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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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Journal of Agricultural and Food Chemistry

1

Development and UFLC-MS/MS Characterization of a Product-Specific

2

Standard for Phenolic Quantification of Maple-Derived Foods

3 4

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

8 9

* Address enquiries to: Tel./Fax +1 401-874-9367/5787, e-mail: [email protected] (Navindra P. Seeram)

1

ACS Paragon Plus Environment


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

2


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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

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having a wide choice of sweeteners, there is increasing consumer interest in natural

33

sweeteners among which pure maple syrup is highly regarded.

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plant-derived natural sweetener obtained by boiling the sap collected from mainly the

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sugar maple (Acer saccharum) species. Worldwide, maple syrup is only produced in

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northeastern North America, primarily in the province of Quebec (in Canada),

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followed by the New England states (in the United States).

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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

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indigenous and modern peoples of eastern North America. Also, with more consumer

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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

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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.

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In addition, in recent years, other value-added maple-derived food products have

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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

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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

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diseases.21, 22

has

attracted

considerable

public3

and

scientific

attention.4-6

Also,

This recent diversification in

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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

64

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,

72

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

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elucidation (by NMR and mass spectrometry) of a wide diversity of phenolic

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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

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secoisolariciresinol (Seco), a prototypical lignan found in flaxseed which has been

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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

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Folin-Ciocalteu assay.6,

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gallic acid, this standard is not always representative of the structural homogeneity

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and diversity of complex plant phenolics.

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academic and industry research laboratories is reported to lead to inaccuracies and

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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

90

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

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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

5



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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

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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

103

food products.

6-9

to purify (by chromatography) and characterize (by UFLC-MS/MS)

104 105

MATERIAL AND METHODS

106

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.

113

Louis, MO, USA). The C18 resin was purchased from Varian (Palo Alto, CA, USA).

114

Ultra-Fast

115

UFLC-MS/MS analyses were performed on a SHIMADZU Prominence UFLC

116

system (Marlborough, MA, USA) consisting of three LC-20AD pumps, a DGU-20A

Liquid

Chromatography

Mass

Spectrometry

6


(UFLC-MS):

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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

119

CORTECS® C18 column (150 mm × 2.1 mm i.d., 2.7 µm. Milford, MA, USA) with a

120

Waters CORTECS® VanGuardTM Pre-Column (5 mm × 2.1 mm i.d., 2.7 µm. Milford,

121

MA, USA). The mobile phase consisted of methanol (A) and 0.1% (v/v) formic acid/

122

water (B) with a gradient elution of 20% A at 0-1 min, 20-25% A at 1-6 min, 25-51%

123

A at 6-214 min. The column temperature was 40 oC, flow rate was 0.25 mL/min, and

124

injection volume was 2.00 µL. Mass spectrometry was performed using a QTRAP

125

4500 system from Applied Biosystems/MDS Sciex (Framingham, MA, USA) coupled

126

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,

128

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

130

analyzed with an IDA (Information-Dependent Acquisition) method, which can

131

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

133

acquired and processed using Analyst 1.6.2 software.

134

Analytical High Performance Liquid Chromatography with Diode Array

135

Detection (HPLC-DAD).

136

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

138

software. Chromatographic separation was performed on an Alltima C18 column (250

All HPLC-DAD analyses were performed on a Hitachi

7



139

× 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

141

33.4% A, 30−80 min, from 33.4% to 71% A, 80−85 min, from 71% to 100% A,

142

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

144

µL, and the detection wavelength was 280 nm.

145

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,

148

Quebec, Canada) and stored at -20 oC until extraction and purification as follows.

149

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

151

in vacuo to yield a maple syrup ethyl acetate extract (280.9 mg) which was purified

152

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

154

methanol:H2O (v:v) to yield seven fractions, A-G, respectively. Based on analytical

155

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

157

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

160

DMSO) were diluted in 50% methanol:H2O (1:1, v/v). All samples were filtered

MaPLES (2 mg/mL) was

8


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(0.22µm, 25 mm i.d.), and stored at -20 oC prior to analyses.

162

Maple-Derived Food Products. The maple-derived food products (see Table 2) were

163

provided by the Federation of Maple Syrup Producers of Quebec (Longueuil, Quebec,

164

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

168

syrup by a slow boiling process to yield a solid which were then crushed and sieved to

169

the desired particle size.

170

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

180

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,

182

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

9



183

µg/mL).

184

RESULTS AND DISCUSSION

185

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

190

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

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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

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HPLC-DAD by comparison to the previously isolated lignan standards) to yield

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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

10


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addition, compounds 17 and 17′ exist as a pair of isomers which corresponded with

206

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

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compounds shown in Table 1.

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[M+Na]+, and MS/MS spectral data of the unknown peaks in MaPLES with the

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authentic lignan standards (corresponding data for the standards are provided in

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Supporting Information), compounds 1-10, 12-16 and 18 were identified as

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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),

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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),

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icariside E4 (12), sakuraresinol (13), acernikol (14), syringaresinol (15), buddlenol E

225

(16),

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2-[4-[2,3-dihydro-3-(hydroxymethyl)-5-(3-hydroxypropyl)-7-methoxy-2-benzofurany

By comparison of tR, pseudo molecular ions

alcohol

(4),

and

11



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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

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5′-methoxy-dehydroconiferyl alcohol.

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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

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as

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(1S,2R)-2-[2,6-dimethoxy-4-[(1S,3aR,4S,6aR)-tetrahydro-4-(4-hydroxy-3,5-

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dimethoxyphenyl)-1H,3H-furo[3,4-c]furan-1-yl]phenoxy]-1-(4-hydroxy-3-methoxyph

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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.

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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).

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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,

12


Nevertheless,

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

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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



271

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

294

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

15



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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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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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antiproliferative effect of maple sap and syrup from Acer saccharum. J. Med. Food.

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Schultz,

H.

Maple

water:

the

new

coconut

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414

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).

21



Figure 1.

22


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Page 23 of 26


Figure 2.

23



Page 24 of 26

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

24


Page 25 of 26


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

25



TOC Graphics

26


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MS Characterization ... - ACS Publications

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