Nelumal A, the active principle from Ligularia nelumbifolia, is a novel farnesoid X receptor agonist

Article abstract of DOI:10.1016/j.bmcl.2012.03.057

A series of 29 oxyprenylated and azoprenylated phenylpropanoids were chemically synthesized and tested in transfected cultured HepG2 cells by means of the dual-luciferase assay as farnesoid X receptor (FXR) agonists, using the endogenous ligand chenodeoxy

Full text of DOI:10.1016/j.bmcl.2012.03.057

Bioorganic & Medicinal Chemistry Letters 22 (2012) 3130–3135
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Nelumal A, the active principle from Ligularia nelumbifolia, is a novel
farnesoid X receptor agonist
Francesco Epifano a, , Salvatore Genovese a, E. James Squires b, Matthew A. Gray b
⇑
a Dipartimento di Scienze del Farmaco, Università ‘G. D’Annunzio’ Chieti-Pescara, Via dei Vestini 31, 66100 Chieti Scalo (CH), Italy
b Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada N1G2W1
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of 29 oxyprenylated and azoprenylated phenylpropanoids were chemically synthesized and
tested in transfected cultured HepG2 cells by means of the dual-luciferase assay as farnesoid X receptor
(FXR) agonists, using the endogenous ligand chenodeoxycholic acid (CDCA) as reference drug. Among the
tested molecules, three compounds, namely auraptene, nelumol A, and nelumal A showed a potency
comparable to the endogenous ligand, with the latter natural product having a level of activity slightly
superior to CDCA. Nelumal A is thus of interest as a valuable potential novel lead compound in the search
for FXR agonists.
Received 17 February 2012
Revised 12 March 2012
Accepted 14 March 2012
Available online 22 March 2012
Keywords:
Oxyprenylated natural phenylpropanoids
Farnesoid X receptors
Nelumal A
Ó 2012 Elsevier Ltd. All rights reserved.
Ligularia nelumbifolia
The nuclear receptor family of transcription factors is intimately
involved in the regulation of a wide variety of metabolic processes,
including synthesis of endogenous compounds as well as metabo-
lism of both endogenous and exogenous substances. In humans, 49
members of this family have been isolated and identified.1 Nuclear
receptors are modular in nature, being made up of a set of distinct
domain types, though the structure of these domains varies exten-
sively across the family. The N-terminus comprises a variable do-
main containing the AF-1 motif, which is highly conserved
between nuclear receptor family members and is implicated in li-
gand independent transactivation. This N-terminal domain is fol-
lowed by the DNA binding domain (DBD), consisting of two Zn
fingers specific for recognizing the specific DNA response elements
in the promoter regions of target genes. Connected to the DBD via a
highly variable hinge region is the ligand binding domain (LBD),
which contains the active ligand binding pocket, shaped to bind
to the distinct class of ligands recognized by the nuclear receptor.
At the C-terminal end of the ligand binding domain is the AF-2 mo-
tif, which is thought to be involved in ligand dependent transacti-
vation.1 The C-terminal end of the protein is also involved in
protein–protein binding, for a number of nuclear receptors forms
homo- or heterodimers upon activation by ligands.2
target genes; these are involved in various pathways, primarily bile
acid homeostasis, lipoprotein metabolism, and glucose metabo-
lism.4 Though initially isolated as a receptor capable of being trans-
activated by farnesol, the most potent agonists of FXR are bile acids
and their metabolic derivatives,5 indicating its role as a major step
in the moderation of bile acid homeostasis. Due to its involvement
in specific metabolic pathways, FXR is predominantly expressed in
the liver, intestine, kidneys, and adrenal glands, though is poorly
expressed in tissues such as brain, heart, and lung.6
The ligand profile of FXR has been shown in recent years to ex-
tend beyond bile acids to both endogenous compounds as well as
exogenous compounds, both natural and synthetic. Wang et al.
have shown that FXR could be transactivated by androsterone, an
androgenic metabolite of testosterone, suggesting that the meta-
bolic pathways induced by FXR may be linked to sex steroid lev-
els.7 As well, it has been shown that the cholesterol derivative
oxysterol 22-(R)-hydroxycholesterol induced FXR transactivation.8
Several natural products have been found to be agonists of FXR,
including bile acid derivatives, marchatins, and ginkgolic acids,9
as well as synthetic compounds, such as the potent activator
GW4064 and its derivatives.10,11 These compounds were tested
to determine their potential as analytical tools or therapeutic
agents. GW4064 and its derivatives have been powerful analytical
tools, though their therapeutic efficacy has been limited due to
bioavailability issues with the crystalline forms, an issue being
addressed using self-emulsifying drug delivery systems.12
The farnesoid X receptor (FXR; NR1I3) is a member of the Class
II subset of nuclear receptors, and as such forms a heterodimer
with retinoid X receptor (RXR) upon ligand activation.3 Upon acti-
vation, FXR targets response elements in the promoter regions of
Dysfunction in the activity of FXR leads to several disease states
and for this reason FXR represents an important pharmacological
target. The loss of FXR in mice (FXRꢀ/ꢀ mice) has been shown to
⇑
Corresponding author.
E-mail address: fepifano@unich.it (F. Epifano).
0960-894X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2012.03.057

F. Epifano et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3130–3135
3131
R2
result in type 2 diabetes, hypertriglyceridemia, cholestasis, and cho-
lesterol gallstone disease.13 These effects are due to the disruption
in the homeostasis of bile acids, triglycerides, and glucose that is
modulated by the transactivation of FXR. As well, FXRꢀ/ꢀ mice were
found to spontaneously develop hepatic cancers, likely due to the
disruption of homeostatic balances within the liver, specifically in
bile acid homeostasis, as well as dysfunction in hepatic regenera-
tion, which FXR has been shown to be intimately involved in.4 As
such, FXR is an important therapeutic target for dealing with a num-
ber of hepatic metabolic diseases, as well as hepatic cancers, and
therefore isolation of compounds that would act as potent agonists
for FXR could be an important step in dealing with these diseases.
Oxyprenylated natural products, such as isopentenyloxy-(C5),
geranyloxy-(C10), and farnesyloxy-(C15) related compounds, repre-
sent a family of secondary metabolites that were considered for
years to be merely biosynthetic intermediates of the more wide-
spread C-prenylated derivatives. These secondary metabolites have
been recognized in the last two decades as interesting and valuable
biologically active phytochemicals. Approximately 300 compounds
have been isolated and structurally characterized from plants, pri-
marily from the families Rutaceae, Compositae, Guttiferae, and
Leguminosae, comprising several edible vegetables and fruits.
The phytochemistry and pharmacology of prenyloxyphenylpropa-
noids was recently reviewed.13
R1O
O
O
1 R1= isopentenyl, R2 = H
2 R1= geranyl, R2 = H
3 R1= isopentenyl, R2 = OH
4 R1= isopentenyl, R2 = OCH3
5 R1= geranyl, R2 = OCH3
R4
R1
R3O
R2
6 R1= trans CH=CH-COOH, R2 = OCH3, R3 = isopentenyl, R4 = H
7 R1= trans CH=CH-COOH, R2 = OCH3, R3 = geranyl, R4 = H
8 R1= trans CH=CH-COOH, R2 = H, R3 = isopentenyl, R4 = H
9 R1= trans CH=CH-COOH, R2 = H, R3 = geranyl, R4 = H
10 R1= COOH, R2 = H, R3 = isopentenyl, R4 = H
11 R1= COOH, R2 = H, R3 = geranyl, R4 = H
12 R1= CHO, R2 = H, R3 = isopentenyl, R4 = H
13 R1= CHO, R2 = OCH3, R3 = geranyl, R4 = H
14 R1= trans CH=CHCHO, R2 = OCH3, R3 = isopentenyl, R4 = H
15 R1= trans CH=CHCHO, R2 = OCH3, R3 = geranyl, R4 = H
16 R1= trans CH=CHCHO, R2 = OCH3, R3 = geranyl, R4 = OCH3
17 R1= CH2OH, R2 = OCH3, R3 = isopentenyl, R4 = OCH3
18 R1= CH2CH2OH, R2 = H, R3 = isopentenyl, R4 = H
19 R1= CH2CH2OAc, R2 = H, R3 = isopentenyl, R4 = H
20 R1= CH2CH2OH, R2 = H, R3 = geranyl, R4 = H
As a continuation of our ongoing studies aimed to better char-
acterize the phytochemical and pharmacological properties of nat-
ural and semisynthetic oxyprenylated and azoprenylated
phenylpropanoids, in this work we synthesized and investigated
the effect of 29 selected compounds belonging to this group on
FXR using a whole cell reporter assay system.
21 R1= CH2CH2CH2OH, R2 = H, R3 = isopentenyl, R4 = H
22 R1= trans CH=CHCH2OH, R2 = OCH3, R3 = geranyl, R4 = H
23 R1= trans CH=CHCH2OH, R2 = OCH3, R3 = isopentenyl, R4 = OCH3
24 R1= trans CH=CHCH2OH, R2 = OCH3, R3 = geranyl, R4 = OCH3
The chemical structures of the compounds that we studied are
illustrated in Figure 1.
The main natural sources of 7-isopentenyloxycoumarin (1),
auraptene (2), 8-hydroxy-7-isopentenyloxy-coumarin (3), lacinar-
tin (4), collinin (5), boropinic acid (6), 40-geranyloxyferulic acid
(7), geranyloxy-p-coumaric acid (9), valencic acid (10), boropinal
(14), (2E)-3-(4-((E)-3,7-dimethylocta-2,6-dienyloxy)-3-methoxy-
phenyl)acrylaldehyde (15), nelumal A (16), (2E)-3-(4-((E)-3,7-dim-
RO
OH
OH
O
25 R = isopentenyl
26 R= geranyl
ethylocta-2,6-dienyloxy)-3-methoxyphenyl)prop-2-en-1ol
(22),
boropinol C (23), nelumol A (24), 4-hydroxycordoin (25), 40-gera-
nyloxyisoliquiritigenin (26), and N-isopentenylanthranilic acid
(27) have been described previously.13–15
COOH
N
H
Geranyloxy-p-benzoic acid (11) has been previously extracted
from enzymatic extracts of Piper crassinervium Kunth (Pipera-
ceae),16 p-isopentenyloxybenzaldehyde (12) has been isolated
from the leaf oil of Clausena anisata Hook f. (Rutaceae),17 geranyl-
oxyvanillin (13) has been obtained from the apolar extracts of
Crithmum maritimum L. (Apiaceae),18 3,5-dimethoxy-4-isopente-
nyloxybenzyl alcohol (17) has been extracted in form of angelate
ester from the roots of Erechtites hieracifolia (L.) Raf ex DC.(Astera-
ceae),19 etrogol (18) and its acetate (19) has been isolated from Cit-
rus spp. (Rutaceae),20 3-(4-geranyloxyphenyl)-1-ethanol (20) is a
juvenile hormone of several insect species,21 3-(4-isopentenyloxy-
phenyl)-1-propanol (21) has been obtained from the roots of
Fagara zanthoxyloides Lam.22 and Zanthoxylum wutaiense Chen
27
COOH
NHAc
O
28
O
O
O
(Rutaceae),23 N-acetyl-O-isopentenyl-
L-tyrosine (28) has been
extracted from the fungus Pithomyces ellis,24 and finally lawsone
2-isopentenyl ether (29) has been isolated from the fungus
Streptocarpus dunnii.25
29
Figure 1. Illustration of the chemical structures studied. The 29 compounds that
we studied belong to six chemical groups: coumarins (1–5), cinnamic and benzoic
acids (6–11, 27), benzaldehydes and cinnamaldehydes (12–16), cinnamyl alcohols
(17–24), chalcones (25 and 26) amino acid derivatives (28), and quinones (29).
The synthesis of compounds (1–10), (14–16), and (22–26) was
accomplished according to the procedures described previously.14
Geranyloxy-p-benzoic acid (11), p-isopentenyloxybenzaldehyde
(12), geranyloxyvanillin (13), etrogol (18), 3-(4-geranyloxyphe-
nyl)-1-ethanol (20) 3-(4-isopentenyloxyphenyl)-1-propanol (21),
commercially available phenolic derivatives by alkylation with
either geranyl or 3,3-dimethylallyl bromide using K2CO3 as the
base in refluxing acetone (Scheme 1).
N-acetyl-O-isopentenyl-L-tyrosine (28), and lawsone 2-isopentenyl
ether (29) were synthesized starting from the corresponding

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F. Epifano et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3130–3135
Br
experimental procedure as above, and then submitted to alkaline
hydrolysis with 50% KOH at 80 °C to provide the desired product
Ar OH
Ar
O
(Scheme 4).26
K2CO3, acetone
reflux 1h
All compounds were then assessed for their effect in a FXR re-
porter assay in transfected HepG2 cells. Chemicals were tested at
7 concentration levels, namely 0.1, 1.0, 5.0, 10, 25, 50, and
Scheme 1. Isopentenylation of aryl ethers.
100 lM, DMSO was used as a negative control at 0.05% v/v, and
CDCA was used as a positive control. Table 1 reports the level of
activation of FXR by the synthesized compounds on FXR as mea-
sured by means of the dual-luciferase assay. Non-active samples
are shaded light grey, while strong agonists are shaded dark grey.
Weak and medium agonists are unshaded. Figure 2 illustrates the
dose response curves for the strong agonists auraptene, nelumal
A and nelumol A compared to CDCA.
O
CH3O
HO
OCH3
From the results obtained and reported in Table 1 it is evident
that only three compounds, namely auraptene (2), nelumal A
(16), and nelumol A (24) can be regarded as FXR agonists exerting
an appreciable activity. All three of these compounds were recently
found to exert appreciable pharmacological activities: auraptene
(2) is nowadays well recognized as an anti-cancer, anti-bacterial,
anti-protozoal, anti-fungal, anti-inflammatory, and anti-oxidant
agent27 in in vitro, in whole cells, and/or in in vivo systems, and re-
cently an effective remedy against metabolic disorders involving li-
ver functionality28,29; nelumol A (24), and nelumal A (16) were
shown to exert mild to good activity against several different hu-
man cancer cell lines.30–33 The effective interaction disclosed by
our study between auraptene and FXR, which is expressed strongly
in liver and is involved in its functionality as stated in the Introduc-
tion, can shed light on the mechanism of action of this geranyloxy-
coumarin as a hepatoprotective agent.28,29 On the other hand, it is
well known that FXR is also a key component of cancer pathogenic-
ity. The central role that FXR plays in bile acid homeostasis impli-
Br
K2CO3, DMF
reflux 30 min.
O
CH3O
O
CH3O
O
OH
NaBH4
H2O/EtOH
OCH3
OCH3
30
17
Scheme 2. Synthesis of compounds 30 and 17.
This simple but very efficient and ‘clean’ reaction provided the
desired products after crystallization (n-hexane) with the follow-
ing yields: 50% (compound 11), 80% (compound 12), 96% (com-
pound 13), 93% (compound 18), 85% (compound 20), 84%
(compound 21), 80% (compound 28), and 69% (compound 29).
3,5-Dimethoxy-4-isopentenyloxybenzyl alcohol (17) was ob-
tained by a two-step synthesis (Scheme 2) from commercially
available syringaldehyde, that was first alkylated in position 4
employing similar reaction conditions as depicted above with the
only modification of substituting acetone with DMF. The use of
an aprotic polar solvent was needed due to the steric hindrance ex-
erted by the two –OCH3 groups in position 3 and 5 to the alkylation
of the phenol group. Intermediate (30) was obtained in 91% yield
and was then reduced to the benzyl alcohol derivative (17) in
99% yield with NaBH4 using a EtOH/H2O mixture as the solvent
at room temperature.
cates it as
a potentially important factor in preventing
tumorigenesis in the liver. It has been found that hepatic tumors
can be initiated through hepatic injury due to elevated bile acid
levels, including through dietary supplementation.15 A similar gen-
eration of hepatic tumors, due to disruption of bile acid homeosta-
sis, has been seen in FXR knockout mice, indicating FXR plays a role
as a metabolic suppressor of tumorigenesis.34,35 FXR also appears
to play a pivotal role as a tumorigenesis repressor in the intestinal
tract; however it appears that its modulation of bile acid levels is
not primary in this preventative role.36 In the intestine, FXR is
down-regulated in tumor progenitor cells, resulting in the disrup-
tion of several cellular pathways that are involved in mucosal bar-
rier maintenance and induction of apoptosis in aberrant cells. As
such, induction of FXR expression in these aberrant cells, and its in-
creased transactivation, could result in prevention of intestinal
tumorigenesis. In this context the observed interaction between
auraptene and FXR could partly account for the reported properties
Etrogol acetate (19) was synthesized in 93% yield from etrogol
(18) using Ac2O and Et3N as the base in Et2O at room temperature
(Scheme 3).
Finally N-isopentenylanthranilic acid (27) was obtained in 91%
yield from commercially available methyl anthranilate that was
first N-alkylated with 3,3-dimethylallyl bromide, using the same
OH
OAc
Ac2O, Et3N
Et2O
O
O
18
19
Scheme 3. Synthesis of etrogol acetate.
CO2H
Br
CO2Me
NH2
K2CO3, acetone, reflux 1h
a.
b.
NH
KOH 50%
27
Scheme 4. Synthesis of compound 27.

F. Epifano et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3130–3135
3133
Table 1
Effect of the 29 compounds under study on the activity of FXR relative to DMSO control
Activity levels are expressed as mean fold changes relative to the control values obtained from the DMSO treated cells with standard errors. Experiments were conducted in
duplicate, repeated three times.
⁄Significant fold change (p <0.05) compared to DMSO controls.
#Compounds with a dose dependent effect (p <0.001), as determined by linear regression.
Figure 2. Response of FXR to CDCA and strong agonists in fold response of the DMSO control (dashed line). Significant fold change (p <0.05) compared to the control is
denoted by (ꢁ), while significant fold changes (p <0.05) to CDCA treatment at the same concentration are denoted by (). Data from duplicates repeated three times
(mean SEM).
of this geranyloxycoumarin as a dietary chemoprotective agent
against colon adenoma and adenocarcinoma.37,38 Although some
reported naturally occurring FXR ligands, like gingkolic acid and
its derivatives, seem to act as membrane disrupters thus leading
to the observed cytotoxicity,39 this is not the case of compounds
tested herein. Although some have shown cytotoxic effects on
cancer cell lines, like recently reported, including auraptene (2)40
and nelumal A (16)15 the integrity of the cell structure after
in vitro incubation with a prenyloxy molecule was assessed by
quantitative videomicroscopy.

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F. Epifano et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3130–3135
In terms of structure–activity relationships, the geranyl substi-
References and notes
tuted compounds were found to be in general more active than those
having an isopentenyloxy side chain. The higher activity recorded for
nelumal A (16) compared to the respective cinnamyl alcohol nelumol
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A (24) led us to hypothesize that the presence of an a,b-unsaturated
conjugated aldehyde as the C3 portion of the phenylpropanoid core of
these natural product, is a crucial structural requirement for the
biological activity, whereas its reduction to an allylic alcohol or its
oxidation to carboxylic acid tended to decrease or abolish the effect.
Nevertheless, another important structural feature, namely the 3,5-
dimethoxy substituted aromatic ring, could be revealed from results
reported in Table 1. In fact, comparing the activity of nelumal A (16)
and its analogue (2E)-3-(4-((E)-3,7-dimethylocta-2,6-dienyloxy)-3-
methoxyphenyl)acrylaldehyde (15), it was found that the first was
about 15-fold more potent than the latter as a FXR agonist, highlight-
ing the importance of substitution of the hydrogen in position 5 of the
aromatic ring with a methoxy group. Also the presence of a coumarin
nucleus, that remains chemically stable once inside the cell41 and so
cannot be related to cinnamic acid derivatives (6)–(9) in terms of SAR
considerations, seemed to provide a certain level of effective interac-
tion as a FXR agonist, auraptene (2) being the most potent compound
compared to the other three coumarins, lacinartin (3), 8-hydroxy-7-
isopentenyloxycoumarin (4), and collinin (5). In this case, however,
4. Wang, Y. D.; Chen, W. D.; Moore, D. D.; Huang, W. Cell Res. 2008, 24, 1087.
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Yamaguchi, T.; Kawanishi, T. J. Pharmacol. Sci. 2008, 107, 285.
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26. Analytical data of all adducts obtained by chemical synthesis described herein
were in full agreement with those already reported in the literature for the
same compounds (see Ref. 15).
only the O-geranyl side chain, together with the a-benzopyrone ring,
seemed to be a crucial structural requirement for the observed activ-
ity. Taken together, these considerations address to the fact that the
pattern of substitution in the aromatic ring is crucial to structurally
define a novel lead compound as FXR agonist. Moreover the configu-
ration of the conjugated double bond seems to have less importance
to this aim, being trans (like in nelumal A (16)) or cis, like in auraptene
(2), substituted compound active to a comparable extent. A more piv-
otal role on the contrary seems to be played by the terminal moiety of
the C3 skeleton in the phenylpropanoid core of these natural prod-
ucts, for which polar groups, like carboxylic acids or alcohols as found
in compounds (6)–(9) and (22)–(24) tended to decrease the activity
as FXR agonists, while moieties featured by low to medium polarity
like a lactone ring or an aldehyde, as found in nelumal A (16) and
auraptene (2), seemed to enhance this kind of effect.
In this manuscript we described for the first time the interac-
tion of some natural prenyloxyphenylpropanoids with FXR. We
discovered that three of these compounds could be claimed to
good to very good agonists of this class of receptor. Nelumal A
was seen to be the most potent one and on this basis it could be
useful to identify a novel class of FXR ligand using (16) as the lead
compound. The naturally widespread geranyloxycoumarin aurap-
tene (2) also displayed an appreciable amount of activity. As re-
ported previously,28 this compound is also found in several
edible fruits and vegetables. This consideration, together with the
statement that FXR plays a pivotal role in liver homeostasis and he-
patic syndromes, could be useful in exploring the effect of dietary
feeding with vegetable-containing auraptene, like agrumes, on the
chemoprevention of liver diseases. In the same way, we recently
provided evidence for the chemoprevention of colon cancer by
the same natural product.37,38,40
7-Isopentenyloxycoumarin (1): Anal. Calcd for C14H14O3: C, 73.03; H, 6.13; O,
20.84. Found: C, 73.01; H, 6.16; O, 20.81.
Auraptene (2): Anal. Calcd for C19H22O3: C, 76.48; H, 7.43; O, 16.09. Found: C,
76.52; H, 7.46; O, 16.05.
8-Hydroxy-7-isopentenyloxy-coumarin (3): Anal. Calcd for C14H14O4: C, 68.28; H,
5.73; O, 25.99. Found: C, 68.24; H, 5.76; O, 25.96.
Lacinartin (4): Anal. Calcd for C15H16O4: C, 69.22; H, 6.20; O, 24.59. Found: C,
69.19; H, 6.16; O, 24.55.
Collinin (5): Anal. Calcd for C20H24O4: C, 73.15; H, 7.37; O, 19.49. Found: C,
73.12; H, 7.34; O, 19.47.
Boropinic acid (6): Anal. Calcd for C15H18O4: C, 68.69; H, 6.92; O, 24.40. Found:
C, 68.72; H, 6.94; O, 24.36.
40-Geranyloxyferulic acid (7): Anal. Calcd for C20H26O4: C, 72.70; H, 7.93; O,
19.37. Found: C, 72.69; H, 7.94; O, 19.34.
Isopentenyloxy-p-coumaric acid (8): Anal. Calcd for C14H16O3: C, 72.39; H, 6.94;
O, 20.66. Found: C, 72.36; H, 6.99; O, 20.64.
Geranyloxy-p-coumaric acid (9): Anal. Calcd for C19H24O3: C, 75.97; H, 8.05; O,
15.98. Found: C, 75.93; H, 8.01; O, 15.96.
Valencic acid (10): Anal. Calcd for C12H14O3: C, 69.89; H, 6.84; O, 23.27. Found:
C, 69.92; H, 6.80; O, 23.24.
Geranyloxy-p-benzoic acid (11): Anal. Calcd for C17H22O3: C, 74.42; H, 8.08; O,
17.49. Found: C, 74.38; H, 8.03; O, 17.45.
Acknowledgment
p-Isopentenyloxybenzaldehyde (12): Anal. Calcd for C12H14O2: C, 75.76; H, 7.42;
O, 16.82. Found: C, 75.78; H, 7.38; O, 16.82.
Geranyloxyvanillin (13): Anal. Calcd for C18H24O3: C, 74.97; H, 8.39; O, 16.64.
Found: C, 74.99; H, 8.33; O, 16.65.
Boropinal (14): Anal. Calcd for C15H18O3: C, 73.15; H, 7.37; O, 19.49. Found: C,
73.18; H, 7.33; O, 19.45.
F.E. and S.G. wish to acknowledge financial support to the re-
search from the University ‘G. D’Annunzio’ of Chieti-Pescara.
(2E)-3-(4-((E)-3,7-Dimethylocta-2,6-dienyloxy)-3-methoxyphenyl)acrylaldehyde
(15): Anal. Calcd for C20H26O3: C, 76.40; H, 8.33; O, 15.27. Found: C, 76.45; H,
8.31; O, 15.25.
Supplementary data
Nelumal A (16): Anal. Calcd for C21H28O4: C, 73.23; H, 8.19; O, 18.58. Found: C,
73.20; H, 8.22; O, 18.55.
3,5-Dimethoxy-4-isopentenyloxybenzyl alcohol (17): Anal. Calcd for C14H20O4: C,
66.65; H, 7.99; O, 25.36. Found: C, 66.60; H, 7.94; O, 25.35.
Supplementary data associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/j.bmcl.
2012.03.057.

F. Epifano et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3130–3135
3135
Etrogol (18): Anal. Calcd for C13H18O2: C, 75.69; H, 8.80; O, 15.51. Found: C,
75.66; H, 8.82; O, 15.54.
27. Inoue, K.; Ueda, S.; Nayeshiro, H.; Moritome, N.; Inouye, H. Phytochemistry
1984, 23, 313.
Etrogol acetate (19): Anal. Calcd for C15H20O3: C, 72.55; H, 8.12; O, 19.33.
Found: C, 72.50; H, 8.13; O, 19.37.
3-(4-Geranyloxyphenyl)-1-ethanol (20): Anal. Calcd for C18H26O2: C, 78.79; H,
9.55; O, 11.66. Found: C, 78.83; H, 9.53; O, 11.67.
28. Genovese, S.; Epifano, F. Curr. Drug Targets 2011, 12, 381.
29. Nagao, K.; Yamano, N.; Shirouchi, B.; Inoue, N.; Murakami, S.; Sasaki, T.;
Yanagita, T. J. Agric. Food Chem. 2010, 58, 9028.
30. Sahebkar, A. Ann. Hepatol. 2011, 10, 575.
3-(4-Isopentenyloxyphenyl)-1-propanol (21): Anal. Calcd for C14H20O2: C, 76.33;
H, 9.15; O, 14.52. Found: C, 76.31; H, 9.11; O, 14.57.
31. Bohlmann, F.; Grenz, M.; Gupta, R. K.; Dhar, A. K.; Ahmed, M.; King, R. M.;
Robinson, H. Phytochemistry 1980, 19, 2391.
(2E)-3-(4-((E)-3,7-Dimethylocta-2,6-dienyloxy)-3-methoxyphenyl)prop-2-en-1ol
(22): Anal. Calcd for C20H28O3: C, 75.91; H, 8.92; O, 15.17. Found: C, 75.87; H,
8.86; O, 15.20.
Boropinol C (23): Anal. Calcd for C16H22O4: C, 69.04; H, 7.97; O, 22.99. Found: C,
69.00; H, 7.92; O, 22.94.
32. Zhao, Y.; Parsons, S.; Baxter, R. L.; Tan, R. X.; Jia, Z. J.; Sun, H. D.; Rankin, D. W. H.
Tetrahedron 1997, 53, 6195.
33. Zhao, Y.; Hao, X.; Lu, W.; Cai, J.; Yu, H.; Sevénet, T.; Guéritte, F. J. Nat. Prod. 2002,
65, 902.
34. Barone, M.; Maiorano, E.; Ladisa, R.; Cuomo, R.; Pece, A.; Berloco, P.; Caruso, M.
L.; Valentini, A. M.; Iolascon, A.; Francavilla, A.; Di Leo, A.; Ierardi, E. Hepatology
2003, 37, 880.
Nelumol A (24): Anal. Calcd for C21H30O4: C, 72.80; H, 8.73; O, 18.47. Found: C,
72.77; H, 8.70; O, 18.44.
4-Hydroxycordoin (25): Anal. Calcd for C20H20O4: C, 74.06; H, 6.21; O, 19.73.
Found: C, 74.02; H, 6.18; O, 19.77.
35. Kim, I.; Morimura, K.; Shah, Y.; Yang, Q.; Ward, J. M.; Gonzalez, F. J.
Carcinogenesis 2007, 28, 940.
36. Yang, F.; Huang, X.; Yi, T.; Yen, Y.; Moore, D. D.; Huang, W. Cancer Res. 2007, 67,
863.
40-Geranyloxyisoliquiritigenin (26): Anal. Calcd for C25H28O4: C, 76.50; H, 7.19;
O, 16.31. Found: C, 76.46; H, 7.18; O, 16.27.
N-Isopentenylanthranilic acid (27): Anal. Calcd for C12H15NO2: C, 70.22; H, 7.37;
N, 6.82; O, 15.59. Found: C, 70.23; H, 7.38; N 6.78; O, 15.56.
N-Acetyl-O-isopentenyl-L-tyrosine (28): Anal. Calcd for C16H21NO4: C, 65.96; H,
37. Modica, S.; Gadaleta, R. M.; Moschetta, A. Nucl. Recept. Signal. 2010, 8, e005.
38. Kohno, H.; Suzuki, R.; Curini, M.; Epifano, F.; Maltese, F.; Prieto Gonzales, S.;
Tanaka, T. Int. J. Cancer 2006, 118, 2936.
7.27; N, 4.81; O, 21.97. Found: C, 65.93; H, 7.23; N 4.78; O, 21.96.
Lawsone 2-isopentenyl ether (29): Anal. Calcd for C15H14O3: C, 74.36; H, 5.82; O,
19.81. Found: C, 74.31; H, 5.76; O, 19.84.
Isopentenyloxysyringaldehyde (30): Anal. Calcd for C14H18O4: C, 67.18; H, 7.25;
O, 25.57. Found: C, 67.17; H, 7.22; O, 25.54.
39. Stasiuk, M.; Kozubek, A. Cell. Mol. Life Sci. 2010, 67, 841.
40. Tanaka, T.; de Azevedo, M. B.; Durán, N.; Alderete, J. B.; Epifano, F.; Genovese,
S.; Tanaka, M.; Tanaka, T.; Curini, M. Int. J. Cancer 2010, 126, 830.
41. Weinstain, R.; Segal, E.; Satchi-Fainaro, R.; Shabat, D. Chem. Commun. 2010, 46,
553.