Phytochemical Content,In Vitro Antioxidant,and Cholinesterase Inhibitory Activities Determination of Endemic Linaria corifolia Desf

Abstract

Objective: In our study, we researched the chemical composition of Linaria corifolia Desf. We also tested in vitro antioxidant, and anticholinesterase activities of different extracts, and compounds from L. corifolia. Methods: We isolated from ethyl acetate and n-butanol extracts of L. corifolia aerial parts. We used various spectroscopic methods. We also compared the results with data in the literature. This allowed us to determine the structure of the compounds. We used different spectroscopic methods and comparisons with literature data to determine the structure of the compounds. We evaluated the antioxidant activities of 20% aqueous methanol, ethyl acetate, and n-butanol extracts using DPPH, ABTS Radical Scavenging Effect, and CUPRAC Assay, and also examined total phenol and flavonoid contents. We used Ellman's method to find the cholinesterase inhibitor activities of the extracts, and isolated compounds. Results: We isolated 6 compounds in ethyl acetate and n-butanol extracts. These compounds have terpenoid (iridoid glycosides), and phenolics (flavonoid, and phenylpropanoid structures). We isolated linariin and acteoside (verbascoside) from ethyl acetate. We isolated antirrhinoside, 6-ß-Hydroxyantirrhide, catalpol, and aucubin from n-butanol extract. The ethyl acetate extract was most active in all antioxidant methods due to its high phenolic content. In contrast to phenolic content, n-butanol extract had more flavonoids. The ethyl acetate extract had higher acetylcholinesterase inhibitory activity at 200 and 400 μg/ml. Linariin had the highest acetylcholinesterase inhibitory effect among the pure compounds. The extracts and pure compounds inhibited butyrylcholinesterase less than acetylcholinesterase. Conclusion: The isolated compounds are new compounds for the L. corifolia plant. The plant's cholinesterase inhibitor activity was investigated for the first time. We found low anti-acetylcholinesterase and butyrylcholinesterase activities.

Keywords

terpenoids phenolics antioxidant acetylcholinesterase butyrylcholinesterase inhibitory activity

Introduction

The genus Linaria Mill. is a member of the Plantaginaceae family and comprises approximately 200 species worldwide.^1–4 In phytochemical studies on this genus, it has been determined that plants contain compounds such as alkaloids, phenolic compounds [flavonoids, phenylpropanoids, etc], and terpenoids [monoterpenes (iridoids), diterpenes, triterpenes].² It has been reported that Linaria species are used as a wound healer, tonic, antiscorbutic, diuretic, laxative, and in diabetes, hemorrhoids, and vascular diseases.^2,5 In biological activity studies on Linaria species have found that they have antitumor, antiacetylcholinesterase, anti-inflammatory and analgesic, antioxidant, antibacterial, cytotoxic, genotoxic, antidiabetic, and diuretic activities.² There are 21 Linaria species in Türkiye and 12 of them are endemic species.^1,5,6 In this study, the endemic L. corifolia Desf. plant, which has a limited number of phytochemical and biological activity studies, was studied. Based on the biological activity studies conducted on Linaria species, the in vitro cholinesterase inhibitory activities of aqueous-methanol, ethyl acetate, and n-butanol extracts were investigated. Alzheimer's disease is a multifactorial, complex, and worldwide prevalent neurological disease. Inflammation, oxidative stress, cholinergic pathways, genetic, and environmental factors play a role in causing Alzheimer's.^7,8 Senile plaques and amyloid-beta peptide deposition are neuropathological hallmarks of Alzheimer's disease. These symptoms are caused by a decrease in the amount of acetylcholine in the brain, so acetylcholinesterase inhibitors are used in treatment to prevent the hydrolysis of acetylcholine. Cholinesterases are the enzyme family responsible for the hydrolysis of acetylcholine into choline and acetic acid. They consist of 2 types of enzymes: Acetylcholinesterases (AChE) and Butyrylcholinesterases (BChE). AChE are found in peripheral and central tissues, while BChE are found mainly in the liver. The treatment of the disease is symptomatic, and the drugs used have side effects such as gastrointestinal, and hepatotoxicity. Thus, developing natural compounds with fewer side effects is important in treating the disease. In our study, the cholinesterase inhibitory effects of the extracts, and isolated compounds were investigated by in vitro Elmann's method.^9–13 When oxidative stress increases, it degrades nucleic acids, proteins, carbohydrates, and fatty acids. This disrupts the integrity of cell membranes, causing apoptosis or amyloid formation.¹⁴ Since oxidative stress and cholinesterase activities affect each other in neurodegenerative diseases such as Alzheimer's disease,¹⁴ the antioxidant effects of plant extracts have been investigated with different methods. We used DPPH, ABTS Radical Scavenging Effects, and CUPRAC Assay, which are commonly used in the evaluation of antioxidant activity, since this assay have not been used before in the evaluation of the activities of the prepared extracts. Since the phenolic compounds found in plants are responsible for the antioxidant effect, we also researched total phenolic, and total flavonoid content of the extracts. We thoroughly investigated the in vitro anticholinesterase activities of various L. corifolia extracts. Also, we identified the chemical composition in the ethyl acetate and n-butanol extracts of the plant for the first.

Materials and Methods

General Experimental Procedures

For the separation and purification of the substances in fractions, chromatographic methods using filler materials such as normal-phase silica gel, Sephadex and reverse-phase silica gel were used. Spectrometer Bruker-Avance Neo 500 MHz (Germany) was used to get nuclear magnetic resonance spectra. Waters Corporation Milford, MA (USA) was used to record Electrospray ionization mass spectrums.

Plant Material

L. corifolia plant was collected from Ankara, Türkiye in June 2020 in the flowering period, plant was identified by Assoc. Prof. Dr. Dilek Ercil and Asst. Prof. Zekiye Ceren Arıtuluk Aydın. Voucher specimens have been previously deposited in Herbarium of the Faculty of Pharmacy, Hacettepe University, Ankara, Türkiye (HUEF 18001).

Extraction and Isolation Process

Dry aerial parts of L. corifolia (899.22 g) were macerated at room temperature with 20% aqueous methanol for a night. The next day, it was extracted at 40 °C, for 6 h, and the extraction process was repeated 4 times. After filtration, the hydroalcoholic filtrate was concentrated at 40 °C under low pressure and dissolved in distilled water. After the lyophilization process, we obtained 75,77 g of extract, yielding 8,43%. Aqueous solution was successively with petroleum ether, CHCl₃, EtOAc (ethyl acetate), and n-BuOH. We conducted isolation studies on ethyl acetate and n-butanol extracts.

We applied the n-butanol extract to the column. The column was prepared with Silica gel for pre-fractionation. Elution was started with 10% methanol chloroform. Then, it continued with 17,5% and 50% ratios. We obtained fractions from this chromatography system. We put them on Sephadex Column Chromatography (elution system: 100% methanol). It separated the compounds by their molecular weight. Fractions obtained from Sephadex column chromatography were purified by the reverse phase column chromatography method. In last method, methanol:water (10:90, 20:80, 30:70) solvent systems were used for isolation.

We applied the ethyl acetate extract to Sephadex column chromatography using 100% methanol. The resulting fractions were purified using varying ratios of methanol: water (5:95, 10:90, 15:85, 25:75, 30:70, 40:60, 50:50, 60:40, 70:30) solvent systems.

The Supplemental material has detailed info. It covers general experimental procedures, plant material, extraction and isolation processes, and methods for determining biological activity.

Results and Discussion

Compounds Identification

We isolated six compounds from the L. corifolia plant. We identified their structures using NMR, ESI mass spectroscopy methods, and comparisons with literature data. Compounds are antirrhinoside (63,4 mg) [1],¹⁵ 6-ß-Hydroxyantirrhide (8,3 mg) [2],¹⁶ catalpol (24,4 mg) [3],^17,18 and aucubin (6,6 mg) [4]^19,20 from n-butanol extract, linariin (30,9 mg) [5],²¹ and acteoside (verbascoside) (4,3 mg) [6]^22,23 from ethyl acetate extract (Figure 1).

Figure 1.

Isolated compounds 1-6 from L. corifolia.

The iridoid glycoside antirrhinoside is a chemotaxonomic marker in the Linaria genus. Although antirride is widespread in the Linaria, 6-ß-Hydroxyantirrhide was found in Linaria genistifolia, L. japonica, and L. purpurea. Catalpol (in L. macroura) and aucubin (in L. vulgaris, L. macroura) rarely exist in Linaria. Linariin is a flavonoid glycoside common in Linaria species. Acetoside was identified in L. haelava² All compounds are newly isolated from L. corifolia.

Biological Activity Studies

In Vitro Antioxidant Activity

DPPH Radical Scavenging Activity

DPPH (2,2-diphenyl-1-picryl-hydrazyl) radical scavenging effects of extracts were investigated.^24,25 High activity was observed in ethyl acetate extract (83,28% at 400 μg/ml concentration) (Figure 2). The IC₅₀ (μg/ml) values for ethyl acetate, n-butanol extract, and ascorbic acid were calculated as 217,75 ± 12,82, 306,58 ± 23,38, and 16,19 ± 2,62 respectively.

Figure 2.

% Inhibition of DPPH radicals.

ABTS Radical Scavenging Activity

ABTS (2,2′-azinobis(3-ethylbenzothiazolin-6-sulphonic acid) radical scavenging activity determinations of extracts were made at concentrations of 100–800 μg/ml.^26,27 When the ABTS Radical Scavenging effects of extracts were evaluated, a higher effect was found in ethyl acetate extract than in other extracts (Table 1). Results are given as trolox equivalent antioxidant capacity (TEAC).

Table 1.

TEAC (mg TE /g) Extract Amount of Extracts (TE: Trolox Equivalent) in ABTS Radical Scavenging Activity.

Extract	TEAC (mg TE/ g extract)
20% aqueous methanol	45,57 ± 2,16
Ethyl acetat	114,66 ± 10,87
n-butanol	69,68 ± 0,46

Cupric Ion Reducing Antioxidant Capacity (CUPRAC) Assay

Cupric (II) ıon reduction antioxidant capacity of extracts was determined at concentrations of 50–400 μg/ml.^27,28 Similar to the ABTS Radical Scavenging Effect results, the ethyl acetate extract was the most effective (Table 2). Table 3 shows a comparison of all antioxidant activity test results.

Table 2.

TEAC (mg TE /g) Extract Amount of Extracts in CUPRAC Assay.

Extract	TEAC (mg TE/ g extract)
20% aqueous methanol	42,21 ± 0,68
Ethyl acetat	202,50 ± 21,96
n-butanol	99,71 ± 1,09

Table 3.

Antioxidant Activities of Extracts at Different Assay.

	DPPH Radical Scavenging Activity	ABTS Radical Scavenging Activity	CUPRAC Assay
Extract		IC₅₀ (μg/ml)
20% aqueous methanol	>400	>800	>400
Ethyl acetat	217,75 ± 12,82	737,39 ± 9,16	115,13 ± 1,36
n-butanol	306,58 ± 23,38	>800	191,28 ± 2,82

Determination of Total Phenolic Content

Total phenolic content of extracts was performed at a concentration of 400 μg/ml.^29,30 The highest total phenolic content in ethyl acetate extract was observed (Table 4).

Table 4.

Total Phenolic Content of Extracts.

Extract	GAE (mg/g)
20% aqueous methanol	71,06 ± 0,82
Ethyl acetat	106,15 ± 7,34
n-butanol	60,00 ± 9,38

Determination of Total Flavonoid Content

Total flavonoid content of extracts was investigated at a concentration of 200 μg/ml.³¹ The n-butanol extract had more flavonoids than other extracts. The total flavonoid contents of the extracts are given in Table 5.

Table 5.

Total Flavonoid Content of Extracts.

Extract	mg quercetin /g
20% aqueous methanol	2,65 ± 0,68
Ethyl acetat	17,42 ± 3,74
n-butanol	47,29 ± 7,71

In another study, Fe ⁺³/ ferricyanide reduction, DPPH radical, and superoxide scavenging activity were measured for ethanol, ethyl acetate, and dichloromethane extracts of L. corifolia aerial parts. The ethanol extract showed higher effects than the other extracts. When the results of total phenolic content and total flavonoid determination were examined, it was found that the ethanol extract had higher phenolic compound and flavonoid content than other extracts.³² In our study, we found that the ethyl acetate extract (at 400 μg/ml) had 83,28% DPPH radical inhibition. In ABTS Radical Scavenging Activity, and CUPRAC Assay TEAC values respectively;114,66 mg, 202,50 mg TE/g extract. It was more active than other extracts in all antioxidant tests. This was linked to its high phenolic compound content. According to the DPPH Radical Scavenging Activity results, it is seen that ethyl acetate extract (83,28% inhibition) at a concentration of 400 μg/ml has a similar effect to ascorbic acid (93,61% inhibition). After ethyl acetate extract, n-butanol extract had 61,19% DPPH radical inhibition at 400 μg/ml. In ABTS Radical Scavenging Activity, and CUPRAC Assay its TEAC values respectively; 69,68 mg, 99,71 mg TE/g extract. It was moderately effective. The 20% aqueous methanol extract had 19,16% DPPH radical inhibition at 400 μg/ml. In ABTS Radical Scavenging Activity, and CUPRAC Assay, its TEAC values respectively; 45,57 mg, 42,21 mg TE/g extract. It was low effective. It has been determined that ethyl acetate and n-butanol extracts have more power to reduce cupric (II) ions. But, they have less power to scavenge ABTS radicals.

In Vitro Anticholinesterase Activity

Extracts and isolated compounds of L. corifolia were investigated for their inhibition effects of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes (Figures 3, 4, 5, and 6).^9,12,33,34 Physostigmine salicylate was used as a standard compound. It had IC₅₀ 1,17 ± 0,18 for AChE and 9,13 ± 0,06 μg/ml for BChE. % Inhibition AChE and BChE values of the standard compound are given in Table 6.

Figure 3.

% Inhibition AChE of extracts.

Figure 4.

% Inhibition BChE of extracts.

Figure 5.

% Inhibition AChE of isolated compounds.

Figure 6.

% Inhibition BChE of isolated compounds (The inhibition value of 6-ß-hydroxyantrirrhide compound at 100 μg/ml could not be calculated.).

Table 6.

% Inhibition AChE and BChE of Physostigmine Salicylate (*:It has not Been Tested at Relevant Concentrations.).

Concentration (μg/ml)	% AChE Inhibition	% BChE Inhibition
1	44,47 ± 0,37	16,12 ± 1,69
2	62,27 ± 2,16	16,12 ± 0,54
2,5	68,59 ± 1,51	28,62 ± 0,25
5	77,80 ± 0,91	34,14 ± 1,01
10	83,60 ± 0,78	52,58 ± 0,47
20	84,94 ± 2,65	73,30 ± 0,34
25	95,80 ± 0,14	*
40	*	89,38 ± 0,14

In cholinesterase inhibitor effect studies conducted on Linaria species, L. reflexa ethyl acetate extract (IC₅₀: 185,6 ± 1,2 µg/mL), a high effect was determined in the isolated linariin, isolinariin A and B compounds, and a lower effect was observed in the linariin (IC₅₀: 0,30 ± 0,05 μM).³⁵ In another study, L. scariosa butanol extract was found to have high acetylcholinesterase inhibitory effect (IC₅₀: 75,47 ± 3,5 µg/mL). It was thought that butanol extract may have high activity because it contains the compound pectolinarin. It was concluded that the extracts may be active due to their flavonoid content.^35,36

Various studies have shown that catalpol does not have an AChE inhibitory effect, and in animal models, it has been shown that it can increase memory and learning by decreasing the M receptor (brain muscarinic acetylcholine receptor), increasing BDNF receptor density, and reducing cholinergic degeneration. In the study examining the effect of catalpol on female mice with neurodegenerative damage, catalpol was administered at concentrations of 5, 15, and 45 mg/kg for 3 months. It has been observed that catalpol strongly increases BDNF expression, memory, and learning ability.³⁷ It is thought that the catalpol compound, which has antioxidant, anti-inflammatory, and anti-apoptotic effects in in vitro and in vivo studies, may be effective in Alzheimer's disease with its neuroprotective effect.³⁸ In the study catalpol, aucubin, acteoside, and other compounds from Verbascum mucranatum Lam. AChE and BChE inhibitory effects were tested, The acteoside compound had a medium AChE inhibitory effect. But, the catalpol, and aucubin were not effective.³⁹

When our experimental results were evaluated; an increase was viewed in the acetylcholinesterase inhibitor activity of n-butanol extract concentration-dependent. Iridoid compounds isolated from n-butanol extract, such as the compound catalpol, which has been found effective in various studies, may be the compounds responsible for the activity of n-butanol extract. However, ethyl acetate extract was determined more active than other extracts at 200 and 400 μg/ml. It has been reported that flavonoids and iridoids may be effective for neurodegenerative diseases such as Alzheimer's due to their neuroprotective and healing effects.^2,36,40 In our study, it is thought that the acetylcholinesterase inhibitory effect of ethyl acetate extract (at 200, and 400 µg/mL) may be due to the phenolic compounds it contains and other flavonoids found together with the isolated linariin, acteoside compound.

When the % Inhibition values of pure compounds were compared, linariin was found to be more effective. Among the iridoid compounds, the catalpol compound was more effective than other iridoids at 25 and 100 μg/ml (33,87 ± 1,94, 26,49 ± 8,62%, respectively). A higher butyrylcholinesterase inhibitory effect was observed in dichloromethane extract of L. scariosa (IC₅₀: 96,02 ± 0,69 µg/mL). Fatty acids such as α-linolenic and palmitic acid have been held responsible for the high butyrylcholinesterase inhibitory effect of the extract.³⁶ Butyrylcholinesterase inhibitory activities of the extracts and isolated compounds are generally low compared to the acetylcholinesterase inhibitory activity. Since the extracts contain mostly polar compounds, it can be said that butyrylcholinesterase activities are low. The cholinesterase inhibitory effects of the extracts and pure compounds were found to be lower compared to physostigmine salicylate.

Detailed information is also available in the supplemental material.

Limitations of Study

Although the ethyl acetate extract contained a large number of substances in our isolation studies, structure determinations could not be carried out because the amounts of the substances obtained were very small. Again, the n-butanol extract contained flavonoids. But, they could not be obtained in pure form despite the using different chromatographic methods. The amounts of aucubin and acteoside compounds were too low. So, we could not evaluate their cholinesterase inhibitory effects. The in vivo effects of antirrhinoside and 6-ß-Hydroxyantirrhide compounds, whose cholinesterase inhibitory effects have not been studied before, can be investigated. The in vivo effects of these compounds can be evaluated together with the in vitro effect results.

Conclusions

In our study, we report for the first time different antioxidant, anticholinesterase activities of L. corifolia extracts. We also report isolation of pure metabolites of ethyl acetat, and n-butanol extracts. Six compounds were isolated from the L. corifolia plant and their structures were identified through NMR, ESI mass spectroscopy methods, and comparisons with literature data. Antirrhinoside, 6-ß-Hydroxyantirrhide, catalpol, aucubin, linariin, and acteoside (verbascoside) compounds are new compounds for the L. corifolia. It has been determined that L. corifolia contains iridoid glycosides, flavonoids, and phenylpropanoids, similar to other Linaria species. As a result of antioxidant activity studies, ethyl acetate extract was found to be more effective extract than other extract due to its high phenolic content. Compared to physostigmine salicylate, all extracts, and pure compounds have lower acetylcholinesterase and butyrylcholinesterase inhibitory activity. However, higher antiacetylcholinesterase activity was observed at concentrations of 200 and 400 μg/ml, depending on the active components of the ethyl acetate extract. Among pure compounds, linariin appears to be more active than other compounds.

Supplemental Material

sj-docx-1-npx-10.1177_1934578X241272734 - Supplemental material for Phytochemical Content, In Vitro Antioxidant, and Cholinesterase Inhibitory Activities Determination of Endemic Linaria corifolia Desf

Supplemental material, sj-docx-1-npx-10.1177_1934578X241272734 for Phytochemical Content, In Vitro Antioxidant, and Cholinesterase Inhibitory Activities Determination of Endemic Linaria corifolia Desf by Melike Utlu and Dilek Ercil in Natural Product Communications

Footnotes

Acknowledgments

We thank Prof. Dr. Hakan Göker (Ankara University, Pharmacy Faculty, Department of Pharmaceutical Chemistry) for performing our NMR analyses.

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

This study was supported by Hacettepe University Scientific Research Projects Coordination Unit (Project No: THD-2021-19442).

Ethical Approval

Ethical approval is not applicable for this article.

ORCID iD

Melike Utlu

Statement of Human and Animal Rights

This article does not contain any studies with human or animal subjects.

Statement of Informed Consent

There are no human subjects in this article and informed consent is not applicable.

Supplemental material

Supplemental material for this article is available online.

References

Davis

. Linaria Miller. In: Davis

, ed. Flora of Turkey and the East Aegean Islands. Edinburgh University Press; 1978:654-672.

Cheriet

Mancini

Seghiri

, et al. Chemical constituents and biological activities of the genus Linaria (Scrophulariaceae). Nat Prod Res. 2015;29:1589-1613.

Albach

Meudt

Oxelman

. Piecing together the “new” Plantaginaceae. Am J Bot. 2005;92:297-315.

Yousefi

Zarre

Heubl

. Molecular phylogeny of the mainly Mediterranean genera Chaenorhinum, Kickxia and Nanorrhinum (Plantaginaceae, tribe Antirrhineae), with focus on taxa in the Flora Iranica region. Nord J Bot. 2016;34:455-463.

Akkol

Ercil

. Antinociceptive and anti-inflammatory activities of some Linaria species from Turkey. Pharm Biol. 2009;47:188-194.

Linaria türleri [Internet]. 2012 [3.10.23]. https://www.bizimbitkiler.org.tr/list.html

Gajendra

Pratap

Poornima

Manjula

Ranjita

. Natural acetylcholinesterase inhibitors: A multi-targeted therapeutic potential in Alzheimer's disease. Eur J Med Chem Rep. 2024;11:1-16. doi: https://doi.org/10.1016/j.ejmcr.2024.100154

Shal

Ding

Ali

Kim

Khan

. Anti-neuroinflammatory potential of natural products in attenuation of Alzheimer's disease. Front Pharmacol. 2018;9:548. doi: https://doi.org/10.3389/fphar.2018.00548

Amir Rawa

Hassan

Murugaiyah

, et al. Anti-cholinesterase potential of diverse botanical families from Malaysia: evaluation of crude extracts and fractions from liquid-liquid extraction and acid-base fractionation. J Ethnopharmacol. 2019;245:112160. doi: https://doi.org/10.1016/j.jep.2019.112160

10.

Zaluski

Kuzniewski

. In vitro Anti-AChE, Anti-BuChE, and antioxidant activity of 12 Extracts of Eleutherococcus species. Oxid Med Cell Longev. 2016;4135135:1-7. doi: https://doi.org/10.1155/2016/4135135

11.

Azizi

Mirshafiey

. The potential role of proinflammatory and antiinflammatory cytokines in Alzheimer disease pathogenesis. Immunopharmacol Immunotoxicol. 2012;34:881-895. doi: https://doi.org/10.3109/08923973.2012.705292

12.

Aissani

Grara

Bensouici

, et al. Algerian Sonchus oleraceus L.: a comparison of different extraction solvent on phytochemical composition, antioxidant properties and anti-cholinesterase activity. Advances in Traditional Medicine. 2021;22(2):383-394. doi:https://doi.org/10.1007/s13596-021-00553-y

13.

Colovic

Krstic

Lazarevic-Pasti

Bondzic

Vasic

. Acetylcholinesterase inhibitors: pharmacology and toxicology. Curr Neuropharmacol. 2013;11(3):315-335. doi: https://doi.org/10.2174/1570159(11311030006

14.

Osunsanmi

Zharare

Mosa

Ikhile

Shode

Opoku

. Anti-oxidant, anti-inflammatory and anti-acetylcholinesterase activity of betulinic acid and 3β-acetoxybetulinic acid from ‘Revolution Gold’. Trop J Pharm Res. 2019;18:303-309. doi: https://doi.org/10.4314/tjpr.v18i2.12

15.

Ercil

Sakar

. Chemical constituents of Linaria aucheri. Turk J Chem. 2004;28:133-139.

16.

Handjieva

Ilieva

Spassov

Popov

. Iridoid glycosides from Linaria species. Tetrahedron. 1993;49(41):9261-9266. doi: https://doi.org/10.1016/0040-4020(93)80012-I

17.

Arslanian

Anderson

Stermitz

. Iridoid glucosides of Penstemon ambiguus. J Nat Prod. 1990;53(6):1485-1489. doi: https://doi.org/10.1021/np50072a013

18.

Tatlı

Akdemir

ZŞ

Bedir

Khan

. 6-O-α-L-Rhamnopyranosylcatalpol Derivative iridoids from Verbascum cilicicum. Turk J Chem. 2003;27:765-772.

19.

Chaudhuri

Salama

Sticher

. Iridoid and aryl glucosides from Globularia nudicaulis and Globularia nana. Helv Chim Acta. 1981;64(7):2401-2404. doi: https://doi.org/10.1002/hlca.19810640748

20.

Chu

Tan

Zhang

. Chemical constituents from Pedicularis rex C.B. Clarke. Z Naturforsch. 2007;62b:1465-1470. doi: https://doi.org/10.1515/znb-2007-1117

21.

Otsuka

. Iridolinarins A, B, and C:iridoid esters of an iridoid glucoside from Linaria japonica. J Nat Prod. 1994;57(3):357-362. doi: https://doi.org/10.1021/np50105a004

22.

Genc

Harput

Saracoglu

. Active compounds isolated from Plantago subulata L. via wound healing and antiinflammatory activity guided studies. J Ethnopharmacol. 2019;241(112030):1-9. doi:https://doi.org/10.1016/j.jep.2019.112030

23.

Geng

Yang

Chou

Wang

. Bioguided isolation of angiotensin-converting enzyme inhibitors from the seeds of Plantago asiatica L. Phytother Res. 2010;24(7):1088-1094. doi:https://doi.org/10.1002/ptr.3071

24.

Jensen

Gotfredsen

Harput

Saracoglu

. Chlorinated iridoid glucosides from Veronica longifolia and their antioxidant activity. J Nat Prod. 2010;73:1593-1596. doi: https://doi.org/10.1021/np100366k

25.

Odekina

Agbo

Omeje

. Antimicrobial and antioxidant activities of novel marine bacteria (Bacillus 2011SOCCUF3) isolated from marine sponge (Spongia officinalis). Pharm Sci. 2020;26:82-87. doi: https://doi.org/10.34172/ps.2019.59

26.

Pellegrini

Proteggente

Pannala

Yang

Rıce-Evans

. Antioxidant activity applying an improved ABTS radical cation decolorization assay. Free Radic Biol Med. 1999;26:1231-1237. doi: https://doi.org/10.1016/s0891-5849(98)00315-3

27.

Arıtuluk

Tatlı

Gençler-Özkan

. Antioxidant activity, total phenolic and flavonoid contents of some Tanacetum L. (Asteraceae) Taxa growing in Turkey. Fabad J Pharm Sci. 2016;41:17-25.

28.

Apak

Güçlü

Özyürek

Karademir

. Novel total antioxidant capacity index for dietary polyphenols and vitamins C and E, using their cupric ion reducing capability in the presence of neocuproine: CUPRAC Method. J Agric Food Chem. 2004;52:7970-7981. doi: https://doi.org/10.1021/jf048741x

29.

Domınguez

Nieto

Marin

Keck

A-S

Jeffery

Cespedes

. Antioxidant activities of extracts from Barkleyanthus salicifolius (Asteraceae) and Penstemon gentianoides (Scrophulariaceae). J Agric Food Chem. 2005;53:5889-5895. doi: https://doi.org/10.1021/jf0504972

30.

Freitas

Nelson

Canelo

Nave

, et al. In vitro antioxidant activity and total phenolic content of root extracts from Phragmanthera glaucocarpa (Peyr.) Balle. Jundishapur J Nat Pharml Prod. 2018;13:1-7. doi: https://doi.org/10.5812/jjnpp.622388

31.

Anh

Luyen

Thom

Huong

. Inhibitory effect on human platelet aggregation, antioxidant activity, and phytochemicals of Canna warszewiczii (A. Dietr) Nb. tanaka. Pharmacognosy Res. 2020;12:47-52. doi:https://doi.org/10.4103/pr.pr_72_19

32.

Gul

Ozturk Cali

Cansaran

, et al. Evaluation of phytochemical content, antioxidant, antimicrobial activity and DNA cleavage effect of endemic Linaria corifolia Desf. (Plantaginaceae). Cogent Chem. 2017;3:1-14. doi: https://doi.org/10.1080/23312009.2017.1337293

33.

Komersova

Komers

Cegan

. New findings about Ellman’s Method to determine cholinesterase activity. Z Naturforsch. 2007;62:150-154. doi:https://doi.org/10.1515/znc-2007-1-225

34.

Dingova

Leroy

Check

Garaj

Krejci

Hrabovska

. Optimal detection of cholinesterase activity in biological samples: modifications to the standard Ellman's assay. Anal Biochem. 2014;462:67-75. doi:https://doi.org/10.1016/j.ab.2014.05.031

35.

Loizzo

Tundis

Menichini

, et al. Acetyl-cholinesterase inhibition by extracts and isolated flavones from Linaria reflexa Desf. (Scrophulariaceae). Nat Prod Commun. 2007;2:759-763. doi: https://doi.org/10.1177/1934578X0700200

36.

Ahmed-Chaouch

Cheriet

Beretta

, et al. Chemical composition, in vitro antioxidant, anticholinesterase and antibacterial activities of Linaria scariosa Desf. Nat Prod Res. 2019;35(10):1-5.

37.

Xia

Zhang

Xia

. Memory defect induced by beta-amyloid plus glutamate receptor agonist is alleviated by catalpol and donepezil through different mechanisms. Brain Res. 2012;1441:27-37. doi: https://doi.org/10.1016/j.brainres.2012.01.008

38.

Chen

Deng

Meng

. Effects of catalpol on Alzheimer's disease and its mechanisms. Evid Based Complement Alternat Med. 2022;2022:1-12. doi: https://doi.org/10.1155/2022/2794243

39.

Kahraman

Tatlı

Orhan

Akdemir

. Cholinesterase inhibitory and antioxidant properties of Verbascum mucronatum lam. and its secondary metabolites. Zeitschrift fur Aturforschung Section C-A Journal of Biosciences. 2010;65:667-674. doi: https://doi.org/10.1515/znc-2010-11-1206

40.

Dinda

Kulsi

Chakraborty

Dinda

. Therapeutic potentials of plant iridoids in Alzheimer's and Parkinson's diseases: a review. Eur J Med Chem. 2019;169:185-199. doi:https://doi.org/10.1016/j.ejmech.2019.03.009

Supplementary Material

Please find the following supplemental material available below.

For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.

For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.

0.00 MB

0.10 MB