1. Lichenologist 34(0): 000–000 (2002)
Halogenated anthraquinones from the rare southern Illinois lichen Lasallia
papulosa
Peter A. COHEN
Abstract:Four anthraquinones were isolatedfromthe foliose lichen, Lasalliapapulosa(Ach.) Llano. Two
of the anthraquinones are known compounds, previously isolatedfrom Lasallia papulosa, while the othertwo
were reportedpreviously as secondarymetabolites fromlaboratory-culturedNephroma laevigatum, andare
isolatedhere forthe first time fromlichens in their natural habitat.All compounds were characterizedby UV
spectrophotometry, mass spectrometry, 1
H NMR and 13
C NMR. The products were identified as 7-
chloroemodin, valsarin (7-chloro-5-hydroxyemodin), 5-chloro-1-Omethylemodin and5-chloro-1-O-methyl-
-hydroxyemodin. 2002 The British Lichen Society
Key words:: ??
Introduction
In our previous examination of pigmentcontaining foliose
lichens, we found several genera of temperate lichens
containing chlorinated anthraquinones (Cohen & Towers
1995a, 1995b, 1997). In this chemical group halogenated
anthraquinones bearing a chlorine atomin the 7-position of
the ring predominate over structural analogues with
chlorine in the 5-position (Huneck & Yoshimura 1996).
This substitution pattern probably reflects the electronic
character of the anthraquinone ring and is consistent with
known in vitro mechanisms of electrophilic chlorination
with halogens (Lam et al. 1972). However, 5-
chloroanthraquinones have been previously isolated from
Nephroma laevigatum when grown in a culture
supplemented with radioactive chlorine (Cohen & Towers
1996), although they have not heretofore been identified in
natural populations of lichens (Huneck & Yoshimura
1996). The compound 5-chloro-1-O-methylemodin has
been previously isolated from a
nonlichenized ascomycete (Ayer &
Trifonov 1994), but has not been
reported previously from Lasallia
papulosa orany otherlichen (Posner
et al. 1990; Posneret al. 1991).
We report here the isolation of two
known naturally-occurring lichen
substances, 7-chloroemodin (1) and
valsarin (2), and two othersecondary
metabolites, 5-chloro1-O-
methylemodin (3) and 5-chloro-1-
Omethyl--hydroxyemodin (4),
known previously only from
laboratory-cultured Nephroma
laevigatum(Cohen & Towers
1996).
The disjunctive global distribution
of Lasallia papulosa has been
described previously (Llano 1950). It
is ratherabundant in the Appalachian
mountains of eastern North America,
uncommon in the western Rocky
Mountains and Black Hills region,
and rare in southern Illinois where it
was collected for this present study
(Brodo et al. 2001). In this region
there is only one published report
from a single location on the
Cretaceous sandstone outcrop known
as the
P. A. Cohen: Department of Biology, Adelphi University,
Garden City, NewYork 11530, U.S.A.

2. ‘Garden of the Gods’ in southern Illinois
(Skorepa 1973). This lichen is often referred to
as ‘toadskin lichen’ because of its brown
0024–2829/02/000000+00 $35.00/0 2002 Published by Elsevier Science Ltd on behalfofThe British Lichen Society.
2 THE LICHENOLOGIST Vol. 33
Table 1. HPLC data for compounds isolated from Lasallia papulosa*
Compound* Retentiontime†(min)
7-Chloroemodin (1) 4·23
Valsarin (2) 3·96
5-Chloro-1-O-methylemodin (3) 3·45
5-Chloro-1-O-methyl--hydroxyemodin (4) 3·23
*All compounds were elutedfroma reversed-phase Waters BondapakC18 column(440cm; 10 M)
with a flowrate of 1 ml min1
.
†Solvent system: gradient of 1:1 MeOH-2% AcOH in CH3CN to 100% MeOH in
15 min.
exterior and warty surface texture (Goward
1996). In general, the lichen is brown on the
exterior, and has a brown to black underside;
however, there are species that are bright red
on the surface and brown-red on the
underside. No highly pigmented forms of
Lasallia papulosa were found in ‘Garden of
the Gods’, although they have been reported
from West Virginia (Brodo et al. 2001).
Highly pigmented varieties [L. papulosa var.
rubiginosa (Pers.)Llano] have been collected
from Table Mountain nearCape Town, South
Africa (Llano 1950).
Materials and Methods
General
Meltingpoints: uncorrected; EIMS; 70 eV; 1
H NMR:
400 MHz; 13
C NMR 125 MHz; DMSO-d6, DMF-d6 and
Me2CO-d6 were usedin the NMR andNOE experiments
(TMS as internal standard); Column Chromatography
(CC): BDH flash silica gel 60 (230– 400 mesh);
preparative TLC: Merck Kieselgel 60 GF254 layers
(0·22020 cm) on glass plates; HPLC: Waters reversed-
phase C18 column (440 cm, gradient elution, 10 m, flow
rate 1 ml min1
)(see
Table 1); UV spectra: MeOH (UV grade); CHCl3 and
CH2Cl2 (solvent grade).
Lichen material
Lasallia papulosa (Ach.) Llano was collected from
two north-facing red sandstone outcrops in the park,
‘Garden of the Gods’, Saline County, southern Illinois,
on 11 November 2000. In a recent survey ofthis region,
two distinct lichen locations were identified, in a region
covering approximately five square miles. The samples
obtainedfor this present study came fromboth locations.
One reference sample has been deposited in the
Herbarium in the Department of Plant Biology at
Southern Illinois University in Carbondale (Herbarium
Number: 42016).
Isolation and identification
The carefully cleaned lichen (100 g dry weight) was
immersed in 500 ml 95% MeOH for 48 h, without damage to
the lichen tissue. The red-brown extract was concentrated in
vacuo yieldinga redwaxy solid. This solidwas freeze-driedto
give a red-brown powder (15 g). This powder was purified by
CC on Sephadex LH-20, using a gradient of CH2Cl2-MeOH
(9:1) to MeOH. Fractions (40 ml) were collectedandanalysed
by TLC and UV light (short-wave and long-wave). The
fractions containinganthraquinones were furtherpurifiedby CC
on Sephadex LH-20, usinga gradient ofCH2Cl2-MeOH(6:4) to
MeOH. Fractions (20ml) were collectedandanalysedby TLC
and UV light. All compounds were further purified by
preparative TLC (CH2Cl2-MeOH 4:1) and repeatedly
crystallized until purity was established to be >99% by RP-
HPLC. All compounds were characterizedby UV, MS, and 1
H
NMR spectra (in addition, compounds 2 and 3 was
characterizedby 13
C NMR spectra).
Preparation of acetylated derivatives
The anthraquinone (2 mg) was suspendedin dry pyridine (1
ml) to which was added 0·5 ml of dry acetic anhydride. The
solutions were left at room temperature over night, and then
concentratedin vacuotoa solidwhich was vacuum driedfor48

3. h. The acetylatedderivatives were purifiedby preparative TLC,
andrecrystallizedfromEtOAc.
Results
The extraction of approximately 100 g (dry weight)
of lichen thalli in MeOH produced a brown-red
solution, which upon TLC development (9:1
CHCl3-MeOH) yielded four (pigmented) primary
spots,and three minor (non-pigmented) spots.The
non-pigmented spots included the known
compounds gyrophoric acid (Rf 0·2) and
umbilicaric acid (Rf 0·3), well-described lichen
depsides A OH O OH
R O
R
1 H 7-Chloroemodin
2 OH Valsarin (7-Chloro-5-hydroxyemodin)
B OH O OCH3
Cl O
R
3 CH3 5-Chloro-1-O-methylemodin
4 CH2OH 5-Chloro-1-O-methyl- -hydroxyemodin ω
F . 1. Anthraquinone isolatedfrom Lasallia papulosa.
A, 7-Chloroanthraquinones; B; 5-
Chloroanthraquinones.
(Culberson 19697). The pigmented spots consisted
of: 1 (Rf 0·5), 2 (Rf 0·4), 3 (Rf 0·65) and 4 (Rf
0·15). The structures of compounds 1, 2, 3 and 4
are shown in Fig. 1
The identity of 1 was established by 1H NMR
and mass spectra. The spectral data are consistent
with previous results (Cohen
& Towers 1995a, b, 1997; Huneck & Yoshimura
1996). Compounds 2, 3 and 4
were confirmed by 1H NMR (2, 3 and 4), 13
C NMR (2 and 3) and mass spectra (2, 3 and 4).
Spectral data,in particular NOE experiments, were
consistent with previous results for 3 obtained from
cultured N. laevigatum (Cohen & Towers 1996).
Thus,when 3 was submitted to irradiation at the H-
2 proton (see Fig. 1), a concomitant enhancement
(2%) of the methoxy proton at C-1 was clearly
observed in the spectrum.In addition, the 13CNMR
spectrumof 3 was indicative of a structure bearing
an electronegative atom (Cl) at C-5 consistent with
ourprevious findings (Cohen & Towers 1996). The
1HNMR spectra are indeed distinct for 1 and 3 (and
4), as can be clearly seen in the spectra for 3 and 4,
where the characteristic H-7 proton shift ( 6·68) is
clearly present indicating that the position between
the two hydroxyl groups at C-6 and C-8 bears a
proton. This proton is naturally lacking in all 7-
chlorosubstituted anthraquinones. The NOE
enhancements also indicate that there is no chlorine
substitution at C-2 (Cohen & Towers 1996).
The identity of 2 was established by 1H
NMR, 13C NMR and mass spectra. We report
here for the first time the 13C NMR spectrum
for valsarin (2). All previous reported
structural assignments for this compound
were based on data derived from UV and IR
spectra, mass spectra, 1H NMR spectra and
elemental analysis (Huneck & Yoshimura
1996; Lam et al. 1972; Posner et al. 1990;
Posner et al. 1991).
The basis for establishing the presence of a
-hydroxy functionality in 4 was the distinctive
splitting pattern (and coupling constant)in the
proton spectrum. The methylene protons
adjacent to the OH group ( 4·64) produced a
d with a J=5·0 Hz, the same coupling constant
observed in our earlier work (Cohen &
Towers 1996).
The Compounds
7-Chloroemodin (1). Compound 1
2002 Author please supply short running head—Cohen 3

4. (12 mg, 0·12% dry weight) was obtained as
orange crystals (EtOAc); mp 282–2840. The 1
13
H and C NMR spectra were in agreement
with the literature (Huneck & Yoshimura
1996).
7-Chloro-5-hydroxyemodin (valsarin) (2).
Compound 2 (23 mg, 0·23% dry weight) was
obtained as red crystals (EtOAc); mp 268–
2700; UV (MeOH) max nm (log ) 238 (4·25),
264 (4·08), 312 (3·89), 350 (3·64), 468
(3·82), 492 (3·55), 520 (3·20), 574 (3·18);
EIMS (70 eV) m/z (rel. int.) 322 [M]+ (30) 320
(100); 1H NMR (400 MHz, DMSO-d6): 2·38
(3H, s, Me-3), 7·12 (1H, s, H-2), 7·52 (1H, s,
H-4);
13
C NMR (125 MHz, DMSO-d6): 21·8
(Me-3), 108·9 (C-9a), 110·2 (C-8a), 120·3
(C-4), 122·3 (C-2), 126·4 (C-7), 133·0
(C10a), 133·4 (C-4a), 144·3 (C-5), 147·6
(C3), 156·3 (C-6), 158·2 (C-8), 159·4 (C-1),
183·4 (C-10), 190·3 (C-9).
7-Chloro-5-hydroxyemodin tetraacetate
(tetraacetylvalsarin). Yellow-orange
crystals from EtOAc; mp 220–2220; CIMS
m/z (rel. int.) 491 [MH]+ (32), 489 (100);
EIMS (70 eV) m/z (rel. int.) 488 [M]+ (8),
446 (10), 436 (23), 404 (38), 362 (52), 322
(22), 320 (100); 1HNMR (400 MHz, Me2CO-
d6): 2·38 (3H, s, Me-3), 2·422·48 (12H, s,
1,5,6 and 8-OAc), 7·18 (1H, s, H-2), 7·78 (1H,
s, H-4).
5-Chloro-1-O-methylemodin (3).
Compound 3 (8 mg, 0·08% dry weight) was
obtained as orange crystals (EtOAc); mp
252–2540; UV (MeOH) max nm (log ) 230
(4·40), 260 (4·34), 316 (4·24), 440 (3·92);
EIMS (70 eV) m/z (rel. int.) 320 [M+] (33)
318 (100); 1H NMR (400 MHz, DMSOd6):
2·48 (3H, s, Me-3), 3·94 (3H, s, OMe-1),
6·78 (1H, s, H-7), 7·36 (1H, s,
H-2), 7·52 (1H, s, H-4); 13C NMR
(125 MHz, DMSO-d6): 22·0 (Me-3), 57·5
(OMe-1), 112·8 (C-7), 113·0 (C-8a), 113·6
(C-9a), 118·6 (C-5), 120·0 (C-4), 121·2
(C-2), 130·4 (C-4a), 135·3 (C-10a), 146·2 (C-
3), 160·0 (C-1), 160·4 (C-8), 162·0 (C-6),
184·3 (C-10), 192·3 (C-9).
5-Chloro-1-O-methyl--hydroxyemodin (4).
Compound 4 (4 mg, 0·04% dry weight) was
obtained as orange-red crystals (AcOH); mp
264–2660; UV (MeOH) max nm (log ) 220
(4·50), 256 (4·20), 322 (3·98), 498 (3·45);
EIMS (70 eV) m/z (rel. int.) 336 [M+] (35)
334 (100); 1H NMR (400 MHz, DMSO-d6):
3·92
(3H,
s, OMe-1), 4·64 (2H, d, J=5·0 Hz, CH2OH3),
6·0 (1H, s, CH2OH-3), 6·78 (1H, s, H-7), 7·48
(1H, s, H-2), 7·78 (1H, s, H-4).
5-Chloro-1-O-methyl--hydroxyemodin
triacetate. Orange crystals from EtOAc; mp
244–2460; CIMS m/z (rel. int.) 463 [MH]+
(33), 461 (100); EIMS (70 eV) m/z (rel. int.)
462 [M]+ (7), 420 (22), 418 (44), 378 (20),
376 (60), 336 (4), 334 (8), 318 (38), 316
(100), 306 (12), 304 (40).
Discussion
Compound 3 had originally been isolated from the
non-lichenized ascomycete fungus Phialophora
alba (Ayer & Trifonov 1994), but this is the first
reported isolation of a 5-chloroanthraquinone from
a lichen collected in the field. Previously,
compound 4 was only known from axenically
cultured Nephroma laevigatum. Since 5-
chloroanthraquinones are relatively infrequent in
both lichenized and non-lichenized ascomycetes
relative to the 7-chloro analogues, one might
ponder on the biochemical mechanisms for
chlorination. Since the 7 position is more
nucleophilic than the 5 position in the
anthraquinone ring (Lam et al.1972), the evidence
suggests that a chloroperoxidase capable of
selectively chlorinating the less-nucleophilic C-5
position must be present in L. papulosa. We have
4 THE LICHENOLOGIST Vol. 33

5. previously demonstrated, in vivo, that axenically
cultured lichen-forming fungi have the capacity to
biosynthesize novel analogues through
(presumably) physiological and biochemical
perturbation of their polyketide pathways that
produce anthraquinones (Cohen & Towers 1996).
Subsequently, we have shown that in vitro
chlorination of anthraquinones with a partially
purified chloroperoxidase isolated from Nephroma
laevigatum, as well as by commercial fungal
chloroperoxidasecatalysed chlorination of
anthraquinones (Cohen & Towers 1997).
Regioselectivity was clearly observed in this
experiment, as the enzyme from the non-lichen-
forming fungus was capable of generating
5-chloroanthraquinones, while the lichen enzyme
strictly catalysed introduction of chlorine into the
C-7 position. It therefore remains to be established
whether the unique geological environment where
L. papulosa was found might have some bearing
on the ability of this lichen to biosynthesize rare
chlorinated isomers of well-known lichen
pigments. Future research will be directed toward
studying the in vitro and in vivo biochemical
mechanisms for chlorination in Lasallia, utilizing
whole organism cultures, purified enzymes and
labelled precursors.
Financial support was providedby theDepartment of Chemistry
andBiochemistryat Southern Illinois University inCarbondale.
I am most grateful toProfessor Cal Y. Meyers forthe use of his
laboratory(Meyers Institute),toMr Paul Sandrockforhis kind
assistance with the proton and carbon spectra, and Dr Steve
Mullen of the Mass SpectrometryLaboratoryat the University
of Illinois Urbana-Champaign for runningmass spectra.
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Accepted for publication 6 September 2002
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