Comparative Study on Assisted Solvent Extraction Techniques for the Extraction of Biologically Active Compounds from Sideritis raeseri and Sideritis scardica

Abstract

The plants in the Sideritis genus are postulated to exhibit several important medicinal properties due to their unique chemical composition. To isolate the targeted phytochemical compounds, the selection of a suitable extraction method is of primary importance. In this work, a comparative study on the phytochemical profiles of various Sideritis raeseri and Sideritis scardica extracts has been carried out. An untargeted metabolomics approach based on ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry was applied to investigate the metabolic differences between extracts obtained by conventional extraction and extractions assisted by microwaves, ultrasounds and high pressure. Additionally, the influence of extraction solvents on HPLC antioxidant profiles obtained following the derivatization of analytes with ABTS reagent was evaluated. A total of 102 metabolites have been putatively identified. The major secondary metabolites groups were classified as flavonoids, terpenoids, phenylethanoid glycosides and phenolic acids. The main antioxidants in the extracts were isoscutellarein and hypolaetin derivatives as well as verbascoside and chlorogenic acid. The results showed that 70% ethanol was the most effective extractant for different classes of phytochemicals including antioxidants. In addition, extraction supported with microwaves, ultrasounds or high pressure improved the overall recovery of metabolites by about 3 times compared to the conventional extraction method.

A Comprehensive Phytochemical Analysis of Sideritis scardica Infusion Using Orbitrap UHPLC-HRMS

“…The identity of asystoside ( 5 ) was suggested by the transitions 583.261→421.209→289.166→161.445, resulting from the losses of hexosyl (162.053 Da), pentosyl (132.043 Da), and oct-1-en-3-ol units (C 8 H 16 O, 128.122 Da) ( Table 1 ). All above-mentioned compounds were previously identified in the species [ 12 ].…”

“…Eight hydroxybenzoic acids ( 9 , 12 , 15 , 16 , 18 , 19 , 21 , and 24 ), four hydroxycinnamic acids ( 17 , 20 , 25 , and 26 ) and their glycosides ( 10 , 11 , 13 , 14 , 22 , and 23 ), together with quinic ( 6 ), oxaloglutaric ( 7 ), and citric acid ( 8 ), were identified based on the comparison with reference standards and literature data in the assayed extract ( Table 1 ) [ 12 , 17 ]. Compound 8 ([M−H] − at m / z 191.018) showed fragment ions at m / z 173.008 [M−H−H 2 O] − , 147.028 [M−H−CO 2 ] − , a base peak at m / z 111.007 [M−H−CO 2 −2H 2 O] − , and was related to citric acid [ 18 ].…”

“…A class of secondary metabolites distinctive for Sideritis species were phenylethanoid glycosides [ 12 ]. The typical fragmentation pattern revealed the loss of 162.05, 146.05, 179.03, 18.01 Da—corresponding to glucosyl and rhamnosyl moieties—deprotonated caffeic acid, and H 2 O, respectively.…”

“…The typical fragmentation pattern revealed the loss of 162.05, 146.05, 179.03, 18.01 Da—corresponding to glucosyl and rhamnosyl moieties—deprotonated caffeic acid, and H 2 O, respectively. Detailed discussion on the MS/MS fragmentation has been previously provided [ 12 ]. Based on a comparison with literature data, 10 phenylethanoid glycosides were dereplicated in the studied S. scardica extract ( Table 1 ).…”

“…The traditional medicinal usage of the species is based on the phytochemical constituents, including phenolic acids (chlorogenic acid, 3-caffeoylquinic acid, feruloylquinic acid, and others), flavonoids and their derivatives (hypolaetin, isoscutellarein, and others), phenylethanoid glycosides (lavandulifolioside, verbascoside, echinacoside, allysonoside, and others), and terpenoids (mostly iridoid glycosides) [ 6 , 8 , 11 , 12 ]. These chemical compounds have been explored in phytochemical studies, operating with various extraction techniques such as hydrodistillation and solvent and supercritical extractions [ 8 , 12 , 13 , 14 , 15 ]. Precisely, the most abundant secondary metabolites of S. scardica water extracts (i.e., when making infusion or decoction) are flavonoids, hydoxycinnamic acid derivatives, and phenylethanoid glycosides [ 7 , 14 , 16 , 17 ].…”