1,8-Substituted anthraquinones, anthrones and bianthrones as potential non-azole leads against fungal infections

Article abstract of DOI:10.1016/j.bioorg.2019.103151

The synthesis of a variety of 1,8-substituted anthraquinones, anthrones and bianthrones and their potential as antifungal agents is evaluated. Preliminary screening against Schizosaccharomyces pombe (S. pombe), a fission yeast, and Saccharomyces cerevisiae (S. cerevisiae), a budding yeast, is reported. Both these yeast species demonstrate close homologue to a number of pathogenic fungi.

Full text of DOI:10.1016/j.bioorg.2019.103151

Journal Pre-Proof
1
,8-Substituted Anthraquinones, Anthrones and Bianthrones as Potential Non-
Azole Leads against Fungal Infections
Murhaf Jalab, Megan E. Critchley, Charlotte M. Taylor, Clare L. Lawrence,
Robert B. Smith
PII:
S0045-2068(18)31231-8
DOI:
https://doi.org/10.1016/j.bioorg.2019.103151
YBIOO 103151
Reference:
To appear in:
Bioorganic Chemistry
Received Date:
Revised Date:
Accepted Date:
29 October 2018
17 June 2019
24 July 2019
Please cite this article as: M. Jalab, M.E. Critchley, C.M. Taylor, C.L. Lawrence, R.B. Smith, 1,8-Substituted
Anthraquinones, Anthrones and Bianthrones as Potential Non-Azole Leads against Fungal Infections, Bioorganic
Chemistry (2019), doi: https://doi.org/10.1016/j.bioorg.2019.103151
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover
page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will
undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing
this version to give early visibility of the article. Please note that, during the production process, errors may be
discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
©
2019 Published by Elsevier Inc.

JOURNAL PRE-PROOF
1,8-Substituted Anthraquinones, Anthrones and Bianthrones
as Potential Non-Azole Leads against Fungal Infections
Murhaf Jalab, Megan E. Critchley, Charlotte M. Taylor, Clare L. Lawrence,
and Robert B. Smithb*
a
b
b
a
aSchool of Pharmacy and Biomedical Sciences, University of Central Lancashire,
Preston, PR1 2HE, UK
bChemistry, School of Physical Sciences and Computing, University of Central
Lancashire, Preston, PR1 2HE, UK
Corresponding Author: rbsmith@uclan.ac.uk
Tel: +44 (0)1772-894384
Abstract
The synthesis of a variety of 1,8-substituted anthraquinones, anthrones and
bianthrones and their potential as antifungal agents is evaluated. Preliminary
screening against Schizosaccharomyces pombe (S. pombe), a fission yeast, and
Saccharomyces cerevisiae (S. cerevisiae), a budding yeast, is reported. Both these
yeast species demonstrate close homologue to a number of pathogenic fungi.
Keywords
Antifungal; Anthraquinones; Anthrones; Bianthrones; Non-Azole; Yeasts
Submitted to
Bioorganic Chemistry
-
Short Communication -

JOURNAL PRE-PROOF
Fungal infections continue to be a serious problem for modern-day healthcare with
incidences rising notably over the last decade, as resistance to classical antifungals
[
1-3]
has become more apparent.
This is combined with the increased susceptibility of
immunocompromised patients to infection from emerging opportunistic fungal
[4-7]
strains.
To counteract this, healthcare professionals and drug companies seek
more aggressive forms of chemotherapeutic treatments with the azoles shown to be
good candidates. There is no doubt that the azoles drugs have revolutionised clinical
mycology, by targeting the biosynthesis of ergosterol. However, these drugs are not
without problems including:
1
. Toxicity – Although the azoles are competitive inhibitors for fungal CYP51,
[8]
these drugs also affect mammalian xenobiotic-metabolising CYP enzymes,
. Resistance – The prolonged and overuse of the azoles has led to the
2
[9,10]
emergence of resistant yeast strains.
With the increase in microbial resistance, there is now a clear and direct need for novel
drug candidates to combat this worrying situation with medicinal chemists now
focusing their attention towards the areas of semi-synthetic and natural product
chemistry.
The quinones, in particular the anthraquinones as shown in Figure 1, are one type of
natural product which is well documented for having wide ranging biological properties,
[
11]
[12]
[13]
[14]
these include anti-bacterial,
anti-ulcer,
anti-cancer,
anti-inflammatory
and
[15]
anti-viral activity. Indeed, various natural and synthetic substituted anthraquinones
and their phenanthroperylene cousin, hypericin, have also been recorded to have
significant antifungal activity.
[
16-20]
Figure 1. Anthraquinones from Rheum emodi (Polygonaceae).
Surprisingly, there is a lack of data on the antifungal activity for the hypericin type
intermediates, the anthones and bianthrones. Inspired by this, we have set out to
create a small library of structurally similar anthraquinones, anthrones and bianthrones
and study their antifungal activity in two different yeast species; Schizosaccharomyces
pombe (S. pombe), a fission yeast; Saccharomyces cerevisiae (S. cerevisiae), a
budding yeast, both used extensively in eukaryotic microbiological research. These
yeast species demonstrate close homologue to a number of pathogenic fungi. For
example, S. cerevisiae is a yeast closely related to Candida albicans, a widespread
commensal and important pathogen of humans, and S.pombe is closely related to
[21]
Pneumocystis jiroveci which is a fungal infection of the lungs. S. cerevisiae itself is
also emerging as an opportunistic pathogen, especially in immunosuppressed and
immunocompromised patients and has been associated with fungemia, endocarditis,

JOURNAL PRE-PROOF
peritonitis, meningitis, ventriculitis, and with polymicrobial fatal pneumonia in AIDS
[
22, 23]
patients.
These yeast can serve as models to learn more about pathogenic fungi,
in particular with regard to regulatory features and drug therapy, because yeast as a
[24]
fungal species shares many characteristics with its pathogenic relatives. Therefore,
the aforementioned yeast can be used as representative species for screening of
chemical libraries for fungicidal activity, without exposure to fungi that are harmful to
[
25]
human health.
Detailed synthetic pathways to target the anthraquinones, anthrones and bianthrones
are shown below in Schemes 1.
O
S
O
S
O
S
1
,8-DHA
OH
O
O
O
O
OH
O
OH
O
O
O
O
O
i
i
O
O
5a
6a
4a
ii
ii
ii
O
S
O
S
O
S
OH
O
O
O
OH
O
OH
O
O
O
O
O
5b
6b
4b
iii
iv
O
S
O
S
O
S
O
O
O
O
O
O
O
O
O
OH
O
OH
OH
O
O
O
O
OH
i
O
OH
O
O
O
OH
S
O
S
O
S
O
6c
5c
4c
°
i. p-TsCl, Et
Scheme 1.
bianthrones (4c–6c).
3
N, MeCN; ii. SnCl
2
, HCl, AcOH; iii. KtOBu, DMF, MW-130 C; iv. KtOBu, DMF, Reflux.
Synthetic route to the anthroquinones (5a-6a), anthrones (4b-6b) and

JOURNAL PRE-PROOF
All compounds made within this study followed standard published methodology. The
mono and tosylation of 1,8-hydroxyanthroquinone 5a and 6a was accomplished using
[
30, 31]
reported methods
(
with minor modifications from 1,8-dihydroxyanthroquinone
4a). The anthrones (4b–6b and 8b) were prepared by chemoselective reduction of
th
the carbonyl group in the 10 position of the 1,8-substituted anthraquinones. This
method of chemoselective reduction has been previously demonstrated by the NOE
th
interaction of the newly introduced protons at the 10 position, with the protons in
[
32]
positions 4 and 5. Finally, the bianthrones (4c-6c and 8c) was formed either under
[33]
under wet or microwave conditions using the newly reduced anthrone. Scheme 2
shows the synthesis of emodin bianthrone (8c) from the starting emodin (8a) using the
same method as above.
O H O O H
O H O O H
O H O O H
i
ii
O H
O H
O H
O H
O
Emodin Anthrone (8b)
O H O O H
Emodin Bianthrone (8c)
Emodin (8a)
°
i. SnCl
2
, HCl, AcOH; ii. KtOBu, DMF, MW-130 C.
Scheme 2.
Synthesis of the emodin anthrone and emodin bianthrone.
One of the main driving factors for the introduction of the tosyloxy functionality was to
determine if amino substituents could be added with relative ease. This was studied
using the mono-protected 5a, which was independently reacted with three 1° diamines
(
ethylenediamine, trimethylenediamine or putrescine) to yield monosubstituted
compounds 7a-c as shown in Scheme 3.
O
S
O H O
O
O
O H O NHR
7
7
7
a R = (CH
b R = (CH
c R = (CH
2
)
)
)
2
3
4
NH
NH
NH
2
i
2
2
2
2
O
5
O
7
i. R-NH
2
, DCM, Reflux, 2h
Scheme 3.
The synthetic route to the mono substituted aminoanthroquinones (7a-c).
The diamines were used in a 4 molar excess; the ability to remove the tosylate groups
being controlled by the selection of an appropriate solvent, which in this case was
[30]
dichloromethane under reported conditions.
The only variation noted using this
procedure being the 4 molar excess of the 1° diamine in comparison to a 250 molar
excess of the amine which had been reported. The amine functionalities were not
added to the anthrones (4b-6b) or bianthones (5c-6c) due to large scale reactivity and
purification issues encountered.
The synthesised compounds were tested in vitro to determine growth inhibitory activity
[
4, 36]
using a standard method.
Minimum inhibitory concentration (MIC) values were

JOURNAL PRE-PROOF
determined in sets by comparison with the following compounds, which are
intermediates towards the natural product hypericin; emodin (8a), emodin anthrone
(
8b) and emodin bianthrone (8c). Emodin itself is a well-known antifungal and has
been used as a positive control for this study. Its mechanism of action is thought to
be due to induction of DNA damage.[34]
Table 1 shown below gives the full set of antifungal data collected in this study. The
substituted anthraquinones, showed varied results between each of the yeast species.
In S. pombe, they were consistently inhibitive at concentrations greater than 1000 μM
(
4a, 5a and 6a). In S. cerevisiae, the results were varied, with emodin (8a) and
compounds 5a and 6a having similar results to that of the S. pombe. However, the
MIC for 4a in S. cerevisiae was twice that for S.pombe, 2910μM compared to 1460μM,
with the unsubstituted 9,10-anthroquinone also showing similar results to 4a.
The amine substituted anthraquinones 7a-c showed a range of activities against both
yeast strains tested, but all MICs were lower than 900μM. When compared against
the control emodin (8a), 7a-c showed lower MICs, with both 7a and 7b being approx.
3
.5 times more active against the S. pombe (440μM and 420μM) and approx. 1.5 times
more active against the S. cerevisiae (886μM and 844μM). It’s interesting to note 7c
showed the greatest activity of the three with the MIC being approx. 6.5 times higher
against both yeast species (200μM), when compared to emodin (8a). It is postulated
that this is due to increasing the length of amine chain, which will increase the
[
35]
lipophilicity of the molecule, allowing for better membrane penetration.
Finally, all
compounds within this family were fungastatic apart from 7b and 7c which were shown
to be fungicidal against S. pombe alone.
The growth inhibition concentrations for the anthrones are shown alongside 8b. It is
interesting to note that 8b is 13 times more active against S. pombe in comparison to
the control 8a (97.6μM versus 1300μM). The anthones 4b, 5b and 6b (55.3μM,
6
5.7μM and 46.8μM) are approx. 1.5 times more active against S. pombe when
compared to the 8b (97.6μM ) and approx. 20 times more active when compared to
a (1300μM). It is also noteworthy that 8b (1950μM) is less active against S.
cerevisiae by a factor of 1.5 when compared against 8a (1300μM), however, 4b
553μM), 5b (329μM) and 6b (234μM) again show superior activity when compared to
8
(
both 8a and 8b respectively. However, the MICs are still significantly higher than that
seen in S. pombe. The unsubstituted anthrone followed the same trend as the other
compounds but were less active against S. pombe in comparison to the other
anthrones, whilst showing the same type of activity against S. cerevisiae as 4b. All
compounds within this family were shown to be fungistatic, apart from 8b that was
fungicidal, against S. cerevisiae.
Finally, the antifungal activity of the bianthrones show a variation in results. 8c, the
bianthrone substited emodin, was showed to be slightly more active than 8a, the
emodin anthraquinone, when compared against both yeast species, 980μM and 1300
μM respectively. Compound 4c showed to be 13 times more active against S. pombe
(
140μM) and 2 times more active against S. cerevisiae (555μM) when compared to
the control emodin (8a) and emodin bianthrone (8c). Compound 5c again showed
almost identical activity against both S. pombe and S. cerevisiae, 460μM and 461μM
respectively. The unsubstituted bianthrone gave the lowest activity against both
activity S. pombe and S. cerevisiae, 1355μM and 2168 μM respectively. Finally 6c,
showed no growth inhibition at the concentrations tested. All compounds tested within
this study, except 6c, were found to be fungistatic in both yeast species. It should be
noted that the cLogP data given in Table 1 shows no correlation to the activity.

JOURNAL PRE-PROOF
Anthraquinones
R8
O
O
R1
O
R = OTs = O S
O
R6
R1
R3
Compound
R3
R6
R8
cLogP
MIC (μM)
S/C
S. pombe
1250
1300
1460
1770
1280
440
S. cerevisiae
2001
1300
2910
1770
1280
886
S/C
S
9
,10-Anthraquinone
H
H
OH
H
H
H
H
H
H
H
CH
H
H
H
H
H
H
H
3.67
3.01
3.13
4.77
6.40
0.9
S
S
S
S
S
S
C
C
Emodin (8a)
OH
OH
OH
OTs
OH
OH
OH
3
OH
OH
OTs
OTs
S
S
S
S
S
S
S
4a
5a
6a
7a
7b
NH(CH
NH(CH
NH(CH
2
2
2
)
)
)
2
3
4
NH
NH
NH
2
2
2
1.44
1.98
420
200
844
201
7
c
Anthrones
R8
O
R1
O
R = OTs = O S
O
R6
R3
Compound
R1
R3
R6
R8
cLogP
MIC (μM)
S. pombe
267
97.6
55.3
65.7
S/C
S
S
S
S
S. cerevisiae
534
S/C
S
C
S
S
Anthrone
Emodin Anthrone (8b)
H
H
OH
H
H
H
H
Me
H
H
H
H
3.49
3.25
3.38
4.80
6.22
OH
OH
OH
OTs
OH
OH
OTs
OTs
1950
553
329
4
5
6
b
b
b
46.8
S
234
S
Bianthrones
R8
O
O
R1
O
R6
R a
R3
R = OTs = O S
R a
6
3
O
R a
R a
1
8
1
R &R1
3
R &R3
6
6
8
8
Compound
R &R a
R & R a
cLogP
MIC (μM)
a
H
OH
OH
OH
OTs
a
H
OH
H
H
S. pombe
1355
980
S/C
S
S
S
S
S. cerevisiae
S/C
S
S
S
S
Bianthrone
Emodin Bianthrone (8c)
H
Me
H
H
H
H
7.69
6.37
6.62
9.06
9.82
2168
980
555
461
α
OH
OH
OTs
OTs
4
5
6
c
c
c
140
460
α
H
-
-
Minimal Inhibitory Growth Concentration (MIC) of synthesised compounds tested in Schizosaccharomyces pombe
4
(
S.pombe), Saccharomyces cerevisiae (S. cerevisiae). Cells were inoculated at a concentration of 3 x 10 /ml.
Culture media tested were in yeast extract broth (YE) for S.pombe and complex growth media (YPD) for S.
cerevisiae. Growth of yeast was determined visually after 24 hours incubation at 30 C. The MIC of the compounds
°
were determined to be the well before yeast growth was first seen. The experiment was repeated three times to
ensure reproducibility of the results. Compounds were determined to be fungicidal (C), if no growth was observed,
and fungistatic (S), if normal growth was seen after inoculation into fresh media. .α - Growth seen in all wells up to
6
00 μM concentration.
Table 1. Structures and growth inhibitory data for the 1,8-substituted anthroquinones.

JOURNAL PRE-PROOF
In conclusion, the anthraquinones (5a and 6a), anthrones (4b-6b and 8b) and
bianthrones (4c-6c and 8c) were all prepared using literature methods in varying yields
from pre-purchased compounds (4a and 8a). The synthesis of the monoamino
substituted anthraquinones (7a-c) was also successfully accomplished using literature
methods with minor modifications. The target anthraquinones, anthrones and
bianthrones are important from a structural viewpoint; the toluenesulphonyl
functionality allows easy addition of amino functionalities, this has the advantage of
greater intrinsic water solubility and allows for further attachments to take place such
as amino acids, mono-clonal antibodies etc. This would be advantageous as it would
be a route to specific cell targeting. Preliminary screen of all the compounds in this
study showed varying levels of antifungal activity, with the control emodin, often
showing poorer activity when compared to the other compounds in this study. As
highlighted earlier in this study, the mechanism of action of emodin (8a) is thought to
[34]
be due to induction of DNA damage. However, the compounds shown in this study
are fungistatic, thus suggesting an alternative mode of action is highly plausible
It should also be noted that there is no correlation between cLogP data given in Table
1
and compound activity, which might suggest the growth inhibition is not the result of
an intracellular mechanism of action. It is clear from these results that the anthrones
(
4b-6b), the bianthrones (4c-5c) and the amino substituted anthraquinones (7a-c)
show promising antifungal activity and should form the structural basis towards
possible new antifungal leads.
Notes
The authors declare no competing financial interest.
Acknowledgement
The authors would like to thank the Faculty of Science and Technology at the
University of Central Lancashire for financially supporting this study.

JOURNAL PRE-PROOF
References
1
2
.
.
Wiederhold, NP. The antifungal arsenal: alternative drugs and future targets,
International Journal of Antimicrobial Agents. 2018;51:333-339.
Ostrosky-Zeichner L, Casadevall A, Galgiani JN, Odds FC, Rex JH. An insight
into the antifungal pipeline: selected new molecules and beyond, Nat. Rev.
Drug Discovery. 2010;9:719-727.
3
4
.
.
Campoy S, Adrio JL. Antifungals, Biochemical Pharmacology. 2017;133:86-96.
Tyler AR, Okoh AO, Lawrence CL, Jones VC, Moffatt C, Smith RB. N-Alkylated
2
,3,3-trimethylindolenines and 2-methylbenzothiazoles. Potential lead
compounds in the fight against Saccharomyces cerevisiae infections, European
Journal of Medicinal Chemistry. 2013;64:222-227.
Kung HC, Huang PY, Chen WT, Ko BS, Chen YS, Chang SC, Chuang YC,
5
.
2
016 Guidelines for the use of antifungal agents in patients with invasive fungal
diseases in Taiwan, Journal of Microbiology. Immunology and Infection.
018;51:1-176.
2
6
7
.
.
Puia-Dumitrescu M, Smith PB, Antifungal Drugs in Newborns and Children,
Pediatric Clinics of North America. 2017;64:1389-1402.
Ajmal S, Mahmood M, Saleh OA, Larson J, Sohail MR. Invasive fungal
infections associated with prior respiratory viral infections in
immunocompromised hosts, Infection. 2018;46:555-558.
8
.
Mortimer CG, Wells G, Crochard JP, Stone EL, Bradshaw TD, Stevens MFG,
Westwell AD, Antitumor Benzo thiazoles. 26.1 2-(3,4-Dimethoxyphenyl)-5-
fluorobenzothiazole (GW 610, NSC 721648), a Simple Fluorinated 2-
Arylbenzothiazole, Shows Potent and Selective Inhibitory Activity against Lung,
Colon, and Breast Cancer Cell Lines, J. Med. Chem. 2006;49:179-185.
Berger S, El Chazli Y, Babu A.F, Coste AT, Azole Resistance in Aspergillus
fumigatus: A Consequence of Antifungal Use in Agriculture?, Front Microbiol.
9
1
1
.
2
017;8:1024.
0.
1.
Revie NM, Iyer KR, Robbins N, Cowen LE. Antifungal drug resistance:
evolution, mechanisms and impact, Current Opinion in Microbiology.
2
018;45:70-76.
Zhang J, Redman N, Litke AP, Zeng J, Zhan J, Chan KY, Chang CW. Synthesis
and antibacterial activity study of a novel class of cationic anthraquinone
analogs, Bioorg Med Chem. 2011;19:498-503.
1
1
2.
3.
Ayo RG. Phytochemical constituents and bioactivities of the extracts of Cassia
nigricans Vahl, Journal of Medicinal Plants Research. 2010;4:1339-1348.
Cichewicz RH, Zhang Y, Seeram NP, Nair MG. Inhibition of human tumor cell
proliferation by novel anthraquinones from day lilies, Life Sci. 2004;74:1791-
1
799.
1
4.
Prati F, Bartolini M, Simoni E, Angela De Simone A, Pinto A, Andrisano V,
Bolognesi ML. Quinones bearing non-steroidal anti-inflammatory fragments as
multitarget ligands for Alzheimer’s disease, Bioorg Med Chem Lett.
2
013;23:6254-6258.

JOURNAL PRE-PROOF
15.
Zhou M, Xing HH, Yang Y, Wang YD, Zhou K, Dong W, Li GP, Hu WY, Liu Q,
Li XM, Hu QF. Three new anthraquinones from the twigs of Cassia fistula and
their bioactivities, Journal of Asian Natural Products Research. 2017;19:1073–
1
078.
1
1
6.
7.
Milošević T, Solujić S, Antimicrobial Activity of the HypercumPerforatum L.
Plant, Bulletin of the Chemists and Technologists of Macedonia. 2006;25:127–
1
30.
Abubakar EMM, Antibacterial activity of crude extracts of Euphorbia hirta
against some bacteria associated with enteric infections, Journal of Medicinal
Plants Research. 2009;3:498-505.
1
1
8.
9.
Saddiqe Z, Naeem I, Maimoona A. A review of the antibacterial activity of
Hypericum perforatum L, Journal of Ethnopharmacology. 2010;131:511-552.
Singh DN, Verma N, Raghuwanshi S, Shuklaband PK, Kulshreshth DK.
Antifungal anthraquinones from Saprosma fragrans, Bioorg Med Chem Lett.
2
006;16:4512–4514.
2
2
2
0.
1.
2.
Arif T, Bhosale JD, Kumar N, Mandal TK, Bendre RS, Lavekar GS. Dabur R.
Natural products – antifungal agents derived from plants, Journal of Asian
Natural Products Research. 2009;11:621-638
Anderson JB, Sirjusingh C, Parsons AB, Boone C, Wickens C, Cowen LE, Kohn
LM, Mode of Selection and Experimental Evolution of Antifungal Drug
Resistance in Saccharomyces cerevisiae, Genetics. 2003;163:1287-1298.
Marcet-Houben M, Gabaldón T. The tree versus the forest: the fungal tree of
life and the topological diversity within the yeast phylome, PLoS One. 2009;4
1
-8.
2
2
2
3.
4.
5.
Skovgaard N. New trends in emerging pathogens, International Journal of Food
Microbiology, 2007;120:217–224.
Hazen KC. New and emerging yeast pathogens. Clinical Microbiology Reviews.
1
995;8:462–478.
Goldstein AL, McCusker JH, Development of Saccharomyces cerevisiae as a
model pathogen. A system for the genetic identification of gene products
required for survival in the mammalian host environment, Genetics. 2001;159:
4
99-513.
26.
Lawrence CL, Maekawa H, Worthington JL, Reiter W, Wilkinson CRM, Jones
N, Regulation of Schizosaccharomyces pombe Atf1 protein levels by Sty1-
mediated phosphorylation and heterodimerization with Pcr1, J Biol Chem.
2
007;282:5160-5170.
2
2
7.
8.
Moreno S, Klar A, Nurse P. Molecular genetic analysis of fission yeast
Schizosaccharomyces pombe, Methods Enzymol. 1991;194:795-823.
Brachmann CB, Davies A, Cost GJ, Caputo E, Li J, Hieter P, Boeke JD.
Designer deletion strains derived from Saccharomyces cerevisiae S288C: a
useful set of strains and plasmids for PCR-mediated gene disruption and other
applications, Yeast. 1998;14:115-132.
2
9.
Treco DA, Lundblad V, Preparation of Yeast Media, In Current Protocols in
Molecular Biology. John Wiley & Sons, Inc.: 2001.

JOURNAL PRE-PROOF
3
3
0.
1.
Zielske AG. (Tosyloxy)anthraquinones. Versatile synthons for the preparation
of various aminoanthraquinones, J. Org. Chem. 1987;52,1305–1309.
Sangthong S, Ha H, Teerawattananon T, Ngamrojanavanich N, Neamati N,
Muangsin N. Overcoming doxorubicin-resistance in the NCI/ADR-RES model
cancer cell line by novel anthracene-9,10-dione derivatives, Bioorg Med Chem
Lett. 2013;23:6156-6160.
32.
Motoyoshiya J, Masue Y, Nishii Y, Aoyama H. Synthesis of Hypericin via
Emodin Anthrone Derived from a Two-fold Diels-Alder Reaction of 1,4-
Benzoquinone, Natural Product Communications. 2007;2:67-70.
3
3
3.
4.
Aigner S, Falk H. A microwave-assisted synthesis of phenanthroperylene
quinones as exemplified with hypericin, Monatsh Chem. 2008;139:991–993.
Sharma R, Tiku AB, Giri A. Pharmacological Properties of Emodin –
Anthraquinone Derivatives, Journal of Natural Products and Resources.
2
017;3:97–101
3
3
5.
6.
Haraguchi H, Kataoka S, Okamoto S, Hanafi M, Shibata K. Antimicrobial
Triterpenes from Ilex integra and the mechanism of antifungal action, Phytother.
Res.1999;13:151-156.
The growth inhibitory activity of the compounds were determined by screening
S. pombe and S.cerevisiae using the following method: Yeast species were
inoculated into relevant media; S. pombe (NJ2 h ura4-D18 leu1-32 ade6-M210
his7-366) into yeast extract broth (YE), and S.cerevisiae (strain BY4741a,
-
[
26]
[27]
[28]
a derivative of S288C, (MATahis3 1 leu2 0 met15 0ura3 0) into complex
media (YPD).
[
29]
o
The culture was then incubated for 12 hours at 30 C with
shaking at 200 rpm. Stock solutions of the compounds were prepared in 20%
(
v/v) DMSO and culture media. DMSO and culture media were used as controls
4
for the experiment. 3 x 10 exponential growing yeast cells were transferred
into the wells of a 96-well plate. A 1:2 serial dilution of the compounds was then
performed. The wells were inspected visually for growth of yeast after 24 hours
°
of incubation at 30 C. Growth was indicated by full or partial white appearance
of yeast on the bottom of the wells. The MIC values of the compounds were
determined to be the well before yeast growth was first seen. The experiment
was repeated three times to ensure reproducibility of the results. To determine
whether compounds had fungistatic or fungicidal activity, cells were taken from
the well on the microtitre plate at the concentration where lack of yeast growth
was first observed. These cells were inoculated into fresh culture media, to
o
strongly dilute the presence of the compound, and grown for 24 hours at 30 C
with shaking at 200rpm. Compounds were determined to be fungicidal, if no
growth was observed, and fungistatic, if normal growth was seen.

JOURNAL PRE-PROOF
Highlight
Synthesis of various anthraquinones, anthrones and bianthrones.
Compounds were tested for their antifungal activity.
Compounds evaluated as either fungistatic or fungicidal.
Graphical Abstract
R
O
R
R
R
O
O
R
R
O
R
R =
OH
OTs
2 2
NH(CH )nNH
R
O