Eugenol derivatives as potential anti-oxidants: Is phenolic hydroxyl necessary to obtain an effect?

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Research Paper

Journal of Pharmacy

And Pharmacology

Eugenol derivatives as potential anti-oxidants: is phenolic

hydroxyl necessary to obtain an effect?

Marília d’ Avila Farias^a, Pathise Souto Oliveira^a, Filipe S. Pereira Dutra^c, Thiely Jacobsen Fernandes^c,

Claudio M. P. de Pereira^a, Simone Quintana de Oliveira^d, Francieli Moro Stefanello^a,

Claiton Leonetti Lencina^c, Alethéa Gatto Barschak^a,b

^aPrograma de Pós-Graduação em Bioquímica e Bioprospecção, UFPel, Campus Universitário s/n, ^bDepartamento de Ciências Básicas da Saúde,

c

Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Centro de Ciências Químicas, Farmacêuticas e de Alimentos,

Universidade Federal de Pelotas, Pelotas, RS, and ^dCentro de Ciências da Saúde, Departamento de Ciências Farmacêuticas, UFSC, Campus

Universitário, Florianópolis, SC, Brazil

Keywords

anti-oxidant activity; eugenol; eugenol

Abstract

Objectives Eugenol, obtained from clove oil (Eugenia caryophyllata), possess

several biological activities. It is anti-inﬂammatory, analgesic, anaesthesic, anti-

pyretic, antiplatelet, anti-anaphylactic, anticonvulsant, anti-oxidant, antibacterial,

antidepressant, antifungal and antiviral. The anti-oxidant activity of eugenol have

already been proven. From this perspective testing, a series of planned structural

derivatives of eugenol were screened to perform structural optimization and con-

sequent increase of the potency of these biological activities.

derivatives; phenolic compounds

Correspondence

Alethéa Gatto Barschak, Universidade Federal

de Ciências da Saúde de Porto Alegre, Rua

Sarmento Leite, 254, Porto Alegre, CEP:

90050-170, RS, Brazil.

E-mail: aletheagatto@gmail.com

Methods In an attempt to increase structural variability, 16 compounds were syn-

thesized by acylation and alkylation of the phenolic hydroxyl group. Anti-oxidant

activity capacity was based on the capture of DPPH radical (2,2-diphenyl-1-picryl-

hydrazyl), ABTS radical 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid),

measure of TBARS (thiobarbituric acid-reactive species), total sulfhydryl and car-

bonyl content (eugenol derivatives ﬁnal concentrations range from 50 to 200 μm).

Key ﬁndings Four derivatives presented an efﬁcient concentration to decrease 50%

of the DPPH radical (EC₅₀) < 100 μm, which has a good potential as a free-radical

scavenger. Three of these compounds also showed reduction of ABTS radical.

Eugenol derivatives presenting alkyl or aryl (alkylic or arylic) groups substituting

hydroxyl 1 of eugenol were effective in reducing lipid peroxidation, protein oxidative

damage by carbonyl formation and increase total thiol content in cerebral cortex

homogenates. In liver, the eugenol derivatives evaluated had no effect.

Received July 13, 2013

Accepted November 16, 2013

doi: 10.1111/jphp.12197

Conclusions Our results suggest that these molecules are promising anti-oxidants

agents.

Introduction

Eugenol (4-allyl-2-metoxy-phenol) is a phenolic com-

pound and the main component of clove oil (Eugenia

caryophyllata).^[1,2]Eugenol is a natural pharmacologically

active aromatic substance present in essential oils of several

plants^[3]and known for its aroma and medicinal values.^[4]

Currently, the most common way to obtain this product is

extraction by vapour drag of ﬂower buttons and ﬂoral

stems of some plants belonging to the family Myrtaceae.^[5,6]

Eugenol already has several proven biological activity.

They include anti-inﬂammatory,^[1,7–11]analgesic,^[1,10,12]

antiviral^[6]activity. In traditional medicine, eugenol has

been used as an antispasmodic in gastrointestinal disor-

ders^[6,8,9]without mutagenic and carcinogenic effects.^[1,9,12]

Furthermore, there is evidence of its hepatoprotective

effect.^[6,9]

Eugenol can prevent lipid peroxidation in the early

stages.^[14]Several studies showed the anti-oxidant capacity

of eugenol and its derivatives, such as isoeugenol to inhibit

the lipid peroxidation induced by reactive oxygen species. It

likewise inhibits the formation of the superoxide radical in

the xanthine-xanthine oxidase system, the generation of

hydroxyl radical, preventing the oxidation of Fe²⁺in the

Haber-Weiss and Fenton reaction.^[15,16]A study of eugenol

anaesthesic,^[13]

antipyretic,^[8,10]

antiplatelet,^[10]

anti-

anaphylactic,^[10]anticonvulsant,^[1]anti-oxidant,^{[1,5,9,11,12]}anti-

bacterial,^{[1,5,8,11,12]}antidepressant,^[12]antifungal^[1,6]and

733

Eugenol derivatives as potential anti-oxidants

Marília d’ Avila Farias et al.

structure activity revealed that in addition to the phenolic

ring, the side chain has an important role in anti-oxidant

activity.^[2,5]

(NMR) spectra were recorded on a Brucker Advance III

instrument (400 MHz) and AC200 (200 MHz). Tri-

methylsilane was used as internal standard for H NMR

and CDCl₃for ¹³C NMR.

1

It is known that cellular redox state is a consequence of

the balance between the levels of oxidizing and reducing

agents, and endogenous anti-oxidants. Reactive species are

kept at physiological levels by anti-oxidant defence systems.

Anti-oxidants are endogenous or exogenous substances that

reduce the formation of reactive species or react promoting

their inactivation. To prevent cellular damage, which can be

caused by the presence of these species, the organism has

enzymatic and non-enzymatic anti-oxidant defences.^[17,18]

Anti-oxidant therapies have emerged as alternatives

for treating chronic degenerative diseases including

cancer, inﬂammation, cardiovascular diseases and neuro-

degenerative diseases (such as Parkinson and Alzheimer,

multiple sclerosis), and thus, biological research aimed at

anti-oxidants and free radicals have produced promising

results with regard to new therapeutic approaches.^[18]

Furthermore, it has been shown that anti-oxidants may be

involved in signalling pathways and cellular responses, and

that many anti-inﬂammatory agents also present anti-

oxidant activity.^[19]

Chemical reactions to synthesis of compounds was

monitored on a thin layer chromatography (TLC) and

Shimadzu GC-MS-2010SE Gas Chromatograph equipped

with an Rtx-Wax polyethylene glycol capillary column

(0.25 mm × 30 m) and a mass spectrometry detector

(Shimadzu, Kyoto, Japan).

Chemistry

Chemical data on synthesized compounds

The structures of eugenol derivatives were conﬁrmed by ¹H

NMR, ¹³C NMR, GC-MS spectral data (see Appendix).

Synthesis of eugenol derivatives 11–19

Eugenol (10 mmol) was dissolved in the solution of NaOH

(12 mmol). The solution was placed in a ﬂat-bottomed

ﬂask, and the chloride derivative (10 mmol) was added. The

mixture was stirred at room temperature on agitation for

30 min. After consumption of the starting material, the

reaction medium was extracted with dichloromethane

(3 × 10 ml) and washed with Na₂CO₃5%. The solvent was

dried with anhydrous Na₂SO₄and evaporated under

reduced pressure; the pure products were obtained by

recrystallization from ethanol.

The technological advances that have contributed to the

search for new compounds involve the discovery of new

molecular tools and evolution of analytical techniques,

puriﬁcation and organic synthesis, resulting in more effec-

tive active or less toxic substances, which can be used as

prototypes of drugs with pharmacological activity similar to

or larger than the originals.^[20]

The anti-oxidant activity of eugenol has been already

conﬁrmed. Thus, the attempt at optimization and conse-

quent increase in the biological activity of eugenol requires

knowledge of its mechanism of action, its therapeutic

targets and its pharmacophoric groups. Hence, testing a

range of planned structural derivatives of eugenol helped

increase this knowledge.

The aim of this study was to perform structural changes

in eugenol to obtain compounds and evaluate their

anti-oxidant capacity and radical scavenging effect. The

radical scavenging activity was evaluated by 2,2-diphenyl-

1-picryl-hydrazyl (DPPH) and 2,2′-azinobis-3-ethyl-

benzothiazoline-6-sulfonic acid (ABTS) scavenging tests;

anti-oxidant activity was assessed by thiobarbituric acid-

reactive species (TBARS) (measure of lipid peroxidation),

and carbonyl and thiol content (parameters of protein

oxidation).

Synthesis of eugenol derivatives 27–33

In one ﬂask, K₂CO₃(20 mmol) was added, dissolved dried

acetone (40 ml) and eugenol (10 mmol), followed by the

respective addition of alkyl chloride (10 mmol) and stirred

at reﬂux for 2 h. After complete consumption of the starting

material (TLC), the reaction was cooled, ﬁltered and

washed with acetone (20 ml). The organic solvent was

evaporated under vacuum. The ﬁnal product was

resuspended in dichloromethane (50 ml) and washed with

H₂O (2 × 25 ml). The organic extract was dried under anhy-

drous Na₂SO₄, and the residual solvent was evaporated in

vacuum. Pure product was obtained by column (n-Hexane:

AcOEt gradient) (Schemes 1 and 2).

Anti-oxidant activity

2,2-diphenyl-1-picryl-hydrazyl and

2,2′-azinobis-3-ethyl-benzothiazoline-6-sulfonic

acid radical scavenging activity

Materials and Methods

All the reagents were used as purchased from commercial

suppliers without further puriﬁcation, and solvents were

The DPPH free radical scavenging assay was performed in

accordance with the procedure reported by Brand-Williams

et al.^[21]with some modiﬁcations. The antiradical activity

1

freshly distilled. H and ¹³C nuclear magnetic resonance

734

Marília d’ Avila Farias et al.

Eugenol derivatives as potential anti-oxidants

R

O

OH

O

NaOH (aq)

O

Cl

+

R

2-10

O

1

11-19

Scheme 1 Reaction of obtaining derivatives 11–19.

R₁

O

OH

R₁Cl

Acetone

K₂CO₃

+

20-26

O

27-33

1

Scheme 2 Reaction of obtaining derivatives 27–33.

was deﬁned as the amount of anti-oxidant necessary to

decrease the initial DPPH concentration by 50% (EC50).

The ABTS radical scavenging activity was evaluated as

described by Re et al.^[22]with some modiﬁcations. Trolox

was used as standard at concentrations 200, 150, 100, 50

and 10 μm. The percentage of radical scavenging was calcu-

lated as trolox equivalent anti-oxidant capacity (TEAC).

Eugenol derivatives were dissolved in dimethyl sulfoxide

(DMSO), and ﬁnal concentrations were 120, 60, 30 and

15 μm for DPPH assay and for ABTS radical scavenging

activity.

Thirty microlitres of hydrogen peroxide (5 mm) and

ferrous sulfate (20 μm), which are responsible for inducing

oxidative damage (TBARS assay, total sulfhydryl content

and carbonyl assay), were added to 440 μl of cerebral cortex

and liver homogenates. Different concentrations of eugenol

derivatives (ﬁnal concentrations were 50, 100 and 200 μm

dissolved in DMSO and diluted in distilled water) were

added to the mixture and incubated for 1 h at 37°C with

inducing damage. After that, an aliquot of tissue homo-

genates were used in the different assays.

Butylated hydroxytoluene (BHT) 25 μm was used as

standard anti-oxidant.^[4]

Subjects and reagents

Thiobarbituric acid-reactive species assay

Male Wistar rats were obtained from the Central Animal

House of Universidade Federal de Pelotas, Pelotas, RS. The

animals were maintained on a 12/12 h light/dark cycle in an

air-conditioned constant temperature (22 1°C) colony

room. Rats had free access to a 20% (w/w) protein commer-

cial chow and water. The Guide for the Care and Use of

Laboratory Animals^[23]was followed in all experiments.

The study was approved by the Ethics Committee of

Universidade Federal de Pelotas, Brazil (CEEA 10263). All

chemicals were purchased from Sigma (St. Louis, MO,

USA).

TBARS, an index of lipid peroxidation, were determined

according to the method described by Buege and Aust^[24]

with some modiﬁcations. Trichloroacetic acid and

thiobarbituric acid were added to samples and incubated

for 25 min at 100°C. A calibration curve was performed

using 1,1,3,3-tetramethoxypropane following the same

treatment as that of the samples. The absorbance was read

at 535 mm, the results were reported as nmol TBARS/mg

protein.

Total sulfhydryl content

Total thiol content was determined using the 5,5′-dithiobis-

2-nitrobenzoic acid method, as described by Aksenov and

Markesbery^[25]with some modiﬁcations. The amount of

5-thio-2-nitrobenzoic acid (TNB) formed was determined

at 412 nm. The results were reported as nmol of TNB/mg

protein.

Tissue and homogenate preparation

Thirty-day-old Wistar rats were sacriﬁced by decapitation

without anaesthesia. The cerebral cortex and liver were

immediately dissected out and homogenized in 10 volumes

(1 : 10, w/v) of 20 mm sodium phosphate buffer, pH 7.4

containing 140 mm KCl. Homogenates were centrifuged at

750g for 10 min at 4°C, the pellet was discarded and the

supernatant was immediately separated and used for the

biochemical measurements.

Carbonyl assay

Oxidatively modiﬁed proteins present an enhancement of

carbonyl content.^[26]In this study, protein carbonyl was

735

Eugenol derivatives as potential anti-oxidants

Marília d’ Avila Farias et al.

assayed by the method of Reznick and Packer,^[27]which

is based on the reaction of protein carbonyls with

dinitrophenylhydrazine forming dinitrophenylhydrazone,

a yellow compound, measured spectrophotometrically at

370 nm. Results were reported as nmol carbonyl/mg

protein.

We also evaluated the effect of eugenol derivatives on

protein oxidative damage by carbonyl formation. The com-

pounds reduced carbonyl content at concentrations from 50

to 200 μm compared with induced control (Figure 3) 28

(F(5,36) = 8.55; P < 0.01); 30 (F(5,19) = 5.98; P < 0.01) and

31 (F(5,34) = 5.14; P < 0.01). However, compound 32

reduced carbonyl content only at 200 μm (F(5,33) = 12.96;

P < 0.01). In liver (Table 2), compound 32 (F(5,23) = 10.37;

P < 0.001) signiﬁcantly reduced carbonyl formation at con-

centrations from 50 to 200 μm compared with induced

control.

Protein determination

Protein was determined by the Lowry et al. method^[28]using

bovine serum albumin as standard.

Anti-oxidant and radical scavenging activity of the com-

pounds were compared with BHT (standard anti-oxidant)

as positive control.

Statistical analysis

Data were expressed as mean standard deviation. The

comparisons of means were analysed by one-way analysis

of variance followed by the Duncan test when the F value

was signiﬁcant. A value of P < 0.05 was considered to be

signiﬁcant.

Discussion

The main structural characteristic responsible for the anti-

oxidant activity of phenolic derivatives, such as eugenol,

is the presence of hydroxyl that can donate hydrogen

atoms, interrupting chain propagation of the oxidative

process.^[4,7,29]Thus, these compounds play an important role

donating hydrogen atoms, suppressing ROS formation,

acting as metal chelants (which catalyse the Fenton reac-

tion) or also as enzyme inhibitors/activators.^[1,30,31]

In this study, we synthesized eugenol derivatives

attempting to ﬁnd compounds with anti-oxidant action.

Some of these compounds have already been tested

for other activity such as 15-lipoxygenase inhibitors and

herbicidal agents.^[32]Sixteen compounds were synthetized

with different modiﬁcations in the hydroxyl group at

1-position of eugenol. The synthesis was divided into

two blocks. These conferred different physical-chemical

characteristics on the lateral chain of the compounds

obtained.

There are important alterations in position 1 of the

eugenol. Differences in size and in the nature of the carbon

chain (aliphatic or aromatic) cause stereo-electronic vari-

ations that help identify characteristics needed to increment

the activity of these molecules. It is known that the pharma-

cological activity of eugenol are related to its chemical and

structural characteristics because different substitutions of

the ring can inﬂuence the biological activity.^[2]As to anti-

oxidant activity, eugenol has the property of neutralizing

the alkyl radicals, peroxy and superoxide because of the dif-

ference in the reduction potential between the radical and

the phenol.^[33]Insaturations are very valuable for the

eugenol activity towards free radicals.

Results

Good yields of the products were obtained after short reac-

tion times using simple synthetic routes. At ﬁrst, the anti-

oxidant activity of 16 eugenol derivatives was evaluated by

DPPH and ABTS assay. The eugenol derivatives 28, 30, 31

and 32 showed an efﬁcient concentration to decrease DPPH

radical with values of EC50 of 60, 43, 19 and 59 μm, respec-

tively. Regarding the ABTS radical test, only compounds 28,

30 and 31 showed a TEAC higher than 0.50 mm (Table 1).

These four compounds, 28, 30, 31 and 32, were tested on

lipid peroxidation in the brain and liver of rats. As shown in

Figure 1, these eugenol derivatives were effective in protect-

ing against lipid peroxidation induced by hydrogen perox-

ide and ferrous sulfate in cerebral cortex homogenate.

All compounds reduce TBARS levels at concentrations

from 50 to 200 μm 28 (F(5,26) = 103.39; P < 0.01)); 30

(F(5,30) = 89.99; P < 0.01); 31 (F(5,42) = 263.32; P < 0.01)

and 32 (F(5,36) = 46.09; P < 0.01) compared with induced

control. In liver (Table 2), 31 (F(5,36) = 32.11; P < 0.001)

and 32 (F(5,36) = 34.26; P < 0.001) reduce lipid peroxi-

dation at concentrations from 50 to 200 μm, while 28

reduced TBARS at 100 and 200 μm (F(5,30) = 20.74;

P < 0.001) compared with induced control.

We tested the effect of eugenol derivatives on total thiol

content in the cerebral cortex and liver of rats. Figure 2

shows that the compounds 30 and 32 signiﬁcantly modify

sulfhydryl levels in the cerebral cortex of rats. Compound

30 (F(5,27) = 9.86; P < 0.01) increased at concentrations

from 50 to 200 μm, while 32 (F(5,26) = 10.80; P < 0.01)

increased thiol content at concentrations of 100 and 200 μm

compared with induced control. In the liver of rats, tested

compounds did not modify the total thiol content com-

pared with induced control (Table 2).

There are studies proving that the phenolic compounds

are more potent anti-oxidants than vitamins E, C and

carotenoids. For a compound to be classiﬁed as an anti-

oxidant, several methods have been used to evaluate the

anti-oxidant activity in vitro.^[34]

736

Marília d’ Avila Farias et al.

Eugenol derivatives as potential anti-oxidants

Table 1 Radical scavenging of eugenol derivatives

O

RO

Compound

R

DPPH EC50 (μM)

ABTS⁺(TEAC)

Eugenol

11

H

72

6.8

O

>100

<0.50

F

12

>100

<0.50

O

13

14

>100

<0.50

Br

O

OCH₃

Cl

O

15

16

>100

<0.50

F

O

17

>100

<0.50

CH₃

737

Eugenol derivatives as potential anti-oxidants

Marília d’ Avila Farias et al.

Table 1 Continued

Compound

18

R

DPPH EC50 (μM)

>100

ABTS⁺(TEAC)

O

<0.50

NO₂

19

>100

<0.50

O

27

28

29

>100

60

<0.50

0.77

O

>100

<0 .50

O

30

31

32

33

-CH₂CH₂Ph

43

19

2.10

12.44

<0.50

-CH₂CH₂CH₂Ph

-CH₂CH₂CH₃

59

-CH₂CH₂CH₂CH₃

>100

ABTS, 2,2′-azinobis-3-ethyl-benzothiazoline-6-sulfonic acid; DPPH, 2,2-diphenyl-1-picryl-hydrazyl; EC50, efﬁcient concentration to decrease 50% of

the DPPH radical; TEAC, trolox equivalent anti-oxidant capacity.

The anti-oxidant capacity of the different eugenol

derivates was screened based on the capture of radical

DPPH and of radical ABTS. The latter methods are

widely used because they are simple, quick, sensitive

methodologies.^[35]

Four compounds of the 16 eugenol derivatives tested pre-

sented EC50 < 100 μm. Derivatives 28, 30, 31 and 32 were

promising as they presented a smaller EC50 than eugenol,

and with an EC50 lower than standard anti-oxidants such

as BHT (EC50 = 60.25 μm).

The DPPH test is an indirect method to determine anti-

oxidant activity. This method is based on the measure of

the reducing ability of anti-oxidants when dealing with the

DPPH radical, usually expressed as EC50. The lower the

EC50, the greater the radical scavenging efﬁciency. One of

the limitations of this methodology is that there is no

DPPH and similar compounds in biological systems.^[36]To

complete the screening of the anti-oxidant activity, the

TEAC was determined. This method is based on the com-

pound capacity to neutralize the ABTS radical.^[22,37]In this

test, 28, 30, 31, presented TEAC > 0.50, but only 31 pre-

sented TEAC higher than eugenol.

Lipid peroxidation and protein oxidation are two impor-

tant indicators of oxidative damage of macromolecules

induced by ROS.^[38]Hence, the compounds that presented

activity in the screening tests (28, 30, 31, 32) were evaluated

for their anti-oxidant capacity on TBARS, and carbonyl and

total thiol content in rat brain and liver. The eugenol

derivatives obtained presented signiﬁcant results in the

TBARS test, proving similar to eugenol at the different

concentrations tested (50–200 μm) in cerebral cortex of

30-day-old rats, reducing the damaged provoked by the

reactive species. But in the liver of these same animals,

only a few compounds presented signiﬁcant results in

lipoperoxidation.

These results are due to the fact that the brain is a

lipid-rich organ with a low level of anti-oxidant de-

fences. Moreover, it has auto-oxidable neurotransmitters,

738

Marília d’ Avila Farias et al.

Eugenol derivatives as potential anti-oxidants

28

30

20

15

10

5

#

15

*

10

5

*#

0

C

I

BHT

50

100

200

C

I

BHT

32

50

100

200

Concentration (µM)

31

20

15

10

5

20

15

10

5

#

*#

50

*#

0

C

I

BHT

50

100

200

C

I

BHT

100

200

Concentration (µM)

Eugenol

20

#

15

10

5

*

#*

0

C

I

BHT

50

100

200

Concentration (µM)

Figure 1 Effect of eugenol derivatives on thiobarbituric acid reactive species in the cerebral cortex of rats. Data are expressed as mean standard

deviation (n = 5–15). The levels of thiobarbituric acid reactive species were reported as nmol thiobarbituric acid reactive species per mg protein.

#Signiﬁcantly different from control (P < 0.05). *Signiﬁcantly different from induced control (P < 0.05). Differences were determined by one-way

analysis of variance followed by Duncan’s post hoc. C, control; I, induced control; BHT, butylated hydroxytoluene.

739

Eugenol derivatives as potential anti-oxidants

Marília d’ Avila Farias et al.

Table 2 Effect of eugenol derivatives on thiobarbituric acid reactive species (TBARS), carbonyl and total thiol content in liver of rats

Concentration (μM)

Eugenol

Derivatives

Control

Induced control

BHT

2.13 0.17*^†

50

2.25 0.13^†

100

2.21 0.10^†

200

2.19 0.13*^†

TBARS

Eugenol

28

1.86 0.11

1.93 0.06

1.85 0.73

1.80 0.013

1.66 0.08

69.58 16.0

58.69 9.63

69.58 16.0

58.69 9.63

69.58 16.0

5.27 0.42

2.30 0.10

3.16 0.23

2.30 0.10

5.27 0.42

2.33 0.19^†

2.80 0.26^†

2.25 0.14^†

2.69 0.16^†

2.42 0.11^†

44.60 8.23^†

44.50 9.63^†

44.40 8.23^†

44.50 3.79^†

44.40 8.23^†

4.95 0.94

2.52 0.24

3.39 0.19

2.52 0.24

4.95 0.94

2.51 0.16*^†

2.07 0.09*^†

2.33 0.20*^†

2.10 0.15*^†

44.93 9.04^†

50.91 3.73^†

44.93 9.04^†

50.91 3.73

44.93 9.04^†

4.92 0.66

2.62 0.17^†

2.50 0.17*^†

2.49 0.12*^†

2.12 0.09*

49.00 6.74^†

42.87 6.16^†

40.90 17.35^†

43.28 9.28^†

42.31 11.11^†

5.13 0.65

2.45 0.09*^†

2.48 0.09*^†

2.43 0.11*^†

1.84 0.14*^†

48.27 8.98^†

43.24 3.74^†

53.50 15.33^†

41.75 6.32^†

57.81 12.08^†

5.10 0.43

2.50 0.12*^†

2.46 0.15*^†

2.51 0.14*^†

1.80 0.18*

44.68 12.36^†

41.42 3.96^†

50.92 9.18^†

51.54 4.84^†

51.95 16.71^†

4.53 0.50

30

31

32

Total thiol

Carbonyl

Eugenol

28

30

31

32

Eugenol

28

2.56 0.23

2.44 0.15

2.58 0.22

2.67 0.16^†

30

3.33 0.22

3.16 0.36

3.19 0.44

3.48 0.48

31

2.56 0.23

2.65 0.12^†

3.55 0.54*^†

2.46 0.10

3.43 0.21*^†

2.72 0.14^†

3.49 0.39*^†

32

4.92 0.66

BHT, butylated hydroxytoluene. Data are expressed as mean standard deviation (n = 6–12). The levels of TBARS were reported as nmol TBARS per

mg protein, thiol content as nmol TNB per mg protein and carbonyl content as nmol of carbonyl per mg protein. Differences were determined by

one-way analysis of variance followed by Duncan’s post hoc. *Signiﬁcantly different from induced control (P < 0.05). ^†Signiﬁcantly different from

control (P < 0.05).

a polyunsaturated fatty acid-rich neuronal membrane, and

a high level of iron.^[39]On the other hand, the liver resists

damage caused by free radicals because besides having high

anti-oxidant levels, it adapts easily to metabolic changes.^[40]

The sulfhydryl content is inversely correlated with the

oxidative damage to the proteins. Therefore, the reduction

of protein thiol groups seen in the in vitro experiment sup-

plies evidence of reduction of oxidative damage to the pro-

teins. Thiol groups (SH) are recognized as being essential

anti-oxidants that have the role of protecting the cellular

and extracellular functions against oxidative stress. The

mammal cells from different tissues, including the brain,

have a system that regulates the redox state of thiol protect-

ing the proteins from excessive oxidation.^[41]

The carbonyl content is the main marker of oxidative

damage to proteins.^[42]The carbonyls can present higher

levels because of protein glycation by sugars, the linkage of

aldehydes to proteins, or also because of direct oxidation of

the lateral chains of amino acids caused by free radicals.^[25,43]

The great majority of compounds tested, reduced, in the

cerebral cortex, the carbonyl content at the concentrations

tested, but in the liver, only two compounds had satisfactory

results.

protein oxidation in biological systems. Although interest-

ing, these results should be treated with caution because it is

a ﬁrst study involving these eugenol derivatives. Further

research is necessary to better understand their anti-oxidant

activity before establishing beneﬁcial effects of eugenol

derivatives. The derivatives that presented promising activ-

ity have alkyl or aryl groups substituting the hydroxyl group

of eugenol. They vary mainly the size of this lateral chain.

Alkyl and linear characteristics appear to favour the activity.

These results suggest the existence of other anti-oxidant

mechanisms in addition to those involving phenolic

hydroxyl. The latter, widely cited as responsible for the anti-

oxidant activity of eugenol, is replaced in the derivatives

that presented more marked anti-oxidant activity than the

aforementioned compound, both in in vitro and ex vivo.

Our results show signs that the presence of phenolic

hydroxyl in position 1 of the eugenol is not essential for

anti-oxidant activity. This creates a possibility for the occur-

rence of mechanisms different from those that go through

the donation of a proton or metal chelation.

Acknowledgements

This work was supported in part by grants from

‘Fundação de Amparo à Pesquisa do Rio Grande do Sul’

(FAPERGS), ‘Coordenação de Aperfeiçoamento de Pessoal

de Nível Superior’ (CAPES) and ‘Conselho Nacional de

Desenvolvimento Cientíﬁco e Tecnológico’ (CNPq), Brazil.

The authors also thank Hedy Hoffmann for the corrections

of the English version.

Conclusion

Sixteen compounds were synthetized based on structural

modiﬁcations in the eugenol. Among these, compounds 28,

30, 31 and 32 presented radical scavenging activity in the

DPPH and ABTS assays. These compounds also showed

anti-oxidant activity, reducing the lipid peroxidation and

740

Marília d’ Avila Farias et al.

Eugenol derivatives as potential anti-oxidants

27

*#

30

*

20

15

20

15

10

5

*

*#

*

#

10

5

0

C

I

BHT

50

100

200

C

I

BHT

50

100

200

Concentration (µM)

31

32

30

20

10

0

30

20

10

0

*

#

C

I

BHT

50

100

200

C

I

BHT

50

100

200

Concentration (µM)

Eugenol

#*

25

20

15

10

5

#*

#

0

C

I

BHT

50

100

200

Concentration (µM)

Figure 2 Effect of eugenol derivatives on total thiol content in the cerebral cortex of rats. Data are expressed as mean standard deviation (n = 5–

14). The levels of thiol content were report as nmol TNB per mg protein. #Signiﬁcantly different from control (P < 0.05). *Signiﬁcantly different from

induced control (P < 0.05). Differences were determined by one-way analysis of variance followed by Duncan’s post hoc. C, control; I, induced

control; BHT, butylated hydroxytoluene.

741

Eugenol derivatives as potential anti-oxidants

Marília d’ Avila Farias et al.

28

30

20

15

10

5

10

#

*

8

6

4

2

0

*

0

C

I

BHT

31

50

100

200

C

I

BHT

50

100

200

Concentration (µM)

32

15

10

5

10

8

#

*

#

*

#

6

*

4

2

0

C

I

BHT

50

100

200

C

I

BHT

50

100

200

Concentration (µM)

Eugenol

20

#

*

15

10

5

*

0

C

I

BHT

50

100

200

Concentration (µM)

Figure 3 Effect of eugenol derivatives on carbonyl content in the cerebral cortex of rats. Data are expressed as mean standard deviation (n = 4–

8). The levels of carbonyl content were report as nmol of carbonyl per mg protein. #Signiﬁcantly different from control (P < 0.05). *Signiﬁcantly dif-

ferent from induced control (P < 0.05). Differences were determined by one-way analysis of variance followed by Duncan’s post hoc. C, control; I,

induced control; BHT, butylated hydroxytoluene.

742

Marília d’ Avila Farias et al.

Eugenol derivatives as potential anti-oxidants

13. Magalhaes DV Atividade antifúngica 26. Stadtman ER, Levine RL. Free radical-

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¹H NMR (400 MHz): δ (ppm) 8.10 (2H, C₆H₄-OCH₃); 7.28

(2H, C₆H₄-OCH₃); 7.05 (1H, C₆H₃); 6.80(2H,C₆H₃); 5.98

(1H, CH₂=CH₂-CH₂); 5.12 (2H, CH₂=CH₂-CH₂); 3.78 (3H,

OCH₃); 3.38 (2H, CH₂=CH₂-CH₂), 2.42 (3H, OCH₃); ¹³C

NMR (100 MHz): 21.8 (CH₂-CH₂-C₆H₃); 40.3 (C₆H₃-O-

CH₃); 56.1 (C₆H₄-O-CH₃); 113.4 (Cm-C₆H₃-O); 116.1

(CH₂=CH₂-CH₂); 121.0 (Co-C₆H₃-O); 123.0 (Cm-C₆H₃-O);

127.1 (Ci-C₆H₄(4OCH₃)-C=O); 129.1 (Cm-C₆H₄(4OCH₃)-

C=O); 130.3 (Co-C₆H₄-(4OCH₃)-C=O); 137.1 (Cp C₆H₃-

O); 138.6 (Ci-C₆H₃-O); 139.0 (CH₂=CH₂-CH₂); 144.3

(OCH₃-Co-C₆H₃-O); 151.5 (Cp-C₆H₄(4OCH₃)-C=O);

165.1 (C=O); Yield = 43%; MP = 170–171°C.

Appendix

Spectroscopic data

4′-allyl-2′-methoxyphenyl-benzoate (11): Chemical

Formula: C₁₇H₁₆O₃; MS m/z: 268.11; NMR Data H NMR

1

(400 MHz): δ (ppm) 8.19 (2H, C₆H₅); 7.55 (1H, C₆H₅); 7.46

(2H, C₆H₅); 7.06 (1H, C₆H₃-O); 6.79 (2H, C₆H₃); 5.97 (1H,

CH₂=CH₂-CH₂); 5.10 (2H, CH₂=CH₂-CH₂); 3.87 (3H,

OCH₃); 3.38 (2H, CH₂=CH₂-CH₂),¹³C NMR (100 MHz):

40.1 (CH₂-CH₂-C₆H₅); 56.0 (O-CH₃); 113.1 (Cm-C₆H₃);

116.0 (CH₂=CH₂-CH₂); 120.7 (Co-C₆H₃); 122.6 (Cm-C₆H₃-

O); 128.6 (O=C-Ci-C₆H₅); 133.2 (Cp-C₆H₅); 137.0 (CH₂-

Cp-C₆H₅); 138.4 (O-Ci-C₆H₅); 138.9 (CH₂=CH₂-CH₂);

151.4 (Co-C₆H₃-OCH₃); 164.8 (C=O); Yield = 86%;

MP = 57–58°C.

4′-allyl-2′-methoxyphenyl-3-chlorobenzoate

(15):

Chemical Formula: C₁₇H₁₅ClO₃; MS m/z: 302.07, NMR Data

¹H NMR (400 MHz): δ (ppm) 8.18 (1H, C₆H₄-Cl); 8.17

(1H, C₆H₄-Cl); 7.56 (1H, C₆H₄-Cl); 7.05 (1H,C₆H₃); 6.0(2H,

C₆H₃); 5.97 (1H, CH₂=CH₂-CH₂); 5.12 (2H, CH₂=CH₂-

CH₂); 3.78 (3H, OCH₃); 3.37 (2H, CH₂=CH₂-CH₂),¹³C

NMR (100 MHz): 40.1 (CH₂-CH₂-C₆H₃); 56.0 (C₆H₃-O-

CH₃); 113.2 (Cm-C₆H₃-O); 116.1 (CH₂=CH₂-CH₂); 120.8

(Cm-C₆H₃-O); 122.6 (Co-C₆H₃-O); 128.3 (Ci-C₆H₄(3Cl)-

C=O); 129.7 (Co-C₆H₄(3Cl)-C=O); 130.2 (Cm-C₆H₄-(3Cl)-

C=O); 131.5 (Co-C₆H₄(3Cl)-C=O); 133.3 (Cp-C₆H₄

(3Cl)-C=O); 134.7 (Cm-C₆H₄-Cl-(C=O)); 137.0 (Cp-C₆H₃-

O); 128.2 (Ci-C₆H₃-O); 139.2 (CH₂=CH₂-CH₂); 151.2

(OCH₃-Co-C₆H₃-O); 163.6 (C=O); Yield = 31%; MP = 48–

50°C.

4′-allyl-2′-methoxyphenyl-2-ﬂuorobenzoate

(12):

Chemical Formula: C₁₇H₁₅FO₃; MS m/z: 286.10; NMR Data

¹H NMR (400 MHz): δ (ppm) 8.22 (2H, C₆H₄-F); 7.22 (2H,

C₆H₄-F); 7.16 (1H, C₆H₃); 6.83 (2H, C₆H₃); 5.98 (1H,

CH₂=CH₂-CH₂); 5.11 (2H, CH₂=CH₂-CH₂); 3.78 (3H,

OCH₃); 3.39 (2H, CH₂=CH₂-CH₂) ¹³C NMR (100 MHz):

39.9 (CH₂-CH₂-C₆H₃); 55.9 (O-CH₃); 113.2 (Cm-C₆H₃-O);

115.5 (Cm-C₆H₄(2-F)-C=O); 115.7 (CH₂=CH₂-CH₂); 116.1

(Ci-C₆H₃-C=O); 120.8 (Co-C₆H₃-O); 122.6 (Cm-C₆H₃-O);

125.9 (Cm-C₆H₄-C=O); 132.8 (Co-C₆H₄-C=O); 137.1 (CH₂-

Cp-C₆H₃); 138.3 (Cp-C₆H₄-C=O); 139.2 (Ci-C₆H₃-O); 151.2

(CH₂=CH₂-CH₂); 163.8 (CH₃O-Co-C₆H₃-O); 164.8 (F-Co-

C₆H₄); 167.4 (C=O); Yield = 67%; MP = 59–60°C.

4′-allyl-2′-methoxyphenyl-4-ﬂuorobenzoate

(16):

4′allyl-2′-methoxyphenyl-3-bromobenzoate

(13):

Chemical Formula: C₁₇H₁₅FO₃; MS m/z: 286.10, NMR Data

¹H NMR (400 MHz): δ (ppm) 8.21 (2H, C₆H₄-F); 7.12 (2H,

C₆H₄-F); 7.05 (1H, C₆H₃); 6.8 (2H, C₆H₃); 5.98 (1H,

CH₂=CH₂-CH₂); 5.11 (2H, CH₂=CH₂-CH₂); 3.78 (3H,

OCH₃); 3.49 (2H, CH₂=CH₂-CH₂), ¹³C NMR (100 MHz):

40.1 (CH₂-CH₂-C₆H₃); 56.0 (C₆H₃-O-CH₃); 113.2 (Cm-

C₆H₃-O); 115.7 (Cm-C₆H₄-(4F)-C=O); 120.7 (CH₂=CH₂-

CH₂); 122.6 (Co-C₆H₃-O); 125.9 (Cm-C₆H₃-O); 132.8 (Co-

C₆H₄(4F)-C=O); 137.0 (Ci-C₆H₄(4F)-C=O); 138.3 (Cp-

C₆H₃-O); 139.1 (Ci-C₆H₃-O); 151.2 (CH₂=CH₂-CH₂); 163.7

(OCH₃-Co-C₆H₃-O); 164.7 (C=O); 167.3 (Cp-C₆H₄(4F)-

C=O); Yield = 64%; MP = 59–60°C.

Chemical Formula: C₁₇H₁₅BrO₃; MS m/z: 346.02, NMR Data

¹H NMR (400 MHz): δ (ppm) 8.33 (1H, C₆H₄-Br); 8.11

(1H, C₆H₄-Br); 7.71 (1H, C₆H₄-Br); 7.34(1H, C₆H₄-Br); 7.05

(1H, C₆H₃); 6.80 (2H, C₆H₃); 5.95 (1H, CH₂=CH₂-CH₂);

5.11 (2H, CH₂=CH₂-CH₂); 3.77 (3H, OCH₃); 3.38 (2H,

CH₂=CH₂-CH₂),¹³C NMR (100 MHz): 40.1 (CH₂-CH₂-

C₆H₃); 55.9 (O-CH₃); 113.2 (Cm-C₆H₃-O); 116.1

(CH₂=CH₂-CH₂); 120.8 (Cm-C₆H₃-O); 122.6 (Br-Cm-

C₆H₄); 122.5 (Co-C₆H₃-O); 128.7 (Co-C₆H₄(3-Br)C=O);

130.0 (Cm-C₆H₄(3-Br)C=O); 131.6 (Ci-C₆H₄(3-Br)C=O);

133.1 (Cp-C₆H₃-O); 136.2 (Ci-C₆H₃-O); 137.0 (CH₂=CH₂-

CH₂); 138.2 (Cp-C₆H₄(3-Br)-C=O); 139.2 (Co-C₆H₄-C(Br);

151.2 (OCH₃-Co-C₆H₃-O); 163.4 (C=O); Yield = 90%;

MP = 54–56°C.

4′-allyl-2′-methoxyphenyl-4-methylbenzoate

(17):

Chemical Formula: C₁₈H₁₈O₃; MS m/z: 282.13, NMR Data

¹H NMR (400 MHz): δ (ppm) 8.07 (2H, C₆H₄-CH3); 7.20

(2H, C₆H₄-CH3); 7.03 (1H, C₆H₃); 6.77 (2H, C₆H₃); 5.92

(1H, CH₂=CH₂-CH₂); 5.06 (2H, CH₂=CH₂-CH₂); 3.76 (3H,

4′-allyl-2′-methoxyphenyl-4-methoxybenzoate

Chemical Formula: C₁₈H₁₈O₄; MS m/z: 298.12, NMR Data

(14):

744

Marília d’ Avila Farias et al.

Eugenol derivatives as potential anti-oxidants

OCH₃); 3.37 (2H, CH₂=CH₂-CH₂), 2.4 (3H, CH3); ¹³C NMR

(100 MHz): 21.6 (CH₃); 40.1 (CH₂-CH₂-C₆H₃); 55.9 (C₆H₃-

O-CH₃); 113.2 (Cm-C₆H₃-O); 115.9 (CH₂=CH₂-CH₂); 120.8

(Co-C₆H₃-O); 122.8 (Cm-C₆H₃-O); 126.7 (Ci-C₆H₄(4CH3)-

C=O); 129.2 (Cm-C₆H₄(4CH3)-C=O); 130.3 (Co-C₆H₄-

(4CH₃)-C=O); 137.1 (Cp-C₆H₃-O); 138.5 (Ci-C₆H₃-O);

144.4 (CH₂=CH₂-CH₂); 151.3 (Cp-C₆H₄-(4CH₃)-C=O);

164.8 (OCH₃-Co-C₆H₃-O); 171.5 (C=O); Yield = 64%;

MP = 93–95°C.

CH₂=CH₂-CH₂); 2.6(2H, O-CH₂-CH₂); 1.8 (2H, O-CH₂-

CH₂); 1.5 (2H, CH₂-CH₂-CH₃); 1.0 (3H, CH₂-CH₂-CH₃);

¹³C NMR (100 MHz): 13.7 (CH₂-CH₃); 22.2 (CH₂-CH₃);

27.1 (CH₂-CH₂-CH₂); 33.8 (O-CH₂); 40.1 (CH₂-CH₂-C₆H₅);

55.8 (O-CH₃); 112.8 (CH₂=CH-CH₂); 116.1 (Cm-C₆H₃);

120.7 (Co-C₆H₃); 122.5 (Cm-C₆H₃-O); 137.1 (CH₂=CH-

CH₂); 138.8 (CH₂-Cp-C₆H₅); 146.5 (O-Ci-C₆H₅); 150.9 (Co-

C₆H₃-OCH₃); 172.0 (C=O); Yield = 43%; Oil.

4′-allyl-2′-methoxyphenyl-2-phenylacetate (29): Chemi-

cal Formula: C₁₇H₁₆O₃; MS m/z: 268.11, NMR Data ¹H NMR

(400 MHz): δ (ppm) 8.2-7.5 (5H, C₆H₅); 7.10 (3H, C₆H₃);

5.9 (1H, CH₂=CH₂-CH₂); 5.10 (2H, CH₂=CH₂-CH₂); 3.8

(3H, OCH₃); 3.4(2H, CH₂=CH₂-CH₂); ¹³C NMR

(100 MHz): 40.1 (CH₂-CH₂-C₆H₅); 55.9 (O-CH₃); 112.9

(Cm-C₆H₃); 116.1 (CH₂=CH₂-CH₂); 120.8 (Cm-C₆H₃-O);

122.7 (Co-C₆H₃); 128.5–133.4 (C₆H₅); 137.1 (CH₂-Cp-

C₆H₅); 138.3 (O-Ci-C₆H₅); 139.1 (CH₂=CH₂-CH₂); 151.2

(Co-C₆H₃-OCH₃); 164.9 (O=C-C₆H₅); Yield = 98%; Oil.

4-allyl-2-methoxy-1-phenethoxybenzene (30): Chemical

4′-allyl-2′-methoxyphenyl-4-nitrobenzoate

(18):

Chemical Formula: C₁₇H₁₅NO₅; MS m/z: 313.10, NMR Data

¹H NMR (400 MHz): δ (ppm) 8.11 (2H, C₆H₄-CH3); 7.26

(2H, C₆H₄-CH3); 7.00 (1H, C₆H₃); 6.82 (2H, C₆H₃); 5.97

(1H, CH₂=CH₂-CH₂); 5.14 (2H, CH₂=CH₂-CH₂); 3.78 (3H,

OCH₃); 3.39 (2H, CH₂=CH₂-CH₂), 2.40 (3H, CH3); ¹³C

NMR (100 MHz): 21.6 (CH₃); 40.2 (CH₂-CH₂-C₆H₃); 55.9

(C₆H₃-O-CH₃); 113.1 (Cm-C₆H₃-O); 115.9 (CH₂=CH₂-

CH₂); 120.8 (Co-C₆H₃-O); 122.8 (Cm-C₆H₃-O); 124.3 (Ci-

C₆H₄(4NO₂)-C=O); 126.1 (Cm-C₆H₄(4NO₂)-C=O); 133.2

(Co-C₆H₄-(4NO₂)-C=O); 137.1 (Cp-C₆H₃-O); 138.5 (Ci-

C₆H₃-O); 144.2 (CH₂=CH₂-CH₂); 151.3 (Cp-C₆H₄-(4CH₃)-

C=O); 164.8 (OCH₃-Co-C₆H₃-O); 171.5 (C=O);

Yield = 77%; MP = 75–77°C.

1

Formula: C₁₆H₂₀O₂; MS m/z: 268.15, NMR Data H NMR

(400 MHz): δ (ppm) 7.3 (5H, C₆H₅); 6.89 (3H, C₆H₃); 5.9

(1H, CH₂=CH₂-CH₂); 5.10 (2H, CH₂=CH₂-CH₂); 3.89 (3H,

OCH₃); 3.7(2H, O-CH₂-CH₂); 3.3(2H, CH₂=CH₂-CH₂); 3.10

(2H, O-CH₂-CH₂); ¹³C NMR (100 MHz): 38.2 (CH₂-CH₂-

C₆H₅); 39.9 (CH₂-CH₂-C₆H₅); 46.0 (CH₂-CH₂-C₆H₅); 55.9

(O-CH₃); 111.2 (Cm-C₆H₃); 114.3 (Co-C₆H₃); 115.5 (Cm-

C₆H₃-O); 121.2 (CH₂=CH₂-CH₂); 126.9 (CH₂-Cp-C₆H₅);

128.6–137.9 (C₆H₅); 131.9 (CH₂=CH₂-CH₂); 138.1

(CH₂=CH₂-CH₂); 143.9 (O-Ci-C₆H₅); 146.5 (Co-C₆H₃-

OCH₃); Yield = 70%; Oil.

4-allyl-2-methoxy-1-phenpropoxybenzene (31): Chemi-

cal Formula: C₁₉H₂₂O₂; MS m/z: 282.16, NMR Data ¹H NMR

(400 MHz): δ (ppm) 7.3 (5H, C₆H₅); 6.89 (3H, C₆H₃); 5.9

(1H, CH₂=CH₂-CH₂); 5.10 (2H, CH₂=CH₂-CH₂); 3.89 (3H,

OCH₃); 3.5(2H, O-CH₂-CH₂); 3.3(2H, CH₂=CH₂-CH₂);

2.8(2H, CH₂-CH₂-CH₂); 2.1(2H, CH₂-CH₂-C₆H₅); ¹³C NMR

(100 MHz): 32.8 (CH₂-CH₂-CH₂); 34.0 (CH₂-CH₂-C₆H₅);

39.9 (CH₂-CH₂-C₆H₅); 44.2 (CH₂-CH₂-C₆H₅); 55.9

(O-CH₃); 111.1 (Cm-C₆H₃); 114.3 (Co-C₆H₃); 115.5 (Cm-

C₆H₃-O); 121.2 (CH₂=CH₂-CH₂); 126.1–126.5 (C₆H₅); 131.9

(CH₂-Cp-C₆H₅); 137.8 (CH₂=CH₂-CH₂); 143.9 (O-Ci-

C₆H₅); 146.5 (Co-C₆H₃-OCH₃); Yield = 66%; Oil.

4′-allyl-2′-methoxyphenyl-2-nitrobenzoate

(19):

Chemical Formula: C₁₇H₁₅NO₅; MS m/z: 313.10, NMR Data

¹H NMR (400 MHz): δ (ppm) 8.10 (2H, C₆H₄-CH3); 7.26

(2H, C₆H₄-CH3); 7.02 (1H, C₆H₃); 6.82 (2H, C₆H₃); 5.97

(1H, CH₂=CH₂-CH₂); 5.11 (2H, CH₂=CH₂-CH₂); 3.78 (3H,

OCH₃); 3.39 (2H, CH₂=CH₂-CH₂), 2.41 (3H, CH3); ¹³C

NMR (100 MHz): 21.6 (CH₃); 40.1 (CH₂-CH₂-C₆H₃); 55.9

(C₆H₃-O-CH₃); 113.2 (Cm-C₆H₃-O); 115.9 (CH₂=CH₂-

CH₂); 120.8 (Co-C₆H₃-O); 122.8 (Cm-C₆H₃-O); 126.9 (Ci-

C₆H₄(4NO₂)-C=O); 129.2 (Cm-C₆H₄(4 NO₂)-C=O); 130.2

(Co-C₆H₄-(4 NO₂)-C=O); 137.1 (Cp-C₆H₃-O); 138.5 (Ci-

C₆H₃-O); 144.2 (CH₂=CH₂-CH₂); 151.3 (Cp-C₆H₄-(4CH₃)-

C = O); 164.8 (OCH₃-Co-C₆H₃-O); 171.5 (C=O);

Yield = 81%; MP = 57–58°C

1-(4′-allyl-2′-methoxyphenyl)-3-methylbutanoate (27):

Chemical Formula: C₁₅H₂₀O₃; MS m/z: 248.14, NMR Data

¹H NMR (400 MHz): δ (ppm) 6.89 (3H, C₆H₃); 5.9 (1H,

CH₂=CH₂-CH₂); 5.10(2H, CH₂=CH₂-CH₂); 3.8(3H, OCH₃);

3.4 (2H, CH₂=CH₂-CH₂); 2.4 (2H,C-CH₂-CH); 2.3 (1H,

CH₃-CH-CH₃); 1.10 (3H, CH₃-CH-CH₃); ¹³C NMR

(100 MHz): 22.4 (CH₃-CH-CH₃); 25.9 (CH₃-CH-CH₃); 40.1

(CH₃-CH-CH₃); 43.1 (CH₂-CH₂-C₆H₅); 55.7 (O-CH₃);

112.7 (Cm-C₆H₃); 116.1 (CH₂=CH-CH₂); 120.7 (Cm-C₆H₃-

O); 122.5 (Co-C₆H₃); 137.1 (CH₂=CH-CH₂); 138.8 (CH₂-

Cp-C₆H₅); 150.9 (O-Ci-C₆H₅); 171.2 (Co-C₆H₃-OCH₃);

191.74 (C=O); Yield = 61%; Oil.

4-allyl-2-methoxy-1-propoxybenzene (32): Chemical

1

Formula: C₁₃H₁₈O₂; MS m/z: 206.13, NMR Data H NMR

(400 MHz): δ (ppm) 6.8 (3H, C₆H₃); 5.9 (1H, CH₂=CH₂-

CH₂); 5.10 (2H, CH₂=CH₂-CH₂); 3.88 (2H, O-CH₂-CH₂);

3.82 (3H, OCH₃); 3.4 (2H, CH₂=CH₂-CH₂), 2.6 (2H, CH₂-

CH₂-CH₃); 1.3(3H, CH₂-CH₂-CH₃); ¹³C NMR (100 MHz):

9.2 (CH₂-CH₃); 27.4 (CH₂-CH₃); 40.1 (CH₂-CH₂-C₆H₅);

55.8 (O-CH₃); 112.8 (Cm-C₆H₃); 116.1 (Co-C₆H₃); 120.7

(CH₂=CH₂-CH₂); 122.5 (Cm-C₆H₃-O); 137.1 (CH₂-Cp-

C₆H₅); 138.8 (CH₂=CH₂-CH₂); 150.9 (O-Ci-C₆H₅); 172.7

(Co-C₆H₃-OCH₃); Yield = 54 %; Oil.

1-(4′-allyl-2′-methoxyphenyl)-pentanoate (28): Chemi-

cal Formula: C₁₅H₂₀O₃; MS m/z: 248.14, NMR Data ¹H NMR

(400 MHz): δ (ppm) 6.89 (3H, C₆H₃); 5.9 (1H, CH₂=CH₂-

CH₂); 5.10(2H, CH₂=CH₂-CH₂); 3.8(3H, OCH₃); 3.3(2H,

745

Eugenol derivatives as potential anti-oxidants

Marília d’ Avila Farias et al.

4-allyl-2-methoxy-1-butoxybenzene (33): Chemical

Formula: C₁₄H₂₀O₂; MS m/z: 220.15, NMR Data H NMR

(CH₂-CH₃); 18.6 (CH₂-CH₃); 35.9 (O-CH₂-CH₂); 40.1

(CH₂-CH₂-C₆H₅); 55.8 (O-CH₃); 112.8 (O-CH₂-CH₂); 116.1

(Cm-C₆H₃); 120.7 (Co-C₆H₃); 122.5 (Cm-C₆H₃-O); 137.1

(CH₂-Cp-C₆H₅); 138.1 (CH₂=CH₂-CH₂); 138.8 (CH₂=CH₂-

CH₂); 150.9 (O-Ci-C₆H₅); 171.9 (Co-C₆H₃-OCH_3;

Yield = 93%; Oil.

1

(400 MHz): δ (ppm) 7.27 (2H, Ar-O-CH₂); 6.8 (3H, C₆H₃);

5.9 (1H, CH₂=CH₂-CH₂); 5.10 (2H, CH₂=CH₂-CH₂); 3.86

(2H, O-CH₂-CH₂); 3.82 (3H, OCH₃); 3.4 (2H, CH₂=CH₂-

CH₂); 2.55(2H, CH₂-CH₂-CH₃); 1.8 (2H, CH₂-CH₂-

CH₃);1.1(3H, CH₂-CH₂-CH₃); ¹³C NMR (100 MHz): 13.6

746

Article Doi

Eugenol derivatives as potential anti-oxidants: Is phenolic hydroxyl necessary to obtain an effect?

DOI: 10.1111/jphp.12197

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Article abstract of DOI:10.1111/jphp.12197

Full text of DOI:10.1111/jphp.12197

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