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Article

LC-MS/MS-QTOF Identification of Phenolic Compounds of Sideritis Species Cultivated in Greece

by
Eleftheria H. Kaparakou
1,
Charalabos D. Kanakis
1,
Maroula G. Kokotou
1,
Georgios Papadopoulos
2 and
Petros A. Tarantilis
1,*
1
Laboratory of Chemistry, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, 11855 Athens, Greece
2
Institute for Design and Analysis of Experiments, University Research Center, Agricultural University of Athens, 11855 Athens, Greece
*
Author to whom correspondence should be addressed.
Separations 2024, 11(8), 229; https://doi.org/10.3390/separations11080229 (registering DOI)
Submission received: 16 June 2024 / Revised: 18 July 2024 / Accepted: 24 July 2024 / Published: 26 July 2024
(This article belongs to the Special Issue Isolation and Identification of Biologically Active Natural Compounds)
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Versions Notes

Abstract

:
Phenolic compounds are plant secondary metabolites, one of the most common and widespread groups of substances in plants, as well as a major group of phytochemicals present in medicinal and aromatic plants. The phytochemical composition of the hydroalcoholic extracts from S. raeseri, S. scardica and S. syriaca was determined by LC-MS/MS-QTOF analysis. A total amount of 23 secondary metabolites were identified, including 17 flavonoids (Fs), 4 phenylethanoid glycosides (PEGs), 1 phenolic acid (PA) and 1 fatty acid (FA). Among the three species, the constituents that have been detected in all of nine samples were: verbascocide/isoverbascoside (PEG), apigenin 7-O- glucoside (F), isoscutellarein 7-O-[6″-O-acetyl]-allosyl(1→2)-glucoside (F) and apigenin 7-(4″-p-coumaroylglucoside) (F). This study contributes to the phytochemical characterization of the Sideritis spp. by providing a comparative study of bioactive compounds present in three different Sideritis species, S. raeseri, S. scardica and S. syriaca, which are widely used as a herbal medicine in Mediterranean region and Balkan Peninsula.

1. Introduction

There are approximately 300,000 species of higher plants on earth, which synthesize a vast number of chemicals with diverse structures and classifications, classified as primary and secondary metabolites [1]. Phenolic compounds are plant secondary metabolites that are one of the most common and widespread groups of substances in plants [2,3,4,5] as well as a major group of phytochemicals present in medicinal and aromatic plants [2,3]. More than 8000 phenolic compounds have been identified from medicinal and aromatic plants, with a wide range of structures [2,4,6,7]. The main subgroups of phenolic compounds are as follows: phenols, phenolic acids, phenylpropanoids, flavonoids, flavones, flavonones, isoflavones, xanthones, aurones, quinines and tannins [2,6,7].
Lamiaceae is a cosmopolitan family comprising approximately 6900–7200 species in 236 genera [6,8,9]. Lamiaceae plants are rich in phytochemicals, especially phenolic compounds [8,10,11,12], and their high biological activity is widely recognized [8,11,12]. The importance of Lamiaceae for medicinal, aromatic, environmental and culinary uses has been known for centuries [13]. Phenolic compounds such as rosmarinic acid, carvacrol and thymol are found in many genera of Lamiaceae and are known for their antioxidant properties [14].
The genus Sideritis belongs to the Lamiaceae Lindl., one of the most common and diverse angiosperm families in the world [15]. The genus name, consisting of over 150 species and several subspecies, is derived from the Greek word “sideros” (iron), referring to the healing properties of the plant [16]. The plants grow in the Mediterranean region and the Balkans on rocky slopes at an altitude of more than 1000 m; they are hardy flowering perennials [15,16,17,18,19].
The Empedoclia section of the genus Sideritis has long been part of the Greek flora [20]. Many chemical constituents have been identified in the genus Sideritis, including terpenes, flavonoids, essential oils, iridoids, coumarins, lignans and sterols [15,21,22,23,24]. Sideritis species are used in folk medicine in the Mediterranean and Balkans for their anti-inflammatory, anti-ulcer, anti-bacterial, anti-rheumatic, anti-seizure, anti-spasmodic, antioxidant and analgesic properties [16,22,23,24,25,26,27]. Numerous secondary metabolites isolated from various extracts of Sideritis species, including diterpenes, flavonoids and phenolic acids, are responsible for the pharmacological activity observed in vivo and in vitro [22] and for the strong antioxidant capacity [23,24] (Figure 1).
Seventeen species of the genus Sideritis are native to Greece [17], of which S. raeseri, S. scardica and S. syriaca are found both wild and cultivated [18,19]. Also, according to the European Union’s herbal monograph (EMA/HMPC/39455/2015), S.scardica, S. raeseri and S. syriaca are used as a traditional herbal medicine to treat inflammation, gastrointestinal disorders and coughs associated with colds [28]. The aim of this research work, as a continuation of the previous one [16], is to determine the phytochemical composition of these important Sideritis species that are part of the Mediterranean diet. It will also provide new knowledge about the chemical composition of this valuable medicinal plant for future use. The main focus of our study is to use LC-MS/MS-QTOF to identify bioactive compounds that can be extracted from S.scardica, S. raeseri and S. syriaca from nine different regions of Greece and are widely recognized for their high biological activity.

2. Materials and Methods

2.1. Chemicals and Reagents

Methanol (HPLC grade), methanol (LC-MS grade), and acetonitrile were purchased from Sigma-Aldrich (St. Louis, MO, USA). Glacial acetic acid was purchased from Fisher Scientific Company (Ottawa, ON, Canada). Water (liquid chromatography–mass spectrometry (LC-MS grade) was purified using a Ultra-pure water (MilliQ purification system) (RephiLe Biosciences Ltd., Acton, MA, USA).

2.2. Plant Material

Aerial parts (stems, leaves, flowers) of Sideritis spp. were harvested from different regions of Greece: the first sample of S. raeseri (SR1) was harvested in the foothills of Mount Othrys, central Greece; the second sample of S. raeseri (SR2) was harvested in the Kastoria region, northern Greece; the third sample of S. raeseri (SR3) was harvested in the area of Elassona, Larissa, in central Greece; the first sample of S. scardica (SSC1) was harvested around Mount Olympus in central Greece (Olympus tea); the second sample (SSC2) was harvested around Mount Mainalo, in Peloponnesos; the third sample (SSC3) was harvested in the Kastoria region, northern Greece; the first sample of S. syriaca (SS1) was harvested in the southern part of Crete, White Mountain (Lefka ori); the second sample (SS2) was harvested, in Crete, in the Anopoli Sfakion area, near the White Mountains (Lefka ori); the third sample (SS3) was harvested in Crete, in the Omalos Chanion area.
Voucher specimens have been deposited (No. 012276: SSC1, No. 012279: SSC2, No. 012293: SSC3, No. 012277: SR1, No. 012294: SR2, No. 012295: SR3, No. 012278: SS1, No. 012291: SS2, No. 012292: SS3) and are managed by the Herbarium of the Agricultural University of Athens.

2.3. Preparation of Extracts

Five grams of plant material was added to an ultrasonic bath (Ultrasonic bath, Grant) along with 500 mL of a 70:30 MeOH/H2O mixture. Extraction was performed at room temperature (≈25 °C) for 15 min. The hydromethanolic extracts were concentrated using a Heidolph Laborota 4000 efficient rotary evaporator (Sigma Labor-zentrifugen GmbH, Osterode am Harz, Germany) until the solvent was removed. The samples were then weighed, placed in lyophilized flasks, and stored in a −18 °C freezer for 24 h. All samples were lyophilized in a Virtis 25 EL Freemobile laboratory lyophilizer (New York, NY, USA) for 48 h. For LC-MS/MS-QTOF analysis, 1 mg of lyophilized samples were redissolved in 70:30 ACN/H2O in a total volume of 1 mL.

2.4. LC-MS/MS-QTOF

Extracts were analyzed on an Agilent 1260 LC system connected to an Agilent 6530 Q-TOF mass spectrometer (Agilent Technologies, Santa Clara, CA, USA). The column used was a reverse-phase Macherey Nagel type with a length of 100 mm, diameter of 4.6 mm, and pore size of 2.7 μm (MACHEREY-NAGEL GmbH & Co. KG, Dueren, Germany). The column temperature was 30 °C. The elution solvents were highly purified water acidified with 0.1% acetic acid (solvent A) and highly purified acetonitrile also acidified with 0.1% acetic acid (solvent B). The elution program was stepwise as follows: 0 min 10%B, 0–8 min 30%B, 8–12 min 40%B, 12–16 min 50%B and 16–18 min 10%B. Chromatograms were recorded at 280, 320, 330, 360 and 560 nm. The elution flow rate was adjusted to 1 mL/min and the injection volume was 10 µL. The mass spectrometer was set to negative ionization and an ESI ionization source was used, and the analytical parameters were as follows: ionization source temperature 350 °C, dry gas flow (N2) 11 L/min, nebulizer pressure 50 psig, Vcap 4000 v and ion record (m/z) 50–1700 m/z. MS/MS spectra were recorded on the auto MS/MS mode. The m/z range was set to 50–800 and the collision energy at 25 V. The fragmentor voltage was set to 150 V.

2.5. Identification of Phenolic Compounds and Statistical Analysis of LC-MS/MS-QTOF Data

The phytochemical composition of hydroalcoholic extracts of S. raeseri, S. scardica and S. syriaca was determined by LC-MS/MS-QTOF analysis in negative ion mode. The Agilent Mass Hunter Data Acquisition software (version B.06.00, Santa Clara, CA, USA) was used for data acquisition, whereas the raw data were handled with the Agilent Mass Hunter Workstation Software Data Acquisition for 6530 series Q-TOF (version B.07.00). Identification of main phenolic compounds was based on the m/z value of the observed molecular ions. Additional, the “Find compounds by molecular feature” option of the MassHunter software was used to generate molecular formulas for the detected compounds. The presence or absence of phenolic compounds was determined for each of the individual Sideritis species to separate them into different taxonomic groups. The binary table (species-phenolic compounds) thus created was used as input for Statgraphics (Centurion XVI) software to produce the associated dendrogram.

3. Results and Discussion

In total, from nine samples of Sideritis species from different areas of Greece, 23 secondary metabolites were identified: 17 flavonoids (Fs), 4 phenylethanoid glycosides (PEGs), 1 phenolic acid (PA) and 1 fatty acid (FA) (Figure 2).
The phytochemical composition of the hydroalcoholic extracts of S. raeseri, S. scardica and S. syriaca are summarized in Table 1.
Major peaks were tentatively attributed by exact mass, mass error, characteristic fragmentation pattern and retention time in comparison to the literature data on the Sideritis genus (see Figure 3 and Figure 4).
In S. raeseri hydromethanolic ectracts (SR1, SR2, SR3), flavonoids were the main group components (Figure 5) followed by phenylethanoid glycosides and phenolic acid (SR1: chlorogenic acid). In the three samples of S. raeseri, only 10 phenolic compounds were common (Figure 6).
Also, one compound was identified: 4′-O-methylhypolaetin 7-O-[6‴-O-acetyl]-allosyl-(1→2)[6″-O-acetyl]-glucoside (compound 16). It was not detected in other species. And in the SR2 sample, four compounds were detected: forsythoside B/lavandulifolioside (PEG) (compound 2), allynoside (PEG) (compound 4), hypolaetin 7-O-[6‴-O-acetyl]-allosyl(1→2)-glucoside(F) (compound 5), hypolaetin 7-O-[2‴,6″-di-O-acetyl]-allosyl(1→2)glucoside (F) (compound 13). They were not detected in the remaining eight samples.
In S. syriaca hydromethanolic ectracts (SS1, SS2, SS3), flavonoids were the main group components (Figure 7) followed by phenylethanoid glycosides and phenolic acids. In the three samples of S. syriaca, only eight phenolic compounds were common (Figure 8).
In S. scardica hydromethanolic ectracts (SSC1,SSC2,SSC3), flavonoids were the main group components (Figure 9) followed by phenylethanoid glycosides, phenolic acid (SSC3: chlorogenic acid) and fatty acid (SSC1: trihydroxy octadecenoic acid). In the three samples of S. scardica, only seven phenolic compounds were common (Figure 10). Also, only in the SSC1 sample, were detected martynoside (PEG) (compound 11) and trihydroxy octadecenoic acid (FA) (compound 19).
Phytochemical studies of the genus Sideritis have revealed the presence of many phytochemicals, including flavonoids, phenylethanoid glycosides and phenolic acids [22,25].
Flavonoids and derivatives (F)
Flavonoids and their derivatives are the major phytochemicals of Sideritis species [29,30]. In this study, 17 of the 23 identified compounds were classified as flavonoids. Most of these compounds were glycosides and acetyl glycosides of flavonoids and their methylated forms, which are characteristic of the genus Sideritis [22,30,32,33]. The main flavonoid aglycons found in the plants studied were isoscutellarein and hypolaetin, as well as their methylated derivatives, and apigenin (Figure 11). The antioxidant and anti-inflammatory effects of these constituents have been reported previously [22,33].
Compounds 5 and 13 with [M−H]− at m/z 667.1507 and 709.1619 have been characterized as hypolaetin 7-O-[6‴-O-acetyl]-allosyl(1→2)-glucoside (hypolaetin acetyl allosyl glucoside) and hypolaetin 7-O-[2‴,6″-di-O-acetyl]-allosyl(1→2)glucoside (hypolaetin diacetyl allosyl glucoside). The common fragment ion of m/z 301 represented deprotonated hypolaetin [30].
Methylhypolaetin glycosides shared the characteristic 315 fragment, which was observed in compound 16 (4′-O-methylhypolaetin 7-O-[6‴-O-acetyl]-allosyl-(1→2)[6″-O-acetyl]-glucoside) ([M−H]− at m/z 723.1772), as well as, in two isomers of methylhypolaetin acetyl glucoside, compounds 8 (4′-O-methylhypolaetin 7-O-[6‴-O-acetyl]-allosyl(1→2)glucoside) and 10 (3′-O-methylhypolaetin7-O-[6‴-O-acetyl]-allosyl(1→2)glucoside)([M−H]− at m/z 681.1660 and 681.1667, respectively).
Compounds 7 (isoscutellarein 7-O-[6″-O-acetyl]-allosyl(1→2)-glucoside) with [M−H]− at m/z 651.1556, 9 (isoscutellarein 7-O-[6″-O-acetyl]-allosyl(1→2)-glucoside) with [M−H]− at m/z 651.1555 and 15 (isoscutellarein 7-O-[6‴-O-acetyl]-allosyl(1→2)-[6″-O-acetyl]-glucoside) with [M−H]− at m/z 693.1659 gave a fragment ion of m/z 285 that correspond to isoscutellarein (Figure 10). Compounds 12 (4′-O-methylisoscutellarein 7-O-allosyl(1→2)glucoside), 14 (4′-O-methylisoscutellarein 7-O-[6″-O-acetyl]-allosyl(1→2)-glucoside) and 21 (4′-O-Methylisoscutellarein7-O-[6‴-O-acetyl]-allosyl(1→2)-[6″-O-acetyl]-glucoside) showed [M−H]− at m/z 623.1608, 665.1718 and 707.1821, respectively. They all gave a fragment ion of m/z 299 which could be attributed to the methylated form of isoscutellarein.
Also, compounds 6 (apigenin 7-O- glucoside) and 20 (apigenin-7-O-(6″-O-4-coumaroyl)-beta-glucoside) with [M−H]− at m/z 431.971 and 577.1338 gave fragments of m/z 269, which correspond to deprotonated apigenin.
Phenylethanoid glycosides (PEGs)
Phenylethanoid glycosides are phenolic derivatives that characterize the genus Sideritis. Numerous pharmacological effects have been reported, including antioxidant, anti-inflammatory and anti-hypertensive effects [34].
Among all detected compounds, 4 was classified as phenylethanoid glycosides, which is a common class of compounds in Sideritis genus [29,30]. Compound 3 with [M−H]− at m/z 623.1970, which was identified as verbascoside (Figure 12), showed the fragmentation pattern of m/z 161 due to the loss of hexose units. Also, compound 4, which was identified as allysonoside (Figure 12), showed a precursor ion at m/z 769.2544 and the fragment ion observed at m/z 175.0392.
Compound 2 with [M−H]− at m/z 755.2390 was identified as forsythoside B/lavandulifolioside (Figure 13). Compound 11 which yielded the base peak at m/z 651.1971 was identified as martynoside (Figure 13) and showed a fragment ion m/z 175 by the loss of a feruloyl unit.
Phenolic acids and fatty acids (PAs, FAs)
Phenolic acids are widely known for their important biological activities. Chlorogenic acid is one of the most abundant phenolic acids in Sideritis species and has been previously studied for its antioxidant, anti-inflammatory, anti-diabetic, anti-obesity and anti-hypertensive effects [35].
From the class of phenolic acids, in the nine samples, the only one was chlorogenic acid (compound 1) (Figure 14), whose main characteristic ion was derived from the quinic acid fragment (191 Da). Also, trihydroxy octadecenoic acid(Trihydroxy-C18:1) (compound 19) was the only fatty acid detected at m/z 329.2327 [M−H].
Among the three species that were analyzed by LC-MS/MS-QTOF, the constituents that have been detected in all were verbascocide/isoverbascoside (PEG), apigenin 7-O-glucoside (F), isoscutellarein 7-O-[6″-O-acetyl]-allosyl(1→2)-glucoside (F) and apigenin-7-O-(6″-O-4-coumaroyl)-beta-glucoside (F), which were studied, in previous studies, for a number of pharmacological activities (Table 2).
The relationship between the chemical composition and the Sideritis species is shown in the dendrogram (Figure 15). Thus, based on the chemical composition, the nine samples are divided into two groups. The first group includes sample SR2, and the second group includes all other samples (SR1, SR3, SSC1, SSC2, SSC3, SS1, SS2, SS3). The samples in the second group are then divided into subgroups: the first subgroup has only one sample (SR2); the second subgroup contains the other samples (SR1, SR3, SS1, SS2, SS3, SSC2, SSC3). In this second subgroup, the samples are divided into smaller subgroups: one subgroup (the third subgroup) consists of the samples SS1, SS2, SSC2, SSC3 and SR1, SR3, SS3 (the fourth subgroup). The third subgroup is further divided into smaller subgroups: the fifth subgroup with SS1 and SS2, and the sixth subgroup with SSC2 and SSC3, and samples of the fourth subgroup comprise the seventh subgroup with SS3 and the eighth subgroup with SR1 and SR3. According to these results, the SR2 extract is distinguished from the other eight extracts by its chemical composition; the same applies to the SSC1 extract; the other two extracts of the S. raeseri sample are both quite different from the others: the S. syriaca (SS1, SS2) and S. scardica (SSC2, SSC3) extracts showed more similar chemical compositions.

4. Conclusions

Plants of the genus Sideritis have been recognized for their health benefits in folk medicine in the Mediterranean and Balkans, and the European Medicines Agency (EMA)’s approval of their use as traditional herbal medicines has further strengthened their efficacy. Three species of the genus Sideritis (S. raeseri, S. scardica, and S. syriaca) cultivated in different regions of Greece were examined by LC-MS/MS-QTOF analysis, and 23 secondary metabolites were identified, including 17 flavonoids, 4 phenylethanoid glycosides, 1 phenolic acid, and 1 fatty acid. Of these 17 flavonoids, those common to 9 samples were only 4: verbascoside/isoverbascoside (PEG), apigenin 7-O-glucoside (F), isoscutellarein 7-O-[6′’-O-acetyl]-allosyl(1→2)-glucoside (F) and apigenin-7-O-(6″-O-4-coumaroyl)-beta-glucoside, which were studied for their pharmacological activities.
This study contributes to the phytochemical characterization of the Sideritis spp. by providing a comparative study of bioactive compounds present in three different Sideritis species, S. raeseri, S. scardica and S. syriaca, which are widely used as herbal medicine in the Mediterranean region and Balkan Peninsula.
The genus Sideritis offers a wide range of research opportunities. Based on the results of this study and considering the value that mountain tea has for the Greeks, future research should focus on the pharmacological activity of Sideritis species who cultivated or growing wild in Greece.

Author Contributions

Conceptualization, E.H.K. and P.A.T.; Data curation, E.H.K. and P.A.T.; Formal analysis, E.H.K.; Investigation, E.H.K.; Methodology, E.H.K.; Project administration, E.H.K. and P.A.T.; Resources, E.H.K., C.D.K., M.G.K., G.P.and P.A.T.; Software, E.H.K. and P.A.T.; Supervision, E.H.K. and P.A.T.; Validation, E.H.K., C.D.K., M.G.K., G.P.and P.A.T.; Visualization, E.H.K. and P.A.T.; Writing—original draft, E.H.K. and P.A.T.; Writing—review and editing, E.H.K., C.D.K., M.G.K., G.P.and P.A.T. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The data presented in this study are available upon request from the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

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Separations 11 00229 g001
Figure 1. Pharmacological activities of Sideritis spp.
Figure 1. Pharmacological activities of Sideritis spp.
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Separations 11 00229 g002
Figure 2. Phenolic compounds in Sideritis extracts.
Figure 2. Phenolic compounds in Sideritis extracts.
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Separations 11 00229 g003
Figure 3. Base peak chromatogram (BPC) in negative mode of S. syriaca (SS2) hydroalcoholic extract (For compound numbering see Table 1; ? unidentified compounds).
Figure 3. Base peak chromatogram (BPC) in negative mode of S. syriaca (SS2) hydroalcoholic extract (For compound numbering see Table 1; ? unidentified compounds).
Separations 11 00229 g003
Separations 11 00229 g004
Figure 4. MS spectrum of identified compounds in S. syriaca (SS2) hydroalcoholic extract: 1: chlorogenic acid; 2: verbascocide/isoverbascoside; 3: apigenin 7-O- glucoside; 4: isoscutellarein 7-O-[6″-O-acetyl]-allosyl(1→2)-glucoside;5:isoscutellarein 7-O-[6″-O-acetyl]-allosyl(1→2)-glucoside;6:3′-O-methylhypolaetin 7-O-[6‴-O-acetyl]-allosyl(1→2)glucoside; 7: proanthocyanidin dimer; 8: apigenin; 9: apigenin-7-O-(6″-O-4-coumaroyl)-beta-glucoside.
Figure 4. MS spectrum of identified compounds in S. syriaca (SS2) hydroalcoholic extract: 1: chlorogenic acid; 2: verbascocide/isoverbascoside; 3: apigenin 7-O- glucoside; 4: isoscutellarein 7-O-[6″-O-acetyl]-allosyl(1→2)-glucoside;5:isoscutellarein 7-O-[6″-O-acetyl]-allosyl(1→2)-glucoside;6:3′-O-methylhypolaetin 7-O-[6‴-O-acetyl]-allosyl(1→2)glucoside; 7: proanthocyanidin dimer; 8: apigenin; 9: apigenin-7-O-(6″-O-4-coumaroyl)-beta-glucoside.
Separations 11 00229 g004
Separations 11 00229 g005
Figure 5. Group components of S. raeseri extracts.
Figure 5. Group components of S. raeseri extracts.
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Figure 6. Common phenolic compounds in S. raeseri extracts.
Figure 6. Common phenolic compounds in S. raeseri extracts.
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Separations 11 00229 g007
Figure 7. Group components of S. syriaca extracts.
Figure 7. Group components of S. syriaca extracts.
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Separations 11 00229 g008
Figure 8. Common phenolic compounds in S. syriaca extracts.
Figure 8. Common phenolic compounds in S. syriaca extracts.
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Separations 11 00229 g009
Figure 9. Group components of S. scardica extracts.
Figure 9. Group components of S. scardica extracts.
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Separations 11 00229 g010
Figure 10. Common phenolic compounds in S. scardica extracts.
Figure 10. Common phenolic compounds in S. scardica extracts.
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Separations 11 00229 g011
Figure 11. Structures of isoscutellarein, hypolaetin and apigenin.
Figure 11. Structures of isoscutellarein, hypolaetin and apigenin.
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Separations 11 00229 g012
Figure 12. Structures of verbascoside/isoverbascocide and allysonoside.
Figure 12. Structures of verbascoside/isoverbascocide and allysonoside.
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Separations 11 00229 g013
Figure 13. Structures of forsythoside B/lavandulifolioside and martynoside.
Figure 13. Structures of forsythoside B/lavandulifolioside and martynoside.
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Separations 11 00229 g014
Figure 14. Structure of chlorogenic acid.
Figure 14. Structure of chlorogenic acid.
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Separations 11 00229 g015
Figure 15. Dendrogram of the chemical variations and relationships between the Sideritis species (statistical analysis was conducted through the package Statgraphics, which was performed using Word’s method).
Figure 15. Dendrogram of the chemical variations and relationships between the Sideritis species (statistical analysis was conducted through the package Statgraphics, which was performed using Word’s method).
Separations 11 00229 g015
Table 1. Phytochemical composition of Sideritis extracts.
Table 1. Phytochemical composition of Sideritis extracts.
No.CompoundRetention Time
(min)		Suggested FormulaExact Mass
[M−H]−		Fragmentation Pattern in (−) ESI-MS/MSS. raeseriS. scardicaS. syriacaRef.
SR1 aSR2SR3SSC1SSC2SSC3SS1SS2SS3
1Chlorogenic acid3.154C16H18O9353.0871191.0506+ b- c---++++[29,30,31]
std
2Forsythoside B/Lavandulifolioside5.755C34H44O19755.2390161.0227-+-------[15,25,29,30,31,32]
3Verbascocide/Isoverbascoside5.959C29H36O15623.1970161.0238+++++++++[15,25,29,30,31,32]
std
4Allysonoside6.803C35H46O19769.2544175.0392-+-------[15,25,29,30,31,32]
5Hypolaetin 7-O-[6‴-O-acetyl]-allosyl(1→2)-glucoside7.039C29H32O18667.1507301.0341-+-------[15,25,29,30,31,32]
6Apigenin 7-O-glucoside7.336C21H20O10431.0971268.0393+++++++++[15,25,30,31,32]
7Isoscutellarein 7-O-[6′-O-acetyl]-allosyl(1→2)-glucoside7.412C29H32O17651.1556285.0396+-+++++++[15,25,29,30,31,32]
84′-O-Methylhypolaetin7-O-[6‴-O-acetyl]-allosyl(1→2)glucoside7.749C30H34O18681.1660315.0510++-++----[15,29,30,31,32]
9Isoscutellarein 7-O-[6″-O-acetyl]-allosyl(1→2)-glucoside7.994C29H32O17651.1555285.0394+++++++++[15,25,29,30,31,32]
103′-O-Methylhypolaetin 7-O-[6‴--O-acetyl]-allosyl(1→2)glucoside8.289C30H34O18681.1667315.0485++++++-++[15,25,29,30,32]
11Martynoside8.533C31H40O15651.1971175.0419---+-----[25,30,31]
124′-O-Methylisoscutellarein 7-O-allosyl(1→2)glucoside8.662C28H32O16623.1608299.0553+-+-----+[15,25,30,31,32]
13Hypolaetin 7-O-[2‴,6″-di-O-acetyl]-allosyl(1→2)glucoside9.405C31H34O19709.1619301.0307-+-------[15,29,30,32]
144′-O-Methylisoscutellarein 7-O-[6″-O-acetyl]-allosyl(1→2)-glucoside10.085C30H34O17665.1718299.0554+-++++--+[15,25,29,30,31,32]
15Isoscutellarein 7-O-[6‴-O-acetyl]-allosyl(1→2)-[6″-O-acetyl]-glucoside10.386C31H34O18693.1659285.0398+++-+++-+[25,29,30,31,32]
164′-O-Methylhypolaetin
7-O-[6‴-O-acetyl]-allosyl-(1→2)[6″-O-acetyl]-glucoside		10.622C32H36O19723.1772315.0518+++------[15,25,29,30,31,32]
17Proanthocyanidin dimer10.926C30H26O12577.1340269.0453+++---+++[30]
18Apigenin11.469C15H10O5269.0452151.0030+++--++++std
19Trihydroxy octadecenoic acid11.884C18H34O5329.2327211.1346---+-----[30,31]
20Apigenin-7-O-(6″-O-4-coumaroyl)-beta-glucoside11.997C30H26O12577.1338269.0442+++++++++[15,25,30,31,32]
214′-O-Methylisoscutellarein
7-O-[6‴-O-acetyl]-allosyl(1→2)-[6″-O-acetyl]-glucoside		12.412C32H36O18707.1821299.0553+++---+-+[15,25,30,31,32]
22Cirsimaritin13.559C17H14O6313.0714283.0251+-+--++-+[30]
23Usnicacid/Eupatorin14.509C18H16O7343.0816313.0350+-++-++-+[30]
a SR1: S. raeseri from Othrys; SR2: S. raeseri from Kastoria; SR3: S. raeseri from Elassona; SSC1: S. scardica from Olympus; SSC2: S. scardica from Mainalo; SSC3: S. scardica from Kastoria; SS1: S. syriaca from Lefka Ori; SS2: S. syriaca from Anopoli Sfakion; SS3: S. syriaca from Omalos. b Tentative identification based on MS, MS2 and literature data for Sideritis species. c not detected.
Table 2. Structures and activities of phenolic compounds identified in 9 samples of Sideritis extracts.
Table 2. Structures and activities of phenolic compounds identified in 9 samples of Sideritis extracts.
CompoundStructureActivityRef.
Verbascoside/
Isoverbascoside		Separations 11 00229 i001anti-inflammatory activity
prevention of red blood cell from free radical damage
tyrosinase and/or melanin production inhibition activity		[22,23,25]
Apigenin-7-O-glucosideSeparations 11 00229 i002antioxidant activity
anti-inflammatory effect
cytotoxicity to cancer cells
promoting apoptosis of cancer cells
anxiolytic effect
memory improvement
neuroprotective effect
protective effect against amyloid-β-neurotoxicity		[25,26]
Isoscutellarein 7-O-[6″-O-acetyl]-allosyl(1→2)-glucosideSeparations 11 00229 i003moderate-to-weak cytotoxicity to cancer cells[25]
Apigenin-7-O-(6″-O-4-cou-maroyl)-beta-glucoside Separations 11 00229 i004antioxidant activity
anti-inflammatory effect
cytotoxicity to cancer cells
promoting apoptosis of cancer cells
anxiolytic effect
memory improvement
neuroprotective effect
protective effect against amyloid-β-neurotoxicity		[25,26]
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Kaparakou, E.H.; Kanakis, C.D.; Kokotou, M.G.; Papadopoulos, G.; Tarantilis, P.A. LC-MS/MS-QTOF Identification of Phenolic Compounds of Sideritis Species Cultivated in Greece. Separations 2024, 11, 229. https://doi.org/10.3390/separations11080229

AMA Style

Kaparakou EH, Kanakis CD, Kokotou MG, Papadopoulos G, Tarantilis PA. LC-MS/MS-QTOF Identification of Phenolic Compounds of Sideritis Species Cultivated in Greece. Separations. 2024; 11(8):229. https://doi.org/10.3390/separations11080229

Chicago/Turabian Style

Kaparakou, Eleftheria H., Charalabos D. Kanakis, Maroula G. Kokotou, Georgios Papadopoulos, and Petros A. Tarantilis. 2024. "LC-MS/MS-QTOF Identification of Phenolic Compounds of Sideritis Species Cultivated in Greece" Separations 11, no. 8: 229. https://doi.org/10.3390/separations11080229

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