New greener alternatives for bioreduction of aromatic aldehydes and decarboxylation of aromatic acids using juice of fruits

Article abstract of DOI:10.1016/j.molcatb.2012.06.004

Cocos nucifera L. and Borassus flabellifer L. juices act as bio catalytic system for the reduction of aromatic aldehydes to alcohols and selective decarboxylation of substituted cinnamic acid to styrene and substituted benzoic acid to polyphenolic compound. Both juices exhibit good activity when aromatic aldehydes and aromatic acids contain electron-donating groups at specific positions. Moreover, C. nucifera juice exhibits good result for the reduction and decarboxylation properties than B. flabellifer juice under the same reaction condition.

Full text of DOI:10.1016/j.molcatb.2012.06.004

Journal of Molecular Catalysis B: Enzymatic 82 (2012) 92–95
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Catalysis B: Enzymatic
journal homepage: www.elsevier.com/locate/molcatb
New greener alternatives for bioreduction of aromatic aldehydes and
decarboxylation of aromatic acids using juice of fruits
Kaushik Misra, Himadri Sekhar Maity, Subhankar Chanda, Ahindra Nag∗
Department of Chemistry, IIT-Kharagpur, West Bengal, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Cocos nucifera L. and Borassus flabellifer L. juices act as bio catalytic system for the reduction of aromatic
aldehydes to alcohols and selective decarboxylation of substituted cinnamic acid to styrene and substi-
tuted benzoic acid to polyphenolic compound. Both juices exhibit good activity when aromatic aldehydes
and aromatic acids contain electron-donating groups at specific positions. Moreover, C. nucifera juice
exhibits good result for the reduction and decarboxylation properties than B. flabellifer juice under the
same reaction condition.
Received 19 March 2012
Received in revised form 10 May 2012
Accepted 2 June 2012
Available online 9 June 2012
Keywords:
Cocos nucifera L.
© 2012 Elsevier B.V. All rights reserved.
Borassus flabellifer L.
Vinylphenol
Polyphenol
Substituted aromatic aldehydes
Substituted benzoic acids
Substituted cinnamic acids
1. Introduction
chemical reagents, by using microwave irradiation, microbial or
enzymatic transformation [1,2,6–9]. However, some procedures
Vinylphenol, polyphenol and benzyl alcohol are bioactive inter-
mediates and have access to different applicative fields. Especially,
vinylphenol derivatives such as 4-vinylphenol, 4-vinylcatechol,
4-vinylguaiacol, and 2,6-dimethoxy-4-vinylphenol are used as fla-
voring substances in perfumery, food, and beverage industries
being approved as FEMA GRAS (Flavor and Extract Manufacturer’s
Association; General Regarded as Safe) [1]. Hydroxylated styrenes
are active initial substances for the synthesis of bioactive com-
pounds and production of resins, elastomers, adhesives, agents
for control of germination, UV-absorbers, electronic materials and
cancer preventive agents [1,2]. Vinylsyringol is the main com-
pound responsible for the antioxidant activity in the polar fraction
of canola oil [3]. In addition, dihydroxylated (catechol) and tri-
hydroxylated (pyrogallol) aromatic rings are often incorporated
into chemical synthesis of biologically active molecules such as
flavonoids, the antibiotic-trimethoprim, and the muscle relaxant
gallamine triethiodide [4]. In 2011, Gülc¸ in et al. reported that
pyrogallol has higher affinity toward human carbonic anhydrase
isoenzymes II and VI [5].
required expensive reagents, harsh conditions and the isolated
yield of the final products were very low [1,2,10]. Furthermore,
protection–deprotection of the phenolic group was important to
avoid the polymerization of vinylphenol [1].
Recently, many plants have been considered as potential
resources of active agents for organic transformation and can serve
as selective, high yielding agents, which are eco-friendly. More-
over, several samples of whole plants were reported as sources
of reductase activity with alcohol dehydrogenase systems such as
Daucus carota [11,12], Manihot species [13], and Saccharum offic-
inarum [14]. In 1993, Yoshida et al. reported that two bacteria,
Klebsiella oxytoca and Erwinia uredovora, which constituted epi-
phytic microflora on yacon (Polymnia sonchifolia) leaves, converted
hydroxycinnamic acids into hydroxystyrenes decarboxylatively
[15].
Coconut juice identified as ACC (água-de-coco do Ceará) and
BFJ (Borassus flabellifer juice) are pleasant and refreshing beverages
derived from Cocos nucifera L. and B. flabellifer L. fruits. The juices
are flavorful, sweet and slightly acidic and rich in many ingredients
used as soft drink in tropical countries and are inexpensive [16,17].
In 2009, Lemos et al. reported that ACC has reducing prop-
erty toward aromatic aldehyde [16]. However, no reports on the
ability of ACC to catalyze decarboxylation are contained in the liter-
ature. In this paper, we report conclusively “green” alternatives are
effective for the production of styrene analogs, poly hydroxylated
To meet the industrial demand, several groups have been
modified in the synthesis of styrene derivatives to replace
∗
Corresponding author. Tel.: +91 3222 281900; fax: +91 3222 255303.
E-mail address: ahinnag@chem.iitkgp.ernet.in (A. Nag).
1381-1177/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molcatb.2012.06.004

K. Misra et al. / Journal of Molecular Catalysis B: Enzymatic 82 (2012) 92–95
93
CO2H
OH
O
R4
H
R1
R1
R3
R2
R3
ACC or BFJ
ACC or BFJ
R4
R2
R4
R2
R2
R3
R3
R1
R1
Scheme 2. Decarboxylation of substituted benzoic acid by ACC and BFJ at room
temperature.
Scheme 1. Reduction of substituted aromatic aldehydes by ACC and BFJ at room
temperature.
benzene and benzyl alcohols from substituted cinnamic acid, sub-
stituted benzoic acid and substituted benzaldehyde in very good
yield under safe reaction condition, without formation of toxic
byproducts. Both the juice properties for organic transformation
have been compared which will give a new insight of organic syn-
thesis. In addition we disclosed new green protocols where uses of
chemicals and reagents are avoided enabling the effective work-up
and purification of the products.
sodium sulfate and evaporated under reduced pressure. After that,
each reaction mixture was purified by column chromatography
using ethyl acetate and n-hexane as eluent to afford the product
and percentage of yield is calculated using conventional formula
by taking weight of initial and final product. NMR spectra were
recorded on a Bruker 400 spectrometer and the residual resonance
of deuterated solvent was used as an internal reference. All spectral
data and melting point of obtained products agreed well with the
reported values [1,2,4,18].
2. Materials and methods
3. Results and discussion
2.1. Solvents and chemicals
Reduction and decarboxylation catalyzed by C. nucifera and B.
flabellifer juices were investigated according to Schemes 1–3. Our
initial experiments have been designed to check the activities of
both juices on substituted aromatic aldehydes and two ketones
shown in Scheme 1.
In separate experiments, substrates 1a–1q (Scheme 1; Table 1)
were added to the freshly prepared ACC and BFJ at room temper-
ature. As can be seen in Table 1 the reducing activity, reaction
time and yield of the reduced product by ACC and BFJ depended
on substituents with respect to aldehyde group in benzene ring
(Table 1).
The result demonstrates that electron donating group present
either at para or at meta position of aromatic aldehydes showed
better activity in the presence of both juices, but ortho substi-
tuted aromatic aldehydes did not produce any alcohol, which may
be due to steric effect on the enzyme’s active site. The methoxy
group present at phenyl ring enhanced the reduction of aldehy-
dic group within few hours. In addition, methoxy group present at
para rather than meta position also led to increased yield within
15–30 h. That is why; we isolated better yield from vanillin (1i)
to isovanillin (1j) to veratraldehyde (1k). However, B. flabellifer
juice produced alcohol from nitro substituted phenyl aldehydes
(Table 1, entries 1l and 1m) but C. nucifera (Table 1, entries 1l
and 1m) water did not catalyze this reaction. Both BFJ and ACC
did not show any activity toward chloro substituted benzaldehyde
acetophenone and benzophenone during 72 h. Subsequently, we
extended the procedure to substituted benzoic acid and substituted
cinnamic acid with decarboxylation being major reaction rather
than reduction (Schemes 2 and 3).
The 17 substituted benzaldehydes, 8 substituted benzoic acids
and all other reagents were purchased from Sigma–Aldrich, Merck
and Fluka. Substituted cinnamic acid such as caffeic acid, ferulic
acid, iso-ferulic acid and sinapic acid were also purchased from
Sigma–Aldrich. All solvents used throughout the experiments were
purchased from Merck and used without further purification.
2.2. Synthesis of some substituted cinnamic acids
Compounds 3a, 3b, 3c, 3g (Scheme 3 and Table 3) were synthe-
sized by Knoevenagel condensation reaction. In each experiment,
substituted benzaldehyde (30 mM), malonic acid (60 mM), pyri-
dine (20 mL), and piperidine (0.5 mL) were mixed well, heated to
80–85 ◦C for 1 h and finally refluxed (110–115 ◦C) for an additional
3 h. The reaction mixture was poured into water and acidified with
conc. HCl. The precipitate obtained was filtered, and washed with
cold water repeatedly. The residue was dissolved in NaOH, diluted,
again acidified to form the precipitate and then washed with cold
water. Then crude product was dried and recrystallized using ethyl
methyl ketone and analyzed spectroscopically to determine its
molecular structure.
2.3. Preparation of two juices
The C. nucifera and B. flabellifer juices were obtained by perforat-
ing the young fruit with a metallic sharp knife. Then it was filtered
through Buchner funnel in vacuum using ordinary filter paper as
soon as possible for the elimination of residue.
From Tables 2 and 3 it was observed that para hydroxy ben-
zoic acid and para hydoxy cinnamic acid produced decarboxylated
products rather than reduced products. When both acids contain
OH group at para position with respect to acid group the reac-
tion time was decreased and yield was increased by ACC and BFJ.
The yield of decarboxylated product also depended upon the num-
ber of electron donating group present in the aromatic ring, on
increase of electron donating groups in the aromatic ring enhanced
the yield of the products by both juices. However, from Tables 1–3
it was clear that C. nucifera juice is more powerful for reduction and
2.4. Typical procedure
In all experiments, substrate (200 mg) separately was added
to the freshly prepared ACC and BFJ (200 mL). The reaction mix-
ture was stirred at room temperature maximum for 72 h under
inert atmosphere (Schemes 1–3). Each individual suspension was
filtered, and the residue was washed with water, as well as
ethyl acetate. The filtrate was then extracted with ethyl acetate
(3 × 100 mL), and the organic phase was demoisturized with

94
K. Misra et al. / Journal of Molecular Catalysis B: Enzymatic 82 (2012) 92–95
OH
R3
R2
R3
O
ACC or BFJ
R2
R1
R1
Scheme 3. Decarboxylation of substituted cinnamic acid by ACC and BFJ at room temperature.
Table 1
Reducing property of ACC and BFJ toward aromatic aldehydes (Scheme 1).
Entry
R1
R2
R3
R4
ACC
BFJ
Reaction time (h)
Yield (%)
Reaction time (h)
Yield (%)
1a
1b
1c
1d
1e
1f
1g
1h
1i
1j
1k
1l
1m
1n
1o
1p
1q
H
OH
H
H
OCH3
H
H
H
OH
H
H
H
H
H
OH
H
H
OCH3
H
H
H
H
H
H
NO2
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
CH3
Ph
72
30
48
72
30
72
72
30
30
20
15
72
72
72
72
72
72
85
70
60
0
76
53
0
72
78
87
92
0
72
30
48
72
30
72
72
30
30
20
15
24
36
72
72
72
72
78
61
55
0
73
40
0
70
69
82
90
45
33
0
OCH3
H
H
OH
OH
OCH3
OCH3
NO2
H
H
Cl
H
H
OH
OCH3
OH
OCH3
H
NO2
H
H
0
0
0
0
0
0
0
H
H
H
H
0
Table 3
decarboxylation properties than B flabellifer juice under the same
reaction condition.
Decarboxylation property of ACC and BFJ toward substituted cinnamic acids
(Scheme 3).
In 2010, Manchenˇo et al. reported that p-coumaric acid decar-
boxylases (PDCs) catalyze the nonoxidative decarboxylation of
hydroxycinnamic acids to generate the corresponding vinyl deriva-
tives where hydrogen atom of p-OH group plays a crucial role. In
our investigation it was observed that, the absence of p-OH group
with respect to acid group in cinnamic acid and benzoic acid, no
product was formed up to 72 h due to non-participation of hydro-
gen atom of hydroxyl group in reaction mechanism. It implies that
the decarboxylation reaction of substituted benzoic acid and sub-
stituted cinnamic acid by ACC or BFJ may follow the enzymatic
route.
Entry R1
R2
R3
ACC
BFJ
Reaction
time (h)
Yield (%) Reaction
time (h)
Yield (%)
3a
3b
3c
3d
3e
3f
H
H
H
H
H
H
H
H
OH
H
H
H
OCH3
72
48
72
48
72
72
72
48
0
73
0
93
94
0
72
48
72
48
48
72
72
48
0
71
0
90
93
0
OH
OCH3
OH
OCH3 OH
OH
OCH3
3g
3h
OCH3 OCH3
OCH3 OH
0
94
0
91
C. nucifera juice contains so many enzymes, proteins, ions and
reducing sugars with different ratio and varies with different age
of the coconut (17) and there is no report in the literature about
the constituents of B flabellifer juice. Therefore, further investiga-
tion is required on constituents of both juices by which they show
reduction and decarboxylation properties with substrates contain-
ing different functional groups.
Table 2
Decarboxylation property of ACC and BFJ toward substituted benzoic acids
(Scheme 2).
4. Conclusion
Entry R1
R2
R3
R4
ACC
BFJ
Reaction
time (h)
Yield (%) Reaction
time (h)
Yield (%)
In conclusion, a simple, substrate selective and satisfactory pro-
cedure has been developed for the preparation of commercially
valuable biologically active polyphenols, 4-vinylphenols and sub-
stituted benzyl alcohols from their corresponding electron rich
acids and aldehydes by using ACC and BFJ juices as solvent, reac-
tant and catalyst which are readily available and inexpensive. In
addition, our investigations are going on to understand the proper
mechanistic pathway, by which the two juices exhibit reduction
and decarboxylation activities. These developed methods provide
an efficient eco-friendly and green alternatives for the synthesis of
2a
2b
2c
2d
2e
2f
2g
2h
2i
H
H
H
OH
H
H
H
H
H
H
H
OH
H
H
H
OH
OH OH
OH OH
H
OH
H
H
H
H
H
H
H
72
48
72
72
72
72
0
77
0
72
48
72
72
72
72
72
48
48
0
71
0
0
0
0
0
83
94
H
0
0
0
0
OCH3
NO2
H
OH 72
48
OH 48
H
88
96

K. Misra et al. / Journal of Molecular Catalysis B: Enzymatic 82 (2012) 92–95
95
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The author Kaushik Misra is indebted to UGC Delhi, for the award
of SRF and for the financial support of this research.
Appendix A. Supplementary data
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