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Development and UFLC-MS/MS Characterization of a ProductSpecific Standard for Phenolic Quantification of Maple-Derived Foods Yongqiang Liu, Hang Ma, and Navindra P. Seeram J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.6b01381 • Publication Date (Web): 21 Apr 2016 Downloaded from http://pubs.acs.org on April 23, 2016
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Development and UFLC-MS/MS Characterization of a Product-Specific
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Standard for Phenolic Quantification of Maple-Derived Foods
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Yongqiang Liu, Hang Ma, and Navindra P. Seeram*
5 6
Bioactive Botanical Research Laboratory, Department of Biomedical and Pharmaceutical
7
Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA
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* Address enquiries to: Tel./Fax +1 401-874-9367/5787, e-mail:
[email protected] (Navindra P. Seeram)
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ABSTRACT 10
The phenolic contents of plant foods are commonly quantified by the Folin-Ciocalteu
11
assay based on gallic acid equivalents (GAEs). However, this may lead to
12
inaccuracies since gallic acid is not always representative of the structural
13
heterogeneity of plant phenolics. Therefore, product-specific standards have been
14
developed for the phenolic quantification of several foods. Currently, maple-derived
15
foods (syrup, sugar, sap/water, and extracts) are quantified for phenolic contents based
16
on GAEs. Since lignans are the predominant phenolics present in maple, herein, a
17
maple phenolic lignan-enriched standard (MaPLES) was purified (by chromatography)
18
and characterized (by UFLC-MS/MS with lignans previously isolated from maple
19
syrup). Using MaPLES and secoisolariciresinol (a commercially available lignan), the
20
phenolic contents of the maple-derived foods increased threefold compared to GAEs.
21
Therefore, lignan-based standards are more appropriate for phenolic quantification of
22
maple-derived foods vs. GAEs. Also, MaPLES can be utilized for the authentication
23
and detection of fake label claims on maple products.
24 25
KEYWORDS: maple, phenolics, lignans, gallic acid equivalents (GAEs),
26
Folin-Ciocalteu assay
27 28
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INTRODUCTION
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The United States is the world’s largest consumer of sweeteners, including corn
31
sweeteners (mainly, high fructose corn syrup) and other edible syrups.1 Despite
32
having a wide choice of sweeteners, there is increasing consumer interest in natural
33
sweeteners among which pure maple syrup is highly regarded.
34
plant-derived natural sweetener obtained by boiling the sap collected from mainly the
35
sugar maple (Acer saccharum) species. Worldwide, maple syrup is only produced in
36
northeastern North America, primarily in the province of Quebec (in Canada),
37
followed by the New England states (in the United States).
38
that this agricultural product is of significant economic importance to this region of
39
the world.
40
and its production is deeply linked with the tradition and culture of both the
41
indigenous and modern peoples of eastern North America. Also, with more consumer
42
interest in locally produced foods, and growing skepticism for artificial ingredients
43
and flavors, there has been increased public and scientific attention on maple-derived
44
food products.2
45
Maple syrup is a
Thus, it is not surprising
Moreover, maple syrup has a positive consumer acceptance worldwide
The most commonly consumed form of maple-derived foods is maple syrup
46
which is produced by boiling maple sap (ca. 40 L sap yields 1 L syrup).
This is
47
followed by maple sugar which is produced by slow boiling of maple syrup until a
48
solid texture is obtained which is then crushed and sieved to the desired particle size.
49
In addition, in recent years, other value-added maple-derived food products have
50
emerged in the market.
These include pasteurized and sterilized maple water (i.e. 3
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maple sap which is ca. 98% water) which is being marketed as a functional beverage
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and
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phenolic-enriched maple syrup-derived extracts are being developed for potential
54
nutraceutical and functional food applications.7
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maple-derived food product portfolio is driven, in part, by several recent published in
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vitro6-15 and animal studies16-20 supporting the potential biological effects of maple
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phytochemicals against oxidation, inflammation, diabetes, and neurodegenerative
58
diseases.21, 22
has
attracted
considerable
public3
and
scientific
attention.4-6
Also,
This recent diversification in
59
Given the premium price and popularity of maple-derived foods, the industry is
60
faced with fake labeling claims and counterfeit products such as artificial maple
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flavored and caramel colored, and simulated corn fructose-based sweeteners that
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falsely claim to contain maple syrup. Consequently, the Food and Drug
63
Administration (FDA) in the United States has recently been petitioned by maple
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producers in North America regarding fake maple labels on food products with
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similar petitions being planned for provincial and federal agencies in Canada.23
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Therefore, given the increasing public and scientific attention on maple-derived foods,
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there is an urgent need to develop appropriate product-specific standards to support
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research authenticity, reproducibility, and future health based studies on maple. To
69
date, maple-derived foods are being quantified for phenolic contents based on the
70
widely used industrial standard, namely, gallic acid equivalents (GAEs), by the
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Folin-Ciocalteu assay (further discussed below).6, 7, 11, 15, 17, 19 In addition, to date,
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there are no chemically characterized product-specific standard/s available for the 4
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authentication of maple products.
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Our group has conducted extensive phytochemical studies on maple-derived food
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products (syrup, sap, and extracts) which have led to the isolation and structure
76
elucidation (by NMR and mass spectrometry) of a wide diversity of phenolic
77
compounds.6-10 Among the different chemical types of phenolic compounds identified
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in maple, the lignan sub-class predominates including compounds such as
79
secoisolariciresinol (Seco), a prototypical lignan found in flaxseed which has been
80
extensively studied for its health benefits,24, 25 as well as several other new and known
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lignan molecules.8, 9
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To date, the majority of published reports on maple-derived food products have
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quantified the phenolic contents of their study materials based on GAEs by the
84
Folin-Ciocalteu assay.6,
85
gallic acid, this standard is not always representative of the structural homogeneity
86
and diversity of complex plant phenolics.
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academic and industry research laboratories is reported to lead to inaccuracies and
88
underestimation of phenolic contents for several foods including grape seeds,26
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chocolate,27 pomegranate,28 and cranberry.29-31 This has led to the development of
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product-specific standards for the phenolic quantification of these aforementioned
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food products.26-31
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structurally representative of maple lignans, herein we sought to develop a maple
93
product-specific standard for: 1) the phenolic quantification and, 2) authentication, of
94
maple-derived food products. For this project, we were able to leverage our group’s
7, 11, 17, 19
However, given the mono-phenolic structure of
In fact, the extensive use of GAEs by
Based on these reports, and given that gallic acid is not
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access to authentic lignan standards (previously isolated and identified by NMR from
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maple syrup)
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the maple phenolic lignan-enriched standard (MaPLES). Also, given that the
98
Folin-Ciocalteu reaction is independent, and that analyses of phenolic mixtures can be
99
recalculated in terms of any other standards,32 several maple-derived food materials
100
were quantified for phenolic contents based on MaPLES and Seco compared to
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GAEs. The findings from the current study support the use of lignan-based standards,
102
rather than gallic acid, for the quantification of phenolic contents of maple-derived
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food products.
6-9
to purify (by chromatography) and characterize (by UFLC-MS/MS)
104 105
MATERIAL AND METHODS
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Chemicals. Sodium carbonate was purchased from Fisher Scientific (Fair Lawn, NJ,
107
USA). ACS grades of methanol, ethyl acetate, and dimethylsulfoxide (DMSO) were
108
obtained from Pharmco-AAPER through Wilkem Scientific (Pawcatuck, RI, USA).
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The lignan standards used for UFLC-MS/MS characterization were previously
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isolated and identified (by NMR and mass spectrometry) from maple syrup and maple
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sap by our laboratory.6-9 Secoisolariciresinol (Seco), gallic acid, Folin-Ciocalteu
112
reagent, and LC-MS grade of methanol were purchased from Sigma-Aldrich (St.
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Louis, MO, USA). The C18 resin was purchased from Varian (Palo Alto, CA, USA).
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Ultra-Fast
115
UFLC-MS/MS analyses were performed on a SHIMADZU Prominence UFLC
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system (Marlborough, MA, USA) consisting of three LC-20AD pumps, a DGU-20A
Liquid
Chromatography
Mass
Spectrometry
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degassing unit, SIL-20AC auto sampler, CTO-20AC column oven and CBM-20A
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communication bus module. Chromatographic separation was performed on a Waters
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CORTECS® C18 column (150 mm × 2.1 mm i.d., 2.7 µm. Milford, MA, USA) with a
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Waters CORTECS® VanGuardTM Pre-Column (5 mm × 2.1 mm i.d., 2.7 µm. Milford,
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MA, USA). The mobile phase consisted of methanol (A) and 0.1% (v/v) formic acid/
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water (B) with a gradient elution of 20% A at 0-1 min, 20-25% A at 1-6 min, 25-51%
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A at 6-214 min. The column temperature was 40 oC, flow rate was 0.25 mL/min, and
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injection volume was 2.00 µL. Mass spectrometry was performed using a QTRAP
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4500 system from Applied Biosystems/MDS Sciex (Framingham, MA, USA) coupled
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with an electrospray ionization (ESI) interface. Nitrogen was used in all cases. In this
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study, the parameters were optimized as follows: ESI voltage, 4500 V; nebulizer gas,
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50; auxiliary gas, 50; curtain gas, 20; turbo gas temperature, 550°C; declustering
129
potential, 45V; entrance potential 10V; collision energy, 22 eV. The samples were
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analyzed with an IDA (Information-Dependent Acquisition) method, which can
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automatically select candidate ions for MS/MS. The mass range was set from m/z 100
132
to 1000 and the mass range for product ion scan was m/z 100-1000. The data were
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acquired and processed using Analyst 1.6.2 software.
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Analytical High Performance Liquid Chromatography with Diode Array
135
Detection (HPLC-DAD).
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Elite LaChrom system (Pleasanton, CA, USA) consisting of a L2130 pump, a L-2200
137
autosampler, and a L-2455 Diode Array Detector, operated by EZChrom Elite
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software. Chromatographic separation was performed on an Alltima C18 column (250
All HPLC-DAD analyses were performed on a Hitachi
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× 4.6 mm i.d., 5 µM; Alltech). The mobile phase consisted of methanol (A) and 0.1%
140
(v/v) trifluoroacetic acid/ water (B) with a gradient elution of 0−30 min, from 5% to
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33.4% A, 30−80 min, from 33.4% to 71% A, 80−85 min, from 71% to 100% A,
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85−86 min, from 100% to 5% A, 86−94 min, 5% A. The column temperature was at
143
room temperature, the flow rate was at 0.75 mL/min, the injection volumes were 20
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µL, and the detection wavelength was 280 nm.
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Purification of the Maple Phenolic Lignan-Enriched Standard (MaPLES). Maple
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syrup (grade C code 14-032428 / baril 882-1; 40 L) was shipped frozen to our
147
laboratory by the Federation of Maple Syrup Producers of Quebec (Longueuil,
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Quebec, Canada) and stored at -20 oC until extraction and purification as follows.
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Briefly, maple syrup (1551 g) was dissolved in deionized water (2 L) and partitioned
150
with ethyl acetate (2 L×3). The combined ethyl acetate fractions were concentrated
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in vacuo to yield a maple syrup ethyl acetate extract (280.9 mg) which was purified
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by C18 chromatography (glass column: 350 mm in height and 50 mm in diameter)
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eluted with a gradient solvent system of 5%, 15%, 30%, 40%, 50%, 60% and 80% of
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methanol:H2O (v:v) to yield seven fractions, A-G, respectively. Based on analytical
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HPLC-DAD profiling, and by comparison of retention times (tR) to lignan standards
156
previously isolated from maple syrup by our laboratory,6-9 fractions C and D were
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combined to yield the maple phenolic lignan-enriched standard (MaPLES; 64.1 mg)
158
(chromatograms provided in Supporting Information).
159
dissolved in 50% methanol:H2O (1:1, v/v) and the lignan standards (solubilized in
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DMSO) were diluted in 50% methanol:H2O (1:1, v/v). All samples were filtered
MaPLES (2 mg/mL) was
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(0.22µm, 25 mm i.d.), and stored at -20 oC prior to analyses.
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Maple-Derived Food Products. The maple-derived food products (see Table 2) were
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provided by the Federation of Maple Syrup Producers of Quebec (Longueuil, Quebec,
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Canada) and consisted of maple water (WahtaTM, Rougemont, Quebec, Canada),6
165
maple syrup (Grade C; code 14-032428 / baril 882-1),8,
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300315-C / baril 882-1), and a food grade phenolic-enriched maple syrup-derived
167
extract (MSX).7
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syrup by a slow boiling process to yield a solid which were then crushed and sieved to
169
the desired particle size.
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Phenolic Quantification of Maple-Derived Food Products. The maple-derived food
171
products were quantified for phenolic contents using the Folin-Ciocalteu method as
172
previously reported.7, 8 Briefly, each sample (200 µL) was diluted with methanol:H2O
173
(1:1, v/v; 3 mL) and incubated at room temperature (for 10 min) with 200 µL of the
174
Folin-Ciocalteu reagent. Subsequently, 600 µL of a 20% sodium carbonate solution
175
was added to each tube with vigorous mixing.
176
o
177
an ice bath. The standards (MaPLES, Seco, and gallic acid) and samples were
178
processed identically. UV absorptions were recorded on a Beckman Coulter DU® 800
179
spectrophotometer (Fullerton, CA, USA) at 755 nm and phenolic contents were
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calculated from the respective curves for each standards which were as follows:
181
MaPLES: y=1.5634x+0.0045, R2=0.999 (52.5-420 µg/mL); Seco: y=1.8001x-0.0083,
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R2=0.999 (62.5-1000 µg/mL); gallic acid: y=5.5801x-0.0079, R2=0.999 (62.5-527
9
maple sugar (Lot SG
The maple sugar was produced from the same batch/grade of maple
Each sample was then incubated at 40
C for an additional 20 min and then immediately cooled to room temperature using
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µg/mL).
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RESULTS AND DISCUSSION
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Purification of Maple Phenolic Lignan-Enriched Standard (MaPLES). Our group
186
has previously isolated (by chromatography) and identified (by NMR and mass
187
spectrometry) a large diversity of phenolic compounds from maple water, maple syrup
188
and maple syrup-derived extracts.6-10 We reported that lignans are the major sub-class
189
of phenolic compounds found in these maple-derived food products. Furthermore, our
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laboratory has developed protocols for the extraction (by partitioning with different
191
organic solvents) and purification (by column chromatography) of phenolic-enriched
192
extracts of maple syrup.6-10 Therefore, using these existing protocols, we generated an
193
ethyl acetate extract of maple syrup which was subsequently purified by medium
194
pressure liquid chromatography (with C18 resin) to yield seven fractions, A-F. The
195
lignan-enriched fractions, namely C-D, were combined (based on analytical
196
HPLC-DAD by comparison to the previously isolated lignan standards) to yield
197
MaPLES (details provided in Supporting Information).
198
UFLC-MS/MS Characterization of MaPLES.
199
in Figure 1) were identified in MaPLES by UFLC-MS/MS analyses (mass spectral
200
data provided in Supporting Information).
201
compounds (1-10, 12-18) were identified by comparison to lignan standards
202
previously isolated and identified (by NMR) from maple syrup by our laboratory,6-10
203
and one compound (11; for which we lacked a standard due to limitations in sample
204
quantity) was tentatively identified based on its pseudo molecular ion [M+Na]+. In
Nineteen lignans (structures shown
Among these lignans, seventeen
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addition, compounds 17 and 17′ exist as a pair of isomers which corresponded with
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the retention times (tR) and pseudo molecular ions [M+Na]+ of standards obtained
207
from our previous isolation studies. A detailed description of the identification of the
208
nineteen lignans in MaPLES is provided below.
209
The total ion chromatography (TIC) of the lignan standards and MaPLES are
210
shown in Figures 2A and 2B, respectively, with accompanying identities of the
211
compounds shown in Table 1.
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[M+Na]+, and MS/MS spectral data of the unknown peaks in MaPLES with the
213
authentic lignan standards (corresponding data for the standards are provided in
214
Supporting Information), compounds 1-10, 12-16 and 18 were identified as
215
leptolepisol D (1), lyoniresinol (2), guaiacylglycerol-β-O-4′-coniferyl alcohol (3),
216
threo-guaiacyl-glycerol-β-O-4′-dihydroconiferyl
217
erythro-guaiacylglycerol-β-O-4′-dihydroconiferyl alcohol (5),
218
5-(3′′,4′′-dimethoxyphenyl)-3-hydroxy-3-(4′-hydroxy-3′-methoxybenzyl)-4-(hydroxy
219
methyl)dihydrofuran-2-one (6),
220
[3-[4-[(6-deoxy-α-L-mannopyranosyl)oxy]-3-methoxyphenyl]methyl]-5-(3,4-dimetho
221
xyphenyl)-dihydro-3-hydroxy-4-(hydroxymethyl)-2(3H)-furanone (7),
222
erythro-1-(4-hydroxy-3-methoxy-phenyl)-2-[4-(3-hydroxypropyl)-2,6-dimethoxyphen
223
oxy]-1,3-propanediol (8), secoisolariciresinol (9), dehydroconiferyl alcohol (10),
224
icariside E4 (12), sakuraresinol (13), acernikol (14), syringaresinol (15), buddlenol E
225
(16),
226
2-[4-[2,3-dihydro-3-(hydroxymethyl)-5-(3-hydroxypropyl)-7-methoxy-2-benzofurany
By comparison of tR, pseudo molecular ions
alcohol
(4),
and
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l]-2,6-dimethoxyphenoxy]-1-(4-hydroxy-3-methoxyphenyl)-1,3-propanediol
(18),
228
respectively.
229
our previous isolation studies), compound 11 [at tR = 116.31 min] was tentatively
230
identified based on the pseudo molecular ion [M+Na]+ at m/z 413 as
231
5′-methoxy-dehydroconiferyl alcohol.
232
isomers with two distinct peaks at tR = 200.50 min (17) and tR = 202.07 min (see
233
Figure 2B) but with the same pseudo molecular ion [M+Na]+ at m/z 637 and the same
234
MS/MS fragment ions at m/z 441. Therefore, compounds 17 and 17′ were identified
235
as
236
(1S,2R)-2-[2,6-dimethoxy-4-[(1S,3aR,4S,6aR)-tetrahydro-4-(4-hydroxy-3,5-
237
dimethoxyphenyl)-1H,3H-furo[3,4-c]furan-1-yl]phenoxy]-1-(4-hydroxy-3-methoxyph
238
enyl)-1,3-propanediol, which have previously been isolated from maple syrup by our
239
laboratory.9 Based on the lignan standards available to us, we were only able to
240
identify nineteen of these compounds in MaPLES.
241
there are several other compounds present in MaPLEs which are currently
242
unidentified. These unidentified peaks are most likely phenolic compounds including
243
other lignans previously isolated from maple syrup but for which we lacked authentic
244
standards (due to limited samples obtained in our previous studies).
245
MaPLES is representative of the majority of lignans present in maple syrup.
246
Phenolic Quantification of Maple-Derived Food Products with Lignan-Enriched
247
Standards (MaPLES and Seco) vs. GAEs by the Folin-Ciocalteu Assay.
248
shown in Table 2, several maple-derived food products, maple water,6 maple syrup,8, 9
In the absence of a standard (due to limited quantities obtained from
a
Compounds 17 and 17′ exist as a pair of
pair
of
isomers
of
However, as shown in Figure 2B,
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As
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maple sugar, and a previously chemically characterized food grade phenolic-enriched
250
maple syrup-derived extract (MSX)7 were quantified for phenolic contents based on
251
lignan-enriched standards (i.e. MaPLES and Seco) equivalents vs. GAEs.
252
As expected, the trend in phenolic contents among the food products was MSX >
253
maple sugar > maple syrup > maple water.
Thus, the phenolic content of maple
254
water (i.e. maple sap) was the lowest since ca. 40 L of maple sap is concentrated (by
255
boiling) to produce ca. 1 L of maple syrup. Similarly, maple syrup is further
256
concentrated to yield maple sugar, and MSX is a highly concentrated and purified
257
phenolic-enriched extract derived from maple syrup.7
258
result was that the phenolic contents of the four maple-derived food products were
259
threefold higher based on the lignan-enriched standards compared to GAEs. However,
260
since the Folin-Ciocalteu reagent can react with reducing substances (vitamins,
261
nitrogen-containing compounds, etc.) apart from phenols,32 further studies using a
262
diversity of maple products (increased sample size and types) are warranted since the
263
four maple products were evaluated in this study as ‘neat/natural’ forms. Nevertheless,
264
our observations are similar to those reported for several other phenolic-rich plat
265
foods including grape seeds, chocolate, pomegranate and cranberry, wherein their
266
respective product-specific generated standards yielded higher phenolic contents
267
compared to GAEs.26-31
Overall, the most striking
268
In conclusion, in the current study, we have purified and chemically characterized
269
a maple phenolic lignan-enriched standard (MaPLES) which contains the majority of
270
the natural occurring lignan constituents found in maple syrup. Based on MaPLES, 13
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and the commercially available lignan standard, Seco, we found that the use of GAEs
272
grossly underestimates the phenolic contents of several maple-derived food products.
273
Therefore, lignan-based standards are more appropriate for the phenolic quantification
274
of maple-derived foods rather than GAEs. However, since GAEs are commonly used
275
as an industrial standard for measuring phenolic contents of many foods, a precise and
276
validated GAE/MaPLES ratio will be required for comparison of the phenolic
277
contents of maple products with those of food products obtained with GAEs. Lastly,
278
given that the maple syrup industry is currently faced with counterfeit and fake
279
labelling claims on products,23 MaPLES can also be utilized for the authentication of
280
maple-derived food products.
281
validation studies as previously reported,28 as well as further refinement of
282
UFLC-MS/MS methods, to evaluate the phenolic content and authenticity of
283
commercially available maple food products using MaPLES.
Our group will be pursuing multi-laboratory and other
284 285
AUTHOR INFORMATION
286
Corresponding Author
287
(N.P.S.) Phone: +1 401-874-9367. Fax: 401-874-5787. E-mail:
[email protected] 288
289
ACKNOWLEDGEMENTS
290
The authors gratefully acknowledge the Federation of Quebec Maple Syrup Producers
291
(Longueuil, Quebec, Canada) and Agriculture and Agri-Food Canada for funding of
292
this research project. We would like to thank Dr. Alvin Bach II for assistance with 14
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accumulating mass spectrometry data. This research was made possible by the use of
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instruments made available through an Institutional Development Award (IDeA) from
295
the National Institute of General Medical Sciences of the National Institutes of Health
296
under grant number P20GM103430.
297 298
ASSOCIATED CONTENT
299
Supporting Information
300 301 302 303 304 305 306 307
The supporting information is available free of charge on the ACS Publications website at DOI: The HPLC-DAD chromatograms of the maple syrup ethyl acetate extract and its fractions used for purification of MaPLES (Figures S1 and S2, respectively), the UFLC-MS/MS spectra of the nineteen compounds 1-16, 17 and 17′, and 18 identified in MaPLES (Figures S3-S21), and the UFLC-MS/MS data for the lignan standards previously isolated from maple syrup (Table S1).
308 309
Notes
310
The authors declare no competing financial interest.
311
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References 312
1.
United States Department of Agriculture Economic Research Service Sugar &
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Sweeteners. http://www.ers.usda.gov/topics/crops/sugar-sweeteners.aspx (accessed 23
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March 2016),
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Chemical & Engineering News April 14, 2014, Volumen 92, isue 5, p 10-13.
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http://www.foodnavigator-usa.com/Suppliers2/Maple-water-The-new-coconut-water
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(accessed 23 March 2016),
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Antioxidant activity, inhibition of nitric oxide overproduction, and in vitro
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antiproliferative effect of maple sap and syrup from Acer saccharum. J. Med. Food.
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2010, 13, 460-468.
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5.
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maple sap and relationships among constituents. J. Food Comp. Anal. 2015, 41,
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129-136.
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Arnaud, C. H., ACS meeting news: looking beyond the sugars in sweeteners.
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the
new
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phenolic-enriched maple syrup extracts for inhibition of carbohydrate hydrolyzing
Li, L.; Seeram, N. P., Further investigation into maple syrup yields 3 new lignans,
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enzymes relevant to type 2 diabetes management. J. Funct. Foods 2011, 3, 100-106.
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16. Nagai, N.; Ito, Y.; Taga, A., Comparison of the enhancement of plasma glucose
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administration of sucrose or maple syrup. J. Oleo Sci. 2013, 62, 737-743.
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17. Watanabe, Y.; Kamei, A.; Shinozaki, F.; Ishijima, T.; Iida, K.; Nakai, Y.; Arai, S.;
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B.; Reed, J. D., Comparison of isolated cranberry (Vaccinium macrocarpon Ait.)
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List of Figure Captions
415 416
Figure 1. Compounds identified in the maple phenolic lignan-enriched standard
417
(MaPLES) by UFLC-MS/MS based on comparison to authentic lignan standards
418
previously isolated from maple syrup.8, 9
419 420
Figure 2. (A) The total ion chromatography (TIC) of lignan standards previously
421
isolated from maple syrup.8, 9 (B) TIC of the maple phenolic lignan-enriched standard
422
(MaPLES).
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Figure 1.
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Figure 2.
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Table 1. UFLC-MS/MS data for compounds identified in MaPLES by comparison of retention times (tR) and mass spectral data with authentic lignan standards previously isolated and identified (by NMR) from maple syrup.8, 9
No.
Compounds
tR (min)
[M+Na]+ (m/z)
MS/MS (m/z)
1
leptolepisol D
20.96
539
539, 491
2
lyoniresinol
40.76
443
-a
3
guaiacylglycerol-β-O-4′-coniferyl alcohol
45.53
399
399, 201
4
threo-guaiacylglycerol-β-O-4′-dihydroconiferyl alcohol
52.85
401
401, 203
5
erythro-guaiacylglycerol-β-O-4′-dihydroconiferyl alcohol
62.19
401
401, 203
6
5-(3′′,4′′-dimethoxyphenyl)-3-hydroxy-3-(4′-hydroxy-3′-
64.03
427
427, 409, 379, 365, 217
76.78
573
methoxybenzyl)-4-(hydroxymethyl)dihydrofuran-2-one 7
[3-[4-[(6-deoxy-α-L-mannopyranosyl)oxy]-3methoxyphenyl]methyl]-5-(3,4-dimethoxyphenyl)-dihydro-3-
573, 525, 511, 427, 409, 379
hydroxy-4-(hydroxymethyl)-2(3H)-furanone 8
erythro-1-(4-hydroxy-3-methoxyphenyl)-2-[4-(3-
86.54
431
431, 233, 219
96.89
385
-a
hydroxypropyl)-2,6-dimethoxyphenoxy]-1,3-propanediol 9
secoisolariciresinol
10
dehydroconiferyl alcohol
109.28
383
-a
11
5′-methoxydehydroconiferyl alcohol
116.31
413
-a
12
icariside E4
119.74
529
529, 383
13
sakuraresinol
133.10
487
487, 411, 395, 381
14
acernikol
141.29
441
-a
15
syringaresinol
180.76
609
-a
16
buddlenol E
197.45
607
607, 411, 395
(1S,2R)-2-[2,6-dimethoxy-4-[(1S,3aR,4S,6aR)-tetrahydro-4-
200.50
637
637, 441, 425
(4-hydroxy-3,5-dimethoxyphenyl)-1H,3H-furo[3,4-c]furan-1-
202.07
637
637 , 441, 425
206.31
609
609, 413
17, 17′
yl]phenoxy]-1-(4-hydroxy-3-methoxyphenyl)-1,3-propanediol 18
2-[4-[2,3-dihydro-3-(hydroxymethyl)-5-(3-hydroxypropyl)-7methoxy-2-benzofuranyl]-2,6-dimethoxyphenoxy]-1-(4hydroxy-3-methoxyphenyl)-1,3-propanediol
a
compound identified in MaPLES by comparison of retention times (tR) and [M+Na]+ with authentic lignan standards previously isolated and identified from maple syrup.8, 9
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Table 2. Quantification of phenolic contents of maple-derived food products by the Folin-Ciocalteu assay based on gallic acid, secoisolariciresinol and MaPLES equivalents (as % or g/100 g).
gallic acid
secoisolariciresinol
MaPLES
maple water
0.0003
0.0009
0.0010
maple syrup
0.03
0.11
0.12
maple sugar
0.09
0.29
0.32
maple syrup-derived extract (MSX)a
13.26
41.15
45.74
a
The food grade maple-syrup derived extract (MSX) has been chemically
characterized as previously reported.7
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