Composition of Essential Oils from Five EndemicSideritisSpecies

Chemical profile of the Anatolian Sideritis species with bioactivity studies

CONTEXT

The genus Sideritis L. (Lamiaceae) is represented by 46 species in Turkey with an 79% endemism ratio, 42 of 46 belonging to the section Empodoclia.

OBJECTIVE

In this review article, Sideritis species growing in Turkey have been evaluated for phytochemical constituents and biological activities.

METHODS

The data for the isolates, components and extracts of the Anatolian Sideritis species and their bioactivity studies were retrieved from the main databases WoS, Scopus and PubMed from 1975 until 31 December 2022.

RESULTS

In this review article, terpenoids, flavonoids, phenolics and other secondary metabolites isolated from Turkish Sideritis species were reported. Anatolian Sideritis species, which primarily consist of monoterpenes and sesquiterpenes, were studied in detail. Sideritis plants are represented by 46 species in Turkey, and 25 of them were investigated for their diterpenoids through isolation or LC-MS studies. Most of the diterpenoids of Turkish Sideritis species have ent-kaurene skeleton, among them linearol, siderol, 7-epicandicandiol and sideridiol were found to be the main compounds. Exceptionally, labdane, pimarane and beyerene diterpenoids were only found in a few species. For phenolics and flavonoids, only 12 species were investigated until now, and they were found to be rich in phenylethanoid glycosides and flavonoid glycosides. In terms of activity, most of the species were tested for antioxidant activity, followed by antimicrobial and anti-ulcer/anti-inflammatory activities. Their cytotoxic, enzyme inhibitory, antinociceptive and antistress activities were less frequently studied.

CONCLUSIONS

Sideritis species should be considered promising therapeutic agents in the treatment of upper respiratory tract and ulcer/inflammatory diseases.

Sideritis L. essential oils: A systematic review

Essential oils are extensively used in the food, cosmetic, perfume, pharmaceutical, and agrochemical industries due to their aroma and pharmacological properties. The Lamiaceae family is mainly represented by widely well-known medicinal and aromatic plants that produce essential oil. Over the years, Sideritis L. essential oils have attracted great interest due to their chemical variability among the different taxa and their pharmacological activities. In-depth research of previously published literature was performed on electronic databases with several key search words for the collection of the available data and a total of 128 scientific studies were used since 1983. To date, 155 accepted Sideritis samples have been studied originating from 15 countries and more than 250 compounds have been reported in 87 Sideritis taxa overall. Furthermore, antimicrobial and antioxidant effects have been the most studied pharmacological activities. This review summarizes and critically discusses the research work on the chemical composition and pharmacological activities of essential oil of the genus Sideritis based on the currently valid taxonomy. Additionally, statistical analysis is encompassed to provide a deeper comprehensive understanding of the high chemical polymorphism of Sideritis essential oils. We expect that this review will encourage researchers to investigate unexplored Sideritis taxa and will contribute to revealing uncharted scientific territory and future perspectives on these plants.

Microscopical Investigation of Sideritis taurica

This research presents the results of the morphological-anatomical study of grass organs above ground (leaves, stems, and flowers) from Sideritis taurica Steph. ex Willd. from the Lamiaceae family. The range of distribution of this species covers Eastern Europe, including Crimea, Caucasus. This plant is commonly found as an ornamental plant and grows in the southern and central regions of Russia. The purpose of this study is the anatomical and morphological study of the vegetative organs of S. taurica and the formation of diagnostic signs for reliable plant identification. The research material used was S. taurica herbicide samples collected in Crimea on the slopes of Mount Ay-Petri. Plant material is fixed in the glycerin : water system in a ratio of 1 : 1. Cross-section of stems and leaves is carried out using blades. The study was conducted with the morphological-anatomical method. The results obtained indicate the anatomical structure of the lamina, stem, and flower of the plant that has been studied. Anomocytic types of stomatal devices, unicellular and multicellular trichomes, located on the upper and lower sides of the leaf, as well as on the corolla stem and epidermis, have been discovered. The study carried out is part of the S. taurica complex pharmacognostic study.

Diterpenoid and phenolic contents of Sideritis hololeuca Boiss & Heldr. Apud Bentham with antioxidant and anticholinesterase activity

The objective of this study is to determine essential oil, diterpenoid and phenolic contents of Sideritis hololeuca along with their biological activities. Phytol was found to be the main component of the essential oil. Seven known kaurane diterpenoids, siderol (140 mg, 0.16%, w/w), 7-acetoxy sideroxol (15 mg, 0.02%, w/w), eubol (6 mg, 0.01%, w/w), eubotriol (5 mg, 0.03%, w/w), 7-epicandicandiol (3 mg, 0.02%, w/w), ent-7α-acetoxy-18-hydroxykaur-16-ene (5 mg, 0.01%, w/w) and linearol [by liquid chromatography-tandem mass spectrometry (LC-MS/MS)] were determined from the species. Moreover, vanillin (21 mg, 0.10%, w/w), which was not isolated from any Sideritis species earlier, was isolated from an acetone extract of S. hololeuca. Quantitative amounts of some phenolic compounds in n-hexane, dichloromethane, acetone, methanol extracts and infusion and decoction of the plants were also investigated by LC-MS/MS. Antioxidant capacity and acetylcholinesterase, butyrylcholinesterase inhibition effects of the species were evaluated. The extracts of methanol and infusion and decoction of species showed moderate butyrylcholinesterase inhibition activity. The highest inhibition was observed from the decoction of species. The Cu2+ reducing power of infusion was determined as 1.435 mmol TR g−1.

Essential Oil Composition, Antioxidant, Anticholinesterase and Anti-tyrosinase Activities of Two Turkish Plant Species: Ferula elaeochytris and Sideritis stricta

The aim of the present study is to characterize chemical compositions and antioxidant, anticholinesterase and anti-tyrosinase activities of Ferula elaeochytris and Sideritis stricta essential oils. The hydrodistilled essential oils were analyzed by GC/FID and GC/MS. A total of thirty-three and twenty-seven compounds representing 99.6 % and 99.4 % were identified in F. elaeochytris and S. stricta, respectively. The main compounds of essential oil of F. elaeochytris were β-cubebene (21.3 %), caryophyllene oxide (17.5 %) and β-caryophyllene (14.9 %), while the major compounds of S. stricta essential oil were δ-cadinene (18.3 %), cubenol (17.6 %) and β-caryophyllene (14.4 %). The antioxidant activity was tested by β-carotene-linoleic acid, DPPH free radical scavenging, ABTS cation radical scavenging, CUPRAC and metal chelating assays. The essential oil of F. elaeochytris showed the highest antioxidant activity in all assays. Also, the anticholinesterase and anti-tyrosinase activities of essential oils were performed against acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and tyrosinase enzymes. F. elaeochytris essential oil indicated the highest anticholinesterase and anti-tyrosinase activities as well. This is the first report describing antioxidant, anticholinesterase and anti-tyrosinase activities of essential oils of F. elaeochytris and S. stricta.

Chemical constituents of the essential oils ofSideritis scardicaGriseb. andSideritis raeseriBoiss and Heldr. from Bulgaria and Macedonia

The essential oils of two species of Sideritis growing spontaneously in Bulgaria and Macedonia are reported, Sideritis scardica and Sideritis raeseri. The oils of S. scardica from different locations differed significantly: in the Macedonian sample alpha-cadinol (20%) predominated, while in the oil of Bulgarian samples the main components were diterpenic compounds and octadecenol (over 20%). This is the first report of ditrpenoids in essential oil of S. scardica. The oil of S. raeseri demonstrated a distinct chemical profile with its high concentration of sesquiterpenes, main components being germacrone (25%) and elemol acetate (15.9%). The observed qualitative variability of the oil composition of S. scardica of different geographic origin could be a result of different ecologic conditions but might also reflect the well-known tendency of some Sideritis species to hybridize.