Unusual amount of (-)-mesquitol from the heartwood of Prosopis juliflora

Article abstract of DOI:10.1080/14786410801940968

A large amount of flavonoid has been extracted and isolated from the heartwood of Prosopis juliflora, an exogenous wood species of Kenya. Structural and physicochemical elucidation based on FTIR, 1H and 13C NMR, GC-MS and HPLC analysis clearly demonstrate

Full text of DOI:10.1080/14786410801940968

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Unusual amount of (-)-mesquitol from
the heartwood of Prosopis juliflora
Peter Sirmah a b , Stéphane Dumarçay a , Eric Masson c & Philippe
Gérardin a
a Laboratoire d'Etudes et de Recherche sur le Matériau Bois
(LERMAB), Equipe de Chimie Organique et Microbiologie,
Université Henri Poincaré Nancy 1, Vandoeuvre les Nancy Cédex,
France
b Department of Wood Science and Technology, Moi University,
Eldoret, Kenya
c CRITT BOIS, Epinal cedex 9, France
Published online: 29 Oct 2009.
To cite this article: Peter Sirmah , Stphane Dumaray , Eric Masson & Philippe Grardin (2009)
Unusual amount of (-)-mesquitol from the heartwood of Prosopis juliflora , Natural Product
Research: Formerly Natural Product Letters, 23:2, 183-189, DOI: 10.1080/14786410801940968
To link to this article: http://dx.doi.org/10.1080/14786410801940968
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Natural Product Research
Vol. 23, No. 2, 20 January 2009, 183–189
Unusual amount of (ꢀ)-mesquitol from the heartwood of Prosopis juliflora
a
Peter Sirmahab, Ste aya, Eric Massonc and Philippe Ge
phane Dumarc¸ rardin
´ ´
*
a
´
Laboratoire d’Etudes et de Recherche sur le Materiau Bois (LERMAB), Equipe de Chimie
Organique et Microbiologie, Universite Henri Poincare Nancy 1, Vandoeuvre les Nancy Cedex,
´
´
´
b
France; Department of Wood Science and Technology, Moi University, Eldoret, Kenya;
cCRITT BOIS, Epinal cedex 9, France
(Received 10 October 2007; final version received 24 January 2008)
A large amount of flavonoid has been extracted and isolated from the heartwood
of Prosopis juliflora, an exogenous wood species of Kenya. Structural and
physicochemical elucidation based on FTIR, 1H and 13C NMR, GC-MS and
HPLC analysis clearly demonstrated the presence of (ꢀ)-mesquitol as the sole
compound without any noticeable impurities. The product was able to slow down
oxidation of methyl linoleate induced by AIBN. The important amount and high
purity of (ꢀ)-mesquitol present in the acetonic extract of P. juliflora could
therefore be of valuable interest as a potential source of antioxidants from a
renewable origin.
Keywords: antioxidant; heartwood; flavonoid; Prosopis juliflora; mesquitol
1. Introduction
Wood is a natural composite constituted mainly of cellulose, lignin and hemicelluloses.
In addition to these polymeric materials it may contain low molecular weight compounds
present in more or less important quantities called extractives. Wood extractives have been
described to have a crucial effect on the natural durability of wood, explaining the
resistance of some wood species to biodegraders (Celimene, Micales, Ferge, & Young,
1999; Haupt et al., 2003; Mori, Aoyama, & Hokkaido, 1997; Neya, Hakkou, Petrissans,
& Gerardin, 2004; Reyes Chilpa, Gomez-Garibay, Moreno-Tores, Jimenez-Estrada,
´
Quiroz-Vasquez, 1998; Windeisen, Wegener, Lesnino, Schumacher, 2002). The aim of the
present article is to report the identification and isolation of (ꢀ)-mesquitol, a relatively
unusual flavonoid, obtained in high yields from the heartwood of Prosopis juliflora, an
exogenous wood species native to South and Central America, and introduced to Kenya in
the early 1970s for rehabilitation of arid and semi arid lands.
2. Results
Extraction of P. juliflora heartwood with acetone leads to a large amount of light brown
extractives ranging between 7 and 8%. Contrary to heartwood, sapwood contains a
smaller amount of extractives of ꢁ2%. 1H NMR analysis of the crude extract indicates the
*Corresponding author. Email: Philippe.Gerardin@lermab.uhp-nancy.fr
ISSN 1478–6419 print/ISSN 1029–2349 online
ß 2009 Taylor & Francis
DOI: 10.1080/14786410801940968
http://www.informaworld.com

184
P. Sirmah et al.
presence of a main component showing typical flavanol signals. Indeed, NMR analysis
indicated a characteristic ABX system corresponding to two hydrogen atoms at the
C4 position of the (C) ring of a flavanol structure at ꢁ2.8 ppm, and two additional signals
at approximately 4.0 and 4.5 ppm, characteristic of hydrogen at C3 and C2 positions,
respectively. Indeed, signals at 2.71 (dd), 2.89 (dd) and 4.09 (m) ppm are characteristic of
an ABX system corresponding to the two hydrogen atoms at the C4 position and to the
hydrogen at the C3 position of the (C) ring of a flavanol structure. This attribution is
corroborated by the presence of a doublet at 4.79 ppm, corresponding to the hydrogen
atom at the C2 position. Moreover, additional signals appearing in the NMR spectra
of the crude extract concern aromatic signals, which could be attributed to
(A) and (B) rings. Comparison with spectral data of reference flavanols like (þ)-catechin
and (ꢀ)-epicatechin, reported in the literature to be present in several wood species
(Mammela, 2001; Mayer, Koch, & Puls, 2006; Pietarinen, Willfor, Vikstrom, & Holmbom,
¨
¨
¨
¨
2006), indicates that the flavanol present in P. juliflora heartwood has a different structure.
For identification purposes, the crude extract was subjected to purification. Column
chromatography over silica gel using an EtOAc/hexane(3/1v/v) mixture leads to a pale
1
yellow solid in 60% yield (Rf 0.45, silica gel, EtOAc), melting at 81–83ꢂC. H NMR
analysis of the purified product presented quite similar signals to those of the crude
acetone extract. According to the large coupling constant observed between H2 and H3
(J ¼ 6.75 Hz), the 30,40-dihydroxyphenyl group at the C2 position is in trans position of the
hydroxyl group at the C3 position. This value is in good agreement with that observed for
(þ)-catechin. The main difference between spectra of reference flavanols and that of
purified product from the extract of P. juliflora concerns the signals of the hydrogen atoms
present on the (A) aromatic cycle. These two protons appear as 2 singlets just under 6 ppm
in reference compounds, while they appear as 2 doublets with a typical benzenic ortho
coupling constant (J ¼ 8.2 Hz) at 6.38 and 6.42 ppm in the isolated product from the
heartwood of P. juliflora. Further detailed analysis of 1H–13C HMQC and 1H–13C HMBC
NMR data (Table 1) allowed unambiguous assignments of the structure of the compound
present in P. juliflora acetonic extracts as 2,3-trans-30,40,7,8-tetrahydroxyflavan-3-ol
(Figure 1). Such a compound has been previously isolated from the bark of
Dichrostachys cinerea and described as (ꢀ)-mesquitol (Madhusudana, Jagadeeshwar,
Ashok, Jhillu, & Kondapuram, 2004; Mammela, 2001). The specific rotation of the
¨
¨
isolated product is similar to that of (ꢀ)-mesquitol reported in the literature
(Madhusudana et al., 2003, 2004), allowing assignment of product configuration (compare
[ꢀ]D ¼ –39 (c 1.0, CH3OH) to a value of –36 in the literature). The FTIR spectrum
indicated characteristic hydroxyl group absorption at 3350 cmꢀ1 and aromatic C ¼ C
skeletal vibrations at 1611, 1518 and 1470 cmꢀ1. Found microanalysis is in good agreement
with that calculated for C15H14O6. GC-MS analyses of the TMS derivatives of the purified
product and of reference flavanols confirm the existence of three isomers appearing at
distinct retention times. MS spectra of the different products present quite similar peaks,
with a molecular ion peak for the penta-TMS derivative at m/z 650 and characteristic
peaks at 355 and 368, similar to those reported in the literature (Soleas, Diamandis,
Karumanchiri, & Goldberg, 1997). High performance liquid chromatography analyses
corroborate preceding results, allowing identification of three different compounds
presenting similar UV absorptions. In both cases, liquid and gas chromatographic analyses
of P. juliflora extract confirmed high purity of the crude extract.
To confirm and generalise the presence of (ꢀ)-mesquitol in the heartwood of
P. juliflora, analysis of extractives was investigated on six different trees selected randomly.

Natural Product Research
185
Table 1. NMR data for (ꢀ)-mesquitol.
Carbon no.
ꢁC (ppm), multiplicity
1H – 13C HMQC
1H – 13C HMBC
2
3
4
83.4, CH
69.2, CH
33.3, CH2
4.79 (d, J ¼ 6.75 Hz, 2H)
2H-4, H-20, H-60
2H-4, H-2
H-2, H-5
H-2, H-5
2H-4
4.09 (m, 1H)
2.71 (dd, J ¼ 15.7, 7.5 Hz, 1H)
2.89 (dd, J ¼ 15.8, 5.0 Hz, 1H)
5
6
7
8
9
10
10
20
30
40
50
60
120.7, CH
109.8, CH
145.5, qC
134.3, qC
151.1, qC
113.7, qC
129.2, qC
115.4, CH
146.7, qC
146.7, qC
120.2, CH
116.5, CH
6.42 (d, J ¼ 8.2 Hz, 1H)
6.38 (d, J ¼ 8.2 Hz, 1H)
H-5
–
–
–
–
H-6, H-5
H-6, H-5
–
2H-4, H-5
H-2, H-60, H-50
H-2
H-20, H-60, H-50
H-20, H-60, H-50
H-2, H-20
H-2
–
6.87 (d, J ¼ 1.6 Hz, 1H)
–
–
6.78 (d, J ¼ 8.0 Hz, 1H)
6.75 (dd, J ¼ 8.0, 1.6 Hz, 1H)
OH
OH
B
OH
OH
B
OH
3′
OH
2′
OH
4′
B
1′
1
8
HO
O
C
9
HO
O
C
HO
O
5′
A
A
2
7
6′
A
5
C
4
6
OH
OH
OH
3
10
OH
OH
(+)-Catechin
(−)-Epicatechin
(−)-Mesquitol
Figure 1. Structure of the different flavanols.
The amount of extractives are similar to those obtained previously (7.5% ꢃ 0.3). 1H NMR
and HPLC analyses clearly demonstrated the presence of (ꢀ)-mesquitol as the sole
compound without any noticeable impurity. The important amount and high purity of the
crude acetonic extract of P. juliflora could therefore be of valuable interest as a potential
source of flavanols, which have been described as powerful antioxidants (Bors, Heller,
Michel, & Saran, 1990; Valcic, Burr, Timmerman, & Liebler, 2000; Raza & John, 2007;
Whiteside, Heimburger, & Johanning, 2004; Nijveldt et al., 2001; Sanchez-Moreno,
Jimenez-Escrig, & Saura-Calixto, 2000; Sang et al., 2003). Antioxidant properties,
estimated using a methyl linoleate oxidation inhibition test (Figure 2), showed that
(ꢀ)-mesquitol, like (þ)-catechin, is able to slow down oxidation of methyl linoleate
induced by AIBN. In both cases, flavanols present higher antioxidant properties compared
to BHT, chosen as the reference antioxidant.
3. Experimental section
3.1. General experimental procedures
Melting points were measured on Buchi Melting Point B-540 apparatus. Micro-analysis
1
was carried out on Thermofinnigan Flash EA 1112 apparatus. H and 13C NMR spectra

186
P. Sirmah et al.
60
50
40
30
20
10
Control
BHT
(+)-Catechin
(−)-Mesquitol
0
0
0.5
1
1.5
2
2.5
3
3.5
Time (hours)
Figure 2. Antioxidant properties estimated using methyl linoleate oxidation inhibition.
were recorded in methanol D4 on a Bruker AM 400 spectrometer. Chemical shifts were
expressed in ppm and was calculated relative to TMS. FTIR spectra were recorded as KBr
disks on a Perkin-Elmer FTIR spectrometer SPECTRUM 2000, between wave number
range of 4000–500 cmꢀ1. Specific rotations were determined on a Perkin-Elmer 141
polarimeter (10 cm cell) at room temperature. Analytical thin-layer chromatography was
performed on Merck 60 F254 pre-coated silica gel plates. Compounds were visualised with
UV light.
3.2. Extraction and isolation
Prosopis juliflora heartwood was collected from the Baringo Forest (latitude 0ꢂ, 200 N,
longitude 35ꢂ, 570E), Kenya. The voucher specimen is kept at the Department of Forestry
and Wood Science, Moi University. Air dried heartwood was ground to fine powder,
passed through a 115-mesh sieve and dried at 60ꢂC before extraction with acetone using an
Accelerated Solvent Extractor (Dionex ASE 200, Voisins Le Bretonneux, France).
Extraction was performed in 33 mL cell size on 8 g of sawdust at 100ꢂC under a pressure of
100 bars (3 static cycles of 5 minutes each). After extraction, the solvent was evaporated
under reduced pressure and the crude extract dried under vacuum in a desiccator over
P2O5. To check reproducibility of the nature and the amount of extractives, six trees about
27 years old growing at different sites were selected, randomly felled, debarked and
transported while fresh to Moi University laboratories. Heartwood was differentiated
from sapwood by colour, separated and extracted as above.
3.3. GC-MS analysis
(þ)-Catechin (98% assay) and (ꢀ)-epicatechin (90% assay) were used as reference controls
and purchased from Fluka-Sigma-Aldrich Chimie SARL (St Quentin Fallavier, France).
Samples were analysed as trimethyl derivatives using the following procedure. In a
screw-capped vial, a sample of ꢁ1 mg of dry extract, (þ)-catechin or (ꢀ)-epicatechin,
was dissolved in 0.5 mL of anhydrous acetonitrile (Acros Organics), and 0.4 mL of
N,O-bis-(trimethylsilyl)trifluoroacetamide
containing
1%
trimethylchlorosilane

Natural Product Research
187
(BSTFA/1% TMCS) (Acros Organics) was added. The solution was sonicated for about
1 min and heated at 60ꢂC for 60 min. After evaporation of the solvent in a stream of dry
nitrogen, the residue was diluted in 1 mL of anhydrous acetonitrile. The GC-MS analysis
was performed on a ClarusÕ 500 GC gas chromatograph (Perkin-Elmer Inc., USA)
coupled to a ClarusÕ 500 MS quadrupole mass spectrometer (Perkin-Elmer Inc., USA).
Gas chromatography was carried out on a 5% diphenyl / 95% dimethyl polysiloxane
fused-silica capillary column (Elite-5ms, 60 m ꢄ 0.25 mm, 0.25 mm film thickness, Perkin-
Elmer Inc, USA). The gas chromatograph was equipped with an electronically controlled
split/splitless injection port. The injection (injection volume of 1 mL) was performed at
250ꢂC in the split mode (split flow of 20 mL minꢀ1). Helium was used as carrier gas, with a
constant flow of 1.2 mL minꢀ1. The oven temperature program was as follows: 200ꢂC
constant for 4 min, 200–330ꢂC at a rate of 5ꢂC minꢀ1 and then constant for 330ꢂC.
Ionisation was achieved under the electron impact mode (ionisation energy of 70 eV). The
source and transfer line temperatures were 250ꢂC and 330ꢂC, respectively. Detection was
carried out in scan mode: m/z 35 to m/z 700 a.m.u. The detector was switched off in the
initial 10 min (solvent delay). The three derivatised samples were analysed separately and
in a mix (ratio 1 : 1 : 1).
The GC/MS spectrum of the penta-TMS derivative of (ꢀ)-epicatechin, retention
time ¼ 22.4 min, m/z (%): 650 (Mþ, 1.7), 383 (2.5), 370 (6.9), 369 (14.3), 368 (47.5), 357
(2.9), 356 (6.3), 355 (20.1), 281 (1.9), 280 (3.1), 268 (1.6), 267 (7.2), 249 (2.0), 179 (9.5), 147
(4.1), 133 (1.7), 75 (5.7), 74 (7.3), 73 (100), 45 (7.1).
The GC/MS spectrum of the penta-TMS derivative of (þ)-catechin, retention
time ¼ 23.4 min, m/z (%): 650 (Mþ, 1.6), 383 (2.0), 370 (6.2), 369 (15.3), 368 (47.8), 357
(2.6), 356 (5.5), 355 (17.8), 281 (2.0), 280 (3.3), 268 (1.4), 267 (6.1), 249 (2.1), 179 (9.1), 147
(4.2), 133 (1.6), 75 (5.1), 74 (7.5), 73 (100), 45 (6.1).
The GC/MS spectrum of the penta-TMS derivative of (ꢀ)-mesquitol, retention
time ¼ 23.7 min, m/z (%): 650 (Mþ, 1.6), 383 (5.8), 370 (6.1), 369 (12.9), 368 (39.7), 357
(1.3), 356 (2.8), 355 (8.7), 281 (1.3), 280 (2.2), 268 (4.5), 267 (19.5), 249 (1.9), 179 (4.7), 147
(3.8), 133 (2.2), 75 (5.3), 74 (7.4), 45 (6.7), 73 (100).
3.4. HPLC analysis
HPLC analysis was performed using a SupercosilTM LC-18 column (250 mm ꢄ 4.6 mm
i.d.) at 35ꢂC on a Waters liquid chromatograph (Waters SAS, Saint Quentin-en Yvelines,
France) equipped with a system controller 600E, a manual injector system with a 20 mL
loop and a Waters 2996 photo diode array (PDA) detector. The data were recorded on a
210–400 nm range with Empower software. Solvents used for elution were solvent A (water
containing 0.05% of trifluroacetic acid) and solvent B (methanol (HPLC grade) containing
0.05% of TFA) at a flow rate of 1 mL minꢀ1. Elution was achieved with a binary gradient
starting at 95% A and 5% B for 1 min, followed by a linear ramp to 50% A and 50% B
at 10 min to finish at 100% B after 20 min. (þ)-Catechin, retention time ¼ 11.35 min,
(ꢀ)-mesquitol, retention time ¼ 12.40 min, (ꢀ)-epicatechin, retention time ¼ 13.05 min.
3.5. Antioxidant activity
Oxidation of methyl linoleate (2 mL of a 0.4 M solution in 1-butanol) was performed in
a closed borosilicate glass reactor containing 1 mL of a 9 ꢄ 10ꢀ3 M solution of AIBN in

188
P. Sirmah et al.
1-butanol as initiator. The double shell reactor was thermostated at 60ꢂC by an external
heating bath. Oxygen (150 Torr) was bubbled by a gas-tight oscillating pump. A small
condenser was inserted on the reactor in the gas circulation to ensure condensation of the
solvent. Oxygen uptake was monitored continuously with a pressure transducer
(Viatron model 104) in the presence of 1 mL of a 10ꢀ4 M solution in butan-1-ol of the
supposed antioxidant compound to evaluate antioxidant properties. The volumes of the
liquid and the gas phases were, respectively, 4 and 100 mL.
Acknowledgement
This work was supported by a grant from the French government through the Embassy in Nairobi.
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