New antitumour fungal metabolites from Alternaria porri

Article abstract of DOI:10.1080/14786410802265415

Chemical investigation of the onion pathogenic fungus Alternaria porri resulted in the isolation of two new phthalides named zinnimide (2) and deprenylzinnimide (8), along with a new bianthraquinone, alterporriol F (10). The structures of the new metabolites were characterised by spectroscopic analysis and chemical degradation. Of the new compounds isolated, alterporriol F was highly cytotoxic towards HeLa and KB cells, with IC50 values of 6.5 and 7.0 g mL-1.

Full text of DOI:10.1080/14786410802265415

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New antitumour fungal metabolites
from Alternaria porri
Preecha Phuwapraisirisan a , Jakaphan Rangsan a , Pongpan
Siripong b & Santi Tip-pyang a
a Natural Products Research Unit, Department of Chemistry,
Faculty of Science , Chulalongkorn University , Bangkok 10330,
Thailand
b Natural Products Research Section, Research Division , National
Cancer Institute , Bangkok 10400, Thailand
Published online: 29 Oct 2009.
To cite this article: Preecha Phuwapraisirisan , Jakaphan Rangsan , Pongpan Siripong & Santi Tip-
pyang (2009) New antitumour fungal metabolites from Alternaria porri , Natural Product Research:
Formerly Natural Product Letters, 23:12, 1063-1071, DOI: 10.1080/14786410802265415
To link to this article: http://dx.doi.org/10.1080/14786410802265415
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Natural Product Research
Vol. 23, No. 12, 15 August 2009, 1063–1071
New antitumour fungal metabolites from Alternaria porri
a
a
b
*
Preecha Phuwapraisirisan , Jakaphan Rangsan , Pongpan Siripong
and Santi Tip-pyanga
aNatural Products Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn
University, Bangkok 10330, Thailand; Natural Products Research Section, Research Division,
National Cancer Institute, Bangkok 10400, Thailand
b
(Received 28 April 2008; final version received 11 June 2008)
Chemical investigation of the onion pathogenic fungus Alternaria porri resulted in
the isolation of two new phthalides named zinnimide (2) and deprenylzinnimide
(8), along with a new bianthraquinone, alterporriol F (10). The structures of the
new metabolites were characterised by spectroscopic analysis and chemical
degradation. Of the new compounds isolated, alterporriol F was highly cytotoxic
towards HeLa and KB cells, with IC50 values of 6.5 and 7.0 mg mLꢀ1
.
Keywords: Alternaria porri; antitumour; fungus; alterporriol F; zinnimide;
deprenylzinnimide
1. Introduction
Alternaria porri is a critical pathogen associated with purple blotch disease, which causes a
30–70% loss of onion production. This fungus attacks the onion’s leaves, stalk and bulb
by releasing phytotoxins that mediate severe lesions. Subsequent investigations have led to
identification of anthraquinones (Suemitsu, Ohnishi, Yanagawase, Yamamoto, &
Yamada, 1989) and phthalides (Stierle, Hershenhorn, & Strobel, 1993) as causative
compounds. The tetrahydroanthraquinone named altersolanol A was proved to be a
potent inhibitor of plant respiration, therefore blocking the uptake of essential metabolites
required for photosynthesis (Haraguchi, Abo, Fukuda, Okamura, & Yagi, 1996). As a
continuation of our interest in the discovery of new fungal secondary metabolites
(Phuwapraisirisan, Rangsan, Siripong, & Tip-pyang, 2006; Phuwapraisirisan, Swang,
Siripong, & Tip-pyang, 2007), we report here the isolation and structure elucidation of two
new phthalides named zinnimide (2) and deprenylsinnimide (8), along with a new
bianthraquinone, alterporriol F (10) (Figures 1 and 2).
2. Results and discussion
Zinnimide (2) was obtained as a yellow amorphous solid. Its molecular formula was
deduced to be C15H17NO4 by HRESIMS, indicating eight degrees of unsaturation. The 1H
NMR spectrum of 2 showed signals ascribable to an NH amide proton [9.64 (brs, 1H)], an
*Corresponding author. Email: preecha.p@chula.ac.th
ISSN 1478–6419 print/ISSN 1029–2349 online
ß 2009 Taylor & Francis
DOI: 10.1080/14786410802265415
http://www.informaworld.com

1064
P. Phuwapraisirisan et al.
O
7
O
1
5
R O
O
1
HO
NH
O
O
8
H C
H C
H C
3
3
3
3
2
R
O
OCH
3
OCH
OCH
3
3
1
2
R
R
5
4
OH
O
4′
3′
1′
H
O
1
2
8
5′
3
R O
O=
O=
H C
OH
3
3
H
6
7
R = CH
3
3
R = H
Figure 1. Phthalides (1, 2 and 8), phthalates (4, 5) and alternariols (6, 7) isolated from A. porri.
HO
O
5
4a
10a
10
OH
CH
3
HO
O
O
7
9
6
R
1a
9a
H CO
3
3
1
O
O
4
R O
CH
3
OH
1′
9′a
1′a
4′a
5
H CO
7′
3
R
9
OH
OH
4
5
6
10
5′
3
R = CH , R = H, R = OH
3
3a R = CH , R = OH, R = OH
3b R = CH , R = H, R = H
3′
10′a
4
5
6
3
7
O
R
4
5
6
HO
3
4
5
6
7
9
R = H, R = H, R = OH
10 R = H
7
11 R = OH
O
HO
O
H CO
CH
OH
3
3
OH
OH
OH
O
H CO
HO
H CO
3
O
O
OH
OH
OH
3
H CO
3
O
OH
OH
OH
OH
O
O
OH
HO
HO
HO
13
12
Figure 2. Anthraquinones (3 and 9) and bianthraquinones (10–13) isolated from A. porri.

Natural Product Research
1065
O
7
O
4′
5
O
1
HO
H C
3′
1′
NH
NH
8
5′
H C
3
3
3
O
O
OCH
OCH
3
3
2
8
Figure 3. Selected HMBC cross peaks of zinnimide (2) and deprenylzinnimide (8).
aromatic proton [7.01 (s, 1H)], and methoxy [3.94 (s, 3H)] and aromatic methyl protons
[2.04 (s, 3H)]. The presence of a prenyl moiety was suggested by resonances of two methyls
(1.67, 6H), an olefinic proton (5.40, 1H) and methylene protons (4.66, 2H). The
orientation of substituent groups on an aromatic ring was established based mainly on
HMBC correlations. The cross peaks between H-10 (ꢀH 4.66) and C-5 (ꢀC 162.8) suggested
that the prenyl moiety was connected to the aromatic ring through an ether linkage. The
singlet methyl (ꢀH 2.04 and ꢀC 8.5) was accommodated at C-4 based on HMBC correlation
from 4-CH3 to C-3, C-4 and C-5, while the cross peak between the methoxy proton
(ꢀH 3.94) and C-3 (ꢀC 156.8) was also observed. The long-range coupling of H-6 to a
carbonyl carbon C-7 (ꢀC 168.2) indicated the connectivity between the benzene ring and an
amide. By default, the remaining element CO (ꢀC 167.0) must be amide carbonyl that
linked the benzene ring at C-2 and formed cyclic diamide, to account for the proposed
molecular formula.
Deprenylzinnimide (8) had a molecular formula C10H9NO4 deduced by HRESIMS.
The 1H NMR spectrum of 8 in acetone-d6 displayed signals principally similar to those of
2, except for the absence of resonances indicative of prenyl moiety. This data suggested
that 8 was a deprenylated congener of 2. The assumption was supported by the molecular
formula and HMBC cross peaks between 5-OH and neighbouring carbons, C-4, C-5 and
C-6. The entire structure was confirmed by 2D NMR analysis (Figure 3).
Alterporriol F (10) was isolated as a red amorphous powder. The molecular formula
C32H26O12 of 10 was obtained from a high-resolution mass measurement of the [M þ Na]
1
ion in HRESIMS. The H NMR recorded in DMSO-d6 showed a pair of downfield
hydroxyl resonances (ꢀH 13.60 and 13.11), four singlet aromatic protons [ꢀH 7.67, 7.53,
6.92 and 6.89], two methoxyls [ꢀH 3.69 (6H)], two singlet methyls (ꢀH 2.17 and 1.13),
oxygenated methines (ꢀH 4.03 and 3.66), and methylene protons (ꢀH 2.78 and 2.30),
including hydroxyl protons (ꢀH ca 4.3–5.4). The 13C NMR displayed signals indicative of
two quinone moieties, ꢀC 189.4, 186.9, 184.1 and 181.3, in addition to resonances of
aromatic compounds. These data suggested that 10 possessed bianthraquinone scaffold.
To establish the entire structure of 10, it was subjected to 2D NMR measurement.
Surprisingly, upon keeping it at room temperature for several days prior to the
measurement, we observed another set of signals resonated nearly identically to the
original ones. An HPLC analysis and ESIMS examination indicated the presence of 10
and its newly generated isomer in a ratio of 1 : 1. Given the original 1H NMR spectrum of
10 in hand, we envisioned structure elucidation using high resolution 2D NMR. The upper
anthraquinone moiety I was constructed based principally on HMBC analysis. The cross
peaks between 7-CH3/C-6, C-7, C-8, H-5/C-6, C-7, C-9a, C-10 and H-8/C-6, C-9, C-10a
were suggestive of a macrosporin moiety (Table 1).
The lower unit II consisted of two separated spin systems, which were
connected to each other by quinone moiety. The left fragment included the

1066
P. Phuwapraisirisan et al.
Table 1. NMR dataa of zinnimide (2) and deprenylzinnimide (8) recorded in acetone-d6.
2
8
Position
ꢀC
ꢀHb
ꢀC
ꢀH
1
2
3
4
5
6
7
134.0
114.5
156.8
125.2
162.8
101.4
168.2
167.0
61.4
134.0
113.2
157.0
123.4
161.7
105.0
168.0
NDc
61.5
7.01 (s)
6.91 (s)
8
3-OCH3
3.94 (s)
2.04 (s)
3.95 (s)
2.03 (s)
9.85 (s)
4-CH3
5-OH
10
8.5
8.5
65.9
119.2
138.3
24.9
4.66 (d, 6.4)
5.40 (m)
20
30
40
1.67 (s)
1.67 (s)
9.64 (brs)
50
NH
17.3
9.65 (brs)
a
1
b
c
Notes: 400 MHz for H and 100 MHz for 13C NMR. (Mult, J in Hz). Signal not detected.
–CH2–CH(OH)– and –CH(OH)– subunits, which were flanked by an oxygenated
quaternary carbon (C-70) while the right fragment possessed pentasubstituted benzene.
The relative configuration of three contiguous chiral centres (C-60, 70 and 80) was deduced
by NOESY data and coupling constant analysis (Figure 4), thus pointing out that the
hydroxylated cyclohexene ring adopted a half-chair conformation. Therefore, the unit II
was identified as altersolanol C (Suemitsu, Ueshima, Yamamoto, & Yanagawase, 1988).
The presence of macrosporin and altersolanol C moieties in 10 was further confirmed by
chemical degradation. Reductive cleavage of 10 in Na2S2O4 solution (Okamura,
Haraguchi, Hashimoto, & Yagi, 1993) afforded macrosporin and altersolanol C, together
with two minor products, 3a and 3b. Although there was no HMBC and NOESY cross
peak observed between units I and II, their connection through a C–C bond at C-1 and
C-10 was inferred from chemical analysis and the occurrence of closely related isomer of
10. Therefore, the complete structure of 10 was depicted as shown. Generally, biaryl
having bulky ortho substituents undergoes restricted rotation about a single bond, thereby
enabling isolation of an individual atropisomer. Although several alterporriols have been
isolated as a single isomer (Okamura et al., 1993; Suemitsu, Yamamoto, Miyai, &
Ueshima, 1987; Suemitsu et al., 1988; Suemitsu, Horiuchi, Kubota, & Okamatsu, 1990),
further study on their stability under susceptible conditions such as high temperature has
not been conducted. It should be noted in this investigation that alterporriol F (10) existed
in slow equilibrium between two axis conformations, 10a and 10b, whose configurations
were arbitrarily designed to be M- and P-configurations, respectively (Figure 5 and
Table 2).
All isolated compounds were submitted to examination for their cytotoxicity against
HeLa and KB cells (Table 3). Zinnimide (2) revealed moderate cytotoxicity, with IC50 values
of 13.0 and 27.0 mg mLꢀ1, respectively, while its deprenylated congener (8) was not active.
On the contrary, alterporriol F (10) was highly cytotoxic against both HeLa (IC50

Natural Product Research
1067
HO
O
O
4a
10a
9a
OH
CH
Unit II
6
3
H CO
1a
3
1
8
3
(I)
9′
10′
8′
6′
5′
7′
OH
O
9′
8′
H C
(II)
1′
3
1′a
OCH
3
HO
6′
3′
HO
10′
4′a
J
J
6 = 5.6 Hz
5eq,
O
OH
,6 = 9.6 Hz
5ax
Figure 4. Selected HMBC (solid curve) and NOESY (dash curve) correlations of 10.
OH
M
O
O
OH
P
OH
CH
HO
H CO
3
3
H C
OCH
O
3
3
O
O
OH
O
Slow
OH
H C
CH
3
OCH
3
3
H CO
3
HO
OH
OH
HO
O
HO
10a
O
HO
10b
*
*
*
*
13.50
13.00
*
*
*
*
*
7.50
7.00
6.50
6.00
5.50
5.00
4.50
4.00
Figure 5. Partial 1H NMR spectrum of a mixture 10a/10b recorded in DMSO-d6. The signals
marked by asterisks arose after the solution was kept for several days.
6.5 mg mLꢀ1) and KB (IC50 7.0 mg mLꢀ1) cells. Anthraquinones and bianthra-quinones have
been reported for their intriguing pharmacological activities, including antitumour activity.
Koyama et al. demonstrated that their elevated cytotoxicity was associated with electronic
properties and redox potentials of the quinone motif (Koyama et al., 2001).

1068
P. Phuwapraisirisan et al.
Table 2. NMR dataa of alterporriol F (10) recorded in DMSO-d6.
ꢀC
ꢀH (mult, J in Hz)
Position
10a
10b
10a
10b
1
1a
2
3
4
4a
5
6
7
8
108.9
124.3
165.9
104.2
164.2
110.8
111.0
161.7
131.4
133.1
181.3
125.3
186.9
126.4
57.2
108.9
124.3
165.9
104.2
164.2
110.8
111.0
161.7
130.3
133.1
181.3
125.3
186.9
126.4
57.2
6.89 s
7.53 s
7.67 s
6.89 s
7.52 s
7.65 s
9
9a
10
10a
2-OCH3
4-OH
6-OH
7-CH3
10
3.69 s
13.60 s
3.69 s
13.65 s
16.5
110.0
109.0
163.9
103.8
165.2
110.8
29.0
16.5
110.0
109.0
163.9
104.2
165.2
110.8
29.0
2.17 s
6.92 s
2.17 s
10a
20
30
6.93 s
40
40a
50
2.78 dd (5.6, 19.6)
2.30 dd (9.6, 19.6)
3.66 m (overlap)
2.73 dd (5.6, 19.6)
2.30 dd (9.6, 19.6)
3.66 m (overlap)
60
67.2
72.3
69.7
184.1
143.2
189.4
144.1
57.1
67.2
72.3
69.3
184.1
143.2
189.4
144.1
57.1
70
80
4.03 d (7.6)
4.01 d (7.6)
90
90a
100
100a
20-OCH3
40-OH
60-OH
70-OH
70-CH3
80-OH
3.69 s
13.11 s
4.64 d (6.8)
4.27 s
1.13 s
3.69 s
13.13 s
4.61 d (6.8)
4.35 s
1.13 s
22.0
22.6
5.31 d (7.6)
5.44 d (7.6)
a
Note: Measured at 400 MHz (1H) and 100 MHz (13C).
3. Experimental
3.1. General procedure
UV spectra were recorded on a UV-160A spectrometer (Shimadzu). ESIMS and
HRESIMS were obtained with a Micromass LCT mass spectrometer. NMR spectra
were carried out using a Varian Mercury þ 400 spectrometer and chemical shifts were
reported in parts per million referenced to solvent residues (ꢀH 2.50 and ꢀC 39.4 ppm for
DMSO-d6 and ꢀH 2.05 and ꢀC 30.8 ppm for acetone-d6).

Natural Product Research
1069
Table 3. Cytotoxicity of isolated compounds against HeLa and KB cells.
Cytotoxicity (IC50, mg mLꢀ1
)
Compound
HeLa
KB
1
2
45.0
13.0
46.0
27.0
3
4
5
6
4100.0
36.0
4100.0
4.3
6.6
4100.0
14.0
59.0
5.5
7
4.5
8
9
10
4100.0
7.3
6.5
90.0
8.6
7.0
11
12
18.0
5.9
50.0
19.0
17.0
47.0
13
Adriamycin
0.018
0.018
3.2. Fungal fermentation
The fungus A. porri used in this experiment was obtained from the Department of
Agriculture, Ministry of Agriculture and Cooperative. The fungus was cultured on potato
dextrose agar (PDA) plates at 25ꢁC for 3 days. The fungus plug was cut into small pieces
and transferred into Erlenmeyer flasks each containing 100 mL of potato dextrose broth
(PDB). After 3-day incubation, the seed media was transferred into production media
(100 ꢂ 250 mL Erlenmeyer flask each containing 100 mL of media). Fermentation was
carried out for 75 days under static conditions.
3.3. Extraction and isolation
The culture (ca. 10 L) was filtered and the filtrate was extracted with CH2Cl2 and EtOAc.
The CH2Cl2 (4.5 g) extract was separated by silica gel using gradient elution from CH2Cl2
to EtOAc. Fractions eluted with 3 : 7 EtOAc : CH2Cl2 were evaporated to afford
zinnimidine (1, 50 mg). The EtOAc was fractionated using silica gel chromatography
using hexane, CH2Cl2–hexane, EtOAc–CH2Cl2, MeOH : EtOAc and MeOH, yielding
seven major fractions. Fraction 3 eluted with 3 : 7 EtOAc : CH2Cl2 was successively
purified using silica gel chromatography using gradients of CH2Cl2 to MeOH to
furnish zinnimide (2, 7 mg), macrosporin (3, 230 mg), 5-(30,30-dimethylallyloxy)-3-
methoxy-4-methylphthalide (4, 2 mg), porriolide (5, 10 mg), alternariol monomethyl
ether (6, 15 mg), alternariol (7, 5 mg), deprenylzinnimide (8, 7 mg) and demethylmacros-
porin (9, 5 mg). Fraction 4 was purified on Sephadex LH-20 (1 : 2 : 2 MeOH–CH2Cl2–
hexane) followed by HPLC (Nova-Pak RP-C18, 2 : 3 MeOH : H2O, UV 254 nm) to afford
alterporriol F (10, 7 mg), alterporriol A/B (11, 270 mg) and alterporriol C (12, 40 mg).
Fraction 6 was chromatographed on silica gel, eluted from CH2Cl2 to MeOH followed by
HPLC (Nova-Pak RP-C18, 2 : 3 MeOH–H2O, UV 254 nm) to yield alterporriol D/E
(13, 20 mg).

1070
P. Phuwapraisirisan et al.
3.4. Zinnimide (2)
Yellow amorphous solid; UV (MeOH) ꢁmax (log ") 320 (3.54), 284 (3.47), 242 (4.32);
HRESIMS m/z [M þ Na]þ 298.1065 (Calcd for C15H17NO4Na, 298.1055); 1H and
13C NMR (Table 1).
3.5. Deprenylzinnimide (8)
Yellow amorphous solid; UV (MeOH) ꢁmax (log ") 322 (3.14), 286 (3.08), 245 (3.86);
HRESIMS m/z [M þ Na]þ 230.0439 (Calcd for C10H9NO4Na, 230.0424); 1H and
13C NMR (Table 1).
3.6. Alterporriol F (10)
28
Red powder; ½ꢂꢃD ꢀ 25.0ꢁ (c 0.04, MeOH); UV (MeOH) ꢁmax (log ") 439 (3.30), 280 (4.18),
226 (4.28); HRESIMS m/z [M þ Na]þ 625.1324 (Calcd for C32H26O12Na, 625.1322);
1H and 13C NMR (Table 2).
3.7. Reductive cleavage of 10
To a solution of 10 (6 mg) in 1.0 M NaOH (5 mL), 0.01 M Na2S2O4 (2 mL) was added.
After warming at 80ꢁC until the yellow solution persisted, the reaction mixture was cooled,
neutralised with 2.0 M HCl and extracted with EtOAc (2 ꢂ 10 mL). The EtOAc layer was
evaporated to dryness and purified on a short silica gel column to afford macrosporin
(3, 2 mg), altersolanol C (2 mg), 3a (0.5 mg) and 3b (0.5 mg).
3.8. MTT colorimetric assay
Cytotoxic activities of the isolated compounds were evaluated using standard MTT
colorimetric method previously described by one of the authors (P.S.) (Kongkathip et al.,
2003). The cell lines used in this experiment were HeLa (human cervical carcinoma) and
KB (human epidermoid carcinoma) and adriamycin was used as the standard antibiotic
antitumour agent.
Acknowledgements
This research was funded by Ratchadapisek Sompot Endownment (Contract no. 46/2549) and the
Commission on Higher Education.
References
Haraguchi, H., Abo, T., Fukuda, A., Okamura, N., & Yagi, A. (1996). Mode of phytotoxic action of
altersolanols. Phytochemistry, 43, 989–992.
Kongkathip, N., Kongkathip, B., Siripong, P., Sangma, C., Luangkamin, S., Niyomdecha, M., et al.
(2003). Potent antitumor activity of synthetic 1,2-naphthoquinones and 1,4-naphthoquinones.
Bioorganic & Medicinal Chemistry, 11, 3179–3191.

Natural Product Research
1071
Koyama, J., Morita, I., Tagahara, K., Ogata, M., Mukainaka, T., Tokuda, H., et al. (2001).
Inhibitory effects of anthraquinones and bianthraquinones on Epstein-Barr virus activation.
Cancer Letters, 170, 15–18.
Okamura, N., Haraguchi, H., Hashimoto, K., & Yagi, A. (1993). Altersolanol-related antimicrobial
compounds from a strain of Alternaria solani. Phytochemistry, 34, 1005–1009.
Phuwapraisirisan, P., Rangsan, J., Siripong, P., & Tip-pyang, S. (2006). 9-epi-Viridiol, a novel
cytotoxic furanosteroid from soil fungus Trichoderma virens. Natural Product Research, 20,
1321–1325.
Phuwapraisirisan, P., Swang, K., Siripong, P., & Tip-pyang, S. (2007). Anhydrocochlioquinone A,
a new antitumor compound from Bipolaris oryzae. Tetrahedron Letters, 48, 5193–5195.
Stierle, A., Hershenhorn, J., & Strobel, G. (1993). Zinniol-related phytotoxins from Alternaria
cichorii. Phytochemistry, 32, 1145–1149.
Suemitsu, R., Horiuchi, K., Kubota, M., & Okamatsu, T. (1990). Production of alterporriols,
altersolanols and macrosporin by Alternaria porri and A. Solani. Phytochemistry, 29,
1509–1511.
Suemitsu, R., Ohnishi, K., Yanagawase, S., Yamamoto, K., & Yamada, Y. (1989). Biosynthesis of
macrosporin by Alternaria porri. Phytochemistry, 28, 1621–1622.
Suemitsu, R., Ueshima, T., Yamamoto, T., & Yanagawase, S. (1988). Alterporriol C: A modified
bianthraquinone from Alternaria porri. Phytochemistry, 27, 3251–3254.
Suemitsu, R., Yamamoto, T., Miyai, T., & Ueshima, T. (1987). Alterporriol A: A modified
bianthraquinone from Alternaria porri. Phytochemistry, 26, 3221–3224.