Diterpenes from European Euphorbia Species Serving as Prototypes for Natural-Product-Based Drug Discovery

1
Diterpenes from European Euphorbia Species
Serving as Prototypes for Natural-Product-Based
Drug Discovery

• Judit Hohmann
• Institute of Pharmacognosy, University of Szeged

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University of Szeged, Faculty of Pharmacy
Faculty of Agriculture Faculty of Arts Faculty of
Dentistry Faculty of Economics and Business
Administration Faculty of Engeneering Faculty of
Health and Social Studies Faculty of Law Faculty
of Medicine Faculty of Music Faculty of Science
and Informatics Juhász Gyula Teacher Training
Faculty Faculty of Pharmacy
University of Szeged

• - Institute of Pharmaceutical Analysis
• - Institute of Clinical Pharmacy
• - Institute of Pharmaceutical Chemistry
• - Institute of Pharmaceutical Technology
• Institute of Pharmacodynamics and Biopharmacy
• Institute of Drug Regulatory Affairs
• - Institute of Pharmacognosy

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Institute of Pharmacognosy

• Education on five faculties (Pharmacy, Medicine,
  Health ? Social Studies, Agriculture, Teacher
  Training)
• Pharmacognosy theory and practice
• Phytotherapy
• Elective courses Separation techniques,
  Biotechnology, Chemotaxonomy
• PhD education in Graduate School of
  Pharmaceutical Sciences
• Research activity aims
• Isolation and structure determination of natural
  compounds,
• Preparative scale purification of plant
  constituents for pharmacological, analytical
  studies
• Standardization, quantitative and qualitative
  analysis of drugs and herbal medicinal products,
  quality control of products and dietary
  supplements
• Chemotaxonomy, production biology, studies on the
  dynamics of accumulation of bioactive substances
  in plants

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Euphorbiaceae family

• Euphorbiaceae family
• around 7.500 species in 300 genera
• morphology non-succulent, succulent or cactiform
• herbs, shrubs or trees
• Widely used Euphorbiaceae species
• Castor oil (Ricinus communis)
• Rubber (Hevea brasiliensis and other species)
• Manihot or cassava starch (Manihot esculenta)
• Kamala (Mallotus philippinensis)
• Croton oil (Croton tiglium)
• Euphorbium (Euphorbia resinifera)
• Other 150 species used in the folk medicine
  against cancer

HartwellJL.Lloydia 1969, 32, 153-205
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Euphorbia genera

• Number of species, characteristics
• one of the largest and most diverse genera in the
  plant kingdom with 2000 species
• irritant milky latex content
• 105 species in Europe (Tutin et al. Flora
  Europaea 1968)
• 36 species in the Carpathian basin
  (Jávorka-Csapodi, Iconographia 1975)
• 24 species in Hungary (Simon T. 1992)
• Chemistry
• Diterpenes lower and higher terpenes (from
  200 species)
• Triterpenes (dammarane, lupane, oleanane,
  cycloartane, seco-derivatives), steroids
• Phenolics, flavonoids, tannins, coumarins
• Cerebroside, glycerols
• Others sesquiterpene, etc.

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Biogenetic origin of diterpenes
Lower terpenes Macrocyclic diterpenes and their
cyclisation products
Higher terpenes Cyclic diterpenes
GGPP
cembrene cation
labdane
pimarane
lathyrane
jatrophane
abietane
kaurane
clerodane
daphnane
ramnopholane
ingenane
tigliane
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Examples of diterpenes in Euphorbia species
Higher terpenes
Lower terpenes
ent-kaurane E. sieboldiana
jatrophane E. platyphyllos
ent-abietane E. fischeriana
ent-atisane E. characias
ent-trachylobane E. wallichii
ent-isopimaranes E. quinquecostata
tigliane E. grandicornis
jatropholane E. lagascae
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Discovery of diterpenes in Euphorbia species

• Aim identification of the irritant,
  proinflammatory compounds
• 1935. Böhm first isolation of phorbol in
  crystalline form from croton oil
• 1960. Hecker structure determination of phorbol
• 1937. Dublyanskaya first isolation of a
  macrocyclic diterpene euphorbiasteroid from
  Euphorbia lathyris
• 1970. Zechmeister Structure determination of
  euphorbiasteroid as the lathyrane diterpene L1

phorbol
euphorbiasteroid
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Diterpenes in Euphorbiaceae species I
Skeletal types of well known phlogistic
compoundsPhorboids
tigliane daphnane
ingenane
Monocyclic Bicyclic
cembrane casbane
jatrophane
modified jatrophane
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Diterpenes in Euphorbiaceae species II
Tricyclic
Tetracyclic
lathyrane jatrophatrion
type jatropholane
euforactin A type paraliane
eufactin type crotopholane
pepluane
euforactin B type segetane
ramnopholane myrsinane
euphoreppinol type
cyclomyrsinane
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Why are Euphorbia diterpenes interesting?

• High biological activity of the compounds
• Many uninvestigated plants
• Structural diversity, promising source for
  finding new chemical entities
• Interesting targets of drug discovery
• Chemotaxonomic significance (markers)

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Drug discovery and Euphorbia diterpenes
prostratin reactivate latent HIV virus phase I
clinical trials
resiniferatoxin ultrapotent TRPV-1 agonist phase
II and III clinical trials
pepluanon anti-inflammatory preclinical phase
Ingenol 3-angelate (Picato) treatment of
keratosis
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Screened Euphorbiaceae species (32)
Hungarian species DC Place of
collectionMercurialis perennis Vértes
montain Euphorbia angulata ? Szent György
montain E. amygdaloides Mecsek montain E.
cyparissias Tápé E. esula Szeged E.
exigua Mosonmagyaróvár E. falcata
Orosháza E. helioscopia Szeged E. lucida
Makó E. maculata Debrecen E. palustris ?
Kiszombor E. pannonica IsaszegE. peplus
Pesthidegkút E. platyphyllos
Csáfordjánosfa E. polychroma ?
Hármashatárhegy E. salicifolia
Pesthidegkút E. segueriana Ásotthalom E.
segueriana Budaors ssp. minor
Hungarian species DC Place of collection E.
serrulata Iklódbördöce E. virgata ?
Budaors E. villosa Vácrátót Not native,
ornamental plants E. davidii Szeged E.
dentata Igal E. grandicornis
Szeged E. lathyris Székesfehérvár E.
myrsinites Szeged E. abyssinica ?
Szeged Outlander plants Acalypha fruticosa
Jemen E. chamaesyce Croatia E. hirta
Zanzibar E. mongolica Mongolia E.
terracina Crete
DC Diterpene content investigated by TLC
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Screening for diterpene content of Euphorbiaceae
species
Plant material
1. Extraction with MeOH (10x)2. Concentration
(1/10)3. Extraction with CH2Cl2
Dichloromethane fraction
Aqueous MeOH fraction
MeOH H2O (32, 41, 10 v/v)
Polyamide
TLC investigation
A
B
Sorbent Kieselgel 60F254Developing system A.
cyclohexane EtOAc EtOH (60301)B. CHCl3
acetone (191)Detection ccH2SO4 10 105 C
1. E. platyphyllos CH2Cl2 extract2. Polyamide
60 MeOH fraction3. Polyamide 80 MeOH fraction
4. Polyamide MeOH fraction
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10 Plant species selected for preparative work
Euphorbia esula undried whole plant Euphorbia
peplus undried whole plant Euphorbia
lathyris undried rootsEuphorbia
serrulata undried whole plant Euphorbia
salicifolia undried whole plant Euphorbia
platyphyllos dried whole plant Euphorbia
mongolica dried whole plantEuphorbia
falcata undried whole plantEuphorbia
exigua undried whole plantEuphorbia
pannonica undried whole plant
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Isolation strategy of Euphorbia diterpenes
Extraction

1. Dried plant material Percolation with
   CHCl3 2. Concentration

1. Fresh plant material Percolation with
   MeOH 2. Solvent-solvent partition

Apolar extract
Crude separations

1. Open column chromatography on polyamide (ICN)
   mobile phase MeOH-H2O (23, 32, 41, 10)

Diterpene fraction
2. Vacuum liquid chromatography sorbent
Kieselgel 60, eluent a/ hexane-EtOAc-EtOH
b/ petrol-EtOAc c/ cyclohexane-acetone d/
CHCl3-acetone e/ cyclohexane-EtOAc gradient
systemsk
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Isolation of diterpenes from Euphorbia species II
Fine separations
1. Open column chromatography on RP-silica
Sorbent LiChroprep RP-18 2. Vacuum liquid
chromatography Sorbent Kieselgel 60 3.
Centrifugal partition chromatography System
nHexane-EtOAc-MeCN-MeOH (8223)4. Preparative
and centrifugal TLC Sorbent Kieselgel 60 5.
NP-HPLC, RP-HPLC Column LiChrospher Si 100,
LiChrospher RP-18
R1 R2A iBu AcB Ac iBuC iBu iBu
LiChrospher Si 100 cyclohexane-EtOAc-EtOH
20101 0.3 ml/min RI detection
Solvent systems On NP-silica On RP-silica
benzene-EtOAc MeOH-H2O
chloroform-acetone MeCN-H2O
chloroform-MeOH cyclohexane-EtOAc-EtOH
nhexane-tetrahydrofuran-acetone dichloromethane
-acetone nhexane-EtOAc benzene-chloroform-diet
hylether
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Structure elucidation I
HRESIMS PL-2 m/z 798,1902 (MCs), C35H44O12
1H NMR (CDCl3, 500 MHz)
4x acetyl
5x methyl
1x benzoyl
skeletal protons
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Structure elucidation II
JMOD spectrum (CDCl3, 125 MHz) ester groups 20
carbon atoms
Quaternary C/CH2 204.0 137.9 90.6 73.7 41.640.1
CH/CH3 141.6 141.6 127.2 77.5 73.7 75.8 67.6 43.
2 40.0 27.9 25.8 18.0 18.5 17.0
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Structure elucidation III
HMQC spectrum assignment of protons and
protonated carbons
1H NMR 13C NMR (? ppm) 1x -CH2- 40.1 2.71 dd,
2.05 d 9x -CH- 127.2 5.73 dd 141.,6 5.99
brs 141.6 5.47 d 77.5 5.86 brd 75.8 5.27
brs 73.7 5.67 s 67.6 5.39 brs 43.2 3.70 dq
40.0 2.33 m 5x -CH3 25.8 0.91 s 27.9 1.13
s 18.5 1.25 d 18.0 0.87 s 17.0 1.43 d
Quaternary carbons 204.0 - 137.9 - 90.6 - 73.7 -
41.6 - OH 3.01 s
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Structure elucidation IV
1H-1H COSY spectrum identification of partial
structures
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Structure elucidation V
HMBC spectrum connection of structural fragment
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Structure elucidation VI
NOESY spectrum determination of stereochemisty8
stereogenic center in Pl-2!
Diagnostic Overhauser effects

• NOEs indicating a positions
• H-3 H-17
• H-3 H-7
• H-3 H-8H-3 H-1b(?)
• H-1b(?) H-13
• H-1b(?) H-16
• NOEs indicating ß positions
• 15-OAc H-2,6
• 6-OH H-9
• E geometry of C-4/C-5
• H-5 15-OAc
• H-5 H-11

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Structure elucidation VII. X-ray diffraction
absolute configuration
Pepluane diterpene Euphorbia peplus
Conformer I
Conformer II
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Euphorbia esula
1
8
13
Acacetyl, iBuisobutanoyl, Bzbenzoyl,
Nicnicotinoyl
9
14
Hohmann, J., Vasas, A., Günther, G., Máthé, I.,
Evanics, F., Dombi, Gy., Jerkovich, Gy. J. Nat.
Prod. 60, 331-335 (1997) Günther, G., Hohmann,
J., Vasas, A., Máthé, I., Dombi, Gy., Jerkovich,
Gy. Phytochemistry 47, 1309-1313 (1998) Günther,
G., Martinek, T., Dombi, Gy., Hohmann, J., Vasas,
A. Magn. Reson. Chem. 37, 365-370 (1999) Vasas,
A., Sulyok, E., Rédei, D., Forgo, P., Szabó, P.,
Zupkó, I., Berényi, Á., Molnár, J., Hohmann, J.
J. Nat. Prod. 74, 1453-1461 (2011)
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Euphorbia salicifolia

R1 R2 17 iBu iBu 18 Ac iBu 13 iBu Ac
19
8
9
Hohmann, J., Evanics, F., Dombi, Gy., Szabó, P.
Tetrahedron Lett. 42, 6581-6584 (2001) Hohmann,
J., Evanics, F., Dombi, Gy., Molnár, J., Szabó,
P. Tetrahedron 57, 211-215 (2001)
27

Euphorbia peplus


R1 R2 R1 R2
R3 20 Ac Ac 23 iBu H
Nic 21 Ac H 24 Ac Ac Ac 22 H
Ac 25 iBu H Ac 26
Ac H Nic
Angangeloyl
R1 R2 R3 R4 R5 R6 R1 R2
R3 27 OAc Bz Ac iBu Nic H 30 Ang H
OH 28 H Bz Ac Ac Ac Ac 31 Ang H
H 29 H Ac Bz Ac Ac Ac 32 H Ang H
Hohmann, J., Evanics, F., Berta, L., Bartók, T.
Planta Med., 66, 291-294 (2000) Hohmann, J.,
Günther, G., Vasas, A., Kálmán, A., Argay, Gy. J.
Nat. Prod. 62, 107-109 (1999) Hohmann, J.,
Vasas, A., Günther, G., Dombi, Gy., Blazsó, G.,
Falkay, Gy., Máthé, I., Jerkovich, Gy.
Phytochemistry 51, 673-677 (1999)
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Diterpenes isolated from E. peplus of different
origin
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Euphorbia serrulata

33 34 R Tig 36
37 RAc 39 RH
38 RBz 40 RAc
41 42 R H
44 45 RH 43 R
Ac
Tigtiglyl
Hohmann, J., Rédei, D., Evanics, F., Kálmán, A.,
Argay, Gy., Bartók, T. Tetrahedron 56, 3619-3623
(2000) Hohmann, J., Molnár, J., Rédei, D.,
Evanics, F., Forgo, P., Kálmán, A., Argay, Gy.,
Szabó, P. J. Med. Chem. 45, 2425-2431 (2002)
Rédei, D., Hohmann, J., Evanics, F., Forgo, P.,
Szabó, P., Máthé, I. Helv. Chim. Acta 86, 280-289
(2003)
30
E. pannonica
E. platyphyllos
48
35 R Bz
39 R H
49
46 RAc
47
Hohmann, J., Forgo, P., Csupor, D., Schlosser, G.
Helv. Chim. Acta 86, 3386-3393 (2003) Sulyok,
E., Vasas, A., Rédei, D., Dombi, G., Hohmann, J.
Tetrahedron 65, 4013-4016 (2009)
31


Euphorbia villosa


50 R Me 52 51 R H
E. lathyris
53 54 55
Vasas, A., Hohmann, J., Forgo, P., Szabó, P.
Tetrahedron 60, 5025-5030 (2004) Hohmann, J.,
Evanics, F., Vasas, A., Dombi, Gy., Jerkovich,
Gy., Máthé, I. J. Nat. Prod. 62, 176-178 (1999)
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Euphorbia falcata
  R
62 Prop
63 iBu
  R1 R2 R3
56 OBz iBu MeBu
57 OBz iBu iBu
58 H Prop iBu
  R1 R2 R3 R4
59 Hex H H H
60 Prop Ac OBz Ac
61 iBu H OBz Ac
  R1 R2 R3 R4
64 Ac Bz Bz H
65 iBu Ac Ac Ac
  R
66 Prop
67 iBu
ProppropanoylHexhexanoyl MeBu2-methyl-butanoyl
Vasas, A., Sulyok, E., Martins, A., Rédei, D.,
Forgo, P., Kele, Z., Zupkó, I., Molnár, J.,
Pinke, G., Hohmann, J. Tetrahedron 68, 1280-1285
(2012) Sulyok, E., Vasas, A., Rédei, D., Forgo,
P., Kele, Z., Pinke, G., Hohmann, J. Tetrahedron
67, 7289-7293 (2011)
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Euphorbia grandicornis


70 R1Ac, R2H 71 R1iBu, R2H 72 R1iBu,
R2Ac 73 R1MeBu, R2Ac
68 RH 69 RAng
74
75
Forgo, P., Rédei, D., Hajdu, Zs. Szabó, P.,
Szabó, L., Hohmann, J. J. Nat. Prod. 74, 639-643
(2011)
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Chemotaxonomic significance of Euphorbia
diterpenes - morphology
E. platyphyllos E. serrulata capsule
covered with hemispherical - cylindrical
tubercles
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Chemotaxonomic significance of Euphorbia
diterpenes - chemistry
E. serrulata
Eser-1 R1CH3 R2HEser-2 R1H R2CH3
Eser-4
Eser-9
Eser-8 Pl-2
E. platyphyllos
Pl-1
Pl-3
Pl-4
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Multidrug resistance reversal activity of
diterpenes

• Multidrug resistance reversing activity
• L5178 Mouse lymphoma cells transfected by pHa
  MDR1/A retrovirus
• Rhodamine 123 exclusion test
• Evaluation by flow cytometry using Becton
  Dickinson FACScan instrument
• Fluorescence activity ratio (R) was calculated

1
2
3
Molnár, J., Engi, H., Hohmann, J., Molnár, P.,
Deli, J., Weselowska, O., Michalak, K., Wang, Q.
Curr. Top. Med. Chem. 10, 1757-1768 (2010)
Vasas,A.,Rédei, D., Csupor, D., Molnár, J.,
Hohmann, J. Eur. J. Org. Chem. 5115-5130 (2012)
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Picato (PEP005) - a new plant chemotype
in the therapy

• Euphorbia peplus metabolite ingenol-mebutate
  ingenol 3-angelate
• FDA appoval 26 January 2012
• Indication actinic (solar) keratosis
• Planed European introduction
• Picato gel 0.015 and 0.05

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First experiment in Szeged

• 1997. Collection of plant material in
  Pesthidegkút, 900 g fresh herb
• 1997-2000. Isolation of diterpenes (13
  compounds) from E. peplus
• 7 jatrophanes
• 3 pepluanes
• Ingenanes PEP005, Pe-2, Pe-3
• Publications
• Hohmann J., Evanics F., Berta L., Bartók T.
  Planta Med. 2000, 66, 291-293
• Hohmann J, Günther G, Vasas A, Kálmán A, Argay G.
  J. Nat. Prod. 62, 107 (1999)
• Hohmann J, Vasas A, Günther G, Dombi G, Blazsó G,
  Falkay G, Máthé I, Jerkovich G. Phytochemistry
  51, 673 (1999)

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Pharmacology of ingenane diterpenes

• Pharmacological investigations
• Proinflammatory activity of the extracts and
  compounds on mouse ear test
• E. peplus extract IC50 25 µg/ear
• Jatrophane diterpenes inactive
• Literature data
• Proinflammatory activity on mouse ear test
• PEP005 IC50 0.04 nmol/ear (4h), 0.12
  nmol/ear (24h)
• Pe-2 IC50 0.17 nmol/ear, 0.48 nmol/ear
  (24h)
• Pe-3 IC50 10 nmol/ear, gt100 nmol/ear
  (24h)
• Co-carcinogenic effect on in vivo mouse skin
  model
• PEP005 tumor yield 0/26 (12 weeks), 0/10 (24
  weeks)
• Pe-1 tumor yield 6/25 (12 weeks)
• Pe-2 tumor yield 0/28 (12 weeks), 2/27 (24 weeks)

PEP005
Pe-2
Pe3
Hohmann J, Vasas A, Günther G, Dombi G, Blazsó G,
Falkay G, Máthé I, Jerkovich G. Phytochemistry
51, 673 (1999) Gotta H, Adolf W, Opferkuch HJ,
Hecker E Z Naturfortsch 39b, 683 (1984) Salah
MAD, Farghaly ZM, Taha H, Gotta H, Hecker E J
Cancer Res Clin Oncol 124, 131 (1998)
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New informations

• Ingenol esters act as protein kinase C (PKC)
  activators
• PKC isoenzyme selectivity in vivo
• a-isoform antiapoptotic
• ?-isoform antiproliferative, proapoptotic
  activity
• PEP005 selective effects on ?-isoforms,
  induction of nuclear translocation of PKC ?
  isoenzyme
• 2004. Preclinical development
• 2005. Clinical trials gt1000 patients
• Euphorbia diterpenes in 44 patents!
• Treatment of solid cancers, melanomas, squammous
  carcinomas and prostate cancer
• Treatment and prophylaxis of acne vulgaris

Kedei N, Lundberg DJ, Tóth A, Welburn P, Garfield
SH, Blumberg PM. Cancer Res 64, 3243 (2004)
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Production of PEP005

• Isolation from plants
• E. peplus, E. antiquorum, E. paralias, E.
  helioscopia, E. drummondii, E. hirta
• Production from E. peplus
• Cultivation, harvesting
• Extraction, fractionation, purification
• Formulation
• By semisynthesis
• From E. lathyris ? ingenol
• Esterification
• Total synthesis (4 methods)

ingenol-3-angelát PEP005
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Summary

• Middle-European flora is still promising source
  of drug discovery
• Known compound may also be interesting
• Pharmacological investigations turned the
  judgement of a molecule
• Complex structure is not a problem, production
  may be made by isolation

Thanks to Andrea Vasas Dóra Rédei Dezso Csupor
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