Essential oil and phenolic compositions of Sideritis brevibracteata P.H. Davis, which is an endemic species in Turkey and commonly used as a herbal tea for some diseases, were determined by GC-MS and Liquid chromatography–mass spectrometry (LC-MS/MS) techniques. While the main components of the essential oil were determined as caryophyllene, germacrene-D, and α-cadinene, the phenolic compounds quercetagetin-3,6-dimethylether and chlorogenic acid were found to be the main compounds in the extracts of the species. The characteristic diterpenoids of Sideritis species such as siderol, linearol, eubotriol, sideridiol, and athonolone were isolated and their structures were elucidated by 1D and 2D NMR (Nuclear Magnetic Resonance) techniques. Weak inhibitory activity of species against butyryl-cholinesterase was determined. Antioxidant capacity of the acetone and methanol extracts was determined by DPPH free radical scavenging activity, β-carotene linoleic acid assays, and CUPRAC assays.

Secondary metabolites of solvent extracts of Origanum vulgare subsp. hirtum and O. vulgare subsp. vulgare were determined using liquid chromatography–mass spectrometry (LC-MS/MS). Curcumin was used as an internal standard. Rosmarinic acid was determined as the main compound of studied extracts together with other phenolic acid derivatives. In LC-MS/MS analyses, relative standard deviations (RSD %) ranged between 0.11-9.47. The correlation values were found to be greater than 0.97 for each investigated analyte.

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.

The phenolic profile, antioxidant and anticholinesterase activities of teas prepared from two Sideritis(L.) species: Sideritis perfoliata subsp. athoa (Papan. &Kokkini) Baden. and Sideritis trojana Bornm, collected from Mount Ida (Kaz Dağı) Turkey, were determined. The teas were prepared by infusion and decoction methods. The quantitative amounts of the phenolic contents were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The major phytochemicals were found to be fumaric acid for infusion and decoction samples of S. trojana and infusion of S. perfoliata subsp. athoa, chlorogenic acid for decoction of S. perfoliata subsp. athoa. The tea samples prepared by decoction method were found to be rich in phenolics. Apart from the fact that the decoction sample of S. trojana exhibited the best antioxidant effect in 2, 2-diphenyl-1-picrylhydrazyl (DPPH), β -carotene bleaching and cupric (Cu2+) ion reducing power assay (CUPRAC) methods among the tested samples at all concentrations, and showed significant inhibition effect at 200 μg/mL against acetylcholinesterase and butyrylcholinesterase enzymes (59.74%, 64.99%, respectively).