2-Furoylglycine as a Candidate Biomarker of Coffee Consumption

Sep 11, 2015 - Specific and sensitive food biomarkers are necessary to support dietary intake assessment and link nutritional habits to potential impa...
0 downloads 0 Views 2MB Size
Subscriber access provided by CMU Libraries - http://library.cmich.edu

Article

2-Furoylglycine as a candidate biomarker of coffee consumption Silke S Heinzmann, Elaine Holmes, Sunil Kochhar, Jeremy Kirk Nicholson, and Philippe Schmitt-Kopplin J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.5b03040 • Publication Date (Web): 11 Sep 2015 Downloaded from http://pubs.acs.org on September 22, 2015

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Journal of Agricultural and Food Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 29

Journal of Agricultural and Food Chemistry

1

2-Furoylglycine as a candidate biomarker of coffee

2

consumption

3 4

Silke S Heinzmann1,*, Elaine Holmes2, Sunil Kochhar3, Jeremy K Nicholson2, Philippe

5

Schmitt-Kopplin1,4

6 7

1 Helmholtz Zentrum München, Research Unit Analytical BioGeoChemistry, 85764

8

Neuherberg, Germany

9

2 Biomolecular Medicine, Section of Computational and Systems Medicine, Department of

10

Surgery and Cancer, Faculty of Medicine, Imperial College London, South Kensington,

11

London SW7 2AZ, UK

12

3 Nestlé Research Center, Nestec, Vers-chez-les-Blancs, 1000 Lausanne 26, Switzerland

13

4 Technische Universität München, Chair of Analytical Food Chemistry, 85354 Freising,

14

Germany

15

* Corresponding author: Silke S. Heinzmann, Helmholtz Zentrum München, Research Unit

16

BioGeoChemistry, 85764 Neuherberg, Germany. E-mail: silke.heinzmann@helmholtz-

17

muenchen.de. Phone: +49 89 3187 3308. Fax: +49 89 3187 2705

18 19

Table of Contents categories: 1) Metabolomics Applied to Agriculture and Food; 2) Food and

20

Beverage Chemistry/Biochemistry; 3) Analytical Methods

21 22 23

1 ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

24

Page 2 of 29

Abstract

25 26

Specific and sensitive food biomarkers are necessary to support dietary intake assessment and

27

link nutritional habits to potential impact on human health. A multistep nutritional

28

intervention study was conducted to suggest novel biomarkers for coffee consumption.

29

1

30

furoylglycine (2-FG) as a novel putative biomarker for coffee consumption. We relatively

31

quantified 2-FG in the urine of coffee drinkers and investigated its origin, metabolism and

32

excretion kinetics. When searching for its potential precursors, we found different furan

33

derivatives in coffee products, which are known to get metabolized to 2-FG. Maximal urinary

34

excretion of 2-FG occurred 2 hours after consumption (p=0.0002) and returned to baseline

35

after 24 hours (p=0.74). The biomarker was not excreted after consumption of coffee

36

substitutes such as tea and chicory coffee and might therefore be a promising acute biomarker

37

for the detection of coffee consumption in human urine.

H NMR metabolic profiling combined with multivariate data analysis resolved 2-

38 39 40

Keywords: coffee biomarker, urine, metabolomics, NMR spectroscopy, 2-furoylglycine,

41

nutritional intervention

42 43

2 ACS Paragon Plus Environment

Page 3 of 29

44

Journal of Agricultural and Food Chemistry

Introduction

45 46

Coffee is an important part of the diet and serves as social, sensory and stimulatory beverage.

47

Its consumption varies greatly between cultures and countries (1). After water, it is the most

48

consumed beverage worldwide (2) and has therefore received extensive attention with regard

49

to evaluation of its beneficial and adverse health effects. These investigations have focused

50

either on the effect of coffee as a whole, or on ingredient-specific effects, e.g. from caffeine.

51

The vasopressor effect of caffeine occur directly with exposure, however no long-term

52

impact of caffeine on proposed hypertension has been confirmed (3), suggesting tolerance

53

towards caffeine and rapid return to baseline blood pressure. Physiological effects attributed

54

to caffeine encompass increased alertness (4, 5), ergogenic effects on exercise (6, 7) and

55

thermogeneic effects on energy metabolism (8-10). Investigations into the inverse association

56

of developing neurodegenerative diseases, such as Alzheimer’s and Parkinson’s disease in

57

relation to coffee drinking habits also primarily discuss the active ingredients caffeine as the

58

main bioactive compound (11-16). Effects on liver, e.g. onset of liver cirrhosis (17, 18) and

59

reduced liver cancer risk (19) are reported within a wider bioactive frame of coffee

60

ingredients and not limited to caffeine alone. Beneficial effects of coffee on other types of

61

cancer are controversially discussed, since other lifestyle factors might bias the observed

62

effects on reduced risk of e.g. colon cancer (20). While no associations were found for

63

cardiovascular diseases (21, 22), both stroke risk (23) and diabetes type 2 risk have been

64

inversely associated with both caffeinated and decaffeinated coffee (24, 25). In summary,

65

overall mortality is not increased with frequent coffee consumption and a moderate inverse

66

association could be found for CVD mortality (26, 27).

67

Questions arise towards which bioactive ingredients, besides caffeine, might be responsible

68

for the aforementioned effects. Coffee is rich in flavonoids, chlorogenic acid and melanoidins

3 ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

Page 4 of 29

69

with antioxidative properties on the one hand (28, 29) and hypercholesteremic and

70

homocysteine raising effects on the other hand (30). Simple heterocyclic rings such as pyrrole

71

and furans have antioxidant properties but also have hepatotoxic and hepatocarcinogenic

72

effects in high doses (31, 32). The composition of coffee with regard to these bioactive

73

ingredients depends largely on the variety, type of roasting and brewing method (33). For

74

example, beans roasted at high temperatures contain increased furan levels (34); on the other

75

hand coffee filters largely remove the diterpenes cafestol and kahweol components of ground

76

coffee (30).

77

Food frequency questionnaires are a great source for determining dietary habits and other

78

food questionnaires such as dietary recalls help to collect more specific data on consumed

79

foods and beverages on the day (35). However, such questionnaires may be susceptible to

80

errors in underreporting of less healthy and overestimation of health beneficial foods. It is

81

therefore of great value to have food biomarkers available, that may accurately allow for

82

quantification or qualitative investigation of consumed foods via measurement of such

83

compounds in urine or plasma. To monitor intake frequency in individuals, it is extremely

84

helpful to have a non-invasive biomarker in hand that is specific to coffee and sensitive

85

enough for detection with straight forward analytical chemistry tool (36). Several biomarkers

86

for coffee have been proposed including caffeine, polyphenols and trigonelline (37-41).

87

Ingestion of caffeine results in excretion of caffeine and other xanthine derivatives (37),

88

chlorogenic acid leads to excretion of different quinic acids and hippuric acids (38-40) and

89

trigonelline and its roasting product N-methylpyridinium are also directly excreted in urine

90

(41). However, most detected markers to date are not specific to coffee consumption. For

91

example, caffeine can be found in other stimulatory beverages and the excretion of

92

polyphenol-derived markers is not specific to coffee, since fruits, vegetables and tea are also

4 ACS Paragon Plus Environment

Page 5 of 29

Journal of Agricultural and Food Chemistry

93

rich in polyphenols (38, 42). Furthermore, metabolism of polyphenols is dependent on the gut

94

microbiota, and therefore subject to high inter-individual variation in humans (43-45).

95

Non-targeted metabolic profiling has in the past been shown to deliver novel food

96

biomarkers, without prior knowledge of ingredients or processing and metabolism steps (46-

97

48). Here, we conducted a multi-step approach for sequentially elucidating novel biomarkers

98

for coffee consumption and established their temporal excretion profiles using 1H NMR

99

based metabolic profiling of a coffee intervention study.

100 101

Materials and Methods

102 103

Dietary Intervention Study

104

A nutritional intervention study was designed to detect urinary biomarkers of different foods

105

consumption by using a non-targeted metabolic profiling approach. The study involved 8

106

volunteers (7 women and 1 man; age range: 28–45 y) who met the following inclusion

107

criteria: healthy, aged 18–45 y, nonsmokers and body mass index (BMI; in kg/m2) 18–25,

108

absence of regular drug intake and regular food supplement intake, and no antibiotic use

109

within the previous 3 months. Participants consumed a standardized breakfast, lunch, and

110

dinner that comprised whole-grain bread and cheese (breakfast), a ham sandwich (lunch), and

111

different dinners on each day (dinner) from the run-in day (day 0) until lunch on day 7.

112

Participants were allowed to drink coffee between 8 am and 12 (i.e. for breakfast and as

113

desired, until 12 am). Urine was collected 4 times/d (first morning urine, before lunch, before

114

dinner, and at bed time), from the morning of day 1 until the evening of day 6. Urine

115

specimens were collected into sterile tubes (Sterilin, Aberbargoed, UK) and kept in the fridge

116

for a maximum of 12 hours before storage at -40°C until analysis. The study was approved by

5 ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

Page 6 of 29

117

Imperial College London Research Ethics Committee and is registered at clinicaltrials.gov as

118

NCT01102049.

119 120

Coffee Study

121

A food study was undertaken to characterize the excretion profile of 2-furoylglycine after

122

coffee consumption. Five volunteers (3 women and 2 men; age range: 24–34 y) who met the

123

inclusion criteria of being self-assessed as healthy, aged 18–45 y, nonsmokers, a BMI of 18–

124

30 kg/m2 and an absence of regular drug intake and regular food supplement intake were

125

recruited. The number of volunteers was based on power calculations with values from the

126

previous dietary intervention study with α = 0.05 and power of the test 0.80. Other than

127

coffee consumption, participants were not restricted in their choice of foods for the duration

128

of the study. Day 0 served as a run-in day, where no coffee consumption was allowed; a

129

coffee challenge (1 espresso with or without milk) was administered on day 1 at 10 am and

130

spot urine specimens were collected on day 1 (i.e., baseline samples, 6 times/d, collected at 8

131

am, 10 am, 12 am, 4 pm, and 8 pm and at bed time); and at 8 am and 10 am on day 2 (study

132

finish). Urine specimens were collected in sterile tubes (Sterilin) and kept in the fridge before

133

they were stored at -80 °C until analysis.

134 135

Standard Spiking experiment

136

The chemical standard of 2-furoylglycine was purchased from Sigma Aldrich, was dissolved

137

in NMR buffer and analyzed with 1H NMR spectroscopy. Furthermore, a representative urine

138

sample from time point “12 am” was analyzed with the same spectroscopic settings as the

139

standard. Lastly, a 1H NMR spectrum of the same urine, spiked with 2-furoylglycine in

140

appropriate physiological amounts was acquired and the resulting spectrum compared with

141

the original spectrum.

6 ACS Paragon Plus Environment

Page 7 of 29

Journal of Agricultural and Food Chemistry

142 143

Coffee analysis

144

Three different kinds of coffee were analyzed, espresso, instant espresso and chicory coffee.

145

Coffees were prepared as per normal consumption, i.e. 12.5 g beans power per 50 mL

146

extraction water, 15 g instant espresso powder per 50 mL water and 8 g chicory coffee

147

powder per 200 mL water, and an aliquot of 50 µL was mixed with 200 µL NMR buffer (90

148

% D2O 500 mM PO4 buffer with 0.1 % TSP, pH 7.4), centrifuged and transferred to 3 mm

149

outer diameter NMR Bruker Match tubes (Hilgenberg GmbH, Malsfeld, Germany).

150 151

NMR spectroscopic analysis

152

Urine analysis

153

An aliquot of each urine sample was analyzed by 1H NMR analysis. Urine and NMR buffer

154

were mixed 2:1, centrifuged and 550uL of the supernatant transferred to 5 mm (dietary

155

intervention study) or 120 uL to 3 mm (coffee study) outer diameter NMR Bruker Match

156

tubes. Urine specimens of the dietary intervention study were acquired on a Bruker 600 MHz

157

spectrometer (Bruker Biospin, Rheinstetten, Germany) that operated at 600.13 MHz. The

158

spectrometer used a standard one-dimensional pulse-sequence [recycle delay (RD)-90°-t1-

159

90°-mixing time (tm)-90°-acquire] free-induction decay (FID) with water-suppression

160

irradiation during a RD of 2 s with tm set to 100 ms and a 90° pulse set to 10 µs. Spectra

161

were acquired with 128 scans into 32 K data points with a spectral width of 12,000 Hz. Urine

162

specimens from the coffee study were analyzed on a Bruker 800 MHz spectrometer operating

163

at 800.35 MHz with a quadrupole inverse cryogenic probe. A standard 1-dimensional (1D)

164

pulse sequence [recycle delay (RD)-90°-t1-90°-tm-90°-acquire FID] was acquired, with water

165

suppression irradiation during RD of 2 s, mixing time (tm) set on 200 ms and a 90° pulse set

166

to 10.13 µs, collecting 512 scans into 64 K data points with a spectral width of 12 ppm. All

7 ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

Page 8 of 29

167

spectra were manually phased, baseline corrected and calibrated to TSP (δ 0.00) with

168

TopSpin 3.2 (Bruker BioSpin, Rheinstetten, Germany). Data were imported to Matlab

169

(Mathworks, Massachusetts, USA) and further processed i.e. water region removed (δ 4.70 –

170

5.21). The spectra were normalized by using a probabilistic quotient normalization algorithm

171

(49) to account for urinary dilution effects and aligned by using a recursive segment-wise

172

peak-alignment algorithm (50). Relative quantification of metabolites of interest was done by

173

integration of the area under the curve (AUC), as outlined in Heinzmann et al. (46) and

174

expressed as relative measure to creatinine concentration.

175 176

Coffee analysis

177

Coffee samples were analyzed with a Bruker 800 MHz spectrometer equipped with a

178

quadrupole inverse cryogenic probe, wherewith 1H NMR spectra and 2D spectra (TOCSY

179

and HSQC) where acquired. For 2D NMR spectra, phase-sensitive sensitivity-improved 2D

180

TOCSY with WATERGATE (3-9-19) and using DIPSI-2, were acquired. For each spectrum,

181

19228 × 1024 data points were collected using 32 scans per increment, an acquisition time of

182

1 s, and 16 dummy scans. The spectral widths were set to 12 and 12 ppm in the F2 and F1

183

dimensions, respectively. For the 2D 1H-13C HSQC spectra, phase-sensitive ge-2D-HSQC

184

using PEP and adiabatic pulses for inversion and refocusing with gradients were used. For

185

each 2D spectrum, 4096 × 1024 data points were collected using 32 scans per increment, an

186

acquisition time of 0.25 s, and 16 dummy scans. The spectral widths were set to 12 and 230

187

ppm in the proton and carbon dimensions, respectively. Processing of the spectra was carried

188

out in TopSpin 3.2. FIDs were multiplied by an exponential decaying function corresponding

189

to a line broadening of 0.3 Hz before Fourier transformation. All spectra were manually

190

phased, baseline corrected and calibrated to TSP (δ 0.00).

191

8 ACS Paragon Plus Environment

Page 9 of 29

Journal of Agricultural and Food Chemistry

192

Multivariate analysis

193

All timed urine specimens of the dietary intervention study that were collected at lunchtime

194

were defined as “coffee samples”, all others (first morning urine, before dinner and before

195

bed) as “no coffee samples”. Volunteers participated in the dietary intervention trial for six

196

days; therefore 24 urine samples per participant were collected. Pairwise orthogonal partial

197

least squares discriminant analysis (OPLS-DA) (51) was carried out with Matlab software.

198

The OPLS-DA loading plots were created with an in-house Matlab script according to the

199

method of Cloarec et al. (52).

200 201 202 203 204 205 206 207

9 ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

208

Page 10 of 29

Results and Discussion

209 210

Discovery Phase: Non-targeted 1H NMR metabolic profiling of urine from a 6-day dietary

211

intervention study

212

To discover novel biomarkers of food consumption, we performed a human dietary

213

intervention trial (n = 8), where participants consumed a standardized breakfast and lunch,

214

and varying dinner each day (for more details see also Heinzmann et al. (46)). As part of the

215

dietary protocol, participants were allowed coffee for breakfast and until 12 am each day (SI

216

Figure 1). Six participants chose coffee, one participant consumed chicory coffee and one

217

deviated from the protocol and drank Earl Grey tea every day. Urinary metabolite profiles

218

were acquired to enable comparison of metabolites excreted after coffee consumption. OPLS-

219

DA analysis of the urines from coffee-drinking volunteers revealed putative biomarker(s)

220

with chemical shifts at δ 8.79 (d), δ 7.20, δ 6.65 (dd), δ 4.40 (s). 2D HSQC NMR suggested

221

these shifts derived from two different metabolites (see SI Figure 2), namely 2-furoylglycine

222

(2-FG) and N-methylpyridinium (NMP). Confirmation of the chemical structures was carried

223

out by standard spiking experiments of the chemical standards 2-FG and NMP into urine

224

samples (Figure 2 and SI Figure 3). 1H NMR shifts of 2-FG standard were δ 6.65 (dd, H-C4

225

of furoyl), δ 7.20 (dd, H-C3 of furoyl), δ 7.71 (d, H-C5 of furoyl), δ 3.93 (s, CH2 of glycine).

226

The standard matched the prediction from the OPLS-DA analysis, with the exception of the

227

two latter signals, which were overlapped with other metabolites and did not resolve in the

228

OPLS-DA loadings plot. NMP has previously been linked to coffee consumption by Lang et

229

al. (41). Urinary excretion of the glycine conjugate of derivatized furan, 2-FG, has not, to our

230

knowledge, been reported to be associated with coffee consumption. In serum, however, it

231

has been previously detected (53). Integration of the H-C3 of furoyl signal confirmed high

232

excretion of 2-FG in coffee consumers especially in the urine samples at lunch time. Neither

10 ACS Paragon Plus Environment

Page 11 of 29

Journal of Agricultural and Food Chemistry

233

chicory coffee nor Earl Grey tea consumption resulted in excretion of 2-FG with urine

234

(Figure 3), and inspection of urine spectra post consumption of these coffee alternatives did

235

not show 1H NMR-detectable quantities of 2-FG (SI Figure 4). Interestingly, hippurate,

236

which is discussed as a potential biomarker for coffee consumption (37), correlated

237

negatively with coffee consumption. The coffee consumption period was closely aligned with

238

breakfast, which was not rich in polyphenols, while dinner (i.e. part of the „non-coffee

239

sample“ group) was always rich in fruit and vegetables (46) and polyphenols can be

240

metabolized to hippurate (45, 54).

241 242

Dietary sourcing phase: Possible sources of 2-furoylglycine in coffee

243

To investigate the origin of 2-FG in participant’s urine samples after coffee consumption, we

244

interrogated existing literature on furan derivates in different coffees, their concentration and

245

possible degradation pathways in humans after consumption (Figure 4). Indeed, furan

246

metabolites arise through roasting of coffee beans via the Maillard reaction (55) and highest

247

concentrations can be found in roasted ground coffee (6900 µg/kg) and considerably lower

248

amounts in instant coffee (569 µg/kg) (56-59). The amount of furan varies, depending on

249

coffee bean species and roast degree (33). Other sources of furan exist, but provide much

250

lower quantities, e.g. baby foods with up to 29 µg/kg and soups and sauces (< 24 µg/kg) and

251

0-4 µg/kg in tea (55, 60, 61) and are therefore not expected to interfere with 2-FG excretion.

252

Dependent on the chosen coffee brewing procedure, about 2-50% of the bean-derived furans

253

get extracted into coffee (59). Moon et al. have identified furans in coffee and found 7

254

different furan derivatives such as furfuryl alcohol and furfural (34). After consumption,

255

furans undergo conversion to furfural and 2-furoic acid, then conjugation with glycine to 2-

256

FG, which can then be excreted via the kidney (62-64), see Figure 4. Remarkably, while the

11 ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

Page 12 of 29

257

roasting process can potentially produce furan and various 2-furan metabolites, the human

258

metabolism reduces such diversity to a single metabolite being excreted, namely 2-FG.

259

From our 1H NMR spectral analysis, we detected furan derivatives such as 2-furoic acid and

260

furfuryl alcohol in relatively high quantities in espresso (Figure 5 and SI Figure 6). Instant

261

espresso also contained 2-furoic acid, and much lower quantities were found in chicory

262

coffee. This overview of furan derivates is in consensus with suggested furan concentrations

263

in existing literature (33, 34, 57-59). Furfuryl alcohol was not found in instant espresso or

264

chicory coffee. Trigonelline and its roasting product NMP could be found in espresso and

265

instant espresso but not in chicory coffee. An additional furan derivate, 5-

266

hydroxymethylfurfural, appeared in instant espresso and in high amounts in chicory coffee,

267

and only little amounts in espresso. This metabolite is proposed to get metabolized to 5-

268

hydroxymethylfuroic acid and 2,5-furandicarboxylfuroic acid and their glycine adducts (65)

269

and is therefore not expected to influence 2-FG excretion in the chicory coffee or instant

270

espresso consumer.

271 272

Confirmation Phase: Excretion kinetics of 2-furoylglycine after coffee consumption

273

In order to confirm the putative biomarker and investigate the mode of excretion, we carried

274

out an additional coffee intervention study where participants avoided coffee for 24 hours and

275

then collected several timed spot urine samples over 24 hours after a single dose of espresso.

276

Excretion of 2-FG was quantified by the ratio of area under the curve integration of 2-FG (δ

277

6.640-6.653) and creatinine (δ 4.0405-4.0475). All participants showed a maximal excretion

278

of 2-FG after 2 hours (p=0.0002) and a rapid decline to near baseline after 24 hours (p=0.74),

279

as shown in Figure 6. In more detail, the mean value of 2-FG/creatinine ratio was 0.0038 and

280

0.0041 2 and 0 hrs pre coffee consumption, where this value is a result of baseline and other

281

peak background integration. At 2 hours post consumption the value increased to 0.031,

12 ACS Paragon Plus Environment

Page 13 of 29

Journal of Agricultural and Food Chemistry

282

dropped rapidly to 0.011 4 hours post consumption and further declined to 0.0044 after 24

283

hours. The inter-individual variation was minimal and all participants showed a similar

284

trajectory (Figure 6). Deviation of the excretion curve, e.g. volunteer A did not decline to

285

baseline after 24 hours, was largely attributed to peak overlap in the spectral region of 2-FG.

286

Overall, the excretion can be described as first order excretion kinetics, as evidenced by a fast

287

accumulation of the metabolite in urine and decline to baseline within 24 hours. It can be

288

discussed however, that more sensitive analytical chemistry measurements such as UPLC-

289

MS might allow detection of 2-FG for a longer period (66). This has been shown by Lang et

290

al. (41), where NMP could be detected up to 5 days post coffee consumption. For

291

comparison, NMP showed similar excretion kinetics to 2-FG (SI Figure 5).

292 293

In summary, we introduced a novel biomarker for coffee consumption, by combining non-

294

targeted 1H NMR metabolic profiling in a nutritional intervention study, investigation of

295

possible dietary sources of the biomarker and finally validation of the putative marker in a

296

second food intervention study. In contrast to previously identified biomarkers such as

297

caffeine and chlorogenic acid degradation products we identified a biomarker that is

298

dependent on the roasting procedure of the coffee bean, and therefore not influenced by

299

consumption of tea, fruit and vegetables or caffeine containing energy drinks, which makes it

300

highly specific to coffee. As a next step, the biomarker could now be further validated in a

301

larger cohort, where coffee drinking behavior, different coffee types and varying amounts of

302

ingested coffee are recorded and matching urine samples are available for quantification of 2-

303

FG to assess its quantitative rather than qualitative value. A combination of data from a well-

304

monitored coffee drinking cohort as assessed by urinary 2-FG quantification with e.g. CVD

305

risk factors such as blood pressure, blood lipid parameters and BMI should deliver valuable

306

information on potential health benefit of coffee consumption on disease risk and disease

13 ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

307

progression. For example, urinary metabolic profiling data from the INTERMAP study

308

highlighted the here assigned coffee biomarker to be inversely associated with BMI (67).

309

Taking advantage of the fact that different coffee biomarkers derive from different

310

ingredients of coffee, a simultaneous analysis of several coffee biomarkers should pave the

311

way to design a biomarker pattern for sensitive and highly specific detection of coffee

312

consumption in individuals and allow meaningful conclusion on the influence of coffee

313

consumption in health and disease.

Page 14 of 29

314

14 ACS Paragon Plus Environment

Page 15 of 29

Journal of Agricultural and Food Chemistry

315

Abbreviations Used

316

NMR, nuclear magnetic resonance

317

TSP, trimethylsilyl-tetradeuteropropionic acid

318

FID, free induction decay

319

HSQC, heteronuclear single quantum coherence

320

TOCSY, total correlation spectroscopy

321

DIPSI, decoupling in the presence of scalar interactions

322

OPLS-DA, orthogonal partial least squares discriminant analysis

323

PEP, preservation of equivalent pathways

324

WATERGATE, water suppression by gradient tailored excitation

325

2-FG, 2-furoylglycine

326

NMP, N-methylpyridinium

327

AUC, area under the curve

328 329

Acknowledgement

330

The authors would like to thank Roman Lang and Thomas Hofmann from Technische

331

Universität München for the kind donation of the chemical standard N-methylpyridinium.

332 333

The authors declare no competing financial interest.

334 335

Supporting Information Description

336

Figure 1: Study design for the 6-day dietary intervention study with n=8 volunteers.

337

Figure 2: Two-dimensional HSQC spectrum of spiked urine with assignments for 2-FG and

338

NMP.

15 ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

Page 16 of 29

339

Figure 3: 1H NMR urine profiles of a sample obtained after coffee consumption with standard

340

addition of 2-furoylglycine and N-methylpyridinium.

341

Figure 4: Urine spectral region of 2-FG (6.63 – 6.67 ppm) in all volunteers.

342

Figure 5: (A) Excretion kinetics of 2-furoylglycine and (B) of N-methylpyridinium after

343

coffee consumption (n=5) over 26 hours.

344

Figure 6: Two-dimensional NMR spectroscopy (1H-1H-TOCSY) of (A) espresso coffee, (B)

345

instant espresso and (C) chiory coffee.

346

16 ACS Paragon Plus Environment

Page 17 of 29

Journal of Agricultural and Food Chemistry

347

References

348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394

1. Fredholm, B. B.; Battig, K.; Holmen, J.; Nehlig, A.; Zvartau, E. E., Actions of caffeine in the brain with special reference to factors that contribute to its widespread use. Pharmacol. Rev. 1999, 51, 83-133. 2. Gilbert, R. M., Caffeine consumption. Prog. Clin. Biol. Res. 1984, 158, 185-213. 3. Myers, M. G., Effects of caffeine on blood pressure. Arch. Intern. Med. 1988, 148, 1189-93. 4. Hindmarch, I.; Rigney, U.; Stanley, N.; Quinlan, P.; Rycroft, J.; Lane, J., A naturalistic investigation of the effects of day-long consumption of tea, coffee and water on alertness, sleep onset and sleep quality. Psychopharmacology 2000, 149, 203-216. 5. Smith, A. P.; Brockman, P.; Flynn, R.; Maben, A.; Thomas, M., Investigation of the effects of coffee on alertness and performance during the day and night. Neuropsychobiology 1993, 27, 21723. 6. Doherty, M.; Smith, P. M., Effects of caffeine ingestion on rating of perceived exertion during and after exercise: a meta-analysis. Scand. J. Med. Sci. Sports 2005, 15, 69-78. 7. Doherty, M.; Smith, P. M., Effects of caffeine ingestion on exercise testing: A meta-analysis. International Journal of Sport Nutrition and Exercise Metabolism 2004, 14, 626-646. 8. Dulloo, A. G.; Geissler, C. A.; Horton, T.; Collins, A.; Miller, D. S., Normal caffeine consumption: influence on thermogenesis and daily energy expenditure in lean and postobese human volunteers. The American journal of clinical nutrition 1989, 49, 44-50. 9. Koot, P.; Deurenberg, P., Comparison of changes in energy expenditure and body temperatures after caffeine consumption. Ann. Nutr. Metab. 1995, 39, 135-42. 10. Bracco, D.; Ferrarra, J. M.; Arnaud, M. J.; Jequier, E.; Schutz, Y., Effects of caffeine on energy metabolism, heart rate, and methylxanthine metabolism in lean and obese women. The American journal of physiology 1995, 269, E671-8. 11. Maia, L.; de Mendonca, A., Does caffeine intake protect from Alzheimer's disease? Eur. J. Neurol. 2002, 9, 377-382. 12. Santos, C.; Costa, J.; Santos, J.; Vaz-Carneiro, A.; Lunet, N., Caffeine Intake and Dementia: Systematic Review and Meta-Analysis. Journal of Alzheimers Disease 2010, 20, S187-S204. 13. Eskelinen, M. H.; Kivipelto, M., Caffeine as a Protective Factor in Dementia and Alzheimer's Disease. Journal of Alzheimers Disease 2010, 20, S167-S174. 14. Hernan, M. A.; Takkouche, B.; Caamano-Isorna, F.; Gestal-Otero, J. J., A meta-analysis of coffee drinking, cigarette smoking, and the risk of Parkinson's disease. Ann. Neurol. 2002, 52, 276284. 15. Hu, G.; Bidel, S.; Jousilahti, P.; Antikainen, R.; Tuomilehto, J., Coffee and tea consumption and the risk of Parkinson's disease. Mov. Disord. 2007, 22, 2242-2248. 16. Ross, G. W.; Abbott, R. D.; Petrovitch, H.; Morens, D. M.; Grandinetti, A.; Tung, K. H.; Tanner, C. M.; Masaki, K. H.; Blanchette, P. L.; Curb, J. D.; Popper, J. S.; White, L. R., Association of coffee and caffeine intake with the risk of Parkinson disease. Jama-Journal of the American Medical Association 2000, 283, 2674-2679. 17. Klatsky, A. L.; Morton, C.; Udaltsova, N.; Friedman, G. D., Coffee, cirrhosis, and transaminase enzymes. Arch. Intern. Med. 2006, 166, 1190-1195. 18. Gallus, S.; Tavani, A.; Negri, E.; La Vecchia, C., Does coffee protect against liver cirrhosis? Ann. Epidemiol. 2002, 12, 202-205. 19. Larsson, S. C.; Wolk, A., Coffee consumption and risk of liver cancer: A meta-analysis. Gastroenterology 2007, 132, 1740-1745. 20. Sinha, R.; Cross, A. J.; Daniel, C. R.; Graubard, B. I.; Wu, J. W.; Hollenbeck, A. R.; Gunter, M. J.; Park, Y.; Freedman, N. D., Caffeinated and decaffeinated coffee and tea intakes and risk of colorectal cancer in a large prospective study. Am. J. Clin. Nutr. 2012, 96, 374-381.

17 ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443

Page 18 of 29

21. Lopez-Garcia, E.; van Dam, R. M.; Willett, W. C.; Rimm, E. B.; Manson, J. E.; Stampfer, M. J.; Rexrode, K. M.; Hu, F. B., Coffee consumption and coronary heart disease in men and women - A prospective cohort study. Circulation 2006, 113, 2045-2053. 22. Sofi, F.; Conti, A. A.; Gori, A. M.; Eliana Luisi, M. L.; Casini, A.; Abbate, R.; Gensini, G. F., Coffee consumption and risk of coronary heart disease: A meta-analysis. Nutrition Metabolism and Cardiovascular Diseases 2007, 17, 209-223. 23. Larsson, S. C.; Orsini, N., Coffee Consumption and Risk of Stroke: A Dose-Response MetaAnalysis of Prospective Studies. Am. J. Epidemiol. 2011, 174, 993-1001. 24. Huxley, R.; Lee, C. M. Y.; Barzi, F.; Timmermeister, L.; Czernichow, S.; Perkovic, V.; Grobbee, D. E.; Batty, D.; Woodward, M., Coffee, Decaffeinated Coffee, and Tea Consumption in Relation to Incident Type 2 Diabetes Mellitus A Systematic Review With Meta-analysis. Arch. Intern. Med. 2009, 169, 2053-2063. 25. Ding, M.; Bhupathiraju, S. N.; Chen, M.; van Dam, R. M.; Hu, F. B., Caffeinated and Decaffeinated Coffee Consumption and Risk of Type 2 Diabetes: A Systematic Review and a DoseResponse Meta-analysis. Diabetes Care 2014, 37, 569-586. 26. Lopez-Garcia, E.; van Dam, R. M.; Li, T. Y.; Rodriguez-Artalejo, F.; Hu, F. B., The relationship of coffee consumption with mortality. Ann. Intern. Med. 2008, 148, 904-+. 27. Bidel, S.; Hu, G.; Qiao, Q.; Jousilahti, P.; Antikainen, R.; Tuomilehto, J., Coffee consumption and risk of total and cardiovascular mortality among patients with type 2 diabetes. Diabetologia 2006, 49, 2618-2626. 28. Spiller, M. A., The chemical components of coffee. Prog. Clin. Biol. Res. 1984, 158, 91-147. 29. Yanagimoto, K.; Ochi, H.; Lee, K. G.; Shibamoto, T., Antioxidative activities of fractions obtained from brewed coffee. J. Agric. Food Chem. 2004, 52, 592-596. 30. Urgert, R.; Katan, M. B., The cholesterol-raising factor from coffee beans. Annu. Rev. Nutr. 1997, 17, 305-324. 31. Casiglia, E.; Spolaore, P.; Ginocchio, G.; Ambrosio, G. B., Unexpected effects of coffee consumption on liver enzymes. Eur. J. Epidemiol. 1993, 9, 293-7. 32. Moser, G. J.; Foley, J.; Burnett, M.; Goldsworthy, T. L.; Maronpot, R., Furan-induced doseresponse relationships for liver cytotoxicity, cell proliferation, and tumorigenicity (furan-induced liver tumorigenicity). Exp. Toxicol. Pathol. 2009, 61, 101-111. 33. Arisseto, A. P.; Vicente, E.; Ueno, M. S.; Amelia, S.; Tfouni, V.; De Figueiredo Toledo, M. C., Furan Levels in Coffee As Influenced by Species, Roast Degree, and Brewing Procedures. J. Agric. Food Chem. 2011, 59, 3118-3124. 34. Moon, J.-K.; Shibamoto, T., Role of Roasting Conditions in the Profile of Volatile Flavor Chemicals Formed from Coffee Beans. J. Agric. Food Chem. 2009, 57, 5823-5831. 35. Bingham, S. A., Limitations of the various methods for collecting dietary intake data Ann. Nutr. Metab. 1991, 35, 117-127. 36. Bates, C. J., Biochemical markers of nutrient intake. In Design Concepts in Nutritional Epidemiology, Nelson, B. M. M. M., Ed. Oxford University Press: Oxford, 1991; pp 192-165. 37. Rothwell, J. A.; Fillatre, Y.; Martin, J.-F.; Lyan, B.; Pujos-Guillot, E.; Fezeu, L.; Hercberg, S.; Comte, B.; Galan, P.; Touvier, M.; Manach, C., New Biomarkers of Coffee Consumption Identified by the Non-Targeted Metabolomic Profiling of Cohort Study Subjects. PLoS ONE 2014, 9. 38. Lloyd, A. J.; Beckmann, M.; Haldar, S.; Seal, C.; Brandt, K.; Draper, J., Data-driven strategy for the discovery of potential urinary biomarkers of habitual dietary exposure. Am. J. Clin. Nutr. 2013, 97, 377-389. 39. Stalmach, A.; Mullen, W.; Barron, D.; Uchida, K.; Yokota, T.; Cavin, C.; Steiling, H.; Williamson, G.; Crozier, A., Metabolite Profiling of Hydroxycinnamate Derivatives in Plasma and Urine after the Ingestion of Coffee by Humans: Identification of Biomarkers of Coffee Consumption. Drug Metab. Disposition 2009, 37, 1749-1758.

18 ACS Paragon Plus Environment

Page 19 of 29

444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494

Journal of Agricultural and Food Chemistry

40. Ito, H.; Gonthier, M. P.; Manach, C.; Morand, C.; Mennen, L.; Remesy, C.; Scalbert, A., Polyphenol levels in human urine after intake of six different polyphenol-rich beverages. Br. J. Nutr. 2005, 94, 500-509. 41. Lang, R.; Wahl, A.; Stark, T.; Hofmann, T., Urinary N-methylpyridinium and trigonelline as candidate dietary biomarkers of coffee consumption. Mol. Nutr. Food Res. 2011, 55, 1613-1623. 42. Mennen, L. I.; Sapinho, D.; Ito, H.; Bertrais, S.; Galan, P.; Hercberg, S.; Scalbert, A., Urinary flavonoids and phenolic acids as biomarkers of intake for polyphenol-rich foods. Br. J. Nutr. 2006, 96, 191-198. 43. Hervert-Hernandez, D.; Goni, I., Dietary Polyphenols and Human Gut Microbiota: a Review. Food Rev. Int. 2011, 27, 154-169. 44. Walker, A. W.; Ince, J.; Duncan, S. H.; Webster, L. M.; Holtrop, G.; Ze, X.; Brown, D.; Stares, M. D.; Scott, P.; Bergerat, A.; Louis, P.; McIntosh, F.; Johnstone, A. M.; Lobley, G. E.; Parkhill, J.; Flint, H. J., Dominant and diet-responsive groups of bacteria within the human colonic microbiota. Isme Journal 2011, 5, 220-230. 45. Heinzmann, S. S.; Merrifield, C. A.; Rezzi, S.; Kochhar, S.; Lindon, J. C.; Holmes, E.; Nicholson, J. K., Stability and Robustness of Human Metabolic Phenotypes in Response to Sequential Food Challenges. Journal of Proteome Research 2011. 46. Heinzmann, S. S.; Brown, I. J.; Chan, Q.; Bictash, M.; Dumas, M.-E.; Kochhar, S.; Stamler, J.; Holmes, E.; Elliott, P.; Nicholson, J. K., Metabolic profiling strategy for discovery of nutritional biomarkers: proline betaine as a marker of citrus consumption. Am. J. Clin. Nutr. 2010, 92, 436-443. 47. O'Sullivan, A.; Gibney, M. J.; Brennan, L., Dietary intake patterns are reflected in metabolomic profiles: potential role in dietary assessment studies. Am. J. Clin. Nutr. 2011, 93, 314321. 48. Lloyd, A. J.; Fave, G.; Beckmann, M.; Lin, W.; Tailliart, K.; Xie, L.; Mathers, J. C.; Draper, J., Use of mass spectrometry fingerprinting to identify urinary metabolites after consumption of specific foods. Am. J. Clin. Nutr. 2011, 94, 981-991. 49. Dieterle, F.; Ross, A.; Schlotterbeck, G.; Senn, H., Probabilistic quotient normalization as robust method to account for dilution of complex biological mixtures. Application in H-1 NMR metabonomics. AnaCh 2006, 78, 4281-4290. 50. Veselkov, K. A.; Lindon, J. C.; Ebbels, T. M. D.; Crockford, D.; Volynkin, V. V.; Holmes, E.; Davies, D. B.; Nicholson, J. K., Recursive Segment-Wise Peak Alignment of Biological 1H NMR Spectra for Improved Metabolic Biomarker Recovery. AnaCh 2009, 81, 56-66. 51. Trygg, J.; Wold, S., PLS regression on wavelet compressed NIR spectra. Chemometrics Intellig. Lab. Syst. 1998, 42, 209-220. 52. Cloarec, O.; Dumas, M. E.; Craig, A.; Barton, R. H.; Trygg, J.; Hudson, J.; Blancher, C.; Gauguier, D.; Lindon, J. C.; Holmes, E.; Nicholson, J., Statistical total correlation spectroscopy: An exploratory approach for latent biomarker identification from metabolic H-1 NMR data sets. AnaCh 2005, 77, 1282-1289. 53. Guertin, K. A.; Loftfield, E.; Boca, S. M.; Sampson, J. N.; Moore, S. C.; Xiao, Q.; Huang, W.-Y.; Xiong, X.; Freedman, N. D.; Cross, A. J.; Sinha, R., Serum biomarkers of habitual coffee consumption may provide insight into the mechanism underlying the association between coffee consumption and colorectal cancer. Am. J. Clin. Nutr. 2015, 101, 1000-1011. 54. van Duijnhoven, F. J. B.; Bueno-De-Mesquita, H. B.; Ferrari, P.; Jenab, M.; Boshuizen, H. C.; Ros, M. M.; Casagrande, C.; Tjonneland, A.; Olsen, A.; Overvad, K.; Thorlacius-Ussing, O.; ClavelChapelon, F.; Boutron-Ruault, M. C.; Morois, S.; Kaaks, R.; Linseisen, J.; Boeing, H.; Noothlings, U.; Trichopoulou, A.; Trichopoulos, D.; Misirli, G.; Palli, D.; Sieri, S.; Panico, S.; Tumino, R.; Vineis, P.; Peeters, P. H. M.; van Gils, C. H.; Ocke, M. C.; Lund, E.; Engeset, D.; Skeie, G.; Suarez, L. R.; Gonzalez, C. A.; Sanchez, M. J.; Dorronsoro, M.; Navarro, C.; Barricarte, A.; Berglund, G.; Manjer, J.; Hallmans, G.; Palmqvist, R.; Bingham, S. A.; Khaw, K. T.; Key, T. J.; Allen, N. E.; Boffetta, P.; Slimani, N.; Rinaldi, S.; Gallo, V.; Norat, T.; Riboli, E., Fruit, vegetables, and colorectal cancer risk: the European Prospective Investigation into Cancer and Nutrition. Am. J. Clin. Nutr. 2009, 89, 1441-1452. 19 ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527

Page 20 of 29

55. Maarse, H.; Visscher, C. A.; Willimsens, L. C., Volatile Compounds in Food: Qualitative and Quantitative Data. 7 ed.; Centraal Instituut voor Voedingsonderzoek, TNO, Zeist.: 1994; Vol. 3. 56. Hasnip, S.; Crews, C.; Castle, L., Some factors affecting the formation of furan in heated foods. Food Addit. Contam. 2006, 23, 219-227. 57. Zoller, O.; Sager, F.; Reinhard, H., Furan in food: Headspace method and product survey. Food Addit. Contam. 2007, 24, 91-107. 58. Kuballa, T.; Stier, S.; Strichow, N., Furan in Kaffee und Kaffeegetränken. Deutsche Lebensmittel-Rundschau 2005, 101, 229-235. 59. Guenther, H.; Hoenicke, K.; Biesterveld, S.; Gerhard-Rieben, E.; Lantz, I., Furan in coffee: pilot studies on formation during roasting and losses during production steps and consumer handling. Food Additives and Contaminants Part a-Chemistry Analysis Control Exposure & Risk Assessment 2010, 27, 283-290. 60. Moro, S.; Chipman, J. K.; Wegener, J.-W.; Hamberger, C.; Dekant, W.; Mally, A., Furan in heat-treated foods: Formation, exposure, toxicity, and aspects of risk assessment. Mol. Nutr. Food Res. 2012, 56, 1197-1211. 61. Stofberg, J.; Grundschober, F., Consumption ratio and food predominance of flavouring materials. Perfumer Flavorist 1987, 12, 27. 62. Rice, E. W., Furfural: exogenous precursor of certain urinary furans and possible toxicologic agent in humans. Clin. Chem. 1972, 18, 1550-1. 63. Nomeir, A. A.; Silveira, D. M.; McComish, M. F.; Chadwick, M., Comparative metabolism and disposition of furfural and furfuryl alcohol in rats. Drug Metab. Dispos. 1992, 20, 198-204. 64. Parkash, M. K.; Caldwell, J., Metabolism and excretion of 14C furfural in the rat and mouse. Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association 1994, 32, 887-95. 65. Hardt-Stremayr, M.; Mattioli, S.; Greilberger, J.; Stiegler, P.; Matzi, V.; Schmid, M. G.; Wintersteiger, R., Determination of metabolites of 5-hydroxymethylfurfural in human urine after oral application. J. Sep. Sci. 2013, 36, 670-676. 66. Wishart, D. S., Advances in metabolite identification. Bioanalysis 2011, 3, 1769-1782. 67. Elliott, P.; Posma, J. M.; Chan, Q.; Garcia-Perez, I.; Wijeyesekera, A.; Bictash, M.; Ebbels, T. M. D.; Ueshima, H.; Zhao, L.; van Horn, L.; Daviglus, M.; Stamler, J.; Holmes, E.; Nicholson, J. K., Urinary metabolic signatures of human adiposity. Science Translational Medicine 2015, 7.

20 ACS Paragon Plus Environment

Page 21 of 29

528

Journal of Agricultural and Food Chemistry

Figure Captions

529 530

Figure 1: OPLS-DA scores and loadings plots of urine specimen after coffee challenge (12

531

am) vs all other urine collection (8 am, 8 pm, bedtime). (A) The scores plot shows a clear

532

separation of coffee vs no coffee groups with a goodness of fit (R2Y) of 0.58 and predictive

533

value (Q2Y) of 0.22. (B) Loadings plot of the coffee challenge indicates putative biomarkers

534

with chemical shifts at a δ 8.79 (d), b δ 7.20, c δ 6.65 (dd), d δ 4.40 (s), with highest

535

correlation coefficient for δ 6.65 (dd).

536 537

Figure 2: Standard addition experiment of 2-furoylglycine to a urine sample. Black: urine

538

sample collected after coffee consumption, green: spiking of 2-furoylglycine to the same

539

urine sample for confirmation of the assumed chemical structure of the biomarker. Chemical

540

shifts are δ 7.71 (d), δ 7.20 (dd), δ 6.65 (dd), δ 3.93 (s).

541 542

Figure 3: Boxplot and individual measurement points (purple) of urinary 2-furoylglycine

543

excretion in volunteers at the 4 different time points. Boxplots are divided into blue: “coffee

544

consumption”, green: “alternative consumption of Earl Grey tea”, magenta: “alternative

545

consumption of Chicory coffee”.

546 547

Figure 4: Summary of origin, extraction, metabolism and excretion of furan metabolites and

548

2-furoylglycine. Abbreviation: 1, furan; 2, furfural; 3, 2-furoic acid; 4, furfuryl alcohol; 5,

549

furfural diacetate; 6, 2-furoylglycine.

550 551

Figure 5: 1H-NMR spectrum of (A) espresso coffee, (B) instant espresso, (C) chicory coffee

552

with main peaks labelled. Spectra of (B) and (C) are enlarged by x 6 and x 24 respectively.

21 ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

Page 22 of 29

553

(D) Two-dimensional NMR spectroscopy (1H-1H-TOCSY) of the aromatic area (δ 9.3 – 6.0)

554

of espresso coffee; 1, trigonelline; 2, N-methylpyridinium; 3, formate; 4, caffeine; 5,

555

chlorogenic acids; 6, fumarate; 7, furfurylalcohol; 8, 2-furoic acid; 9, 5-

556

hydroxymethylfurfural (5-HMF); 10, unknown compound (signals linked in TOCSY).

557 558

Figure 6: Excretion kinetics of 2-furoylglycine after coffee consumption (n=5) over 26

559

hours. Coffee was consumed at 10 am. 2-FG was relatively quantified by integration of the

560

spectral region δ 6.640 – 6.654, including the doublet of doublets at δ 6.647 in relation to

561

creatinine (δ 4.056 – 4.072). The five individuals showed similar trajectory in 2-FG excretion

562

with maximal excretion of the biomarker at 2 hours post coffee consumption and little inter-

563

individual variation.

564

22 ACS Paragon Plus Environment

Page 23 of 29

Journal of Agricultural and Food Chemistry

64x20mm (300 x 300 DPI)

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

72x25mm (300 x 300 DPI)

ACS Paragon Plus Environment

Page 24 of 29

Page 25 of 29

Journal of Agricultural and Food Chemistry

99x95mm (300 x 300 DPI)

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

130x85mm (300 x 300 DPI)

ACS Paragon Plus Environment

Page 26 of 29

Page 27 of 29

Journal of Agricultural and Food Chemistry

214x424mm (300 x 300 DPI)

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

78x62mm (300 x 300 DPI)

ACS Paragon Plus Environment

Page 28 of 29

Page 29 of 29

Journal of Agricultural and Food Chemistry

75x56mm (300 x 300 DPI)

ACS Paragon Plus Environment