Phytochem Rev (2017) 16:295–308 DOI 10.1007/s11101-016-9474-0

The chemistry and pharmacology of Edelweiss: a review

Jan Tauchen . Ladislav Kokoska

Received: 11 February 2016 / Accepted: 11 July 2016 / Published online: 15 July 2016 Ó Springer Science+Business Media Dordrecht 2016

Abstract Leontopodium nivale ssp. alpinum (syn. preparations and isolated compounds of Edelweiss Leontopodium alpinum) is a perennial herb commonly support the view that these might be used in the known as Edelweiss, which has a long tradition in development of agents with therapeutic benefit in Alpine countries and adjacent regions as a medicinal various human diseases. Some suggestions for further plant. This review discusses current knowledge on the research on chemical characterization and pharmaco- traditional uses, chemistry, biological activities and logical properties are also given in this review. toxicology of this species. Several different classes of compounds such as terpenoids (analogues of Keywords Asteraceae Á Leontopodium alpinum Á sesquiterpenes, bisabolenes), phenylpropanoids (phe- Leontopodium nivale Á Medicinal plant Á Secondary nolic acids, flavonoids, coumarins, lignans), fatty metabolites acids and polyacetylenes were previously isolated from various parts of Edelweiss. Different types of extracts and compounds derived from this plant have been found to possess a broad spectrum of pharma- Introduction cological activities on the cardiovascular and nervous systems. Furthermore, the plant have known anti- Leontopodium nivale ssp. alpinum (Cass.) Greuter inflammatory, antimicrobial, antioxidant and chemo- (family Asteraceae), commonly known as Edelweiss, protective effects. The observed pharmacological is a perennial heliophytic herb growing up to 20 cm activities as well as toxicological profile of high (Fig. 1) native to the Pyrenees, the European Alps, the Tatra and the Balkan Mountains, where it naturally occurs on limy soils, stony meadows and J. Tauchen even on rocks. It is usually found between 1000 and The Department of Quality of Agricultural Products, The 3400 m above sea level (Maugini 1962; Sugar 1971; Faculty of Agrobiology, Food and Natural Resources, The Siljak et al. 1974; Erhardt 1993;Ho¨randl et al. 2011; Czech University of Life Sciences Prague, Kamycka 129, Neblea et al. 2012; Khela 2013; Finkenzeller 2014). 165 21 Prague 6 – Suchdol, The Czech Republic The centre of diversity of the genus Leontopodium is L. Kokoska (&) located in Asia, comprising 41 species including some The Department of Crop Sciences and Agroforestry, The presumed hybrids. Only one species is native to Faculty of Tropical AgriSciences, The Czech University Europe: L. nivale (Ten.) Huet ex Hand.-Mazz (Handl- of Life Sciences Prague, Kamycka 129, 165 21 Prague 6 – Suchdol, The Czech Republic Mazzetti 1928; Lee et al. 2011; Safer et al. 2011a, b). e-mail: [email protected] So far, the relationship between L. nivale and L. 123 296 Phytochem Rev (2017) 16:295–308

applied as a compress (especially in the treatment of breast cancer) (Tabernaemontanus 1993; Dobner et al. 2003b). Today, extracts of the aerial parts of Edel- weiss are used for their antioxidant properties in cosmetic preparations such as sunscreen products (Schwaiger et al. 2005, 2006). Due to intensive collection from its natural habitats for various human needs, populations of this plant have significantly declined. The species is nowadays regarded as rare, however it is listed as Least Concern (LC) in the IUCN Red List of Threatened Species (Khela 2013). The collection of wild individuals of Edelweiss is currently forbidden by law in many countries (Blascakova et al. 2011; Keller and Vittoz 2015), hence the main bulk of its production comes from successful cultivation in Switzerland (Schwaiger et al. 2005, 2006). Besides which, Edelweiss has demonstrated promising results when propagated via cell tissue culture techniques, facilitating even more the commercial availability of this plant for industrial Fig. 1 Flowering individual of Edelweiss (Leontopodium uses (e.g. cosmetics, pharmacology) (Hook 1993; nivale ssp. alpinum (Cass.) Greuter). Photograph by courtesy Trejgell and Tretyn 2010). of Thomas Lichtenberg Because of its wide popularity, well-documented ethno-medicinal uses and scientifically confirmed pharmacological properties, Edelweiss has evoked alpinum has not been entirely resolved. Some authors renewed interest as a promising source material for the treat these as separate species (Blo¨ch et al. 2010), development of plant-derived drugs which might be while others recognize just one species with two used in clinical practice in the treatment of various subspecies (L. nivale ssp. nivale and L. nivale ssp. human diseases. alpinum, respectively) (Greuter 2003). The literature now contains an unfortunate combination of the approaches to two nomenclature, though the original Chemical composition name L. alpinum is most often employed. Edelweiss is a very important part of the cultural In a period of almost 50 years, several different classes heritage for people living in its native areas. This fact of secondary metabolites were isolated from various can be illustrated by various reports of its traditional plant parts of Edelweiss, with the main group being uses in folk medicine (Matthioli 1931). Extracts of terpenoids, phenylpropanoid derivatives and various different plant parts of Edelweiss were applied in the aliphatic compounds. A list of known Edelweiss treatment of several human and livestock diseases for constituents, including plant part(s) where particular conditions such as abdominal disorders, angina pec- compounds were detected is given in Table 1. toris and other heart diseases, bronchitis, diarrhoea, One of the first phytochemical investigations deal- dysentery, fever, pneumonitis, rheumatic pain, tonsil- ing with the terpenoid compounds of Edelweiss litis, and various types of cancers (Tabernaemontanus revealed that the roots are comprised of approximately 1993; Stuppner et al. 2002; Dobner et al. 2003a, b; 0.6–2 % essential oil, containing more than 30 com- Speroni et al. 2006; Hornick et al. 2008; Daniela et al. pounds, of which 20 were detected in concentrations 2012). Historical literature records Edelweiss being above 1 % with 2 compounds representing nearly applied either orally—i.e. the herb was boiled in wine 60 % of the oil (Bicchi et al. 1975; Comey et al. 1992a; and mixed with milk; or topically, where the material Hook 1994). Further detailed investigation into this was boiled in water and the extract so acquired was essential oil, as obtained by steam distillation from 123 Phytochem Rev (2017) 16:295–308 297

Table 1 Secondary metabolites of Edelweiss (Leontopodium nivale ssp. alpinum (Cass.) Greuter) Structure Compound* Plant part(s)a References number

Terpenoids 1 isocomene Hairy root cultures, roots Grey et al. (1999), Hornick et al. (2008) 2 14-acetoxyisocomene Hairy root cultures, roots Grey et al. (1999), Hornick et al. (2008) 3 methyl isocomen-14-oate Hairy root cultures, roots (Grey et al. 1999) 4 b-isocomene Roots Schwaiger et al. (2002), Dobner et al. (2003b), Hornick et al. (2008) 5 silphinene Roots Schwaiger et al. (2002), Dobner et al. (2003b), Hornick et al. (2008) 6 silphiperfolene acetate Roots Schwaiger et al. (2002), Dobner et al. (2003b), Hornick et al. (2008) 7 modhephene Hairy root cultures, roots Grey et al. (1999), Schwaiger et al. (2002), Dobner et al. (2003b), Hornick et al. (2008) 8 15-acetoxymodhephene Hairy root cultures, roots Grey et al. (1999), Dobner et al. (2003a), Hornick et al. (2008) 9 6-acetoxy-3(15),7(14)-caryo-phylladiene Hairy root cultures, roots Grey et al. (1999) 10 T-cadinol (cedrelanol) Roots Schwaiger et al. (2004) 11 (1R*,3S*,4R*,6S*)-4,9-bis(acetoxy)-1- Roots Stuppner et al. (2002) [(2Z)-2-methylbut-2-enoyloxy]bisabol- 10(11)-eneb 12 (1R*,4S*,6R*)-4,9-bis(acetoxy)-1-[(2Z)- Roots Stuppner et al. (2002) 2-methylbut-2-enoyloxy]bisabol- 2(3),10(11)-dienec 13 (1R*,4R*,5R,6R*)-1,4,5-tris(acetoxy)-9- Roots Stuppner et al. (2002) [(2Z)-2-methylbut-2-enoyloxy]bisabol- 2(3),10(11)-diened 14 (1R*,3S*,4R*,6S*)-9-(acetoxy)-4- Roots Schwaiger et al. (2004) hydroxy-1-[(2Z)-2-methylbut-2- enoyloxy]bisabol-10(11)-ene 15 sitosterol Cell suspension cultures, roots and Hennessy et al. (1989) leaves obtained by micropropagation 16 ent-kaur-16-en-19-oate Roots Schwaiger et al. (2004) 17 methyl ent-7a,9a-dihydroxy-15b-[(2Z)-2- Roots Schwaiger et al. (2004) methyl-but-2-enoyloxy]kaur-16-en-19- oate Phenylpropanoid derivatives 18 luteolin Aerial parts Tira et al. (1970), Schwaiger et al. (2006) 19 apigenin Aerial parts Schwaiger et al. (2006)

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Table 1 continued Structure Compound* Plant part(s)a References number

20 luteolin-7,40-di-O-b-D-glucoside Aerial parts Schwaiger et al. (2006) 21 luteolin-7-O-b-D-glucoside Aerial parts Tira et al. (1970), Schwaiger et al. (2006) 22 luteolin-40-O-b-D-glucoside Aerial parts Tira et al. (1970), Schwaiger et al. (2006) 23 luteolin-30-O-b-D-glucoside Aerial parts Schwaiger et al. (2006) 24 6-hydroxy-luteolin-7-O-b-D-glucoside Aerial parts Schwaiger et al. (2006) 25 quercetin-3-O-b-D-glucoside Aerial parts Schwaiger et al. (2006) 26 apigenin-7-O-b-D-glucoside Aerial parts Schwaiger et al. (2006) 27 chrysoeriol-7-O-b-D-glucoside Aerial parts Schwaiger et al. (2006) 28 (S)-2,6-dimethylchroman-4-one Hairy root cultures, roots Comey et al. (1997) 29 1-{(2R*,3S*)-2-[1- Roots Dobner et al. (2003a) (hydroxymethyl)vinyl]-3-[b-D- glucosyloxy]-2,3-dihydro-1-benzofuran- 5-yl}-ethanone 30 obliquin Roots Dobner et al. (2003a) 31 5-hydroxyobliquin Roots Dobner et al. (2003a) 32 5-methoxyobliquin Roots Dobner et al. (2003a) 33 chlorogenic acid Cell suspension cultures, roots and Hennessy et al. (1989), Schwaiger leaves obtained by et al. (2006) micropropagation, roots, aerial parts 34 3,4-di-O-caffeoylquinic acid Cell suspension cultures, roots and Hennessy et al. (1989) leaves obtained by micropropagation 35 3,5-di-O-caffeoylquinic acid Aerial parts Schwaiger et al. (2006) 36 leontopodic acid Aerial parts Schwaiger et al. (2005) 37 leontopodic acid B Aerial parts Schwaiger et al. (2006), Cicek et al. (2012) 38 leoligine Hairy root cultures, roots Dobner et al. (2003a), Reisinger et al. (2009), Wawrosch et al. (2014) 39 5-methoxyleoliginf Hairy root cultures, roots Schwaiger et al. (2004), Wawrosch et al. (2014) 40 5,50-dimethoxyleoliging Roots Schwaiger et al. (2004) Aliphatic compounds 41 linoleic acid Aerial parts Schwaiger et al. (2002), Dobner et al. (2003b)

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Table 1 continued Structure Compound* Plant part(s)a References number

42 linolenic acid Aerial parts Schwaiger et al. (2002), Dobner et al. (2003b) 43 1-acetoxy-3-angeloyloxy-(4E,6E)- Roots Schwaiger et al. (2004) tetradeca-4,6-diene-8,10,12-triyne 44 1-acetoxy-3-angeloyloxy-(4E,6Z)- Roots Schwaiger et al. (2004) tetradeca-4,6-diene-8,10,12-triyne * Synonymous names a Aerial parts and roots refer to plant material obtained from field-cultivated sources b (1R*,2S*,4R*,5S*)-4-(acetyloxy)-2-[3-(acetyloxy)-1,5-dimethylhex-4-enyl]-5-methylcyclohexyl (2Z)-2-methylbut-2-enoate c (1R*,4S*,6R*)-4-(acetyloxy)-6-[3-(acetyloxy)-1,5-dimethylhex-4-enyl]-3-methylcyclohex-2-en-1-yl (2Z)-2-methylbut-2-enoate d 3-methyl-1-{2-[(1R*,2R*,5R*,6S*)-2,5,6-tris(acetyloxy)-4-methylcyclohex-3-en-1-yl]propyl}but-2-enyl (2Z)-2-methylbut-2- enoate e [(2S,3R,4R)-4-(3,4-dimethoxybenzyl)-2-(3,4-dimethoxyphenyl)tetrahydrofuran-3-yl]methyl (2Z)-2-methylbut-2-enoate) f {[(2S,3R,4R)-4-(3,4-dimethoxybenzyl)-2-(3,4,5-trimethoxyphenyl)-tetrahydrofuran-3-yl]-methyl-(2Z)-2-methylbut-2-enoate)} g {[(2S,3R,4R)-4-(3,4,5-trimethoxybenzyl)-2-(3,4,5-trimethoxyphenyl)-tetrahydrofuran-3-yl]-methyl-(2Z)-2-methylbut-2-enoate} hairy root cultures and the underground parts of plants apigenin, chrysoeriol, luteolin and quercetin (18–27) grown under field conditions, has discovered the were detected in the aerial parts (Tira et al. 1970; presence of various sesquiterpenoids, particularly Schwaiger et al. 2006; Fischer et al. 2011; Ganzera isocomene (1), its two analogues 14-acetoxyiso- et al. 2012). Comey et al. (1997) isolated (S)-2,6- comene (2) and methyl isocomen-14-oate (3), mod- dimethylchroman-4-one (28) from the steam distilled hephene (7), its derivative 15-acetoxymodhephene (8) essential oil acquired from hairy root cultures and the and one caryophyllene derivative 6-acetoxy- roots of field-cultivated plants. Beside the above- 3(15),7(14)-caryo-phylladiene (9) (Grey et al. 1999; mentioned flavonoid-related compounds, Edelweiss Hornick et al. 2008). More recently, compounds was also found to produce various derivatives of related to isocomene and modhephene structures were phenolic acids. A study by Hennessy et al. (1989) found in roots of field-cultivated plants: b-isocomene reported the isolation of chlorogenic (33) and 3,4-di- (4), silphinene (5) and silphiperfolene acetate (6) O-caffeoylquinic (34) acids from cell suspension (Schwaiger et al. 2002; Dobner et al. 2003a; Hornick cultures and leaves and roots produced by microprop- et al. 2008). Additional research has revealed the agation. Afterwards, chlorogenic acid and its analogue presence of other sesquiterpene-derived constituents 3,5-di-O-caffeoylquinic acid (35), together with other such as T-cadinol (syn. cedrelanol; 10) and various phenolic acids, leontopodic acid (36) and leontopodic analogues of bisabolene (11–14) in the roots of plants acid B (37), were discovered in the aerial parts of grown under field conditions (Stuppner et al. 2002; plants obtained from cultivated sources (Schwaiger Schwaiger et al. 2004). Only one steroidal structure, et al. 2006; Cicek et al. 2012; Ganzera et al. 2012). sitosterol (15), was detected in Edelweiss so far; Leoligin (38), a lignan, was firstly isolated from the however only in plants produced by various in vitro roots of Edelweiss by Dobner et al. (2003a). The methods (Hennessy et al. 1989). Schwaiger et al. presence of lelogin in the underground parts was later (2004) have found two derivatives of ent-kaurenoic also confirmed by other studies (Reisinger et al. 2009). acids (16, 17) in the roots. The structures of the The analogues of leoligin 5-methoxyleoligin and 5,50- terpenoid and steroidal compounds are given in Fig. 2. dimethoxylelogin (39 and 40, respectively) have been With regard to phenylpropanoid derivatives, sev- detected in hairy root cultures as well as in the roots of eral authors have demonstrated the presence of various field-cultivated plants (Schwaiger et al. 2004; phenolic acids, flavonoids, coumarins and lignans in Wawrosch et al. 2014). Several coumarins, e.g. Edelweiss. Different analogues of the flavonoids obliquin (30) and its 5-hydroxy- and 5-methoxy-

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O OMe O O

1 3 2

O O 4 5 6

O O

O O

7 8 9

O

O O H O

O H OH 10 O

11

O O

OH O O O O O O

O O O O

O O O

O O O

14 12 13

O

H H O HO H H HO H HH HO O MeO O 16 17 HO 15

Fig. 2 Structures of terpenoid compounds of Edelweiss (Leontopodium nivale ssp. alpinum (Cass.) Greuter)

123 Phytochem Rev (2017) 16:295–308 301 derivatives (31 and 32, respectively) and one benzo- and 70 % aqueous methanol) in mice with Croton oil- furan (29) (Dobner et al. 2003a) have been detected in induced ear dermatitis. It was observed that topically the sub-aerial parts. Several of the above-mentioned administered dichloromethane extracts induced the constituents, such as leoligin and the leontopodic acids most significant dose-dependent oedema reduction. were first described in Edelweiss and were named after Noticeably, samples from the aerial parts were more the species. The structures of the phenylpropanoid active in comparison with the root samples 2 derivatives are shown in Fig. 3. (ID50 = 221 and 338 lg/cm , respectively). The Various aliphatic compounds such as linoleic (41) authors suggested that fatty acids might perhaps be and linolenic acids (42) (Dobner et al. 2003a), responsible for the detected anti-inflammatory effect polyacetylene (43) and its (6Z)-analogue (44) (Sch- of dichloromethane extracts of the aerial parts, whilst waiger et al. 2004) (Fig. 4) were isolated from bisabolene, tricyclic sesquiterpenes, coumarins and Edelweiss as well. Polyacetylenes were principally lignans were presumably involved in the activity of the detected in the roots, whereas the above-mentioned root extract. fatty acids were present in the aerial parts. Concerning In another in vivo study, dichloromethane, metha- the other compounds, there are several reports of nol and supercritical CO2 extracts of the root and aerial anthocyanins also being present in Edelweiss. parts of Edelweiss exhibited promising anti-inflam- Nonetheless, only scarce information is available matory results in a rat paw oedema assay. In this case,

(Comey et al. 1992b; Hook 1994). Further investiga- oral pre-treatment of dichloromethane and CO2 tion of Edelweiss anthocyanins, and other classes of extracts (200 mg/kg) of the aerial parts led to a compounds (including those so far not discovered) significant reduction (by 80 %) of the swelling, and could further provide interesting information on the the efficacy was comparable to that of indomethacin chemistry and pharmacology of this species. (Speroni et al. 2006). Likewise, in a study by Dobner et al. (2004), extract of the aerial parts demonstrated higher activity in the comparison to the root extract. Biological activities Based on these parallel findings, it has been suggested that fatty acids might be responsible for the observed Anti-inflammatory properties anti-oedema activity of the aerial parts. On the other hand, diverse terpenes, lignans, coumarins, and ben- One of the first in vitro studies of the anti-inflamma- zofuran derivatives seem to be the active principles of tory activity of Edelweiss was conducted by Sch- the root extract (Speroni et al. 2006). waiger et al. (2004), who assayed several compounds Summarized research data are indicating significant (isolated from the roots) via a leukotriene biosynthesis positive effects of Edelweiss-derived extracts and its inhibition test. Among these bisabolene derivatives compounds in inflammatory-based conditions in both lignans and ent-kaurenoic acids demonstrated the in vitro as well as animal models. Hence, these studies highest activities with half maximal inhibition con- (at least partially) verify the reported ethno-medicinal centrations (IC50) detected at range of 7.7–11.4 lM. In information on Edelweiss (traditional use in the a more recent study, ethanol extract of callus cultures treatment of various inflammatory disorders). Clinical of Edelweiss have significantly decreased inflamma- studies are required in order to confirm possible use of tory responses (induced by cytokines, lipopolysaccha- this plant and its constituents in medicinal practice. ride, oxidised low density lipoprotein and UV light) in primary human keratinocytes and endotheliocytes The impact on the cardiovascular system in vitro. Since the tested extract was mainly composed of leontopodic acid (55 %), it was proposed that this Reisinger et al. (2009) have examined leoligin, the particular constituent is responsible for the observed major lignan of Edelweiss, in an in vitro human suppression of pro-inflammatory pathways (Daniela saphenous vein organ culture and mouse models for its et al. 2012). Concerning in vivo experiments on the ability to inhibit intimal hyperplasia after arterial anti-inflammatory activity of Edelweiss, Dobner et al. bypass grafting. During these experiments, leoligin (2004) have examined various extracts from roots and has shown very promising anti-hyperplastic activity, the aerial parts (dichloromethane, 100 % methanol subsequently explained by its ability to inhibit 123 302 Phytochem Rev (2017) 16:295–308

OH

R1 R2 R3 R1 O R4 18 OH OH OH R2 R3 19 H H H O O OH O

2 20 OGlc OGlc OH R R1 R2 R3 R4 21 OGlc OH OH R1 O 24 OGlc OH H OH R3 22 OH OGlc OH 25 OH H OGlc OH 23 OH OH OGlc OH O 26 OGlc H H H

27 OGlc H H OMe

O O OGlc R 30 R = H OH O 31 R = OH O O O O O 32 R = OMe 28 29

HO 33 R1 = R2 = H R1O O CO2H 34 R1 = caffeoyl, R2 = H HO OR2 OH O 35 R1 = H, R2 = caffeoyl O OH R O O HO OH O O HO O OH OH O HO O OH O 36 R =

= 37 R H HO OH

OMe MeO R1

O R1 R2 O 38 HH O 39 H OMe R2 MeO 40 OMe OMe OMe

Fig. 3 Structures of phenylpropanoid derivatives of Edelweiss (Leontopodium nivale ssp. alpinum (Cass.) Greuter)

123 Phytochem Rev (2017) 16:295–308 303 proliferation of vascular smooth cells through the revealed that this compound induces upregulation of induction of cell cycle arrest in the G1-phase. CYP26B1. In the in vivo test, the administration of Furthermore, it was discovered that the administration 5-methoxyleoligin caused a higher regeneration rate of leoligin was not accompanied by cell death in of arterioles in the peri-infarction and infarction area, smooth muscle and endothelial cells. Complications reduced myocardial muscle loss and led to a signif- resulting from coronary arterial bypass grafts (includ- icant increase in left ventricular function in rat hearts. ing neointima formation, hyperplasia and atheroscle- Apparently, the interference of 5-methoxyleoligin rosis) are currently treated with chemotherapeutics or with CYP26B1 might be the mechanism underlying immunosuppressive agents, such as heparins, angio- the arteriogenic action of this compound, but this still tensin-converting enzyme inhibitors, antagonists to needs to be clarified. According to the authors, growth factors, cytostatic agents and antibiotics. Some 5-methoxyleoligin would be one of the first low- of these remedies possess only partial efficiency and/ molecular weight compounds with cardioprotective or serious adverse effects to human health (Dzau et al. properties and the ability to augment heart regenera- 2002; Halliwell and Gutteridge 2007; Reisinger et al. tion in clinical practice, making it very promising in 2009; Nussbaumer et al. 2011). Leoligin thus seems a post-myocardial infarction therapy. non-thrombogenic and endothelial integrity-preserv- In the light of the above-mentioned results, leoligin ing alternative to commonly used drugs. and its derivatives have demonstrated promising Leoligin was also reported to significantly affect therapeutic benefits in various diseases related to the lipoprotein metabolism through interference with cardiovascular system. However, clinical trials of cholesteryl ester transfer protein (CETP), both these compounds would be needed in order to prove in vitro (rabbit and human plasma) and in transgenic their possible practical use. mice (Duwensee et al. 2011). Interestingly, higher doses of leoligin (1 mM) have induced CETP inhibi- Antioxidant and chemo-protective properties tion, whereas lower concentrations (between 0.1 and 1 nM) of this compound have increased the activity of Leontopodic acid is the only constituent of Edelweiss CETP. Due to their ability to interfere with cholesterol ever submitted to antioxidant assays (Cicek et al. levels in blood, some of the CETP inhibitors and 2012). Schwaiger et al. (2005) have determined its activators have undergone clinical trials as potential antioxidant efficacy with the use of various in vitro agents to fight coronary artery disease. Unfortunately, methods—i.e. the Briggs-Rauscher oscillating reac- the experiments were stopped after discovering very tion (BR) method, a trolox equivalent antioxidant serious side effects, including higher occurrence of capacity (TEAC) assay and a damaged DNA detection cardiovascular complications and overall mortality in (3D) assay. Leontopodic acids demonstrated signifi- the former group (e.g. TorcetrabipÒ), whilst there cant free radical scavenging ability; the compound were considerably decreased levels of plasma high was shown to possess approximately 4-times higher density lipoproteins (HDL) in the latter (i.e. probucol) activity than resorcinol in a BR assay and a 2-times (Yamamoto et al. 1986; Ritsch et al. 2010). No adverse higher efficacy than trolox in a TEAC assay. In effects were observed in the aforementioned experi- comparison to other natural antioxidant substances mental settings with leoligin. This agent thus appears tested with BR and TEAC methods, leontopodic acid to be a promising HDL metabolism-altering drug to be was identified as a compound with moderate antiox- used in the treatment of various cardiovascular idant effect (Re et al. 1999; Koleva et al. 2001; diseases. Cervellati et al. 2001, 2002). Nevertheless, in a 3D Recently, Messner et al. (2013) have examined an assay, a method based on the measurement of the analogue of leoligin, 5-methoxyleoligin, for its poten- degree up to which a particular compound can protect tial to induce angiogenesis in vitro and the possible DNA from free radical-induced damage, leontopodic stimulation of arteriogenesis in an in vivo model (rats acid exhibited outstanding antioxidant potential, being with myocardial infarction). It was found that considerably more active than silymarin and chloro- 5-methoxyleoligin encouraged endothelial tube for- genic acid (used as positive controls). Leontopodic mation and angiogenic sprouting in a chicken acid was thus verified in vitro as a potent natural chorioallantoic membrane assay. Further analyses antioxidant. Remarkably, Edelweiss extracts 123 304 Phytochem Rev (2017) 16:295–308

O

OH 41 O

OH 42 O

O

O

O

43 O

O

O

O

44

Fig. 4 Aliphatic compounds of Edelweiss (Leontopodium nivale ssp. alpinum (Cass.) Greuter)

(dichloromethane, methanol and supercritical CO2) other hand, the toxic effect of aflatoxin B1 is caused by tested with a BR assay have shown relatively low its capability to irreversibly bind to guanine residues in antioxidant activity (Speroni et al. 2006). host DNA (Bhatnagar et al. 2003; Dewick 2009). Leontopodic acid was further investigated for its Here, leontopodic acid was found unable to aggravate possible cytoprotective effects against mycotoxin- glutathione S-transferase (GST) activity, an enzyme induced toxicity (Costa et al. 2009). A battery of responsible for the formation of non-toxic aflatoxin- in vitro tests have indicated that leontopodic acid is B1 and glutathione conjugates (b1-8,9-epoxide). Thus able to protect histiocytic lymphoma cells (U937) it was suggested that increase of detoxifying enzyme against deoxynivalenol-induced damage, however not activity might be (together with the antioxidant hepatocarcinoma cells (Hep-G2) from aflatoxin B1. activity mentioned above) the mechanism underlying Apart from its ability to inhibit protein biosynthesis the chemo-protective action of this compound. How- through binding to ribosomes (Dewick 2009), ever this activity was only observed as regards deoxynivalenol is believed to significantly elevate deoxynivalenol. reactive oxygen species (ROS). Leontopodic acid was In the latest study regarding the antioxidant and additionally observed to increase the activity of cytoprotective properties of leontopodic acid, Costa glutathione peroxidase (GPx) in U937 cells. On the et al. (2010) demonstrated this compound 123 Phytochem Rev (2017) 16:295–308 305 considerably reduces ROS formation in two in vitro to be properly clarified. In spite of the above- cell viability models: pig kidney cells (LLC-PK1) mentioned observations, isocomene and related com- exposed to mycotoxin ochratoxin A and differentiated pounds of Edelweiss seem to be promising compounds human neuroblastoma cells (SH-SY5Y) exposed to of interest as a potential means in the treatment of amyloid b (Ab) aggregates (a main component of various neurodegenerative conditions associated with senile plaque in Alzheimer’s disease) (Piccini et al. cholinergic deficits, such as Alzheimer’s disease. 2005). However, similar to previous study, leon- topodic acid did not increase cell survival. Antimicrobial activity Leontopodic acid appears to be a valuable com- pound in the preventive management of trichothecene- Up to now, only one study addressed the antimicrobial mediated toxicity trough the induction of activity of activity of Edelweiss. Extracts of the aerial parts and detoxifying enzymes. Furthermore, since leontopodic roots, as well as sole compounds, were examined for acid possesses significant antioxidant efficacy, it could their possible antimicrobial action towards both gram- possibly be used as a supportive agent in the treatment positive as well as gram-negative bacteria using agar of oxidative stress-related diseases and conditions diffusion and broth microdilution assays (Dobner et al. (e.g. cancer, neurodegenerative disorders). However, 2003b). Dichloromethane extracts of both the aerial in vitro studies on additional cell models, as well as parts and roots demonstrated significant growth in vivo research regarding the chemo-protective and inhibitory activity against different strains of Bacillus antioxidant potential of this constituent should be subtilis, Escherichia coli, Pseudomonas aeruginosa, carried out in order to verify its spectrum of Staphylococcus aureus, and Streptococcus pyogenes. application. Among the tested compounds, fatty acids have shown the highest efficacy with minimal inhibitory concen- Effects on neurodegenerative disorders trations (MIC) at 4 lg/ml. Fatty acids have also exhibited activity towards multidrug-resistant S. au- Regarding experiments on the neuroprotective action reus DSM 13661, however with MIC’s in a range of of Edelweiss, Hornick et al. (2008) discovered that a 16–32 lg/ml. Similar results regarding the antimicro- dichloromethane extract of the roots, fractions and bial activity of fatty acids have been also detected isolated compounds of this plant displayed acetyl- elsewhere (Desbois 2012). Other compounds, namely choline-enhancing activity in microplate assays as two bisabolenes, several sesquiterpenes (including well as in mice behavioural and surgical tests. isocomene, b-isocomene, and silphinene), and one Dichloromethane extracts exhibited significant acetyl- coumarin (i.e. 5-hydroxyobliquin), were also consid- choline esterase (AChE) inhibitory activity in vitro, erably effective against Enterococcus faecium, S. au- and furthermore, considerably increased extracellular reus, S. pneumoniae, and S. pyogenes. These levels of acetylcholine in the rat brain. The sesquiter- observations are justifying traditional uses of this penes were suggested to be the most active of all plant for the treatment of abdominal aches, diarrhoea, constituents present in the dichloromethane extract. and dysentery. Despite the fact that various extracts This was subsequently proved with an in vitro AChE- and sole compounds have demonstrated significant inhibition assay of isolated compounds, where iso- antimicrobial activity in vitro, no in vivo studies nor comene and related molecules—e.g. 14-acetoxyiso- clinical trials have ever been conducted (except for comene, silphinene and silphiperfolene, demonstrated certain fatty acids) (Kitahara et al. 2004; Chopra the most promising results. Isocomene was further 2013). investigated in various behavioural tasks in scopo- lamine-treated mice. The compound was shown to improve learning, memory and to have a significant Toxicology impact on behaviour. In addition, after the adminis- tration of isocomene, the anticholinergic effect of No serious adverse effects have been indicated in any scopolamine was considerably reduced. The mecha- of the available studies regarding the pharmacological nism underlying the pro-cholinergic action of iso- activities of Edelweiss. At present, the only perceived comene is not completely understood and still remains health risk of Edelweiss are the lipoprotein 123 306 Phytochem Rev (2017) 16:295–308 metabolism-altering properties of leoligin (Duwensee Acknowledgments We would like to express our gratitude to et al. 2011). Overall, this plant is generally regarded as Thomas Lichtenberg for providing us with the picture of Edelweiss in its natural habitat. We are also very grateful to safe. However, toxicological studies and clinical trials Ludvı´k Bortl who read the manuscript and provided critical of Edelweiss and its compounds would be required in comments. Finally, great appreciation goes to Micheal Ua order to avoid any complications in connection with Seaghdha for his final linguistic revision of the English text. their possible clinical use, especially when higher doses are applied. References

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