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molecules
Article
Identification of Three Dalbergia Species Based on
Differences in Extractive Components
Xiaoqian Yin 1, Anmin Huang 1,*ID , Shifeng Zhang 2, Ru Liu 1ID and Fang Ma 3
1Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091, China;
yxqwzy@163.com (X.Y.); liuru@criwi.org.cn (R.L.)
2
Beijing Key Laboratory of Wood Science and Engineering, Beijing Forestry University, Beijing 100083, China;
shifeng.zhang@bjfu.edu.cn
3Department of Chemistry, Tsinghua University, Beijing 100084, China; mf690772309@163.com
*Correspondence: hbham2000@sina.com; Tel.: +86-10-6288-9437
Received: 3 August 2018; Accepted: 24 August 2018; Published: 28 August 2018
Abstract:
Dalbergia cultrate,Dalbergia latifolia, and Dalbergia melanoxylon are precious and valuable
traded timber species of the genus Dalbergia. For chemotaxonomical discrimination between these
easily confused species, the total extractive content of the three wood species was determined
using four different organic solvents. Fourier transform infrared (FTIR) spectroscopy was used
to analyze functional group differences in the extractive components, inferring the types of
principal chemical components according to characteristic peak positions, intensities, and shapes.
Gas chromatography-mass spectrometry (GC-MS) was carried out a detailed characterization of the
extractive components. The relative content of individual chemical components was determined by
area normalization. Results revealed differences in the chemical components and total and individual
extract contents of the three Dalbergia species, indicating that FTIR and GC-MS spectroscopy
can be applied to identify and discriminate between Dalbergia cultrate,Dalbergia latifolia, and
Dalbergia melanoxylon.
Keywords: Dalbergia spp.; distinction; extractives; FTIR; GC-MS
1. Introduction
Wood extractives are non-structural wood molecules that represent a minor fraction in wood,
specifically defined as compounds that can be extracted by polar, non-polar, or neutral solvents [
1
,
2
].
Wood extractives account for approximately 2% to 5% of wood content, however, relatively high
amounts of extractives can be found in some tropical woods, especially chemical extractives that are
highly concentrated in heartwood [
3
–
5
]. Studies have demonstrated that many extractive components
exhibit various biological activities and are important in medical applications [
6
,
7
]. Wood extractives
include an array of compounds, usually aliphatic, terpenoid and phenolic in nature. According to the
literature [
8
], Dalbergia spp. are rich in aromatic compounds, however, significant differences have
been found in the types and contents of wood extractives, even within the same genus [3].
Dalbergia is a genus of trees belonging to the Fabaceae (pea) family, that includes approximately
250 species. All species of Dalbergia spp. were listed in the 17th Convention on International Trade
in Endangered Species of Wild Fauna and Flora [
9
]. Dalbergia cultrate (Benth.), Dalbergia latifolia
(Roxb.), and Dalbergia melanoxylon (Guill. & Perr.) are high-profile species renowned for their use in
high-quality products worldwide [
10
,
11
]. These species are used in luxury furniture, artwork, and
musical instruments due to their refined colors and excellent hardness and intensity properties [
12
,
13
].
Chemical and physical properties are greatly influenced by extractives, with characteristic colors
and textures generating extensive market demand and heavy deforestation. Hence, these species are
Molecules 2018,23, 2163; doi:10.3390/molecules23092163 www.mdpi.com/journal/molecules
Molecules 2018,23, 2163 2 of 11
protected by Appendix II of CITES, D. cultrate is included in the list of national key preserved wild
plants in the People’s Republic of China (first batch). However, any species appearing in Appendix II
of CITES are banned from international commercial trade except for those with an import and export
license or re-export certificate [
14
]. Therefore, a more persuasive method for distinguishing closely
related species is needed.
Traditional wood anatomy identification methods based on macroscopic and microscopic
characteristics have been well-established for several years [
15
]. However, wood anatomy is
too specialized for legal identification, especially when considering leaves, flowers, fruits, and
other information to provide the extent of identification required by CITES [
16
]. By contrast,
chemotaxonomical and genetic methods are useful in wood identification [
17
]. Previous investigations
have found chemotaxonomical identification based on the analysis of extractive compounds to be an
effective method for distinguishing extremely similar wood species [18–20].
To the best of our knowledge, Fourier transform infrared (FTIR) spectroscopy is a fast, simple,
non-destructive method and a powerful technology to determine functional groups in the fingerprint
region. This approach has been widely used in identification of complex systems such as traditional
Chinese medicines and is suitable for analyzing woody materials [
21
,
22
]. In recent years, research
on infrared spectroscopy in wood extractive studies has grown in popularity [
23
–
25
]. Additionally,
gas chromatography-mass spectrometry (GC-MS) offers clear advantages when analyzing complex
mixtures; the combination of an ideal separation technique (GC) with a sensitive identification
technique (MS) constitutes a reliable and commonly used method for qualitative and quantitative
analysis of compounds [
26
–
28
]. GC-MS has been widely applied in establishing chromatographic
fingerprints for quality evaluation of herbal medicines [
29
]. It has also been well-established in the
characterization and identification of wood extractive compounds [30–32].
Little research has been carried out to identify the three similar Dalbergia species Dalbergia cultrate,
Dalbergia latifolia, and Dalbergia melanoxylon based on chemical taxonomy. This paper examines
differences in extractive contents and components using FTIR and GC-MS approaches to discriminate
chemotaxonomically between the extractive components in Dalbergia spp. Functional group analysis
using FTIR spectroscopy and detailed analysis of their components by GC-MS allow one to classify
similar species by their chemical nature. These two techniques also facilitate comprehensive analysis of
chemical components to support the chemotaxonomical classification of wood. GC-MS data provide a
persuasive basis for specific compounds identified by infrared absorption spectra, as the two methods
are complementary and valuable in chemotaxonomical identification.
2. Results and Discussion
2.1. Contents Analysis of Extractives
The extractive contents of the three Dalbergia species are listed in Table 1.Dalbergia cultrate,
Dalbergia latifolia, and Dalbergia melanoxylon were extracted with four different polar organic
solvents, the extractive contents were calculated, and the average value of three experiments was
taken. The findings indicated that the non-polar solvent n-hexane was not suitable for wood
extraction, indicating that the extractable components of these three kinds of wood are mostly
polar. After successfully extracting samples with ethanol/water, benzene/ethanol, ethyl acetate
respectively, the extract contents were clearly different. Among the benzyl alcohol and ethyl
acetate extracts of the three species Dalbergia cultrate had the lowest content, whereas the content of
Dalbergia melanoxylon was highest. With ethanol/water (9:1, v/v), the content of Dalbergia cultrate
was slightly higher than that in Dalbergia latifolia but clearly lower than in Dalbergia melanoxylon.
Therefore, Dalbergia melanoxylon contained more types of main compounds than Dalbergia cultrate, and
Dalbergia latifolia had the fewest kinds of principle compounds, likely because it contained fewer polar
components. In general, the effect of ethanol/water (9:1, v/v) was better than benzyl alcohol and
ethyl acetate, and more components could be obtained. Therefore, to analyze the primary extractive
Molecules 2018,23, 2163 3 of 11
components in Dalbergia cultrate,Dalbergia latifolia, and Dalbergia melanoxylon, ethanol/water (9:1, v/v)
was used as the final solvent in this experiment.
Table 1. Comparison of extractive contents in different solvents.
Species
Yield of Extractives (%)
Ethanol/Water
(9:1, v/v)
Benzene/Ethanol
(2:1, v/v)Ethyl Acetate n-Hexane
Dalbergia cultrate 11.6 8.6 6.2 -
Dalbergia latifolia 10.1 9.65 6.8 -
Dalbergia melanoxylon
16.65 16.05 13.0 -
2.2. FTIR Analysis
The FTIR spectra of the Dalbergia cultrate,Dalbergia latifolia, and Dalbergia melanoxylon extractives
are illustrated in Figure 1. Detailed peak positions are summarized in Table 2. The characteristic
infrared absorption peaks of the functional groups of the main extractive components were reflected
in the FTIR spectra. In the region of 3401–2839 cm
−1
, all spectra exhibited strong, broad peaks
attributable to the stretching vibration of O-H or N-H along with a moderate-intensity peak ascribed
to methyl and methylene stretching vibrations. Benzene ring characteristic peaks (1602, 1510, and
1450 cm
−1
) of the three species were clear and strong, indicating a large proportion of aromatic
substances [
33
]. However, the relative intensity of these three peaks was distinctly different. Especially
for Dalbergia cultrate, the intensity of peaks at 1602 cm
−1
and 1445 cm
−1
was stronger, suggesting that
the number, location, and properties of substituents on aromatic rings varied between the three species.
Moreover, Dalbergia cultrate showed strong absorption bands around 1691 cm
−1
for C=O, a peak
around 1555 cm
−1
with medium intensity for C=C of the aromatic ring, and strong absorption peaks
at 1286 cm
−1
and 1153 cm
−1
for C-O-C [
34
]; these findings were presumably due to skeletal stretching
vibration of the aromatic rings A and B and the functional group C-O-C of ring C of flavonoids [
24
,
35
].
These peaks were clearly visible only in Dalbergia cultrate; the C=O was weak for Dalbergia melanoxylon
and was essentially invisible for Dalbergia latifolia, indicating an abundance of flavonoid compounds in
Dalbergia cultrate.
Dalbergia cultrate also generated a stronger sharp absorption peak at 1378 cm
−1
. In general, methyl
groups have two absorption peaks around 1375 cm
−1
and 1450 cm
−1
, corresponding to symmetric
bending vibrations and asymmetric bending vibrations, respectively [
36
]; this finding explains why the
peak strength of Dalbergia cultrate at 1445cm
−1
was so strong. Then, the absorption peaks at 1366 cm
−1
of Dalbergia melanoxylon and 1352 cm
−1
of Dalbergia latifolia were ascribed to either CH
3
symmetrical
bending or in-plane C-OH bending, as the spectral band shape was low and wide.
Peaks in the region ranging from 910 cm
−1
to 1300 cm
−1
were mainly due to C-O single
bond stretching vibrations. The extractives of the three species exhibited clear, strong peaks at
1200 cm
−1
primarily due to C-O-C stretching; however, the band intensity of the three species included
typical vibrations around 1270 cm
−1
(Ar-O) and 1023 cm
−1
(R-O) for C-O vibrations, although the
peak intensity at 1270 cm
−1
in Dalbergia melanoxylon was stronger than that in Dalbergia latifolia.
Dalbergia melanoxylon likely contained more aromatic ether functional groups; a peak appeared
at 1130 cm
−1
for C-OH stretching of the alcohol groups [
36
]. C-OH stretching near 1114 cm
−1
was found exclusively in Dalbergia cultrate. A C-H out-of-plane bending peak was seen around
999 cm
−1
in the spectrum of Dalbergia cultrate and around 917 cm
−1
in the spectrum of Dalbergia latifolia.
Unique vibrations near 700 cm
−1
were ascribed to the stretching vibration of C-S, which was obvious
in Dalbergia cultrate and Dalbergia latifolia.
Molecules 2018,23, 2163 4 of 11
Molecules 2018, 23, x FOR PEER REVIEW 4 of 11
Figure 1. FTIR spectra: (a) D. cultrate, (b) D. latifolia, (c) D. melanoxylon.
Table 2. FTIR band assignment.
Wavenumbers(cm−1)
D. Cultrata D. Latifolia D. Melanoxylon Band Assignments
3381 3400 3401 O-H stretch; N-H stretch
2932 2933 2935 C-H stretch: CH2
2849 2839 2841 C-H stretch:CH3
1691 1669 1675 C=O stretch; C=N stretch
1602 1602 1602 C=C stretching of aromatic skeleton
1555 - - C=C stretching of aromatic skeleton
1510 1508 1510 C-C stretch bands within ring skeleton
- 1452 - Skeletal C-C stretching; CH3 symmetrical bending
vibrations ;CH2 scissoring
1445 1444
Aromatic stretching(flavonoids); CH3 symmetrical
bending vibrations
1378 - - CH3 asymmetrical bending vibrations
1366
CH3 symmetrical bending; in-plane C-OH bending
rical bending
- 1352 CH3 symmetrical bending; in-plane C-OH bending
C-N-C asymmrtric vibration of aromatic compounds
- 1318 - in-plane C-OH bending; C-O stretching
1286 - - C-O-C stretching (flavonoids)
- 1270 1273 C-O vibration
1203 1200 1199 C-O-C stretching
- 1170 - C-O stretching
C-O-C stretching or frame vibration (flavonoids)
1153 - -
C-O-C stretching(flavonoids); in-plane C-OH bending
C-O-C stretching or frame vibration (flavonoids)
- - 1130 C-OH stretching
1114 - - C-OH stretching
1016 1029 1023 C-O stretching
999 - - C-H out-of-plane bend
C-O stretching
- 917 - C-H out-of-plane bend
875 878 874 C-O stretching
- 839 836 C-H stretching out of plane of aromatic ring; C-N
wagging
699 700 C-H stretching out of plane of aromatic ring; C-S
stretching
Figure 1. FTIR spectra: (a)D. cultrate, (b)D. latifolia, (c)D. melanoxylon.
Table 2. FTIR band assignment.
Wavenumbers(cm−1)
D. Cultrata D. Latifolia D. Melanoxylon Band Assignments
3381 3400 3401 O-H stretch; N-H stretch
2932 2933 2935 C-H stretch: CH2
2849 2839 2841 C-H stretch:CH3
1691 1669 1675 C=O stretch; C=N stretch
1602 1602 1602 C=C stretching of aromatic skeleton
1555 - - C=C stretching of aromatic skeleton
1510 1508 1510 C-C stretch bands within ring skeleton
- 1452 - Skeletal C-C stretching; CH3symmetrical bending
vibrations ;CH2scissoring
1445 1444 Aromatic stretching(flavonoids); CH3symmetrical bending
vibrations
1378 - - CH3asymmetrical bending vibrations
1366 CH3symmetrical bending; in-plane C-OH bending
rical bending
- 1352 CH3symmetrical bending; in-plane C-OH bending
C-N-C asymmrtric vibration of aromatic compounds
- 1318 - in-plane C-OH bending; C-O stretching
1286 - - C-O-C stretching (flavonoids)
- 1270 1273 C-O vibration
1203 1200 1199 C-O-C stretching
- 1170 - C-O stretching
C-O-C stretching or frame vibration (flavonoids)
1153 - - C-O-C stretching(flavonoids); in-plane C-OH bending
C-O-C stretching or frame vibration (flavonoids)
- - 1130 C-OH stretching
1114 - - C-OH stretching
1016 1029 1023 C-O stretching
999 - - C-H out-of-plane bend
C-O stretching
- 917 - C-H out-of-plane bend
875 878 874 C-O stretching
- 839 836 C-H stretching out of plane of aromatic ring; C-N wagging
699 700 C-H stretching out of plane of aromatic ring; C-S stretching
Molecules 2018,23, 2163 5 of 11
2.3. GC-MS Analysis
The GC-MS chromatograms of Dalbergia cultrata, Dalbergia latifolia, and Dalbergia melanoxylon
extractives are presented in Figure 2. The results show clearly the different characteristic peaks of the
three species. The peak area was chosen as the analytical signal for the relative amount. The relative
content of each chemical component was calculated by area normalization and the average value of
the three experiments. Identified chemical components (peak area above 1.0%) and the relative content
of these compounds are listed in Table 3. The main chemical components of the three species were
determined to be aromatic compounds. In general, these compounds were classified into flavonoids,
miscellaneous, quinones, phenols, esters, stilbenoids, and amide compounds. The components of the
extracts of Dalbergia cultrata,Dalbergia latifolia, and Dalbergia melanoxylon are detailed below.
Molecules 2018, 23, x FOR PEER REVIEW 5 of 11
2.3. GC-MS Analysis
The GC-MS chromatograms of Dalbergia cultrata, Dalbergia latifolia, and Dalbergia melanoxylon
extractives are presented in Figure 2. The results show clearly the different characteristic peaks of the
three species. The peak area was chosen as the analytical signal for the relative amount. The relative
content of each chemical component was calculated by area normalization and the average value of
the three experiments. Identified chemical components (peak area above 1.0%) and the relative
content of these compounds are listed in Table 3. The main chemical components of the three species
were determined to be aromatic compounds. In general, these compounds were classified into
flavonoids, miscellaneous, quinones, phenols, esters, stilbenoids, and amide compounds. The
components of the extracts of Dalbergia cultrata, Dalbergia latifolia, and Dalbergia melanoxylon are
detailed below.
Figure 2. Total ion chromatogram: (a) D. cultrate, (b) D. latifolia, (c) D. melanoxylon.
Table 3 reveals there were only two common compounds among the three species and each
species also contained unique chemical components. The following three compounds were specific
to Dalbergia cultrata: 3,3′,4,4′-tetramethoxystilbene (peak 3, 1.49%), 3,7,3′,4′-tetrahydroxyflavone (peak
4, 10.78%), and parietin (peak 7, 24.81%). Particular compounds found exclusively in Dalbergia latifolia
included the following: 1,7,7-trimethyl-3-phenethylidenebicyclo- [2.2.1]heptan-2-one (peak 8, 3.28%),
4,4′-methylenebis-2,6-dimethylphenol (peak 9, 1.60%), 4,2′,3′,4′-tetramethoxy-5′-methyl-6-
methylaminomethyl-1,1′-biphenyl (peak 10, 29.75%), (4-methyl- sulfanylphenyl)carbamic acid 2,6-
dimethoxyphenyl ester (peak 11, 1.38%). GC-MS analysis of Dalbergia melanoxylon revealed five
distinct compounds: 10,11-dihydro-10-hydroxy- 2,3-dimethoxydibenz(b,f)oxepin (peak 12, 4.57%), 2-
(4-methoxy-2,5-dimethylphenyl)-9-methyl-2H- benzo[g]indazole (peak 13, 3.14%), 10,11-dihydro-10-
hydroxy-2,3,6-trimethoxydibenz(b,f)oxepin (peak 14, 37.30%), 10,11-dihydro-2,3,6-
trimethoxydibenz(b,f)oxepin-10-one (peak 15, 8.32%), and pilloin (peak 16, 7.77%).
According to the GC-MS analysis results, the principal components of the three species varied.
Seven constituents were identified as having higher relative contents in Dalbergia cultrate: 3,7,3′,4′-
tetrahydroxyflavone (peak 4, 10.78%), 7-methoxy-1-thioflavone (peak 5, 25.55%), and parietin (peak
7, 24.81%). 7-Methoxy-1-thioflavone is a flavonoid derivative. Some thioflavones have been reported
to function as novel neuroprotective agents and exhibit antiviral activities. 3,7,3′,4′-
Tetrahydroxyflavone is a natural flavonol in foods and plants and has been identified as showing
various biological activities. Parietin is an anthroquinone and has been identified in the traditional
Chinese herbal medicines Polygoni multiflora and Eryngium foetidum L.
Figure 2. Total ion chromatogram: (a)D. cultrate, (b)D. latifolia, (c)D. melanoxylon.
Table 3reveals there were only two common compounds among the three species
and each species also contained unique chemical components. The following three
compounds were specific to Dalbergia cultrata: 3,3
0
,4,4
0
-tetramethoxystilbene (peak 3, 1.49%),
3,7,3
0
,4
0
-tetrahydroxyflavone (peak 4, 10.78%), and parietin (peak 7, 24.81%). Particular compounds
found exclusively in Dalbergia latifolia included the following: 1,7,7-trimethyl-3-phenethylidenebicyclo-
[2.2.1]heptan-2-one (peak 8, 3.28%), 4,4
0
-methylenebis-2,6-dimethylphenol (peak 9, 1.60%),
4,2
0
,3
0
,4
0
-tetramethoxy-5
0
-methyl-6-methylaminomethyl-1,1
0
-biphenyl (peak 10, 29.75%),
(4-methyl- sulfanylphenyl)carbamic acid 2,6-dimethoxyphenyl ester (peak 11, 1.38%). GC-MS
analysis of Dalbergia melanoxylon revealed five distinct compounds: 10,11-dihydro-10-hydroxy-
2,3-dimethoxydibenz(b,f)oxepin (peak 12, 4.57%), 2-(4-methoxy-2,5-dimethylphenyl)-9-methyl-2H-
benzo[g]indazole (peak 13, 3.14%), 10,11-dihydro-10-hydroxy-2,3,6-trimethoxydibenz(b,f)oxepin (peak
14, 37.30%), 10,11-dihydro-2,3,6-trimethoxydibenz(b,f)oxepin-10-one (peak 15, 8.32%), and pilloin
(peak 16, 7.77%).
According to the GC-MS analysis results, the principal components of the three species
varied. Seven constituents were identified as having higher relative contents in Dalbergia cultrate:
3,7,3
0
,4
0
-tetrahydroxyflavone (peak 4, 10.78%), 7-methoxy-1-thioflavone (peak 5, 25.55%), and
parietin (peak 7, 24.81%). 7-Methoxy-1-thioflavone is a flavonoid derivative. Some thioflavones
have been reported to function as novel neuroprotective agents and exhibit antiviral activities.
3,7,3
0
,4
0
-Tetrahydroxyflavone is a natural flavonol in foods and plants and has been identified as
showing various biological activities. Parietin is an anthroquinone and has been identified in the
traditional Chinese herbal medicines Polygoni multiflora and Eryngium foetidum L.
Molecules 2018,23, 2163 6 of 11
Table 3. Chemical composition of extractives analyzed by GC/MS.
ID RT(min) Compounds Molecular Structure Releative Content (%) *
D. Cultrate D. Latifolia D. Melanoxylon
1
24.97
Phenol,4-methyl-2-[5-(2-thienyl)pyrazol-3-yl]-
Molecules 2018, 23, x FOR PEER REVIEW 6 of 11
Table 3. Chemical composition of extractives analyzed by GC/MS.
ID RT
(min) Compounds Molecular
Structure
Releative Content (%) *
D. Cultrate D. Latifolia D. Melanoxylon
1 24.97 Phenol,4-methyl-2-[5-(2-thienyl)pyrazol-3-yl]-
4.76 12.41 (0.7) 1.47
6 29.66 13-Docosenamide, (
Z
)-
2.08 (0.2) 2.17 (0.2) 1.26 (0.1)
2 25.13 Naphtho[2,3-b]furan-4,9-dione, 2-isopropyl-
1.54 1.36 (0.2) -
5 28.90 1-Thioflavone, 7-methoxy-
25.55 (0.2) 4.23 -
3 26.44 3,3′,4,4′-Tetramethoxystilbene 1.49 - -
4 27.26 3,7,3′,4′-Tetrahydroxyflavone
10.78 (0.1) - -
7 32.49 Parietin
24.81 (0.4) - -
8 24.11 1,7,7-Trimethyl-3-
phenethylidenebicyclo[2.2.1]heptan-2-one
- 3.28 -
9 24.73 Phenol, 4,4′-methylenebis[2,6-dimethyl-
- 1.60 -
10 26.32 1,1′-Biphenyl, 4,2′,3′,4′-tetramethoxy-5′-methyl-6-
methylaminomethyl-
- 29.75 (0.8) -
11 27.88 (4-Methylsulfanylphenyl)carbamic acid, 2,6-
dimethoxyphenyl ester
- 1.38 -
12 27.76 10,11-Dihydro-10-hydroxy-2,3-
dimethoxydibenz(b,f)oxepin
- - 4.57
4.76 12.41 (0.7) 1.47
6
29.66 13-Docosenamide, (Z)-
Molecules 2018, 23, x FOR PEER REVIEW 6 of 11
Table 3. Chemical composition of extractives analyzed by GC/MS.
ID RT
(min) Compounds Molecular
Structure
Releative Content (%) *
D. Cultrate D. Latifolia D. Melanoxylon
1 24.97 Phenol,4-methyl-2-[5-(2-thienyl)pyrazol-3-yl]-
4.76 12.41 (0.7) 1.47
6 29.66 13-Docosenamide, (
Z
)-
2.08 (0.2) 2.17 (0.2) 1.26 (0.1)
2 25.13 Naphtho[2,3-b]furan-4,9-dione, 2-isopropyl-
1.54 1.36 (0.2) -
5 28.90 1-Thioflavone, 7-methoxy-
25.55 (0.2) 4.23 -
3 26.44 3,3′,4,4′-Tetramethoxystilbene 1.49 - -
4 27.26 3,7,3′,4′-Tetrahydroxyflavone
10.78 (0.1) - -
7 32.49 Parietin
24.81 (0.4) - -
8 24.11 1,7,7-Trimethyl-3-
phenethylidenebicyclo[2.2.1]heptan-2-one
- 3.28 -
9 24.73 Phenol, 4,4′-methylenebis[2,6-dimethyl-
- 1.60 -
10 26.32 1,1′-Biphenyl, 4,2′,3′,4′-tetramethoxy-5′-methyl-6-
methylaminomethyl-
- 29.75 (0.8) -
11 27.88 (4-Methylsulfanylphenyl)carbamic acid, 2,6-
dimethoxyphenyl ester
- 1.38 -
12 27.76 10,11-Dihydro-10-hydroxy-2,3-
dimethoxydibenz(b,f)oxepin
- - 4.57
2.08 (0.2) 2.17 (0.2) 1.26 (0.1)
2
25.13 Naphtho[2,3-b]furan-4,9-dione, 2-isopropyl-
Molecules 2018, 23, x FOR PEER REVIEW 6 of 11
Table 3. Chemical composition of extractives analyzed by GC/MS.
ID RT
(min) Compounds Molecular
Structure
Releative Content (%) *
D. Cultrate D. Latifolia D. Melanoxylon
1 24.97 Phenol,4-methyl-2-[5-(2-thienyl)pyrazol-3-yl]-
4.76 12.41 (0.7) 1.47
6 29.66 13-Docosenamide, (
Z
)-
2.08 (0.2) 2.17 (0.2) 1.26 (0.1)
2 25.13 Naphtho[2,3-b]furan-4,9-dione, 2-isopropyl-
1.54 1.36 (0.2) -
5 28.90 1-Thioflavone, 7-methoxy-
25.55 (0.2) 4.23 -
3 26.44 3,3′,4,4′-Tetramethoxystilbene 1.49 - -
4 27.26 3,7,3′,4′-Tetrahydroxyflavone
10.78 (0.1) - -
7 32.49 Parietin
24.81 (0.4) - -
8 24.11 1,7,7-Trimethyl-3-
phenethylidenebicyclo[2.2.1]heptan-2-one
- 3.28 -
9 24.73 Phenol, 4,4′-methylenebis[2,6-dimethyl-
- 1.60 -
10 26.32 1,1′-Biphenyl, 4,2′,3′,4′-tetramethoxy-5′-methyl-6-
methylaminomethyl-
- 29.75 (0.8) -
11 27.88 (4-Methylsulfanylphenyl)carbamic acid, 2,6-
dimethoxyphenyl ester
- 1.38 -
12 27.76 10,11-Dihydro-10-hydroxy-2,3-
dimethoxydibenz(b,f)oxepin
- - 4.57
1.54 1.36 (0.2) -
5
28.90 1-Thioflavone, 7-methoxy-
Molecules 2018, 23, x FOR PEER REVIEW 6 of 11
Table 3. Chemical composition of extractives analyzed by GC/MS.
ID RT
(min) Compounds Molecular
Structure
Releative Content (%) *
D. Cultrate D. Latifolia D. Melanoxylon
1 24.97 Phenol,4-methyl-2-[5-(2-thienyl)pyrazol-3-yl]-
4.76 12.41 (0.7) 1.47
6 29.66 13-Docosenamide, (
Z
)-
2.08 (0.2) 2.17 (0.2) 1.26 (0.1)
2 25.13 Naphtho[2,3-b]furan-4,9-dione, 2-isopropyl-
1.54 1.36 (0.2) -
5 28.90 1-Thioflavone, 7-methoxy-
25.55 (0.2) 4.23 -
3 26.44 3,3′,4,4′-Tetramethoxystilbene 1.49 - -
4 27.26 3,7,3′,4′-Tetrahydroxyflavone
10.78 (0.1) - -
7 32.49 Parietin
24.81 (0.4) - -
8 24.11 1,7,7-Trimethyl-3-
phenethylidenebicyclo[2.2.1]heptan-2-one
- 3.28 -
9 24.73 Phenol, 4,4′-methylenebis[2,6-dimethyl-
- 1.60 -
10 26.32 1,1′-Biphenyl, 4,2′,3′,4′-tetramethoxy-5′-methyl-6-
methylaminomethyl-
- 29.75 (0.8) -
11 27.88 (4-Methylsulfanylphenyl)carbamic acid, 2,6-
dimethoxyphenyl ester
- 1.38 -
12 27.76 10,11-Dihydro-10-hydroxy-2,3-
dimethoxydibenz(b,f)oxepin
- - 4.57
25.55 (0.2) 4.23 -
3
26.44 3,30,4,40-Tetramethoxystilbene
Molecules 2018, 23, x FOR PEER REVIEW 6 of 11
Table 3. Chemical composition of extractives analyzed by GC/MS.
ID RT
(min) Compounds Molecular
Structure
Releative Content (%) *
D. Cultrate D. Latifolia D. Melanoxylon
1 24.97 Phenol,4-methyl-2-[5-(2-thienyl)pyrazol-3-yl]-
4.76 12.41 (0.7) 1.47
6 29.66 13-Docosenamide, (
Z
)-
2.08 (0.2) 2.17 (0.2) 1.26 (0.1)
2 25.13 Naphtho[2,3-b]furan-4,9-dione, 2-isopropyl-
1.54 1.36 (0.2) -
5 28.90 1-Thioflavone, 7-methoxy-
25.55 (0.2) 4.23 -
3 26.44 3,3′,4,4′-Tetramethoxystilbene 1.49 - -
4 27.26 3,7,3′,4′-Tetrahydroxyflavone
10.78 (0.1) - -
7 32.49 Parietin
24.81 (0.4) - -
8 24.11 1,7,7-Trimethyl-3-
phenethylidenebicyclo[2.2.1]heptan-2-one
- 3.28 -
9 24.73 Phenol, 4,4′-methylenebis[2,6-dimethyl-
- 1.60 -
10 26.32 1,1′-Biphenyl, 4,2′,3′,4′-tetramethoxy-5′-methyl-6-
methylaminomethyl-
- 29.75 (0.8) -
11 27.88 (4-Methylsulfanylphenyl)carbamic acid, 2,6-
dimethoxyphenyl ester
- 1.38 -
12 27.76 10,11-Dihydro-10-hydroxy-2,3-
dimethoxydibenz(b,f)oxepin
- - 4.57
1.49 - -
4
27.26 3,7,30,40-Tetrahydroxyflavone
Molecules 2018, 23, x FOR PEER REVIEW 6 of 11
Table 3. Chemical composition of extractives analyzed by GC/MS.
ID RT
(min) Compounds Molecular
Structure
Releative Content (%) *
D. Cultrate D. Latifolia D. Melanoxylon
1 24.97 Phenol,4-methyl-2-[5-(2-thienyl)pyrazol-3-yl]-
4.76 12.41 (0.7) 1.47
6 29.66 13-Docosenamide, (
Z
)-
2.08 (0.2) 2.17 (0.2) 1.26 (0.1)
2 25.13 Naphtho[2,3-b]furan-4,9-dione, 2-isopropyl-
1.54 1.36 (0.2) -
5 28.90 1-Thioflavone, 7-methoxy-
25.55 (0.2) 4.23 -
3 26.44 3,3′,4,4′-Tetramethoxystilbene 1.49 - -
4 27.26 3,7,3′,4′-Tetrahydroxyflavone
10.78 (0.1) - -
7 32.49 Parietin
24.81 (0.4) - -
8 24.11 1,7,7-Trimethyl-3-
phenethylidenebicyclo[2.2.1]heptan-2-one
- 3.28 -
9 24.73 Phenol, 4,4′-methylenebis[2,6-dimethyl-
- 1.60 -
10 26.32 1,1′-Biphenyl, 4,2′,3′,4′-tetramethoxy-5′-methyl-6-
methylaminomethyl-
- 29.75 (0.8) -
11 27.88 (4-Methylsulfanylphenyl)carbamic acid, 2,6-
dimethoxyphenyl ester
- 1.38 -
12 27.76 10,11-Dihydro-10-hydroxy-2,3-
dimethoxydibenz(b,f)oxepin
- - 4.57
10.78 (0.1) - -
7
32.49 Parietin
Molecules 2018, 23, x FOR PEER REVIEW 6 of 11
Table 3. Chemical composition of extractives analyzed by GC/MS.
ID RT
(min) Compounds Molecular
Structure
Releative Content (%) *
D. Cultrate D. Latifolia D. Melanoxylon
1 24.97 Phenol,4-methyl-2-[5-(2-thienyl)pyrazol-3-yl]-
4.76 12.41 (0.7) 1.47
6 29.66 13-Docosenamide, (
Z
)-
2.08 (0.2) 2.17 (0.2) 1.26 (0.1)
2 25.13 Naphtho[2,3-b]furan-4,9-dione, 2-isopropyl-
1.54 1.36 (0.2) -
5 28.90 1-Thioflavone, 7-methoxy-
25.55 (0.2) 4.23 -
3 26.44 3,3′,4,4′-Tetramethoxystilbene 1.49 - -
4 27.26 3,7,3′,4′-Tetrahydroxyflavone
10.78 (0.1) - -
7 32.49 Parietin
24.81 (0.4) - -
8 24.11 1,7,7-Trimethyl-3-
phenethylidenebicyclo[2.2.1]heptan-2-one
- 3.28 -
9 24.73 Phenol, 4,4′-methylenebis[2,6-dimethyl-
- 1.60 -
10 26.32 1,1′-Biphenyl, 4,2′,3′,4′-tetramethoxy-5′-methyl-6-
methylaminomethyl-
- 29.75 (0.8) -
11 27.88 (4-Methylsulfanylphenyl)carbamic acid, 2,6-
dimethoxyphenyl ester
- 1.38 -
12 27.76 10,11-Dihydro-10-hydroxy-2,3-
dimethoxydibenz(b,f)oxepin
- - 4.57
24.81 (0.4) - -
8
24.11 1,7,7-Trimethyl-3-
phenethylidenebicyclo[2.2.1]heptan-2-one
Molecules 2018, 23, x FOR PEER REVIEW 6 of 11
Table 3. Chemical composition of extractives analyzed by GC/MS.
ID RT
(min) Compounds Molecular
Structure
Releative Content (%) *
D. Cultrate D. Latifolia D. Melanoxylon
1 24.97 Phenol,4-methyl-2-[5-(2-thienyl)pyrazol-3-yl]-
4.76 12.41 (0.7) 1.47
6 29.66 13-Docosenamide, (
Z
)-
2.08 (0.2) 2.17 (0.2) 1.26 (0.1)
2 25.13 Naphtho[2,3-b]furan-4,9-dione, 2-isopropyl-
1.54 1.36 (0.2) -
5 28.90 1-Thioflavone, 7-methoxy-
25.55 (0.2) 4.23 -
3 26.44 3,3′,4,4′-Tetramethoxystilbene 1.49 - -
4 27.26 3,7,3′,4′-Tetrahydroxyflavone
10.78 (0.1) - -
7 32.49 Parietin
24.81 (0.4) - -
8 24.11 1,7,7-Trimethyl-3-
phenethylidenebicyclo[2.2.1]heptan-2-one
- 3.28 -
9 24.73 Phenol, 4,4′-methylenebis[2,6-dimethyl-
- 1.60 -
10 26.32 1,1′-Biphenyl, 4,2′,3′,4′-tetramethoxy-5′-methyl-6-
methylaminomethyl-
- 29.75 (0.8) -
11 27.88 (4-Methylsulfanylphenyl)carbamic acid, 2,6-
dimethoxyphenyl ester
- 1.38 -
12 27.76 10,11-Dihydro-10-hydroxy-2,3-
dimethoxydibenz(b,f)oxepin
- - 4.57
- 3.28 -
9
24.73 Phenol, 4,40-methylenebis[2,6-dimethyl-
Molecules 2018, 23, x FOR PEER REVIEW 6 of 11
Table 3. Chemical composition of extractives analyzed by GC/MS.
ID RT
(min) Compounds Molecular
Structure
Releative Content (%) *
D. Cultrate D. Latifolia D. Melanoxylon
1 24.97 Phenol,4-methyl-2-[5-(2-thienyl)pyrazol-3-yl]-
4.76 12.41 (0.7) 1.47
6 29.66 13-Docosenamide, (
Z
)-
2.08 (0.2) 2.17 (0.2) 1.26 (0.1)
2 25.13 Naphtho[2,3-b]furan-4,9-dione, 2-isopropyl-
1.54 1.36 (0.2) -
5 28.90 1-Thioflavone, 7-methoxy-
25.55 (0.2) 4.23 -
3 26.44 3,3′,4,4′-Tetramethoxystilbene 1.49 - -
4 27.26 3,7,3′,4′-Tetrahydroxyflavone
10.78 (0.1) - -
7 32.49 Parietin
24.81 (0.4) - -
8 24.11 1,7,7-Trimethyl-3-
phenethylidenebicyclo[2.2.1]heptan-2-one
- 3.28 -
9 24.73 Phenol, 4,4′-methylenebis[2,6-dimethyl-
- 1.60 -
10 26.32 1,1′-Biphenyl, 4,2′,3′,4′-tetramethoxy-5′-methyl-6-
methylaminomethyl-
- 29.75 (0.8) -
11 27.88 (4-Methylsulfanylphenyl)carbamic acid, 2,6-
dimethoxyphenyl ester
- 1.38 -
12 27.76 10,11-Dihydro-10-hydroxy-2,3-
dimethoxydibenz(b,f)oxepin
- - 4.57
- 1.60 -
10
26.32 1,10-Biphenyl, 4,20,30,40-tetramethoxy-
50-methyl-6-methylaminomethyl-
Molecules 2018, 23, x FOR PEER REVIEW 6 of 11
Table 3. Chemical composition of extractives analyzed by GC/MS.
ID RT
(min) Compounds Molecular
Structure
Releative Content (%) *
D. Cultrate D. Latifolia D. Melanoxylon
1 24.97 Phenol,4-methyl-2-[5-(2-thienyl)pyrazol-3-yl]-
4.76 12.41 (0.7) 1.47
6 29.66 13-Docosenamide, (
Z
)-
2.08 (0.2) 2.17 (0.2) 1.26 (0.1)
2 25.13 Naphtho[2,3-b]furan-4,9-dione, 2-isopropyl-
1.54 1.36 (0.2) -
5 28.90 1-Thioflavone, 7-methoxy-
25.55 (0.2) 4.23 -
3 26.44 3,3′,4,4′-Tetramethoxystilbene 1.49 - -
4 27.26 3,7,3′,4′-Tetrahydroxyflavone
10.78 (0.1) - -
7 32.49 Parietin
24.81 (0.4) - -
8 24.11 1,7,7-Trimethyl-3-
phenethylidenebicyclo[2.2.1]heptan-2-one
- 3.28 -
9 24.73 Phenol, 4,4′-methylenebis[2,6-dimethyl-
- 1.60 -
10 26.32 1,1′-Biphenyl, 4,2′,3′,4′-tetramethoxy-5′-methyl-6-
methylaminomethyl-
- 29.75 (0.8) -
11 27.88 (4-Methylsulfanylphenyl)carbamic acid, 2,6-
dimethoxyphenyl ester
- 1.38 -
12 27.76 10,11-Dihydro-10-hydroxy-2,3-
dimethoxydibenz(b,f)oxepin
- - 4.57
- 29.75 (0.8) -
Molecules 2018,23, 2163 7 of 11
Table 3. Cont.
ID RT(min) Compounds Molecular Structure Releative Content (%) *
D. Cultrate D. Latifolia D. Melanoxylon
11
27.88 (4-Methylsulfanylphenyl)carbamic acid,
2,6-dimethoxyphenyl ester
Molecules 2018, 23, x FOR PEER REVIEW 6 of 11
Table 3. Chemical composition of extractives analyzed by GC/MS.
ID RT
(min) Compounds Molecular
Structure
Releative Content (%) *
D. Cultrate D. Latifolia D. Melanoxylon
1 24.97 Phenol,4-methyl-2-[5-(2-thienyl)pyrazol-3-yl]-
4.76 12.41 (0.7) 1.47
6 29.66 13-Docosenamide, (
Z
)-
2.08 (0.2) 2.17 (0.2) 1.26 (0.1)
2 25.13 Naphtho[2,3-b]furan-4,9-dione, 2-isopropyl-
1.54 1.36 (0.2) -
5 28.90 1-Thioflavone, 7-methoxy-
25.55 (0.2) 4.23 -
3 26.44 3,3′,4,4′-Tetramethoxystilbene 1.49 - -
4 27.26 3,7,3′,4′-Tetrahydroxyflavone
10.78 (0.1) - -
7 32.49 Parietin
24.81 (0.4) - -
8 24.11 1,7,7-Trimethyl-3-
phenethylidenebicyclo[2.2.1]heptan-2-one
- 3.28 -
9 24.73 Phenol, 4,4′-methylenebis[2,6-dimethyl-
- 1.60 -
10 26.32 1,1′-Biphenyl, 4,2′,3′,4′-tetramethoxy-5′-methyl-6-
methylaminomethyl-
- 29.75 (0.8) -
11 27.88 (4-Methylsulfanylphenyl)carbamic acid, 2,6-
dimethoxyphenyl ester
- 1.38 -
12 27.76 10,11-Dihydro-10-hydroxy-2,3-
dimethoxydibenz(b,f)oxepin
- - 4.57
- 1.38 -
12
27.76 10,11-Dihydro-10-hydroxy-2,3-
dimethoxydibenz(b,f)oxepin
Molecules 2018, 23, x FOR PEER REVIEW 6 of 11
Table 3. Chemical composition of extractives analyzed by GC/MS.
ID RT
(min) Compounds Molecular
Structure
Releative Content (%) *
D. Cultrate D. Latifolia D. Melanoxylon
1 24.97 Phenol,4-methyl-2-[5-(2-thienyl)pyrazol-3-yl]-
4.76 12.41 (0.7) 1.47
6 29.66 13-Docosenamide, (
Z
)-
2.08 (0.2) 2.17 (0.2) 1.26 (0.1)
2 25.13 Naphtho[2,3-b]furan-4,9-dione, 2-isopropyl-
1.54 1.36 (0.2) -
5 28.90 1-Thioflavone, 7-methoxy-
25.55 (0.2) 4.23 -
3 26.44 3,3′,4,4′-Tetramethoxystilbene 1.49 - -
4 27.26 3,7,3′,4′-Tetrahydroxyflavone
10.78 (0.1) - -
7 32.49 Parietin
24.81 (0.4) - -
8 24.11 1,7,7-Trimethyl-3-
phenethylidenebicyclo[2.2.1]heptan-2-one
- 3.28 -
9 24.73 Phenol, 4,4′-methylenebis[2,6-dimethyl-
- 1.60 -
10 26.32 1,1′-Biphenyl, 4,2′,3′,4′-tetramethoxy-5′-methyl-6-
methylaminomethyl-
- 29.75 (0.8) -
11 27.88 (4-Methylsulfanylphenyl)carbamic acid, 2,6-
dimethoxyphenyl ester
- 1.38 -
12 27.76 10,11-Dihydro-10-hydroxy-2,3-
dimethoxydibenz(b,f)oxepin
- - 4.57
- - 4.57
13
28.66 2-(4-Methoxy-2,5-dimethyl-phenyl)-9-
methyl-2H-benzo[g]indazole
Molecules 2018, 23, x FOR PEER REVIEW 7 of 11
13 28.66 2-(4-Methoxy-2,5-dimethyl-phenyl)-9-methyl-2
H
-
benzo[g]indazole
- - 3.14
14 28.88 10,11-Dihydro-10-hydroxy-2,3,6-
trimethoxydibenz(b,f)oxepin
- - 37.30 (0.8)
15 30.06 10,11-Dihydro-2,3,6-trimethoxydibenz(b,f)oxepin-
10-one
- - 8.32 (0.2)
16 34.86 Pilloin
- - 7.77 (0.1)
* The percentage was calculated based on the peak area. Values in the parentheses are the deviations of three replicates. Deviations lower than 0.1% are not listed in the
table.
- - 3.14
14
28.88 10,11-Dihydro-10-hydroxy-2,3,
6-trimethoxydibenz(b,f)oxepin
Molecules 2018, 23, x FOR PEER REVIEW 7 of 11
13 28.66 2-(4-Methoxy-2,5-dimethyl-phenyl)-9-methyl-2
H
-
benzo[g]indazole
- - 3.14
14 28.88 10,11-Dihydro-10-hydroxy-2,3,6-
trimethoxydibenz(b,f)oxepin
- - 37.30 (0.8)
15 30.06 10,11-Dihydro-2,3,6-trimethoxydibenz(b,f)oxepin-
10-one
- - 8.32 (0.2)
16 34.86 Pilloin
- - 7.77 (0.1)
* The percentage was calculated based on the peak area. Values in the parentheses are the deviations of three replicates. Deviations lower than 0.1% are not listed in the
table.
- - 37.30 (0.8)
15
30.06 10,11-Dihydro-2,3,6-
trimethoxydibenz(b,f)oxepin-10-one
Molecules 2018, 23, x FOR PEER REVIEW 7 of 11
13 28.66 2-(4-Methoxy-2,5-dimethyl-phenyl)-9-methyl-2
H
-
benzo[g]indazole
- - 3.14
14 28.88 10,11-Dihydro-10-hydroxy-2,3,6-
trimethoxydibenz(b,f)oxepin
- - 37.30 (0.8)
15 30.06 10,11-Dihydro-2,3,6-trimethoxydibenz(b,f)oxepin-
10-one
- - 8.32 (0.2)
16 34.86 Pilloin
- - 7.77 (0.1)
* The percentage was calculated based on the peak area. Values in the parentheses are the deviations of three replicates. Deviations lower than 0.1% are not listed in the
table.
- - 8.32 (0.2)
16
34.86 Pilloin
Molecules 2018, 23, x FOR PEER REVIEW 7 of 11
13 28.66 2-(4-Methoxy-2,5-dimethyl-phenyl)-9-methyl-2
H
-
benzo[g]indazole
- - 3.14
14 28.88 10,11-Dihydro-10-hydroxy-2,3,6-
trimethoxydibenz(b,f)oxepin
- - 37.30 (0.8)
15 30.06 10,11-Dihydro-2,3,6-trimethoxydibenz(b,f)oxepin-
10-one
- - 8.32 (0.2)
16 34.86 Pilloin
- - 7.77 (0.1)
* The percentage was calculated based on the peak area. Values in the parentheses are the deviations of three replicates. Deviations lower than 0.1% are not listed in the
table.
- - 7.77 (0.1)
* The percentage was calculated based on the peak area. Values in the parentheses are the deviations of three replicates. Deviations lower than 0.1% are not listed in the table.
Molecules 2018,23, 2163 8 of 11
Analysis also revealed the presence of eight compounds in Dalbergia latifoli with 4-methyl-
2-[5-(2-thienyl)pyrazol-3-yl]phenol (peak 1, 12.41%) and 4,2
0
,3
0
,4
0
-tetramethoxy-5
0
-methyl-6-methyl-
aminomethyl-1,1
0
-biphenyl (peak 10, 29.75%) being the most predominant. Both compounds
were previously identified in Dalbergia Stevenson based on GC-MS results [
25
,
37
].
Seven components were recognized in Dalbergia melanoxylon, with larger proportions of
10,11-dihydro-10-hydroxy-2,3,6-trimethoxydibenz(b,f)oxepin (peak 12, 37.30%), 10,11-dihydro-
2,3,6-trimethoxydibenz(b,f)oxepin-10-one (peak 14, 8.32%), and pilloin (peak 16, 7.77%).
10,11-Dihydro-10-hydroxy-2,3,6-trimethoxydibenz(b,f)oxepin was previously identified in
Dalbergia Stevenson [
19
,
37
]. Pilloin is a flavonoid extracted from the Ovidia pillo-pillo plant,
Marrubium cylleneum, and propolis.
3. Materials and Methods
3.1. Wood Samples
The Latin names, trade names, and places of origin of the Dalbergia species are presented in Table 4.
The three Dalbergia heartwood samples were obtained from the Research Institute of Wood Industry
at the Chinese Academy of Forestry, China. Figure 3shows tangential sections of the three kinds of
Dalbergia heartwood. Three replicates were analyzed per sample.
Table 4. Latin and trade names and places of origin of investigated Dalbergia species.
Latin Name Trade Name Place of Origin
Dalbergia cultrate Benth. Burmese blackwood Laos
Dalbergia latifolia Roxb. Indian rosewood Indonesia
Dalbergia melanoxylon (Guill. & Perr.) African blackwood Mozambique
Molecules 2018, 23, x FOR PEER REVIEW 8 of 11
Analysis also revealed the presence of eight compounds in Dalbergia latifoli with 4-methyl- 2-[5-
(2-thienyl)pyrazol-3-yl]phenol (peak 1, 12.41%) and 4,2′,3′,4′-tetramethoxy-5′-methyl-6-methyl-
aminomethyl-1,1′-biphenyl (peak 10, 29.75%) being the most predominant. Both compounds were
previously identified in Dalbergia Stevenson based on GC-MS results [25,37]. Seven components were
recognized in Dalbergia melanoxylon, with larger proportions of 10,11-dihydro-10-hydroxy-2,3,6-
trimethoxydibenz(b,f)oxepin (peak 12, 37.30%), 10,11-dihydro- 2,3,6-trimethoxydibenz(b,f)oxepin-
10-one (peak 14, 8.32%), and pilloin (peak 16, 7.77%). 10,11-Dihydro-10-hydroxy-2,3,6-
trimethoxydibenz(b,f)oxepin was previously identified in Dalbergia Stevenson [19,37]. Pilloin is a
flavonoid extracted from the Ovidia pillo-pillo plant, Marrubium cylleneum, and propolis.
3. Materials and Methods
3.1. Wood Samples
The Latin names, trade names, and places of origin of the Dalbergia species are presented in Table
4. The three Dalbergia heartwood samples were obtained from the Research Institute of Wood
Industry at the Chinese Academy of Forestry, China. Figure 3 shows tangential sections of the three
kinds of Dalbergia heartwood. Three replicates were analyzed per sample.
Table 4. Latin and trade names and places of origin of investigated Dalbergia species.
Latin Name Trade Name Place of Origin
Dalbergia cultrate Benth. Burmese blackwood Laos
Dalbergia latifolia Roxb. Indian rosewood Indonesia
Dalbergia melanoxylon (Guill.& Perr.) African blackwood Mozambique
(a) (b) (c)
Figure 3. Heartwood of (a) Dalbergia cultrate, (b) Dalbergia latifolia and (c) Dalbergia melanoxylon.
3.2. Preparation of Wood Extracts
Heartwoods were chopped into thin pieces, air-dried, and finely powdered using an electric
grinder (Baijie, Hangzhou, China). Then, 40–60 mesh powders (0.2 g) were extracted in ethanol/water
(10 mL, 9:1, v/v), benzene/ethanol (2:1, v/v), and ethyl acetate in an ultrasonic bath for 1 h at room
temperature. Ethanol (99.8% purity), benzene (99.7% purity), ethyl acetate (99.0% purity), n-hexane
(98.0% purity) were purchased from Aladdin (Shanghai, China). Next, the mixture was centrifuged
for 5 min and filtered through a 0.45-µm pore size filter before the extraction solvent was dried in an
oven at 103 ± 2 °C to reach a consistent weight for further analysis.
3.3. FTIR Analysis
Two mg of the 90% ethanol extract were mixed with 100 mg of KBr powder in a smooth agate
mortar. Then, the mixture was ground and pressed into a transparent pellet. FTIR spectra were
Figure 3. Heartwood of (a) Dalbergia cultrate, (b) Dalbergia latifolia and (c) Dalbergia melanoxylon.
3.2. Preparation of Wood Extracts
Heartwoods were chopped into thin pieces, air-dried, and finely powdered using an electric
grinder (Baijie, Hangzhou, China). Then, 40–60 mesh powders (0.2 g) were extracted in ethanol/water
(10 mL, 9:1, v/v), benzene/ethanol (2:1, v/v), and ethyl acetate in an ultrasonic bath for 1 h at room
temperature. Ethanol (99.8% purity), benzene (99.7% purity), ethyl acetate (99.0% purity), n-hexane
(98.0% purity) were purchased from Aladdin (Shanghai, China). Next, the mixture was centrifuged for
5 min and filtered through a 0.45-
µ
m pore size filter before the extraction solvent was dried in an oven
at 103 ±2◦C to reach a consistent weight for further analysis.
Molecules 2018,23, 2163 9 of 11
3.3. FTIR Analysis
Two mg of the 90% ethanol extract were mixed with 100 mg of KBr powder in a smooth agate
mortar. Then, the mixture was ground and pressed into a transparent pellet. FTIR spectra were
obtained within a scanning range of 4000–400 cm
−1
at a resolution of 4 cm
−1
and 16 total scans using
a Spectrum ONE spectrometer (Perkin Elmer, Waltham, MA, USA) equipped with a DTGS detector at
room temperature. The instrument was free of H2O and CO2.
3.4. GC-MS Analysis
GC/MS analysis was carried out by a triple quadrupole GC-MS system 450GC-320MS,
(Bruker Billerica, MA, USA). Separation was achieved using a DB-5MS column (30 m
×
0.25 mm
×
0.25
µ
m; Agilent Technologies, Santa Clara, CA, USA) with a temperature program from 50
◦
C (5 min)
to 290
◦
C (12 min) at 10
◦
C/min with helium as the carrier gas (1 mL/min). The solvent was delayed
4.5 min; the injection volume was 1
µ
L at a split ratio of 10. The mass spectrometer was operated in
electron impact mode (70 eV), and masses were scanned over a range of 40–800 m/z. The transmission
line temperature was 250
◦
C, and the ion source temperature was 200
◦
C. Peak assignment was
accomplished by comparing the MS spectra to the National Institute of Standards and Technology
(NIST 2010) library.
4. Conclusions
This study reveals that Dalbergia cultrate,Dalbergia latifolia, and Dalbergia melanoxylon can be
successfully distinguished based on extractive analysis. Initially, the extract content of the three
species was found to be different, with Dalbergia melanoxylon demonstrating the highest extractive
content. By comparing different solvents, the extraction components were found to be mostly
polar. Then, FTIR spectra effectively revealed additional information about the functional groups of
the extractive components. We also identified the unique and primary components using GC-MS.
The main chemical components of the three species varied, and 7-methoxy-1-thioflavone, 4,2
0
,3
0
,4
0
-
tetramethoxy-5
0
-methyl-6-methylaminomethyl-1,1
0
-biphenyl and 10,11-dihydro-10-hydroxy-2,3,6-
trimethoxydibenz(b,f)oxepin exhibited the highest relative content of the three species, respectively.
Furthermore, each species contained its own characteristic components, a useful finding for
distinguishing between the three species. In summary Dalbergia cultrate,Dalbergia latifolia, and
Dalbergia melanoxylon can be distinguished successfully according to differences in extractive content,
functional groups, and chemical composition.
Author Contributions:
X.Y. performed the experiments, analyzed the data, and wrote the manuscript; A.H.
conceived and designed the experiments; S.Z. reviewed the manuscript; R.L. and F.M. contributed to the
analysis tools.
Funding: This work was supported by the National Natural Science Foundation of China (No. 31670564).
Conflicts of Interest: The authors declare no conflict of interest.
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Sample Availability: Samples of the compounds are not available from the authors.
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