Hemi-Synthesis and Anti-Oomycete Activity of Analogues of Isocordoin

Article abstract of DOI:10.3390/molecules22060968

An efficient synthesis of a series of 4-oxyalkyl-isocordoin analogues (2–8) is reported for the first time. Their structures were confirmed by¹H-NMR,¹³C-NMR, and HRMS. Their anti-oomycete activity was evaluated by mycelium and spores inhibition assay against two selected pathogenic oomycetes strains: Saprolegnia parasitica and Saprolegnia australis. The entire series of isocordoin derivatives (except compound 7) showed high inhibitory activity against these oomycete strains. Among them, compound 2 exhibited strong activity, with minimum inhibitory concentration (MIC) and minimum oomyceticidal concentration (MOC) values of 50 μg/mL and 75 μg/mL, respectively. The results showed that 4-oxyalkylated analogues of isocordoin could be potential anti-oomycete agents.

Full text of DOI:10.3390/molecules22060968

molecules
Article
Hemi-Synthesis and Anti-Oomycete Activity of
Analogues of Isocordoin
1
2,3
3
4
5
Beatriz Escobar , Iván Montenegro , Joan Villena , Enrique Werner , Patricio Godoy ,
6
1,
Yusser Olguín and Alejandro Madrid *
1
Departamento de Química, Facultad de Ciencias Naturales y Exactas, Universidad de Playa Ancha,
Avda. Leopoldo Carvallo 270, Playa Ancha, Valparaíso 2340000, Chile; escobarbeatriz25@gmail.com
Escuela de Obstetricia y Puericultura, Facultad de medicina, Campus de la Salud,
2
Universidad de Valparaíso, Angamos 655, Reñaca, Viña del Mar 2520000, Chile; ivan.montenegro@uv.cl
Centro de Investigaciones Biomédicas (CIB), Escuela de Medicina, Universidad de Valparaíso,
3
Av. Hontaneda Nº 2664, Valparaíso 2340000, Chile; juan.villena@uv.cl
Departamento De Ciencias Básicas, Campus Fernando May Universidad del Biobío.
4
Avda. Andrés Bello s/n casilla 447, Chillán 3780000, Chile; ewerner@ubiobio.cl
Instituto de Microbiología Clínica, Facultad de Medicina, Universidad Austral de Chile, Los Laureles s/n,
5
Isla Teja, Valdivia 5090000, Chile; patricio.godoy@uach.cl
Center for Integrative Medicine and Innovative Science (CIMIS), Facultad de Medicina,
6
Universidad Andrés Bello, Santiago 8320000, Chile; yusser.olguin@unab.cl
*
Correspondence: alejandro.madrid@upla.cl; Tel.: +56-032-250-0526
Received: 25 May 2017; Accepted: 8 June 2017; Published: 10 June 2017
0
Abstract: An efficient synthesis of a series of 4 -oxyalkyl-isocordoin analogues (
2
–
8) is reported
for the first time. Their structures were confirmed by 1H-NMR, C-NMR, and HRMS.
Their anti-oomycete activity was evaluated by mycelium and spores inhibition assay against two
selected pathogenic oomycetes strains: Saprolegnia parasitica and Saprolegnia australis. The entire
13
series of isocordoin derivatives (except compound
7) showed high inhibitory activity against these
oomycete strains. Among them, compound exhibited strong activity, with minimum inhibitory
2
concentration (MIC) and minimum oomyceticidal concentration (MOC) values of 50
µ
g/mL and
0
75
µg/mL, respectively. The results showed that 4 -oxyalkylated analogues of isocordoin could
be potential anti-oomycete agents.
Keywords: isocordoin; oxyalkyl derivates; anti-oomycete activity; Saprolegnia sp.
1
. Introduction
Chalcones bearing prenyl groups are an abundant subclass of naturally occurring chalcones [1].
The biosynthesis of C-prenyl chalcones involves the coupling of products from the shikimic and
mevalonic acid pathways. The latter produces the prenyl group, while the former produces
the aromatic compound. The two products are linked together by prenyl tranferase enzymes [2].
Almost 80% of these molecules are monoprenylated and the remaining 20% consist of di and/or
0
triprenyl derivatives. C-prenylation takes place more frequently on ring A at positions 3 and/or
0
5
, as well as 3 and/or 5 [
3
]. Prenylated chalcones have been isolated from plants mainly
]. This class of compounds has
been found to display a variety of biological activities that are anticarcinogenic, antiprotozoal,
larvicidal, anti-inflammatory, antibacterial, antioxidant, and antifungal [ ]. A representative
example of naturally occurring bioactive C-prenylated chalcones, isocordoin ( ), was isolated
from Lonchocarpus species [ ] or Aeschynomene fascicularis [ ]. Isocordoin has been found to
have a range of interesting biological properties in vitro that may have therapeutic and industrial
belonging to the families of Leguminosae and Moraceae [
4
5,6
1
7,8
9
Molecules 2017, 22, 968; doi:10.3390/molecules22060968
www.mdpi.com/journal/molecules

Molecules 2017, 22, 968
2 of 9
utilities including antiprotozoal (for treatment of Leishmania mexicana, L. braziliensis, L. amazonensis
and Trypanosoma cruzi) [10 11], insect antifeedant (for treating lepidopterous larvae of Spodoptera
,
littoralis and S. exempta, which are considered one of the most destructive pests of crops) [12] and
a vasorelaxant effect [13], as well as a potential “broad-spectrum” anticancer agent (applicable to
both oral-laryngeal and prostate cancers) [
of researchers in the preparation of isocordoin. The synthesis of
condensation was obtained in unsatisfactory yields [15 16]. In contrast, the enzymatic prenylation of
,4 -dihydroxychalcone with cell cultures of Morus nigra biosynthetically produced isocordoin in very
high yield [16 17]. Recent works have explored the introduction of isoprenoids into the structure of
9,
10,
14]. These bioactivities have stimulated the interest
1
via the Claisen–Schmidt
,
0
0
2
,
chalcones to obtain more active hybrid compounds [18], or even with new biological properties for
the development of novel products either in medicine or in agrochemistry. In this paper, a series of
4-oxyalkyl-isocordoin analogues
2–8 were synthesized and evaluated for their anti-oomycete activity
against Saprolegnia parasitica and S. australis.
2
. Results and Discussion
2
.1. Synthesis and Characterization
One naturally occurring chalcone, 1, and seven oxyalkyl derivates, 2–8, were synthesized.
The synthetic strategies applied for the synthesis of new chalcones are outlined in Scheme 1 [19,20].
O
OH
O
HO
OH
O
O
O
4
O
OH
O
OH
O
OH
O
i, A
i, E
8
9.0%
79.0%
O
O
HO
6
2
1
O
HO
OH
O
O
O
Scheme 1.
Synthesis of 4-oxyalkyl-isocordoin derivatives
2
–
8
.
Reagents and conditions:
) 2-methyl-1-propenyl
◦
(
i) K CO /CH CN, reflux at 80 C for 4 h.; (
A
) CH I; (
B
) allyl bromide; (
C
2
3
3
3
bromide; (D) crotyl bromide; (E) prenyl bromide; (F) geranyl bromide; (G) farnesyl bromide.

Molecules 2017, 22, 968
3 of 9
Isocordoin (
1) was purified in analogy to the procedures described in [21
,22] with small variations
from the resinous exudate of Adesmia balsamica. The targeted compounds
2–8 were easily attained
in high yields (70–92%) through nucleophilic substitution of isocordoin with the appropriate alkyl
halide in acetonitrile. This reaction resulted in the exclusive formation of the 4-oxyalkyl-derivative,
0
due to steric hindrance caused by the the prenyl chain in position 3 of the aromatic ring A [23
,24] and
the influence exerted by the intramolecular hydrogen bond present in the isocordoin [25].
The structures of compounds
techniques. 13C-NMR assignments were achieved by 2D heteronuclear single quantum correlation
HSQC) and heteronuclear multiple bond correlation (HMBC) experiments.
The IR, NMR, and MS data of compound concurred with those reported for the known
chalcone, commonly named as isocordoin, previously reported from Lonchocarpus xuul [ ].
showed a number of signals that correspond
to an isocordoin-type structure. The spectra of these compounds showed two trans-olefinic protons at
= 7.89 and 7.60 ppm (d, J = 15.4 Hz) readily assigned to those of the 8 and 7 position, respectively;
two aromatic protons at ortho positions (d, J = 9.1 Hz at = 6.48 and 7.77 ppm); and the presence
of a prenyl group (d, J = 7.1 Hz, 2H at = 3.39–3.40 ppm; m, 1H at = 5.25 ppm; and two
singlets, 3H each, at = 1.68 and 1.80 ppm), and two multiplets at
1–8 were established on the basis of IR, NMR, and HR-MS
(
1
8
1
0
The H spectrum of 4 -oxyalkyl-isocordoin derivatives 2–8
δ
δ
δ
δ
δ
δ
= 7.65 ppm (2H) and 7.42 ppm
1
(
3H), corresponding to the five protons of a unsubstituted aromatic ring. The H-NMR spectrum
of
2–
8
showed a chelated hydroxyl-proton signal at
δ
13.39–13.37 ppm, together with a chelated
carbonyl-carbon resonance at
position 4 of isocordoin. The compound
δ = 192.1 ppm, were consistent with the selectivity of the O-alkylation at
0
2
, obtained as an amorphous bright yellow solid, proved to
0
be identical to derricin, previously reported from Lonchocarpus sericeus [26]. For 4 -oxyalkyl-isocordoin
1
derivatives
3
–8
the H-NMR spectrum revealed resonances at
δ
= 4.54–4.65 ppm (d, 2H) ascribed to
0
O-CH protons of alkoxy chain linking 4 -OH-chalcone ring. This is characteristic of allylic chains
2
1
on aromatic rings, resulting by the alkylation reaction. For example, the H-NMR spectrum of
0
0
compound
a carbon atom at
3
showed the signal at 4.65 ppm (d, J = 5.1 Hz, 2H, H-1 ) correlated (by 2D HSQC) with
65.4 ppm (C-1”), indicating the coupling point between the allyl fragment and
δ
the aromatic hydroxyl group. These data also were corroborated by 2D HMBC correlations, where H-1”
3
00 0
showed heteronuclear J correlations with the carbons signal at
δ = 117.6 (C-3 ) and 162.6 (C-4 ) ppm.
2
Heteronuclear J correlations were also observed at δ 132.7 (C-2”) (Figure 1).
1
13
Figure 1. The most important correlations shown by 2D H- C HMBC, compound 3.
2
.2. Anti-Oomycete Activity Assays of Compounds 1–8
In this study, isocordoin (
1) and a series of seven oxyalkylated derivatives (2–8) were screened for
minimum inhibitory concentration (MIC) values (Table 1).

Molecules 2017, 22, 968
4 of 9
Table 1. The MIC values a of the compounds 1–8 against Saprolegnia species.
MIC (µg/mL)
Compounds
S. parasitica
S. australis
1
2
>200
75
200
50
3
4
5
6
7
8
100
125
100
150
>200
150
>200
125
100
75
125
75
125
>200
75
175
150
100
Bronopol
Clotrimazole
Itraconazole
a
Each value represents the mean ± SD of three experiments (p < 0.05), performed in quadruplicate.
Among them, isocordoin (
Saprolegnia with MIC values
activities with MIC 150.0
anti-Saprolegnia activities with MIC values of 50 and 75 µg/mL, respectively.
Table 2 lists the minimum oomyceticidal concentration (MOC) values of compounds
Saprolegnia spores at 72 h. The results reveal that derricin ( ) showed significant anti-oomycete activity
1
≥
) and compound
200.0 g/mL, while the other six compounds showed anti-oomycete
g/mL, in which derricin ( ) and compound had the most promising
7 were considered to have no inhibition effect against
µ
≤
µ
2
3
1–8 against
2
with an MOC value of 75 µg/mL, followed by compound 3 with a value of 100 µg/mL.
Table 2. The MOC values a of the compounds 1–8 against spores at 72 h.
MOC (µg/mL)
Compounds
S. parasitica
S. australis
1
2
>200
75
>200
75
3
4
5
6
7
8
100
125
125
150
>200
150
>200
150
100
100
125
100
150
>200
100
200
175
100
Bronopol
Clotrimazole
Itraconazole
a
Each value represents the mean ± SD of three experiments, performed in quadruplicate.
Table 3 lists the mycelial growth inhibition (MIG) percentage values of compounds 1–8 against
Saprolegnia mycelium at 48 h.
The growth inhibition rate of Saprolegnia after 48 h of exposure to derricin (2) to was partially
affected by the concentration of the chemical. However, it was more than twice as effective as bronopol,
a broad-spectrum biocide, that has been used as an effective and economically acceptable alternative in
the treatment and control of Saprolegnia sp. [20]. The inhibition of S. parasitica and S. australis was 52%
and 58%, respectively, with concentrations of derricin at 200 µg/mL.
The results of this research provides evidence that lipophilicity is an important characteristic of
anti-oomycete agents, such as ketoconazole and clotrimazole [27–30], and it is also evident that drugs
with oxyalkyl chains on the A-ring contribute to an increase in anti-oomycete activity [20
has proven effectiveness in the treatment of Saprolegniasis.
,31], which

Molecules 2017, 22, 968
5 of 9
Table 3. The MIG values of the compounds 1–8 against mycelium at 48 h.
MIG (%)
Compounds (200 µg/mL)
S. parasitica
S. australis
1
2
3
4
5
6
7
8
0
0
52
38
35
25
28
0
58
42
38
30
30
0
31
0
33
33
Bronopol
3
. Materials and Methods
3
.1. General
All chemicals were obtained from Aldrich (St. Louis, MO, USA) and were used without
further purification. A detailed description of conditions used to register Fourier transform infrared
1
13
13
(
FT-IR) spectra, high resolution mass spectra, and H, C, C DEPT-135, gs-2D Heteronuclear
Single Quantum Coherence (HSQC) and gs-2D HMBC spectra has been given elsewhere [32].
Column chromatography (CC) was performed with silica gel 60 from Merck (Darmstadt, Germany),
and thin layer chromatography (TLC) was carried out on precoated silica plates F-254 from Merck
(Darmstadt, Germany). Melting points were determined on an electrothermal instrument and
are uncorrected.
3
.2. Plant Material
Adesmia balsamica were collected in Melosillas, Casablanca, Chile, in October 2016. A voucher
specimen was deposited at the Valparaíso (VALP) Herbarium, Department of Biology, Universidad
de Playa Ancha, Valparaíso, Chile and was identified by comparison with the herbarium specimen
(collection number 1899).
3
.3. Isolation and Characterization of Isocordoin (1)
The fresh plant (1.0 kg) extracted with cold dichloromethane (5 L) at room temperature for 40 s.
The organic extract was concentrated in a rotatory evaporator to give a residue of 120.5 g of resin. Pure
isocordoin ( ) was isolated to obtain 166.5 mg of a solid yellow powder. Its structure was established by
comparison of their spectroscopic data ( H and C-NMR and HRMS) with those in the literature [8].
1
1
13
3
.4. General Procedure for the Synthesis of 4-Oxyalkyl-isocordoin Analogues (2–8)
A solution of isocordoin ( ) (5 mmol), alkyl halide (6 mmol), and K CO (6.5 mmol) in anhydrous
1
2
3
◦
acetonitrile (3 mL) was refluxed for 4 h at 80 C. After the reaction, the mixture was distilled to remove
the solvent. The residue was poured into ice water (40 mL), and then filtered. The resulting filtrate
was extracted three times with ethylacetate. The resulting organic phase was dried over anhydrous
magnesium sulfate, and distilled in vacuo to remove the solvent to provide the target compounds
2E)-1-[2-Hydroxy-4-methoxy-3-(3-methylbut-2-en-1-yl)phenyl]-3-phenylprop-2-en-1-one ( ). Yellow solid.
were consistent with those
2–8.
(
2
Yield: 89.0%. Spectroscopic data and physical properties of compound
reported in the literature [26].
2
(
2E)-1-[4-(Allyloxy)-2-hydroxy-3-(3-methylbut-2-en-1-yl)phenyl]-3-phenylprop-2-en-1-one (
3
). Yellow solid.
◦
−1
Yield: 92.0%, melting point: 93–96 C. IR (KBr, cm ): 3024, 2895, 1647, 1577, 1298, 1195, and 1134.
1
0
H-NMR (400 MHz, CDCl3):
δ 13.37 (s, 1H, 2 -OH), 7.88 (d, J = 15.4 Hz, 1H, H-8); 7.77 (d, J = 9.1 Hz,

Molecules 2017, 22, 968
6 of 9
0
1
H, H-6 ); 7.65 (m, 2H, H-2 and H-6); 7.60 (d, J = 15.4 Hz, 1H, H-7); 7.42 (m, 3H, H-3, H-4 and
0
00
00
00
H-5); 6.48 (d, J = 9.0 Hz, 1H, H-5 ); 6.07 (m, 1H, H-2 ); 5.45 (m, 1H, H-3 b); 5.31 (m, 1H, H-3 a);
.26 (m, 1H, H-8 ); 4.65 (d, J = 5.1 Hz, 2H, H-1 ); 3.40 (d, J = 7,1 Hz, 1H, H-7 ); 1.80 (s, 3H, H-10 );
.68 (s, 3H, H-11 ). C-NMR (100 MHz, CDCl ):
34.8 (C-1); 132.7 (C-2 ); 131.8 (C-6 ); 130.5 (C-9 ); 129.1 (C-4); 129.0 (C-2 y C-6); 128.5 (C-3 y C-5);
21.9 (C-8 ); 120.6 (C-8); 118.4 (C-3 ); 117.6 (C-3 ); 114.6 (C-1 ); 103.2 (C-5 ); 65.4 (C-1 ); 25.8 (C-11 );
1.8 (C-7 ); 17.9 (C-10 ). MS: M + H ion m/z 349.4432 (C H O : 348.4348).
0 00 0 0
5
0
13
0
0
1
1
1
2
δ
192.4 (C-9); 163.2 (C-2 ); 162.4 (C-4 ); 144.1 (C-7);
3
0
0
0
0
0
0
00
0
0
00
0
0
0
23
24
3
(
2E)-1-[4-[(2-Methylprop-2-en-1-yl)oxy]-2-hydroxy-3-(3-methylbut-2-en-1-yl)phenyl]-3-phenylprop-2-en-1-one (
4
).
◦
−1
Yellow solid. Yield: 85.0%, melting point: 99–101 C. IR (KBr, cm ): 2958, 1635, 1519, 1243, and 1131.
1
0
H-NMR (400 MHz, CDCl ):
δ 13.39 (s, 1H, 2 -OH), 7.87(d, J = 15.5 Hz, 1H, H-8); 7.77 (d, J = 9.0 Hz, 1H,
3
0
H-6 ); 7.65 (m, 2H, H-2 and H-6); 7.60 (d, J = 15.4 Hz, 1H, H-7); 7.42 (m, 3H, H-3, H-4 and H-5); 6.48 (d,
J = 9.0 Hz, 1H, H-5 ); 5.26 (m, 1H, H-2 ); 5.11 (s, 1H, H-3b ); 5.01 (s, 1H, H-3a ); 4.54 (s, 2H, H-1 );
3
MHz, CDCl ):
1
1
0
00
00
00
00
0 00 0 0
13
.43 (d, J = 7.1Hz, 1H, H-7 ); 1.84 (s, 3H, H-4 ); 1.80 (s, 3H, H-10 ); 1.68 (s, 3H, H-11 ). C-NMR (100
0 0 00 0
δ 192.2 (C-9); 163.2 (C-2 ); 162.4 (C-4 ); 144.1 (C-7); 140.3 (C-2 ); 134.9(C-1); 131.8 (C-6 );
3
0
0
0
0
0
30.5 (C-9 ); 129.1 (C-4); 129.0 (C-2 and C-6); 128.5 (C-3 and C-5); 122.0 (C-8 ); 120.6 (C-8); 117.8 (C-3 );
14.6 (C-1 ); 113.0 (C-3 ); 103.2 (C-5 ); 71.9 (C-1 ); 25.8 (C-11 ); 21.8 (C-7 ); 19.3 (C-4 ); 17.9 (C-10 ).
00
0
00
0
0
00
MS: M + H ion m/z 363.4702 (C24 H O : 362.4616).
26
3
(
2E)-1-[4-(Crotyloxy)-2-hydroxy-3-(3-methylbut-2-en-1-yl)phenyl]-3-phenylprop-2-en-1-one (
5
). Yellow solid.
◦
−1
1
Yield: 85.0%, melting point: 93–94 C. IR (KBr, cm ): 2958, 1635, 1519, 1243, and 1131. H-NMR (400
0
0
MHz, CDCl3):
H, H-2 and H-6); 7.60 (d, J = 15.4 Hz, 1H, H-7); 7.42 (m, 3H, H-3, H-4 and H-5); 6.49 (d, J = 9,0 Hz,
δ 13.37 (s, 1H, 2 -OH), 7.87 (d, J = 15.5 Hz, 1H, H-8); 7.77 (d, J = 9.1 Hz, 1H, H-6 ); 7.65 (m,
2
1
3
0 00 00 0 00
H, H-5 ); 5.87 (m, 1H, H-2 ); 5.82 (m, 1H, H-3 ); 5.26 (m, 1H, H-8 ); 4.57 (d, J = 5.9 Hz, 2H, H-1 );
0 0 00 0
13
.40 (d, J = 7.2 Hz, 1H, H-7 ); 1.80 (s, 3H, H-10 ); 1.77 (s, 3H, H-4 ); 1.68 (s, 3H, H-11 ). C-NMR (100
0 0 0 0
δ 192.2 (C-9); 163.2 (C-2 ); 162.6 (C-4 ); 144.0 (C-7); 134.9 (C-1); 131.7 (C-6 ); 130.5 (C-9 );
MHz, CDCl3):
1
1
00 00 0
30.3 (C-4); 129.1 (C-2 ); 129.0 (C-2 and C-6); 128.5 (C-3 and C-5); 125.6 (C-3 ); 122.0 (C-8 ); 120.7 (C-8);
0
0
0
0
00
0
0
0
18.0 (C-3 ); 117.8 (C-3 ); 115.6 (C-1 ); 103.3 (C-5 ); 69.0 (C-1 ); 25.8 (C-11 ); 21.8 (C-7 ); 17.9 (C-10 ); 17.8
00
C-4 ). MS: M + H ion m/z 363.4702 (C H O : 362.4614).
24 26 3
(
(
2E)-1-[4-(Prenyloxy)-2-hydroxy-3-(3-methylbut-2-en-1-yl)phenyl]-3-phenylprop-2-en-1-one (
6
). Yellow solid.
◦
−1
Yield: 79.0%, melting point: 106–108 C. IR (KBr, cm ): 2959, 1631, 1519, 1374, 1211, 1147, and 990.
1
0
H-NMR (400 MHz, CDCl ):
δ 13.37 (s, 1H, 2 -OH), 7.87 (d, J = 15.5 Hz, 1H, H-8); 7.77 (d, J = 9.1 Hz,
3
0
1
H, H-6 ); 7.65 (m, 2H, H-2 and H-6); 7.60 (d, J = 15.4 Hz, 1H, H-7); 7.42 (m, 3H, H-3, H-4 and
0
00
0
H-5); 6.49 (d, J = 9.0 Hz, 1H, H-5 ); 5.48 (m, 1H, H-2 ); 5.25 (m, 1H, H-8 ); 4,62 (d, J = 6.6 Hz, 2H,
H-1 ); 3.39 (d, J = 7.2 Hz, 1H, H-7 ); 1.80 (s, 6H, H-4 and H-10 ); 1.75 (s, 3H, H-5 ); 1.68 (s, 3H,
H-11 ). C-NMR (100 MHz, CDCl ):
1
1
2
0
0
0
0
00
0
00
13
0
0
00
0
0
δ
192.1 (C-9); 163.2 (C-2 ); 162.8 (C-4 ); 144.0 (C-7); 138.1 (C-3 );
3
0
0
34.9 (C-1); 131.7 (C-6 ); 130.5 (C-9 ); 129.1 (C-4); 129.0 (C-2 and C-6); 128,5 (C-3 and C-5); 122.1 (C-8 );
20.7 (C-8); 119.5 (C-2 ) 117.9 (C-3 ); 114.5 (C-1 ); 103.3 (C-5 ); 65.3 (C-1 ); 25.8 (C-4 ); 25.7 (C-11 );
1.8 (C-7 ); 18.3 (C-5 ); 17.8 (C-10 ). MS: M + H ion m/z 377.4972 (C H O : 376.4880).
0
0
0
0
0
00
00
0
00
0
25
28
3
(
2E)-1-[4-(Geranyloxy)-2-hydroxy-3-(3-methylbut-2-en-1-yl)phenyl]-3-phenylprop-2-en-1-one (7). Yellow
◦
−1
solid. Yield: 73.0%, melting point: 78–80 C. IR (KBr, cm ): 2940, 2865, 1631, 1530, 1512, 1338, 1241,
1
J = 9.1 Hz, 1H, H-6 ); 7.65 (m, 2H, H-2 and H-6); 7.60 (d, J = 15.4 Hz, 1H, H-7); 7.42 (m, 3H, H-3, H-4 and
H-5); 6.49 (d, J = 9.0 Hz, 1H, H-5 ); 5.48 (m, 1H, H-2 ); 5.25 (m, 1H, H-8 ); 5.08 (m, 1H, H-6 ); 4.65 (d,
1
0
129, 817. H-NMR (400 MHz, CDCl ):
δ
13.37 (s, 1H, 2 -OH), 7,87 (d, J = 15.5 Hz, 1H, H-8); 7.77 (d,
3
0
0
00
0
00
0
0
0
00
00
0
J = 6.4 Hz,2H, H-1 ); 3.39 (d, J = 7.2 Hz, 1H, H-7 ); 2.10 (m, 4H, H-4 and H-5 ); 1.80 (s, 3H, H-10 ); 1.75
0
0
00
0
13
(
(
(
(
1
s, 3H, H-9 ); 1.68 (s, 3H, H-8 ); 1.61 (s, 3H, H-11 ). C-NMR (100 MHz, CDCl ):
δ
191.1 (C-9); 163.1
3
00
0
0
00
0
0
C-2 ); 162.8 (C-4 ); 144.0 (C-7); 141.3 (C-3 ); 134.9 (C-1); 131.9 (C-6 ); 131.7 (C-7 ); 130.5 (C-9 ); 129.1
0
00
0
C-4); 129.0 (C-2 and C-6); 128.5 (C-3 and C-5); 123.7 (C-8 ); 120.7 (C-8); 119.3 (C-2 ); 117.8 (C-3 ); 114.4
0 0 00 00 00 0 00 0 0
C-1 ); 103.3 (C-5 ); 65.4 (C-1 ); 39.5 (C-4 ); 26.3 (C-5 ); 25.8 (C-11 ); 25.7 (C-8 ); 21.8 (C-7 ); 17.9 (C-10 );
00 00
7.7 (C-10 ); 16.7 (C-9 ). MS: M + H ion m/z 445.6261 (C H O : 444.6051).
30 36 3

Molecules 2017, 22, 968
7 of 9
(
2E)-1-[4-(Farnesyloxy)-2-hydroxy-3-(3-methylbut-2-en-1-yl)phenyl]-3-phenylprop-2-en-1-one (
8
). Yellow
◦
−1
solid. Yield: 70.0%, melting point: 62–64 C. IR (KBr, cm ): 2955, 1632, 1541, 1374, 1203, 1140, 978.
1
0
H-NMR (400 MHz, CDCl ):
δ 13.37 (s, 1H, 2 -OH), 7.87 (d, J = 15.5 Hz, 1H, H-8); 7.77 (d, J = 9.1 Hz,
3
0
1
6
4
H, H-6 ); 7.65 (m, 2H, H-2 and H-6); 7.60 (d, J = 15.4 Hz, 1H, H-7); 7.42 (m, 3H, H-3, H-4 and H-5);
.49 (d, J = 9.0 Hz, 1H, H-5 ); 5.48 (m, 1H, H-2 ); 5.25 (m, 1H, H-8 ); 5.08 (m, 2H, H-6 and H-10 );
0
0
00
0
00
00
00
0
0
00
00
00
.65 (d, J = 6.6 Hz, 2H, H-1 ); 3.39 (d, J = 7.2 Hz, 1H, H-7 ); 2.09 (m, 4H, H-4 , H-5 , H-8 and H-9 );
0 00 0 00 00 13
1
.80 (s, 6H, H-10 and H-13 ); 1.75 (s, 3H, H-11 ); 1.67 (s, 6H, H-14 and H-15 ). C-NMR (100 MHz,
0 0 00 00
δ 192.1 (C-9); 163.2 (C-2 ); 162.9 (C-4 ); 144.0 (C-7); 141.3 (C-3 ); 135.3 (C-7 ); 134.9 (C-1);
CDCl3):
0 00 0 00
31.5 (C-9 and C-11 ); 131,3 (C-6 ); 130.5 (C-4); 129.0 (C-2 and C-6); 128.5 (C-3 and C-5); 124.3 (C-6 );
1
1
3
0
0
00
0
00
0
0
0
00
0
23.6 (C-10 ); 122.1 (C-8); 120.7 (C-8); 119.3 (C-2 ) 117.9 (C-3 ); 114.5 (C-1 ); 103.3 (C-5 ); 65.4 (C-1 );
9.7 (C-4 ); 39.5 (C-8 ); 26.7 (C-9 ); 26.2 (C-5 ); 25.8 (C-12 ); 25.7 (C-11 ); 21.8 (C-7 ); 17.9 (C-10 );
0
0
00
00
00
0
00 00 0
7.7 (C-15 ); 16.7 (C-14 ); 16.0 (C-13 ). MS: M + H ion m/z 513.7351 (C H O : 512.7220).
35 44 3
1
3
.5. Oomycete Strain
Pure strains of S. parasitica and S. australis were received from the Cell Biology Laboratory, Faculty
of medicine, Universidad de Valparaíso, placed on potato dextrose agar (PDA) slants, and stored at
◦
4
C. This pure strain was isolated from Salmo salar carp eggs [33].
3
.6. Minimum Inhibitory Concentration Evaluation
The method used in this study for anti-oomycete activity assay was performed according to
methods previously reported [34]. The compounds
1–8 were tested at 200.0, 150.0, 100.0, 50.0, 25.0,
1
2.5, 6.3, and 3.1 g/L to find a preliminary minimum inhibitory concentration (MIC) interval.
µ
The MIC values were recorded visually on the basis of mycelia growth. All the independent
experiments were conducted three times with quadruplicates at each test concentration. Ethanol
solution 1% in water was the negative control and bronopol, clotrimazole, and itraconazole
were the positive controls.
3
.7. Spores Germination Inhibition Assay
The spore germination assay against Saprolegnia strains was performed according to the agar
dilution method [35]. The minimum oomyceticidal concentration (MOC) and detailed protocols for
the biological assays was defined previously [34].
3
.8. Mycelial Growth Inhibition Assay
Inhibition of mycelial growth was assayed using the method described by Hu [29] with small
modifications. Oomycete growth was measured as the colony diameter, and toxicity of the compounds
against Saprolegnia strains was measured in terms of the percentage of mycelia inhibition by
a formula described in detail elsewhere [34].
1–8
3
.9. Statistical Analysis
The statistical data of recovery rates were performed by comparison within isolates and between
culturing media following a standard method [20].
4
. Conclusions
In the current study, we demonstrated that the novel oxyalkylated analogues of isocordoin
) showed higher inhibitory effect, but isocordoin and chalcone with a geranyl group, such
as 7, showed very weak activity, when compared with bronopol, clotrimazole, and itraconazole.
Derricin ( ) and compound are the main compounds responsible for the observed biological activity
(2
–
8
1
2
3
against Saprolegnia strains and are potential candidates for drug development based on their effective
anti-oomycete activities.

Molecules 2017, 22, 968
8 of 9
Acknowledgments: The authors thank FONDECYT (grant No. 11140193) and the Dirección General de
Investigación of Universidad de Playa Ancha.
Author Contributions: A.M. supervised the whole study. B.E. performed the synthesis of all compounds. P.G.
contributed to the identification and sequencing of Saprolegnia parasitica strains. I.M. conceived and designed the
biologic experiments; I.M., J.V. and E.W. performed the biologic experiments. A.M., I.M. and Y.O. collaborated in
the discussion and interpretation of the results. A.M. wrote the manuscript. All authors read and approved the
final manuscript.
Conflicts of Interest: The authors declare no conflict of interest.
References
1
.
Sugamoto, K.; Matsusita, Y.; Matsui, K.; Kurogi, C.; Matsui, T. Synthesis and antibacterial activity of chalcones
bearing prenyl or geranyl groups from Angelica keiskei. Tetrahedron 2011, 67, 5346–5359. [CrossRef]
Yazaki, K.; Sasaki, K.; Tsurumaru, Y. Prenylation of aromatic compounds, a key diversification of plant
secondary metabolites. Phytochemistry 2009, 70, 1739–1745. [CrossRef] [PubMed]
2
.
3
4
.
.
Barron, D.; Ibrahim, R. Isoprenylated flavonoids—A survey. Phytochemistry 1996, 43, 921–982. [CrossRef]
Botta, B.; Vitali, A.; Menendez, P.; Misitia, D.; Delle Monache, G. Prenylated flavonoids: Pharmacology and
biotechnology. Curr. Med. Chem. 2005, 12, 713–739. [CrossRef]
5.
6.
7.
8.
9.
Chen, X.; Mukwaya, E.; Wong, M.S.; Zhang, Y. A systematic review on biological activities of prenylated
flavonoids. Pharm. Biol. 2014, 52, 655–660. [CrossRef] [PubMed]
Patil, V.; Barragan, E.; Patil, S.A.; Patil, S.; Bugarin, A. Direct Synthesis and antimicrobial evaluation of
structurally complex chalcones. Chem. Sel. 2016, 1, 3647–3650. [CrossRef]
Delle Monach, F.; Cuca Suarez, L.E.; Marini-Bettolo, G.B. Flavonoids from the seeds of six Lonchocarpus
species. Phytochemistry 1978, 27, 1812–1813. [CrossRef]
Borges-Argáez, R.; Peña-Rodríguez, L.M.; Waterman, P. Flavonoids from two Lonchocarpus species of
the Yucatan Peninsula. Phytochemistry 2002, 60, 533–540. [CrossRef]
Caamal-Fuentes, E.E.; Peraza-Sánchez, S.R.; Torres-Tapia, L.W.; Moo-Puc, R.E. Isolation and identification
of cytotoxic compounds from Aeschynomene fascicularis, a Mayan medicinal plant. Molecules 2015, 20,
1
3563–13574. [CrossRef] [PubMed]
1
0. Borges-Argáez, R.; Poot-Díaz, M.E.; Waterman, P.G.; Peña-Rodríguez, L.M. Cytotoxic and antiprotozoal
activity of flavonoids from Lonchocarpus spp. Phytomedicine 2007, 14, 530–533. [CrossRef] [PubMed]
1. Borges-Argáez, R.; Vela-Catzín, T.; Yam-Puc, A.; Chan-Bacab, M.J.; Moo-Puc, R.E.; Cáceres-Farfán, M.
Antiprotozoal and cytotoxic studies on some isocordoin derivatives. Planta Med. 2009, 75, 1336–1338.
1
[CrossRef] [PubMed]
1
1
2. Simmonds, M.S.J.; Blaney, W.M.; Delle Monache, F.; Marini-Bettolo, G.B. Insect antifeedant activity associated
with compounds isolated from species of Lonchocarpus and Tephrosia. J. Chem. Ecol. 1990, 16, 365–380.
[CrossRef] [PubMed]
3. Avila-Villarreal, G.; Hernández-Abreu, O.; Hidalgo-Figueroa, S.; Navarrete-Vázquez, G.; Escalante-Erosa, F.;
Peña-Rodríguez, L.M.; Villalobos-Molina, R.; Estrada-Soto, S. Antihypertensive and vasorelaxant effects of
dihydrospinochalcone-A isolated from Lonchocarpus xuul Lundell by NO production: Computational and ex
vivo approaches. Phytomedcine 2013, 20, 1241–1246. [CrossRef] [PubMed]
1
1
1
1
4. Zhang, E.H.; Wang, R.F.; Guo, S.Z.; Liu, B. An update on antitumor activity of naturally occurring chalcones.
Evid. Based Complement Altern. Med. 2013, 2013, 815621. [CrossRef] [PubMed]
5. Shen, J.H.; Shi, S.C.; Ma, X.J.; Zhou, B.N. Total synthesis of two prenylated flavanonols from Maackia tenuifolia.
Nat. Prod. Lett. 1992, 1, 99–102. [CrossRef]
6. Vitali, A.; Ferrari, F.; Monache, G.D.; Bombardelli, E.; Botta, B. Synthesis and biosynthesis of isocordoin.
Planta Med. 2001, 67, 475–477. [CrossRef] [PubMed]
7. Bolasco, A.; Fioravanti, R.; Rossi, F.; Rossi, P.; Vitali, A. Use of cyclodextrins in biotransformation reactions
with cell cultures of Morus nigra: Biosynthesis of prenylated chalcone isocordoin. Biotechnol. Appl. Biochem.
2
010, 56, 77–84. [CrossRef] [PubMed]
1
8. Basabe, P.; de Román, M.; Díez, D.; Marcos, I.S.; Blanco, A.; Bodero, O.; Mollinedo, F.; Sierra, B.G.; Urones, J.G.
Prenylflavonoids and prenyl/alkyl-phloroacetophenones: Synthesis and antitumour biological evaluation.
Eur. J. Med. Chem. 2010, 45, 4258–4269. [CrossRef] [PubMed]

Molecules 2017, 22, 968
9 of 9
1
2
2
2
9. Seyedi, S.; Jafari, Z.; Attaran, N.; Sadeghian, H.; Saberi, M.; Riazi, M. Design, synthesis and SAR studies
of 4-allyoxyaniline amides as potent 15-lipoxygensae inhibitors. Bioorg. Med. Chem. 2009, 17, 1614–1622.
CrossRef] [PubMed]
0. Flores, S.; Montenegro, I.; Villena, J.; Cuellar, M.; Werner, E.; Godoy, P.; Madrid, A. Synthesis and Evaluation
[
0
0
of novel oxyalkylated derivatives of 2 ,4 -dihydroxychalcone as anti-oomycete agents against bronopol
resistant strains of Saprolegnia sp. Int. J. Mol. Sci. 2016, 17, 1366. [CrossRef] [PubMed]
1. Modak, M.; Rojas, M.; Torres, R. Chemical analysis of the resinous exudate isolated from Heliotropium
taltalense and evaluation of the antioxidant activity of the phenolics components and the resin
in homogeneous and heterogeneous systems. Molecules 2009, 14, 1980–1989. [CrossRef] [PubMed]
2. Madrid, A.; Espinoza, L.; González, C.; Mellado, M.; Villena, J.; Santander, S.; Silva, V.; Montenegro, I.
Antifungal study of the resinous exudate and of meroterpenoids isolated from Psoralea glandulosa (Fabaceae).
J. Ethnopharmacol. 2012, 144, 809–811. [CrossRef] [PubMed]
2
2
2
3. Kito, T.; Yamamoto, K.; Hirao, I. The O-alkylation of phenols of esters II. The steric hindrance and electronic
effect in the O-alkylation of phenols by esters. Bull. Chem. Soc. Jpn. 1977, 50, 706–709. [CrossRef]
4. Lei, T.; Wang, J.Y.; Pei, J. Roles of Flexible Chains in Organic Semiconducting Materials. Chem. Mater. 2014
6, 594–603. [CrossRef]
,
2
5. Da Silva, G.; da Silva, M.; Souza, E.; Barison, A.; Simões, S.; Varotti, F.; Barbosa, L.; Viana, G.; Villar, J.
Design and Synthesis of New Chalcones Substituted with Azide/Triazole Groups and Analysis of Their
Cytotoxicity Towards HeLa Cells. Molecules 2012, 17, 10331–10343. [CrossRef] [PubMed]
2
2
2
6. Do nascimento, M.C.; Mors, W.B. Chalcones of the root bark of Derris sericea. Phytochemistry 1972, 11,
3
023–3028. [CrossRef]
7. Tse, B.; Balkovec, J.M.; Blazey, C.M.; Hsu, M.J.; Nielsen, J.; Schmatz, D. Alkyl side-chain derivatives of
sordaricin as potent antifungal agents against yeast. Bioorg. Med. Chem. Lett. 1998, 8, 2269–2272. [CrossRef]
8. Schreier, S.; Malheiros, S.V.P.; Paula, E. Surface active drugs: Self-association and interaction with membranes
and surfactants. Physicochemical and biological aspects. Biochim. Biophys. Acta. 2000, 1508, 210–234.
[CrossRef]
2
9. Mousa, W.K.; Raizada, M.N. The Diversity of Anti-Microbial Secondary Metabolites Produced by Fungal
Endophytes: An Interdisciplinary Perspective. Front. Microbiol. 2013, 4, 65. [CrossRef] [PubMed]
3
0. Warrilow, A.G.S.; Hull, C.; Rolley, N.J.; Parker, E.; Nes, W.N.; Smith, S.N.; Kelly, D.E.; Kelly, S.T. Clotrimazole
as a Potent Agent for Treating the Oomycete Fish Pathogen Saprolegnia parasitica through Inhibition of Sterol
1
4α-Demethylase (CYP51). Appl. Environ. Microbiol. 2014, 80, 6154–6166. [CrossRef] [PubMed]
3
3
1. Kandaswamy, N.; Raveendiran, N. Synthesis, Characterization, and In Vitro Antimicrobial and Anticancer
Evaluation of Copolyester Bearing 4-Arylidene Curcumin in the Main Chain. Int. Sch. Res. Not. 2014, 495927.
[CrossRef]
2. Madrid Villegas, A.; Espinoza Catalán, L.; Montenegro Venegas, I.; Villena García, J.; Carrasco Altamirano, H.
New Catechol derivatives of safrole and their antiproliferative activity towards breast cancer cells. Molecules
2
011, 16, 4632–4641. [CrossRef] [PubMed]
3
3. Zaror, L.; Collado, L.; Bohle, H.; Landskron, E.; Montaña, J.; Avendaño, F. Saprolegnia parasitica en salmones y
truchas del sur de Chile. Arch. Med. Vet. 2004, 36, 71–78. [CrossRef]
3
4. Madrid, A.; Godoy, P.; González, S.; Zaror, L.; Moller, A.; Werner, E.; Cuellar, M.; Villena, J.; Montenegro, I.
Chemical Characterization and Anti-Oomycete Activity of Laureliopsis philippianna Essential Oils against
Saprolegnia parasitica and S. australis. Molecules 2015, 20, 8033–8047. [CrossRef] [PubMed]
5. Hu, X.G.; Liu, L.; Hu, K.; Yang, X.L.; Wang, G.X. In vitro screening of fungicidal chemicals for antifungal
activity against Saprolegnia. J. World Aquacult. Soc. 2013, 44, 528–535. [CrossRef]
3
Sample Availability: Samples of the compounds 1–8 are available from the authors.
©
2017 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access
article distributed under the terms and conditions of the Creative Commons Attribution
(CC BY) license (http://creativecommons.org/licenses/by/4.0/).