich essential oil according to the classification of Kirimer.

Comparative Chemical Composition and Antioxidant Properties of the Essential Oils of three Sideritis libanotica Subspecies

“…Differently, in Ln terpenoids were scarce (25.7%), while fatty acids and esters (32.2%) and phenols (13.4%) were present in major percentages. The composition of the investigated samples differed greatly from the results reported earlier for other species of Sideritis, which generally contain essential oils rich in monoterpene hydrocarbons such as α-pinene, β-pinene, sabinene, myrcene, and limonene, or, to a lesser extent, in sesquiterpene hydrocarbons such as δ-cadinene and β-caryophyllene [4,13]. The quantitative prevalence of diterpenoids in Lb and Lm is worth mentioning as they do not appear very often in the essential oil of Sideritis species because of their low volatility.…”

“…In fact, only five species of this genus, S. hirsuta from Spain [4], S. italica from Sicily (South Italy) [6] and Camerino (Central Italy) [13], S. perfoliata and S. dichotoma from Turkey [12] and S. scardica from Bulgaria [14] have been previously described to present diterpenes as major or particularly abundant constituents. Different phytochemical studies have revealed that ent-kaurene type diterpenoids are the most frequently found in Sideritis species, particularly those growing in the Eastern Mediterranean Basin [3], and sideridiol in particular has been already isolated from the acetone extract of S. libanotica ssp.…”

HPTLC Fingerprint Authentication of Selected Sideritis spp. Using a Pharmacognostic Approach

“…According to Giuliani et al (2011), S. italica is described in the Flora italica" as S. syriaca [40]. Comparing the fingerprints of both species (▶ Fig.…”