Allylphenols as a new class of human 15-lipoxygenase-1 inhibitors

Article abstract of DOI:10.1002/ddr.21749

In this study, a series of mono- and diallylphenol derivative were designed, synthesized, and evaluated as potential human 15-lipoxygenase-1 (15-hLOX-1) inhibitors. Radical scavenging potency of the synthetic allylphenol derivatives was assessed and the results were in accordance with lipoxygenase (LOX) inhibition potency. It was found that the electronic natures of allyl moiety and para substituents play the main role in radical scavenging activity and subsequently LOX inhibition potency of the synthetic inhibitors. Among the synthetic compounds, 2,6-diallyl-4-(hexyloxy)phenol (42) and 2,6-diallyl-4-aminophenol (47) showed the best results for LOX inhibition (IC₅₀ = 0.88 and 0.80 μM, respectively).

Full text of DOI:10.1002/ddr.21749

Received: 31 August 2020
DOI: 10.1002/ddr.21749
Revised: 16 September 2020
Accepted: 19 September 2020
R E S E A R C H A R T I C L E
Allylphenols as a new class of human 15-lipoxygenase-1
inhibitors
Seyed Jamal Alavi1 | Seyed Mohammad Seyedi2 | Satar Saberi3 | Hadi Safdari1
Hossein Eshghi2 | Hamid Sadeghian1,4
|
1Department of Laboratory Sciences, School
Abstract
of Paramedical Sciences, Mashhad University
of Medical Sciences, Mashhad, Iran
In this study, a series of mono- and diallylphenol derivative were designed, synthe-
sized, and evaluated as potential human 15-lipoxygenase-1 (15-hLOX-1) inhibitors.
Radical scavenging potency of the synthetic allylphenol derivatives was assessed and
the results were in accordance with lipoxygenase (LOX) inhibition potency. It was
found that the electronic natures of allyl moiety and para substituents play the main
role in radical scavenging activity and subsequently LOX inhibition potency of the
synthetic inhibitors. Among the synthetic compounds, 2,6-diallyl-4-(hexyloxy)phenol
(42) and 2,6-diallyl-4-aminophenol (47) showed the best results for LOX inhibition
(IC50 = 0.88 and 0.80 μM, respectively).
2Department of Chemistry, Faculty of Science,
Ferdowsi University of Mashhad,
Mashhad, Iran
3Department of Chemistry, Faculty of Science,
Farhangian University, Tehran, Iran
4Antimicrobial Resistance Research Center,
Mashhad University of Medical Sciences,
Mashhad, Iran
Correspondence
Hamid Sadeghian, Neurogenic Inflammation
Research Center, Mashhad University of
Medical Sciences, Mashhad 91857-63788,
Iran.
K E Y W O R D S
Email: sadeghianh@mums.ac.ir
15-hLOX-1, allylphenol, Claisen rearrangement, DPPH, MBTH
Funding information
Mashhad University of Medical Sciences,
Grant/Award Number: 980124
1
|
INTRODUCTION
15-LOX-II), 12R-LOX (arachidonate 12R-LOX) and eLOX-3 (Epidermis-type
LOX) (Butovich & Lukyanova, 2008).
Catalyzed peroxidation of unsaturated lipid in animals and plants is
intimately linked to the activity of 15-lipoxygenase (LOX) enzymes.
The activity of LOX enzymes causes a variety of diseases such as
inflammation, sensitivities, skin disorder, and some cancers in
mammals.
The immediate products of fatty acid oxidation by LOX have been
shown to be associated with acute and chronic diseases such as
stroke, myocardial infarction, asthma, cancer, inflammation and many
other diseases and pathological states. Due to the importance of LOX
as therapeutic target, there is currently much interest for the discov-
ery and synthesis of novel and potent LOX inhibitors (Alavi,
Sadeghian, Seyedi, Salimi, & Eshghi, 2018; Mousavian et al., 2020;
Sadeghian, Seyedi, Saberi, Arghiania, & Riazi, 2008).
There are two enzymatic pathways for stereospecific peroxidation of
polyunsaturated fatty acids such as linoleic acid (LA) and arachidonic acid
(AA): cyclooxygenase and LOX pathway (Butovich & Lukyanova, 2008).
The LOX enzymes are
a
family of iron-containing proteins in
Three main categories have been classified for inhibition of the
LOX activity. They are: (a) redox inhibitors, which inhibit the formation
of radical or trap it in redox cycle of hydroperoxidation, (b) iron-ligand
inhibitors, which are excellent ligands to forming complex whit the
iron core of the enzyme active site, (c) nonredox competitive inhibi-
tors, which compete with AA for occupying the active site (Pontiki &
Hadjipavlou-Litina, 2008).
animals and plants that play a key role in catalyzing AA conversion to
hydroperoxyeicosatetraenoic acids, hydroxyeicosatetraenoic acids, and
particularly leukotrienes, potent mediators of hypersensitivity and
inflammatory reactions (Pontiki & Hadjipavlou-Litina, 2008). Mam-
malian LOXs are commonly classified into six major groups according to
insertion of molecular oxygen into AA: 5-LOX (arachidonate 5-LOX),
12-LOX (arachidonate 12-LOX; platelet LOX), 12/15-LOX or 15-LOX-1
(arachidonate 15-LOX-I; reticulocyte 15-LOX) and 15-LOX-2 (arachidonate
At the recent decade, several quantitative structure activity rela-
tionship studies concerning LOX inhibitors base on pyridazinone
Drug Dev Res. 2020;1–8.
wileyonlinelibrary.com/journal/ddr
© 2020 Wiley Periodicals, LLC.
1

2
ALAVI ET AL.
analogues (Kim, Martin, Brooks, Dyer, & Carter, 1994), catechol deriva-
tives (Naito et al., 1991), hydroxamic acids (Summers et al., 1990), satu-
rated monohydric alcohols (Mitsuda, Yasumoto, & Yamamoto, 1967),
ω-phenylalkylhydroxamic acids, ω-naphthylalkylhydroxamic acids,
preparation and full characterization of the monoallyl compounds,
The LOX inhibitory potency was studied against 15-hLOX-1 using
the modified oxidative coupling of 3-methyl-2-benzothiazolinone
(MBTH) with 3-(dimethylamino) benzoic acid (DMAB), which was
reported by Alavi et al. (Alavi et al., 2018). After investigating the
enzyme inhibition results of the monoallyl compounds, the best
inhibitors were selected for converting to diallyl analogs.
15-hLOX-1 was prepared from isolated human eosinophil based
on the procedure reported by Jabbari et al. (Jabbari, Mousavian,
Seyedi, Bakavoli, & Sadeghian, 2017).
eicosatetraenoic acids, and 1H-benzimidazole-4-ols (Gupta
&
Gupta, 1990) have been done (Pontiki & Hadjipavlou-Litina, 2002;
Pontiki & Hadjipavlou-Litina, 2003; Pontiki & Hadjipavlou-Litina, 2008).
All of the mentioned researches showed that various parameters, such
as hydrophobicity, molecular size and electronic properties, affected
inhibitory potency of LOX inhibitors.
Eugenol (4-allyl-2-methoxyphenol) is a natural allyl phenol mainly
extracted from clove, basil, cinnamon, and nutmeg. The mentioned
compound is known as bactericidal (Devi, Nisham, Sakthivel, &
Among para-substituted phenols, which ones have no commercially
accessible starting materials, were synthesized according to previous
literatures (Figure 1) (Vyas & Shah, 1951).
Pandian, 2010), monoamine oxidase inhibitor (Kabuto, Tada,
&
The allylation procedure for synthesis of mono and diallylphenols
was carried out according to the procedure reported by Claisen
(Claisen, 1912). For this purpose, compounds 10–18 as starting mate-
rials were prepared by coupling the hydroquinone with the related
alkyl bromide and subsequently allylbromide. Finally, the products
were heated at 180ꢀC (Claisen rearrangement) to forming of mono-
allyl compounds (19–27) (Figure 1) (Sanford, Lis, & McPherson, 2009).
Finally, the obtained products were evaluated for both15-hLOX-1
inhibition and radical scavenging.
Kohno, 2007), antioxidant, and anti-inflammatory agent (Baskaran,
Periyasamy, & Venkatraman, 2010; Jirovetz et al., 2006; Ogata, Hoshi,
Urano, & Endo, 2000). It is widely used as a flavoring agent in food
and cosmetic products. LOX inhibitory activity of eugenol esters on
soybean 15-LOX (SLO) was firstly reported by our research team in
2008. In the mentioned work, it was found that acylation of phenol
hydroxyl mainly did not decrease the LOX inhibitory activity of euge-
nol and in some cases inhibitory potency significantly was increased.
Finally, it was concluded that similarity between allyl benzenes moiety
of the synthetic esters and 1,4-dien portion of LA was the key factor
of the inhibitory activity (Sadeghian et al., 2008).
Evaluation of LOX inhibitory activities of monoallyl phenols was
firstly carried out. Among the mentioned monoallyl compounds,
2-allyl-4-methoxyphenol (compound 22) was the most potent LOX
inhibitor by IC50 value of 3.7 μM. Replacing the 4-methoxy group by
the other electron-donating and electron-withdrawing groups such as
hydrogen (19), chloro (20), methyl (21), aldehyde (26), and NO2 (27)
lead to decrease in LOX inhibition activities (Table 1).
SLO inhibitory activity of some allyl aryl ethers such as methyl
eugenol was also reported (Sadeghian, Seyedi, Attaran, Jabbari, &
Jafari, 2011). A few of them showed more activity compared to
eugenol.
Herein, LOX inhibitory activity of some synthetic hydroxyallybenzenes
(allylphenols) was studied. Considering antioxidant and radical scaveng-
ing property of phenols, substitution of allyl on benzenes ring could
possibly increase the LOX inhibitory activity of these compounds.
Based on the aforementioned theory a series of 4-hydroxyallylbenzens
and 4-hydroxydiallylbenzens were synthesized (by considering the elec-
tronic property of the substituents) and then their LOX inhibitory activ-
ity were studied against human 15-LOX-1 (15-hLOX-1).
The Lineweaver–Burk plot showed that 2-allyl-4-methoxyphenol
(compound 22) inhibited LOX activity by noncompetitive mechanism
(Figure 2).
Due to good LOX inhibition result of 22, compounds 23 (O-pentyl),
24 (O-hexyl), and 25 (O-heptyl) were synthesized to considering the
effect of the chain length of 4-alkoxy moiety on LOX inhibitory potency.
Evaluation of enzymatic inhibitory results showed that increasing of
the alkoxy chain length from methyl to hexyl leads to more than two folds
increase of inhibition activity: IC50 (22) = 3.7 μM versus IC50 (24) = 1.4 μM.
Radical scavenging activities of the monoallylphenol compounds
were comparatively tested using DPPH bleaching method. It is worth
noting that the results of radical scavenging activity of monoallylphenols
were nearly consistent with LOX inhibition potency (Table 1).
2
|
RESULTS AND DISCUSSION
First, LOX inhibitory activity of eugenol (para substitution of OH
toward allyl moiety) was measured in comparison with its isomer,
2-hydroxy-4-methoxyallylbenzene (22), with ortho substitution of OH
toward allyl portion. In both of them, there is mesomeric effect (elec-
tron donation) between OH and allyl group. It was interesting that
LOX inhibitory potency of eugenol was eightfold less than its isomer
while radical scavenging activity of it was twofold lower. So it was
decided to develop new derivatives of 22 by considering the electron-
donating-withdrawing nature of the substituents and finally observing
the mentioned structural changes on their inhibitory potency.
Conformity between IC50 variations and DPPH bleaching indicates
that the electronic property is the major factor for the LOX inhibition
potency of the aforementioned allylphenol compounds (Table 1).
It seems that the electronic nature of both X (substituted group
at the para position of phenol ring) and the allyl moiety has an effec-
tive role on LOX inhibition and radical scavenging potency.
In order to clarify the effective role of the allyl moiety on LOX
inhibition activity, some derivatives without allyl group were synthe-
sized and both LOX inhibition and DPPH bleaching activities of them
were evaluated (Table 1, entry 2–5). The results showed that elimina-
tion of the allyl side chain lead to missing of LOX inhibition.
The desired allyl and diallyl phenols were synthesized by
Claisen rearrangement on the related allyoxyphenols. After

ALAVI ET AL.
3
FIGURE 1 General procedure for the synthesis of mono and diallyl phenols
TABLE 1 Lipoxygenase inhibition and DPPH bleaching potencies of the synthetic monoallyl compounds in comparison with 4-methyl-2-(4
methylpiperazinyl)pyrimido[4, 5-b]benzothiazine (4-MMPB)
IC50 (μM) LOX
IC50 (μM) (DPPH
IC50 (μM) LOX
IC50 (μM) (DPPH
Compd.
19
X
inhibition
bleaching)
Compd.
X'
inhibition
bleaching)
H
>1,000
301.3 15.5
>1,000
2
Me
>1,000
>1,000
>1,000
>1,000
18 0.1
-
169 10.4
>1,000
20
Cl
>1,000
3
Cl
21
Me
>1,000
>1,000
4
OMe
29.7 2.9
10.5 1.1
-
22
OMe
OPen
OHex
OHep
CO
3.7 0.2
1.8 0.1
1.4 0.2
1.9 0.2
55.9 3.8
27.9 0.4
42.9 6.3
33.2 3.1
31.5 2.5
17.4 1.9
356.2 15.7
401.2 18.4
5
OPen
23
4-MMPB
NDGA
Eugenol
-
-
-
24
5.1 1.2
95.5 4.1
25
32.4 2.3
26
27
NO2
Note: Data are shown as SD.
The previous results indicated that the electronic nature of the
substituents at position 4 of the phenol ring significantly affects LOX
inhibition potency. After confirming the effective role of the allyl moi-
ety, to reach more potent allyl phenols inhibitors, diallyl derivatives
were designed and synthesized.
Structure modification from mono allyl to diallyl led to significant
increase in LOX inhibition potency compared to the corresponding com-
pounds of 19–21 (more than500 folds decrease in IC50). It was interesting
that no significant changes observed for diallyl derivatives of 22–27:40–45
(less than two folds decrease in IC50). The results are shown in Table 2.

4
ALAVI ET AL.
FIGURE 2 Lineweaver–Burk
plots of 15-hLOX-1 inhibition by
compound 22
TABLE 2 Lipoxygenase inhibition and DPPH bleaching potencies of the synthetic diallyl compounds in comparison with 4-methyl-2-(4
methylpiperazinyl)pyrimido[4, 5-b]benzothiazine (4-MMPB)
IC50 (μM) LOX
IC50 (μM) (DPPH
IC50 (μM) LOX
IC50 (μM) (DPPH
Compd.
37
X
inhibition
bleaching)
Compd.
46
X
inhibition
bleaching)
H
2.17 0.12
1.46 0.10
1.35 0.15
1.30 0.10
1.21 0.02
0.88 0.02
1.20 0.11
49.26 3.80
10.98 0.04
108.1 6.1
37.0 2.6
37.1 3.1
16.4 1.3
16.1 1.1
14.1 1.0
15.0 0.9
356.2 15.7
385.2 18.4
CH2OH
3.00 0.22
0.80 0.04
18 0.1
74.5 6.8
27.6 2.4
-
38
Cl
47
NH2
-
39
Me
4-MMPB
40
OMe
OPen
OHex
OHep
CO
41
42
43
44
45
NO2
Note: Data are shown as SD.
Among the diallyl derivatives, compound 42 (X: OHex)
showed the best inhibitory activity by IC50 value of 0.88 μM, after
that compounds 43, 41, and 40 were in the next rank. It is inter-
esting that the same variation was seen for radical scavenging
activity.
3,5-diallyl-4-hydroxybenzaldehyde (44) and 2,6-diallyl-4-nitrophenol
(45) in comparison with the other diallyl phenols showed lower
LOX inhibition and radical scavenging activities. So, it was decided
to change the electron-withdrawing groups (aldehyde and nitro) to
electro-donating substituents via synthesis of the related alcohol
(46) and amine (47). So 2,6-diallyl-4-(hydroxymethyl)phenol (46)
and 2,6-diallyl-4-aminophenol (47) were synthesized via reduction
procedures(Figure 1) (Redemann & Redemann, 1949).As shown in
Table 2 2,6-diallyl-4-aminophenol (47) showed more potent LOX
inhibition (IC50 = 0.80 μM) than 46 (IC50 = 3.0 μM).
Compounds 40–43 were synthesized according to the former syn-
thetic procedure of 2-allyl-4-substituted phenol derivatives (19–27) via
furthermore allylation and Claisen rearrangement. In comparison with
40 (IC50 = 1.30 μM), increase of the alkoxy chain length showed no sig-
nificant variations in LOX inhibition.

ALAVI ET AL.
5
3
|
CONCLUSIONS
out for 10 min at 30ꢀC. A control test was performed with the same
volume of ethanol. After the preincubation, LA solution (25 μL) was
added to start the peroxidation reaction at 30ꢀC, and, 10 min later,
solution A (135 μL) and then solution B (65 μL) were added to start
the color formation. Furthermore, 3 min later, 100 μL of a 2% SDS
solution was added to terminate the reaction. The absorbance at
598 nm was compared with the control test. These experiments were
performed in triplicate. The data analysis was performed using
graphpad prism 5.01.
In summary, we have synthesized and introduced a new series of
mono and diallyl phenols as LOX inhibitors. Radical scavenging
potency of the synthetic diallyl phenols was assessed and the result
showed the important role of the allyl moieties and para substitutions
in LOX inhibition potency. DPPH bleaching assessments indicate that
the electronic property of the substituents is the major factor in LOX
inhibition variations. Among the synthetic compounds, 2,6-diallyl-
4-alkoxyphenols and 2,6-diallyl-4-aminophenol showed the best
result for LOX inhibition. As the synthesized allyl phenols inhibit the
LOX activity by noncompetitive redox mechanism and also by consid-
ering the main role of their electronic properties in enzyme inhibition,
doing docking analyses is not advantage.
4.4
|
Determination of DPPH bleaching
DPPH solution of 25 μM in absolute ethanol was prepared. This solu-
tion was added to an equal volume of the solution of the test com-
pounds (dissolved in ethanol) to obtain a desired concentration.
Ethanol was used as control solution. After 30 min at room tempera-
ture, the absorbance was recorded at 517 nm and compared to NDGA
(nordihydroguaiaretic acid).
4
|
EXPERIMENTAL
| Instruments
4.1
1H NMR (300 MHz) spectra were obtained by using a Bruker Avance
DRX-300 Fourier transformer spectrometer. Chemical shifts are
reported in parts per million (δ) downfield from tetramethylsilane. The
melting points were recorded on an electrothermal type 9,100 melting
point apparatus. The mass spectra were scanned on a Varian Mat
CH-7 instrument at 70 eV. Elemental analysis was obtained on a
Thermo Finnigan Flash EA microanalyzer. All measurements of DPPH
bleaching and LOX activities were carried out using Spekol 1,500
spectrophotometer and BioTek ELX800 plate reader. The 2-Hydroxy-
3-methoxybenzaldehyde, 2-Hydroxy-4-methoxybenzaldehyde and
2-Hydroxy-6-methoxybenzaldehyde were obtained from Alfa Aesar
and other chemicals were purchased from Sigma, Aldrich, and
Merck Co.
4.5
|
General procedure for preparation of p-
alkyloxyphenol (5–7)
A mixture of hydroquinone (10.0 g, 90.82 mmol) and desired alkyl
bromide (40 mmol), anhydrous potassium carbonate (40 mmol), and
dried acetone (40 ml) was heated under reflux for 6 hr and then
cooled. The mixture was diluted with 100 ml water and 1 M NaOH
(50 ml) was added and extracted with EtOAc for removing the
1,4-dialkoxybenzene. Acidified the solution by
extracted by EtOAc.
1 M HCl and
Then the organic phase was washed with water (3*100) and dried
over sodium sulfate. After evaporating the organic layer, the alkyl
substituted products obtained as white powder (Vyas & Shah, 1951).
4.2
|
Enzyme preparation
4.6
|
General procedure for preparation of 10–18
Enzyme preparation was done according to the pervious method
which had been reported by Jabbari et al. (Jabbari et al., 2017).
A mixture of p-substituted phenol (0.1 mol), ally1 bromide (0.15 mol),
and anhydrous potassium carbonate (0.1 mol) in 50 ml of dry acetone
was heated under reflux condition for 8 hr. After cooling, the mixture
was diluted with 200 ml water and the organic phase was separated.
Then the organic phase was washed with 1 M NaOH (2*50 ml) and
dried over potassium carbonate. The mixture was filtered yielding to
colorless to pale yellow oil (Hong, Lee, Tsai, & Liao, 1998; Kürti &
Czakó, 2005).
4.3
|
LOX inhibitory assessment
LA and two assay solutions (A and B) were prepared in advance.
Solution A was 50 mM DMAB in an l00 mM phosphate buffer (pH 7.0).
Solution B was a mixture of l0 mM MBTH (3 ml), hemoglobin
(5 mg/ml, 3 ml) in 50 mM phosphate buffer at pH 5.0 (25 ml). An LA
solution was prepared by mixing 5.6 mg of LA (Sigma Aldrich, L1376)
with 0.5 ml methanol and then diluted with KOH 100 mM to a final
volume of 5 ml (4 mM).
4.7
|
General procedure for preparation of
19–27via the Claisen rearrangement
In the standard assay, the sample in DMSO (12.5 μL), 15-LOX-1
(90–115 units/ml; 30 μL), and phosphate buffer, and pH 7.0 (50 mM;
435 μL) were mixed in 48-well plates, and preincubation was carried
The corresponding allyloxyl compounds 10–18 were heated to 180ꢀC
for 2 hr to undergo Claisen reaction as the known procedure (Wang,

6
ALAVI ET AL.
Hsu, Lin, & Huang, 2002) to give 19–27. The reaction mixture was
cooled, dissolved in hexane (50 ml), and extracted with sodium
hydroxide solution (3*25 ml). The combined aqueous solutions were
acidified with concentrated hydrochloric acid and extracted with
methyl tert-butyl ether (50 ml). The combined organic layers were
dried over sodium sulfate and filtered. After evaporating the ether,
the product was obtained as oil (White, Donald, Schmitt, Girard, &
Fife, 1958).
4.11
|
General procedure for preparation of
2,6-diallyl-4-aminophenol (47)
A mixture of 45 (5.5 mmol) and 2.1 g (12 mmol) of sodium dithionite
(Na2S2O4) in 15 ml of deionized water and 4 ml of ammonium hydrox-
ide was heated to 50ꢀC for 1 hr. After cooling, the precipitated solid
was filtered, washed with water, and crystallized from normal hexane
to afford compound 47 as pure yellowish crystals (Redemann &
Redemann, 1949).
4.8
|
General procedure for the preparation
of 28–36
4.12
|
2-allyl-4-(pentyloxy)phenol (23)
In a similar manner as described for 10–18, To a solution of 19–27
(50 mmol) in acetone (30 ml), dry powdered potassium carbonate
(9.1 g, 66 mmol) and allyl bromide (5.4 ml, 62 mmol) were added,
and the mixture was stirred under reflux for 8 hr. After cooling, the
mixture was diluted with 200 ml water and the organic phase was
Yellow powder (mp: 53–55ꢀC),1H NMR (301 MHz, Chloroform-d) δ
6.75 (d, 1H), 6.74 (s, 1H), 6.60 (s, 1H), 6.05–5.84 (m, 1H), 5.09 (m, 1H),
5.06–5.01 (m, 1H), 4.68 (s, 1H), 3.85–3.80 (t, J = 6.8 Hz, 2H), 3.29 (d,
J = 6.3 Hz, 2H), 1.67 (m, 2H), 1.41–1.24 (m, 4H), 0.85 (t, J = 7.0 Hz,
3H);13C NMR (76 MHz, Chloroform-d) δ 153.18, 147.87, 136.26,
126.46, 116.69, 116.42, 115.40, 113.28, 68.67, 35.32, 29.12, 28.25,
22.53, 14.08. MS (EI, 70 eV): m/z = 220 [M+]; Anal. calcd for
separated. The organic phase was washed with
1 M NaOH
(2*50 ml) and dried over potassium carbonate. After filtering, the
product obtained as oil and it was employed for the next step with-
out further purification (Yashiro, Hanaya, Shoji, & Sugai, 2015).
C14H20O2: C, 76.33; H, 9.15. Found: C, 76.40; H, 9.10.
4.13
|
2-allyl-4-(hexyloxy)phenol (24)
4.9
|
General procedure for preparation of
37–45via the Claisen rearrangement of 28–36
Yellow powder (mp: 70–72ꢀC), 1H NMR (301 MHz, Chloroform-d) δ
6.76 (d, 1H), 6.74 (s, 1H), 6.66 (s, 1H), 5.88 (m, 1H), 5.09 (m, 1H),
5.07–5.03 (m, 1H), 4.63 (s, 1H), 3.82 (t, J = 6.3 Hz, 2H), 3.29 (d,
J = 6.3 Hz, 2H), 1.73–1.62 (m, 2H), 1.38 (m, 2H), 1.25 (m, 4H), 0.83 (t,
J = 6.2 Hz 3H);13C NMR (76 MHz, Chloroform-d) δ 153.19, 147.86,
136.25, 126.42, 117.51, 115.68, 115.39, 113.29, 68.67, 35.34, 31.65,
29.39, 25.78, 22.65, 14.09. MS (EI, 70 eV): m/z = 234 [M+]; Anal.
calcd for C15H22O2: C, 76.88; H, 9.46. Found: C, 76.85; H, 9.45.
In a similar manner as described for 19–27, the 2-allyl-p-substituted
phenol 28–36 was heated to 180ꢀC for 2 hr. The red-brownish reac-
tion mixture was cooled, dissolved in hexane (50 ml), and extracted
with sodium hydroxide solution (3*25 ml). The combined aqueous
solutions were acidified with hydrochloric acid (36%) and extracted
with methyl tert-butyl ether (50 ml). The combined organic layers
were dried over sodium sulfate and filtered. After evaporating the
organic layer, the crude product was purified by chromatography on
silica gel (ethyl acetate: hexane 1:8) to obtain the pure product.
4.14
|
2-allyl-4-(heptyloxy)phenol (25)
White powder (mp: 83–85ꢀC), 1H NMR (301 MHz, Chloroform-d) δ
6.65 (d, J = 8.2 Hz, 1H), 6.61 (s, 1H), 6.57 (d, J = 6.2 Hz, 1H), 6.01–5.84
(m, 1H), 5.13–5.02 (m, 2H), 4.66 (s, 1H), 3.81 (t, J = 6.6 Hz, 2H), 3.29 (d,
J = 6.3 Hz, 2H), 1.67 (p, J = 6.5 Hz, 2H), 1.34 (m, 2H), 1.23 (m, 6H), 0.81
(m, J = 6.8, 3H); 13C NMR (76 MHz, Chloroform-d) δ 153.30, 147.85,
136.24, 126.42, 116.71, 116.45, 115.41, 113.31, 68.62, 35.35, 31.83,
29.44, 29.13, 26.06, 22.66, 14.15. MS (EI, 70 eV): m/z = 248 [M+]; Anal.
calcd for C16H24O2: C, 77.38; H, 9.74. Found: C, 77.40; H, 9.75.
4.10
|
General procedure for preparation of
2,6-diallyl-4-(hydroxymethyl)phenol (46)
2,6-diallyl-4-(hydroxymethyl)phenol was prepared by reduction
of 44 with sodium borohydride as previously reported (Yang
et al., 2016). A solution of 44 (40 mmol) in cooled methanol (50 ml)
was treated with sodium borohydride (2.3 g, 60 mmol) at 0ꢀC
during 2 hr. The solvent was removed under reduced pressure and
the residue was poured into water (50 ml), and extracted with
EtOAc. The organic layer was dried by anhydrous sodium sulfate,
filtered, and the solvent removed under reduced pressure to afford
the crude product.
4.15
|
2-allyl-4-nitrophenol (27)
Slightly yellow powder (mp: 79–80ꢀC), 1H NMR (301 MHz, Chloroform-
d) δ 7.99 (s, 1H), 7.98 (d, J = 7.7 Hz, 1H), 6.84 (d, J = 9.1 Hz, 1H), 6.29 (s,
1H), 5.93 (ddt, J = 16.8, 10.2, 6.5 Hz, 1H), 5.19–5.06 (m, 2H), 3.39 (d,
J = 6.4 Hz, 2H); 13C NMR (76 MHz, Chloroform-d) δ 160.06, 141.35,
The crude product was purified by chromatography (ethyl
acetate: hexane 1:8) affording the pure product as yellowish
oil 46.

ALAVI ET AL.
7
134.65, 126.86, 126.40, 124.33, 117.89, 115.81, 34.47. MS (EI, 70 eV):
m/z = 179 [M+]; Anal. calcd for C9H9NO3: C, 60.33; H, 5.06; N. 7.82.
Found: C, 60.12; H, 5.00; N. 7.78.
70 eV): m/z = 274 [M+]; Anal. calcd for C18H26O2: C, 78.79; H, 9.55.
Found: C, 78.54; H, 9.45.
4.21
|
2,6-diallyl-4-(heptyloxy)phenol (43)
4.16
|
2,6-diallylphenol (37)
Yellow oil, 1H NMR (301 MHz, Chloroform-d)
δ 6.50 (s, 2H),
Colorless oil, 1H NMR (301 MHz, Chloroform-d) δ 7.10 (d, J = 7.5 Hz,
2H), 6.93 (t, J = 6.5 Hz, 1H), 6.18–6.04 (m, 2H), 5.27–5.24 (m, 2H),
5.26 (s, 1H), 5.21 (t, J = 1.5 Hz, 2H), 3.50 (d, J = 6.4 Hz, 4H); 13C NMR
(76 MHz, Chloroform-d) δ 152.70, 136.67, 128.78, 125.72, 120.72,
116.44, 35.35. MS (EI, 70 eV): m/z = 174 [M+]; Anal. calcd for
6.07–5.84 (m, 2H), 5.15–5.02 (m, 4H), 4.67 (s, 1H), 3.80 (t, J = 6.6 Hz,
2H), 3.30 (d, J = 6.4 Hz, 4H), 1.70–1.62 (m, 2H), 1.43–1.17 (m, 8H),
0.82 (t,, J = 6.6 Hz, 3H); 13C NMR (76 MHz, Chloroform-d) δ 152.96,
146.29, 136.47, 126.76, 116.41, 114.52, 68.45, 35.52, 31.83, 29.47,
29.13, 26.07, 22.65, 14.14. MS (EI, 70 eV): m/z = 288 [M+]; Anal.
calcd for C19H28O2: C, 79.12; H, 9.79. Found: C, 78.69; H, 9.12.
C
12H14O: C, 82.72; H, 8.10. Found: C, 82.72; H, 8.09.
4.17
|
2,6-diallyl-4-chlorophenol (38)
4.22
|
3,5-diallyl-4-hydroxybenzaldehyde (44)
Yellowish oil,1H NMR (301 MHz, Chloroform-d) δ 6.90 (s, 2H),
5.99–5.79 (m, 2H), 5.11–5.09 (m, 2H), 5.07–5.04 (m, 2H), 5.03 (s, 1H),
3.27 (d, J = 6.4 Hz, 4H); 13C NMR (76 MHz, Chloroform-d) δ 151.22,
135.73, 128.28, 127.42, 117.08, 116.26, 35.05. MS (EI, 70 eV): m/
z = 208 [M+]; Anal. calcd for C12H13ClO: C, 69.07; H, 6.28. Found: C,
69.10; H, 6.27.
Yellow powder (mp: 53–55ꢀC),1H NMR (301 MHz, Chloroform-d) δ
9.76 (s, 1H), 7.51 (s, 2H), 6.03–5.91 (m, 2H), 5.90 (s, 1H), 5.15 (m, 2H),
5.11 (dq, J = 7.9, 1.4 Hz, 1H), 3.40 (d, J = 6.4 Hz, 4H); 13C NMR
(76 MHz, Chloroform-d) δ 191.29, 158.40, 135.50, 130.97, 129.70,
126.33, 117.42, 34.98. MS (EI, 70 eV): m/z = 202 [M+]; Anal. calcd for
C13H14O2: C, 77.20; H, 6.98. Found: C, 77.16; H, 7.08.
4.18
|
2,6-diallyl-4-methylphenol (39)
4.23
|
2,6-diallyl-4-nitrophenol (45)
Yellow oil, 1H NMR (301 MHz, Chloroform-d) δ 6.73 (s, 2H), 5.92 (ddt,
J = 16.7, 10.2, 6.4 Hz, 2H), 5.11–5.05 (dq, J = 8.2, 1.6 Hz, 1H), 5.03
(m, 2H), 4.92 (s, 1H), 3.28 (d, J = 6.4 Hz, 4H), 2.16 (s, 3H); 13C NMR
(76 MHz, Chloroform-d) δ 150.38, 136.81, 129.83, 129.27, 125.52,
116.31, 35.38, 20.57. MS (EI, 70 eV): m/z = 189 [M+]; Anal. calcd for
Yellow oil, 1H NMR (301 MHz, Chloroform-d) δ 7.68 (s, 2H), 7.09 (s,
1H), 5.93 (m, 2H), 5.89–5.69 (m, 4H), 3.49 (d, J = 6.4 Hz, 4H).13
C
NMR (76 MHz, Chloroform-d) δ 161.06, 151.35, 136.65, 126.86,
117.98, 115.91, 33.47. MS (EI, 70 eV): m/z = 219 [M+]; Anal. calcd for
C12H13NO3: C, 65.74; H, 5.98; N, 6.39. Found: C, 65.80; H,
C
13H16O: C, 82.94; H, 8.57. Found: C, 83.05; H, 8.74.
6.00; N, 6.40.
4.19
|
2,6-diallyl-4-methoxyphenol (40)
4.24
|
2,6-diallyl-4-(hydroxymethyl)phenol (46)
Yellow oil, 1H NMR (301 MHz, Chloroform-d)
δ
6.51 (s, 2H),
Yellowishoil,1H NMR (301 MHz, Chloroform-d) δ 6.93 (s, 2H), 6.74 (s,
1H), 5.93 (m, 2H), 5.15–4.95 (m, 4H), 4.48 (s, 2H), 3.33 (d, J = 6.1 Hz,
4H), 2.00 (s, 1H)13C NMR (76 MHz, Chloroform-d) δ 150.88, 136.74,
129.06, 125.58, 116.29, 111.52, 68.85, 35.37. MS (EI, 70 eV): m/
z = 204 [M+]; Anal. calcd for C13H16O2: C, 76.44; H, 7.90. Found: C,
77.01; H, 8.08.
6.03–5.85 (m, 2H), 5.10 (m, 2H), 5.07–5.03 (m, 2H), 4.70 (s, 1H), 3.68
(s, 3H), 3.31 (d, J = 6.4 Hz, 4H); 13C NMR (76 MHz, Chloroform-d) δ
153.39, 146.43, 136.41, 126.84, 116.47, 113.81, 55.65, 35.52. MS
(EI, 70 eV): m/z = 204 [M+]; Anal. calcd for C13H16O2: C, 76.44; H,
7.90. Found: C, 77.01; H, 7.96.
4.20
|
2,6-diallyl-4-(hexyloxy)phenol (42)
4.25
|
2,6-diallyl-4-aminophenol (47)
Yellow oil, 1H NMR (301 MHz, Chloroform-d) δ 6.50 (s, 2H), 5.91 (m,
2H), 5.08 (dq, J = 4.5, 1.5 Hz, 1H), 5.04 (t, J = 1.5 Hz, 2H), 4.70 (s, 1H),
3.80 (t, J = 6.6 Hz, 2H), 3.29 (d, J = 6.4 Hz, 4H), 1.74–1.60 (m, 2H),
1.43–1.30 (m, 2H), 1.24 (m, 4H), 0.82 (t, J = 6.8 Hz, 3H); 13C NMR
(76 MHz, Chloroform-d) δ 153.29, 147.86, 136.25, 126.41, 116.68,
113.28, 68.59, 35.33, 31.65, 29.40, 25.77, 22.65, 14.09. MS (EI,
Yellow crystals (mp: 77–78ꢀC),1H NMR (301 MHz, Chloroform-d) δ
6.43 (s, 2H), 6.02 (ddt, J = 16.0, 10.9, 6.4 Hz, 2H), 5.18 (dq, J = 6.5,
1.7 Hz, 2H), 5.14 (m, 2H), 3.36 (b, 7H); 13C NMR (76 MHz,
Chloroform-d) δ 145.34, 139.65, 136.68, 126.98, 116.21, 115.75,
35.34. MS (EI, 70 eV): m/z = 189 [M+]; Anal. calcd for C12H15NO: C,
76.16; H, 7.99; N, 7.40. Found: C, 76.16; H, 7.99; N, 7.40.

8
ALAVI ET AL.
Kabuto, H., Tada, M.,
&
Kohno, M. (2007). Eugenol [2-methoxy-
ACKNOWLEDGMENTS
4-(2-propenyl)phenol] prevents 6-hydroxydopamine-induced dopa-
mine depression and lipid peroxidation inductivity in mouse striatum.
Biological and Pharmaceutical Bulletin, 30, 423–427.
The authors gratefully acknowledged for partial financial support of
this study (Grant No. 980124) by Research Council of Mashhad Uni-
versity of Medical Science.
Ogata, M., Hoshi, M., Urano, S., & Endo, T. (2000). Antioxidant activity of
eugenol and related monomeric and dimeric compounds. Chemical and
Pharmaceutical Bulletin, 48, 1467–1469.
CONFLICT OF INTEREST
Baskaran, Y., Periyasamy, V., & Venkatraman, A. C. (2010). Investigation of
antioxidant, anti-inflammatory and DNA-protective properties of
eugenol in thioacetamide-induced liver injury in rats. Toxicology, 268,
204–212.
The authors declare that they have no conflict of interest.
DATA AVAILABILITY STATEMENT
Jirovetz, L., Buchbauer, G., Stoilova, I., Stoyanova, A., Krastanov, A., &
Schmidt, E. (2006). Chemical composition and antioxidant properties
of clove leaf essential oil. Journal of Agricultural and Food Chemistry,
54, 6303–6307.
The data used to support the findings of this study are available from
the corresponding author upon request.
ORCID
Sadeghian, H., Seyedi, S. M., Attaran, N., Jabbari, A., & Jafari, Z. (2011).
Synthesis and SAR comparative studies of 2-allyl-4-methoxy-
1-alkoxybenzenes as 15-lipoxygenase inhibitorsJournal of. Enzyme
Inhibition and Medicinal Chemistry, 26, 238–244.
Hamid Sadeghian https://orcid.org/0000-0001-7894-5002
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How to cite this article: Alavi SJ, Seyedi SM, Saberi S,
Safdari H, Eshghi H, Sadeghian H. Allylphenols as a new class
of human 15-lipoxygenase-1 inhibitors. Drug Dev Res. 2020;
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