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Published in final edited form as: Food Chem. 2013 Sep 12;146:289–298. doi: 10.1016/j.foodchem.2013.08.089

Profiling polyphenols of two diploid strawberry (Fragaria vesca) inbred lines using UHPLC-HRMSn

Jianghao Sun a, Xianjin Liu b, Tianbao Yang c, Janet Slovin d, Pei Chen a,*
PMCID: PMC3902803  NIHMSID: NIHMS527035  PMID: 24176345

Abstract

Phenolic compounds in the fruits of two diploid strawberries (Fragaria vesca f. semperflorens) inbred lines-Ruegen F7-4 (a red-fruited genotype) and YW5AF7 (a yellow-fruited genotype) were characterised using ultra-high-performance liquid chromatography coupled with tandem high-resolution mass spectrometry (UHPLC-HRMSn). The changes of anthocyanin composition during fruit development and between Ruegen F7-4 and YW5AF7 were studied. About 67 phenolic compounds, including taxifolin 3-O-arabinoside, glycosides of quercetin, kaempferol, cyanidin, pelargonidin, peonidin, ellagic acid derivatives, and other flavonols were identified in these two inbred lines. Compared to the regular octoploid strawberry, unique phenolic compounds were found in F. vesca fruits, such as taxifolin 3-O-arabinoside (both) and peonidin 3-O-malonylglucoside (Ruegen F7-4). The results provide the basis for comparative analysis of polyphenolic compounds in yellow and red diploid strawberries, as well as with the cultivated octoploid strawberries.

Keywords: Strawberry, Fragaria vesca, UHPLC, HRMS, Flavonoids, Anthocyanins

1. Introduction

Strawberries are an economically important horticultural crop and much research has been conducted on maximising fruit growth in the field and increasing postharvest fruit quality (Goulas & Manganaris, 2011; Reganold et al., 2010; Shin et al., 2008; Villa-Rojas, Lopez-Malo, & Sosa-Morales, 2011; Wojdylo, Figiel, & Oszmianski, 2009; Yang et al., 2010). In 2011, the worldwide production of strawberries was near 4.6 million tons and the value of strawberry production in the United States valued at over $2 billion (www.faostats.fao.org). Commercial strawberry Fragaria × ananassa is an octoploid (2n = 8 × = 56) hybrid of two octoploid species, Fragaria chiloensis and Fragaria virginiana, native to America (Sun & Shi, 2008). Fragaria vesca is a widely distributed diploid (2n = 2 × = 14) species whose ancestor is believed to be an ancestral genome donor to the octoploid strawberries. The small size of the F. vesca plant, its transformability with Agrobacterium, its small genome and available genome sequence, and the existing inbred lines support F. vesca as a useful reference plant for strawberry {Shulaev, 2011 #11;Slovin, 2009 #12;Kim, 2003 #16263}. Strawberry fruits contain high levels of vitamin C, folate, and phenolic compounds, and are considered to be beneficial to human health. Thus, many studies have been done on the characterisation of these secondary metabolites, their biosynthesis, and their accumulation during fruit development (Bianco et al., 2009; Zhang et al., 2011). The phenolic compounds of regular strawberry fruits, including anthocyanins, proanthocyanindins, flavonols, flavanols, and derivatives of hydroxycinnamic and ellagic acid, are well-studied (Aaby, Ekeberg, & Skrede, 2007; Aaby, Mazur, Nes, & Skrede, 2012; Aaby, Wrolstad, Ekeberg, & Skrede, 2007; Buendia et al., 2010; Hilt et al., 2003; Kelebek & Selli, 2011; Maatta-Riihinen, Kamal-Eldin, & Torronen, 2004). However, there are not much detailed polyphenol content studies on F. versa. In a recently published study on F. versa, agrimoniin was isolated in the fruit of F. vesca and identified as the one of the main ellagitannins (Vrhovsek et al., 2012). High-resolution mass spectrometry (HRMS) has gained popularity in the last few years. HRMS instruments are being used in both quantitative and confirmative food analysis (Kaufmann, 2012). The higher resolution of HRMS provides enough resolving power to calculate the molecular formula for an analyte, so a suggested structure can be confirmed or denied. For example, HRMS can reliably differentiate between a glucosyl (C6H10O5) and caffeoyl (C9H6O3), a rhamnosyl (C6H10O4) and a coumaroyl (C9H6O2), which are commonly seen substituent groups in polyphenols from strawberry while these two pairs of substituent groups exhibit the same mass weights on unit mass spectrometers.

Two inbred lines, F. vesca, YW5AF7 and Ruegen F7-4 have yellow fruit with tan achenes and red fruit with red achenes respectively, and were specifically developed for genetic and genomic studies (Kim et al., 2003). To assist the future molecular, genetic, and genomic studies of F. vesca, it is necessary to perform a detailed study on the polyphenols in these two diploid lines. Thus an ultra-high-performance liquid chromatography (UHPLC) with diode array detection (DAD) and multi-stage high-resolution mass spectrometry (HRMSn) detection method was established for this purpose, which leads to the identification of 67 phenolic compounds, including taxifolin 3-O-arabinoside, glycosides of quercetin, kaempferol, cyanidin, pelargonidin, peonidin, ellagic acid derivatives, and other flavonols.

2. Experimental

2.1. Materials

Diploid strawberry (F. vesca) inbred lines YW5AF7 and Ruegen F7-4, as well as octoploid strawberry (F. × ananassa) cv. Fort Laramie, were grown in a greenhouse with a diurnal rhythm of 16 h light and 8 h darkness following normal cultivation practices. Five fruits (octoploid) and 20 fruits (diploids) were collected from the greenhouse. The fruits at different stages were classified based upon the fruit size and colour of achenes and receptacles. Green: small fruit with green achene and receptacle; turning: fruit with white receptacles and tan (YW5AF7 and Fort Laramie) or red (F7-4) achenes; ripe: ripe fruit with yellow (YW5AF7) or red (F7-4 and Fort Laramie) receptacles (Figure S1). The fruit collection and extraction experiments were repeated at least three times. After harvest, all the fruits from different stages were washed in water, cut into quarters, immediately frozen in liquid nitrogen and kept at −80 °C for future use.

HPLC-grade methanol, acetonitrile, and formic acid were purchased from Sigma-Aldrich (St. Louis, MO). Pelargonidin 3-O-glucoside, cyanidin 3-O-glucoside, peonidin 3-O-glucoside, ellagic acid, quercetin 3-O-glucuronide, quercetin 3-O-glucoside, kaempferol 3-O-glucuronide and (+)-catechin were purchased from Chromadex Inc. (Irvine, CA).

2.2. Sample preparation

One gram of each freezed-dried sample was homogenised with 50 mL of extraction solution (methanol/water/formic acid; 60:40:1 v/v/v) using an Ultra Turrax T18 Basic Disperser (IKA Werke GmbH & Co, Staufen, Germany) for 1 min on ice followed by sonication in an ultrasound bath for 15 min (Branson 3200; Branson, Danbury, CT). The homogenates were then centrifuged at 5000g for 10 min (IEC clinical centrifuge; IEC, Needham Heights, MA). The upper layer was filtered through a 0.22-µm PTFE filter, transferred into a 2-mL HPLC vial, and 2 µL was injected for UHPLC-HRMSn analysis.

2.3. The UHPLC-HRMSn conditions

The UHPLC-HRMSn system consisted of an LTQ Orbitrap XL MS with an Accela 1250 binary pump, a PAL HTC Accela TMO autosampler, an Accela PDA detector (Thermo Fisher Scientific, San Jose, CA), and an Agilent G1316A column compartment (Agilent, Santa Clara, CA). The separation was carried out on a Hypersil Gold C18 column (200 × 2.1 mm, 1.9 µm particle size; Thermo Fisher Scientific, San Jose, CA) with a flow rate of 0.3 mL/min. Mobile phase A was H2O (0.1% formic acid) and B was acetonitrile (0.1% formic acid). The linear gradient was 4–20% B (v/v) from 0 to 40 min, to 35% B at 60 min, to 100% B at 61 min, and was held at 100% B to 65 min for column washing. The column temperature was set at 60 °C and UV/Vis spectra were recorded between 200 and 700 nm. High-accuracy mass measurements were carried out under both positive and negative ionisation modes. The MS conditions were set as follows: sheath gas at 70 (arbitrary units), auxiliary and sweep gas at 10 (arbitrary units), spray voltage at 4.5 kV for positive ionisation mode and 4 kV for negative ionisation mode, capillary temperature at 250 °C, capillary voltage at 40 V for positive ionisation mode and −50 V for negative ionisation mode, and tube lens at 150 V. For FTMS, the mass range is from m/z 100 to 1500 with a resolution of 15,000, AGC target value of 200,000 and 100,000 in full scan and FTMS/MS AGC target at 1e5, isolation width of 1 amu, and max ion injection time of 750 ms; the ion trap settings used were: AGC target value of 30,000 and 10,000 in full scan and MSn mode, respectively, maximum ion injection time of 200 ms. The most intense ion was selected for the data-dependent scan with normalisation collision energy at 35%.

3. Results and discussions

The basic structures of the above mentioned compounds are shown in Figure S2. Since different classes of phenolic compounds exhibit absorbance maxima at different wavelengths, two wavelengths were selected for real-time monitoring: 280 nm for non-anthocyanin phenolic compounds and 520 nm for anthocyanins. HRMSn detection in both the positive and the negative ionisation modes was used to obtain information on the structural features and the conjugated forms of phenolic compounds. Identification of the phenolic compounds was based on chromatographic behaviour, UV/Vis and mass spectra, accurate mass measurements, consecutive MS2–MS4 analyses, and comparison with data in the literature (Buendia et al., 2010; Kelebek & Selli, 2011; Maatta-Riihinen et al., 2004; Mikulic-Petkovsek et al., 2013; Zhang et al., 2011; Zheng, Song, Doncaster, Rowland, & Byers, 2007). Seventy-four compounds, including anthocyanins, dihydroflavonols and flavonols, flavan-3-ols, proanthocyanidins, and ellagic acid and its derivatives were identified from the two F. vesca inbred lines. The basic structures of the abovementioned compounds are shown in Fig. 1 and summarised in Table 1, where the compounds are numbered according to their retention times as shown in typical chromatograms (Fig. 1).

Fig. 1.

Fig. 1

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The HPLC chromatograms of anthocyanin (A, at 520 nm) and non-anthocyanin polyphenols (A, at 280 nm) from F × vesca var. Ruegen.

Table 1.

Compounds identified from Fragaria vesca var. Ruegen and YW5AF7.

Peak
no.		 tR(min) m/z Error
(mmu)		 Formula Adduct MS2 to MS4 data UV λmax
(nm)		 Tentative
identification
1 1.82 341.1083 −0.64 C12H22O12 [M–H]− MS2[341]: 179(100), 161(18), 143(23), 119(13), 113(18), 101(6) MS3[341 → 179]: 161(100), 149(21), 143(97), 131(27), 125(8), 119(45), 113(18), 106(12), 101(8), 89(94), 87(11)MS4[341 → 179 → 161]: 113(100), 101(32), 71(69) – Hexosyl hexose
2 1.89 191.0193 −0.41 C6H8O7 [M–H]− MS2[191]: 173(100), 111(64)MS3[191 → 173]: 155(27), 111(100)MS4[191 → 173 → 111]: 67(100) – Citric acid
3 2.38 191.0194 −0.33 C6H8O7 [M–H]− MS2[191]: 173(20), 111(100)MS3[191 → 111]: 67(100) – Citric acid isomer
4 3.34 629.0411 −0.96 C27H18O18 [M–H]− MS2[629]: 615(31), 613(9), 601(100), 599(9)MS3[629 → 601]: 573(45), 557(16), 529(6), 449(33), 439(6), 431(100), 405(15), 389(7), 387(14), 287(26), 286(13), 261(12)MS4[629 → 601 → 431]: 403(41), 387(62), 371(17), 369(12), 359(8), 343(9), 327(6), 312(6), 299(19), 287(100), 286(94), 285(16), 283(8), 273(10), 271(12), 261(98), 257(8), 245(6), 243(14), 227(9), 225(8), 217(27), 216(10), 215(13), 189(18), 187(7) – Gallotannin
5 3.67 783.0665 −1.3 C34H24O22 [M–H]− MS2[783]: 481(31), 301(100), 275(17)MS3[783 → 301]: 301(36), 300(9), 284(39), 257(100), 229(76), 201(13), 185(27) – bis-HHDP-glucose
6 3.95 947.0433 0.052 C41H24O27 [M–H]− MS2[947]: 929(100), 901(73), 883(16), 875(8) – Unknown ellagitannin
7 5.58 289.0921 −0.761 C12H18O8 [M–H]− MS2[289]: 161(100), 113(6), 101(8)MS3[289 → 161]: 143(28), 129(22), 125(12), 113(62), 101(100), 99(13), 97(14), 89(6), 85(7), 73(10), 71(29) 275,229 Furaneol hexoside
8 6.34 957.0535 −1.041 C89H48O50 [M– 2H]2− MS2[957]: 1557(25), 1224(17), 1099(33), 1096(42), 1026(17), 986(8), 967(17), 943(33), 939(58), 937(25), 934(33), 932(17), 930(100), 928(17), 926(25), 922(17), 917(25), 916(17), 912(25), 911(25), 907(50), 901(17), 899(17), 895(50), 872(25), 842(17), 837(8), 817(8), 814(17), 778(17), 754(25), 739(8), 731(17), 717(8), 655(42), 541(8), 493(8), 469(8), 413(8), 397(17), – Unknown ellagitannin
9 6.40 965.0516 −0.428 C89H48O51 [M– 2H]2− MS2[965]: 1859(11), 948(16), 947(16), 942(11), 929(16), 921(11), 920(11), 916(21), 903(26), 897(11), 889(11), 887(11), 885(11), 871(21), 852(37), 823(11), 797(11), 795(11), 783(100), 781(16), 764(11), 591(11), 481(11), 479(16), 421(16) – Unknown ellagitannin
10 6.50 285.0611 −0.144 C12H14O8 [M–H]− MS2[285]: 165(7), 153(100), 152(28), 109(9)MS3[285 → 153]: 109(100) – 1-O-protocatechuyl-beta-xylose
11 6.54 203.0822 −0.451 C11H12O2N2 [M–H]− MS2[203]: 186(10), 159(100), 142(15), 116(37)MS3[203 → 159]: 144(9), 132(30), 130(56), 129(100), 128(42), 116(58), 115(30) 280, 230 D or L-tryptophan
12 6.84 187.0248 −0.451 C7H8O6 [M–H]− MS2[187]: 143(100)MS3[187 → 143]: 99(100), 85(9) – 2-methylaconitate or its isomer
13 7.16 577.1346 −0.569 C30H26O12 [M–H]− MS2[577]: 559(16), 451(46), 425(100), 407(59), 299(7), 289(27), 287(11)MS3[577 → 425]: 407(100), 273(6)MS4[577 → 425 → 407]: 389(29), 363(6), 339(14), 297(45), 285(100), 284(11), 283(28), 281(88), 269(6), 256(8), 255(20), 253(17), 243(17) – Proanthocyanidin b1 (catechin-catechin)
14 8.11 289.0713 −0.441 C15H14O6 [M–H]− MS2[289]: 247(7), 245(100), 231(7), 205(33), 179(9)MS3[289 → 245]: 227(27), 217(8), 203(100), 202(7), 188(15), 187(24), 175(9), 161(17) 233, 280, 334 (+)-Catechin*
15 8.75 865.1973 1.096 C45H38O18 [M–H]− MS2[865]: 848(25), 739(55), 713(39), 695(100), 587(22), 577(52), 575(33), 569(9), 557(6), 543(11), 451(19), 449(15), 425(17), 423(6), 413(8), 407(23), 405(7), 395(6), 289(6), 287(16)MS3[865 → 695]: 677(38), 586(8), 585(10), 543(100), 525(23), 451(28), 407(16), 405(33), 391(11), 387(6), 363(22), 299(11), 289(15), 243(33) – Proanthocyanidin C1 (catechin trimer)
16 9.09 1153.2596 1.225 C42H58O37 [M–H]− MS2[1153]: 1136(73), 1110(8), 1101(10), 1070(6), 1028(65), 1010(12), 1002(33), 991(6), 984(35), 983(20), 965(6), 917(6), 908(41), 906(8), 865(100), 863(49), 861(10), 857(12), 850(8), 847(14), 846(8), 831(20), 822(6), 814(6), 739(25), 723(6), 713(6), 701(27), 695(16), 694(10), 587(25), 577(22), 575(55), 557(24), 549(8), 533(8), 501(6), 459(6), 457(6), 455(6), 449(12), 423(22), 407(24), 405(10) 233, 271, 360 Proanthocyanidin tetramer
17 9.44 331.1033 −0.305 C14H20O9 [M–H]− MS2[331]: 313(8), 289(46), 287(7), 271(100), 235(11), 203(9), 169(24), 165(6), 127(10) 233, 271 Galloyl glucose
18 9.57 865.197 −1.517 C45H38O18 [M–H]− MS2[865]: 848(17), 739(62), 720(8), 713(51), 695(100), 587(20), 577(64), 575(38), 557(9), 543(19), 533(6), 525(8), 451(18), 449(15), 425(25), 423(6), 413(9), 407(18), 405(12), 395(9), 363(8), 289(9), 287(27) 233, 271 Proanthocyanidin trimer
19 9.81 561.1398 −0.465 C30H26O11 [M–H]− MS2[561]: 543(42), 435(52), 425(13), 407(17), 289(100), 271(11)MS3[561 → 289]: 247(6), 245(100), 205(33), 203(11), 179(12) 233, 271 Unknown
20 10.74 447.0931 0.952 C21H21O11+ [M–2H]− MS2[465]: 339(8), 285(100), 241(13)MS3[465 → 285]: 257(9), 243(21), 241(100), 217(19), 199(10), 149(9) 233, 271, 514 Cyanidin 3-O-glucoside*
21 11.18 849.2023 −1.353 C45H38O17 [M–H]− MS2[849]: 831(24), 723(100), 697(43), 695(32), 679(19), 577(95), 571(51), 559(78), 553(10), 541(9), 517(6), 451(19), 433(19), 425(22), 407(30), 397(12), 299(7), 289(15), 287(14) – Propelargonidin trimer (afz-cat-cat)
22 11.55 631.0565 −0.13 C27H20O18 [M–H]− MS2[631]: 613(12), 451(100)MS3[631 → 451]: 433(79), 423(9), 407(78), 405(28), 395(10), 379(37), 377(10), 367(6), 363(8), 351(100), 337(7), 335(24), 323(21), 311(28), 307(25), 295(14), 285(88), 283(7), 165(8) 215, 233 Castalin or its isomer
23 12.32 331.1026 0.241 C14H20O9 [M–H]− MS2[331]: 313(22), 312(6), 289(15), 288(6), 271(25), 253(21), 235(33), 211(14), 205(6), 203(32), 193(63), 181(11), 169(64), 161(10), 151(42), 127(100), 125(29), 113(11), 101(9), 97(9) 232, 275 Unknown
24 13.21 431.0979 0.591 C21H21O11 [M–2H]− MS2[431]: 413(10), 387(6), 269(100)MS3[431 → 269]: 241(59), 225(29), 199(12), 197(7), 147(100) 233, 271, 500 Pelargonidin 3-O-glucoside*
25 13.83 401.1448 −1.272 C18H26O10 [M-H] MS2[401]: 383(18), 357(8), 356(6), 355(6), 293(9), 269(100), 233(9), 161(20) – Apigenin pentose
26 13.90 635.0881 −1.44 C27H24O18 [M–H]− MS2[635]: 465(100)MS3[635 → 465]: 313(100), 295(9), 235(9), 169(19)MS4[635 → 465 → 313]: 295(21), 253(41), 241(31), 223(6), 211(6), 193(17), 169(100), 151(9), 125(15) 233, 270 Trigalloylglucose
27 14.53 525.1964 −0.243 C25H34O12 [M–H]− MS2[525]: 363(100), 345(6), 179(6), 165(10)MS3[525 → 363]: 345(27), 315(19), 239(8), 221(7), 179(32), 165(100) – GA8-hexose gibberellin
28 14.74 351.1292 0.577 C14H24O10 [M–H]− MS2[351]: 333(25), 249(100), 231(10), 113(8)MS3[351 → 249]: 231(100), 189(18), 175(18), 157(7), 129(11), 115(18), 113(86), 111(21), 109(7), 99(18), 95(11), 85(29), 83(21), 75(7) – Unknown
29 14.87 463.1227 −0.838 C22H23O11 [M–H]− MS2[463]: 301(100), 300(54)MS3[463 → 301]: 301(12), 284(14), 257(100), 229(21), 185(9) – Ellagic acid-hexoside
30 14.95 463.0506 −0.188 C20H16O13 M+ MS2[463]: 301(100)MS3[463- > 301]: 286(100) 233, 271, 512 Peonidin 3-O-glucoside*
31 15.46 517.1552 0.028 C22H30O14 [M–H]− MS2[517]: 499(10), 471(8), 355(18), 337(46), 295(35), 265(49), 235(55), 193(100), 175(32), 160(14) – Unknown
32 15.66 449.1079 0.227 C21H22O11 [M–H]− MS2[449]: 355(100), 329(8), 287(40), 269(28), 193(13)MS3[449 → 355]: 193(100), 192(10), 165(6)MS4[449 → 355 → 193]: 165(100), 137(14) – Ferulic acid hexose derivative
33 16.71 371.0977 0.417 C16H20O10 [M–H]− MS2[371]: 249(100)MS3[371 → 249]: 231(87), 175(14), 113(100), 111(8), 103(7), 99(9), 95(11), 85(21) – Unknown
34 17.49 585.2184 −0.479 C27H38O14 [M–H]− MS2[585]: 377(100), 329(13)MS3[585 → 377]: 329(100)MS4[585 → 377 → 329]: 314(100), 164(10) – Unknown
35 18.07 535.1075 −0.692 C24H23O14 M+ MS2[535]: 287(100)MS3[535- > 287]: 287(100), 269(68), 259(28), 245(11), 241(36), 231(46), 217(6), 216(9), 213(74), 199(12), 189(16), 185(32), 175(35), 163(9), 137(17) 233, 515 Cyanidin 3-O-malonylglucoside
36 18.08 935.0771 −1.357 C41H28O26 [M–H]− MS2[935]: 633(100), 301(41)MS3[935 → 633]: 463(8), 301(100) – Galloyl bis-hexahydroxydiphenoyl (HHDP)-glucose
37 19.28 433.0408 −0.479 C19H14O12 [M–H]− MS2[433]: 301(100), 300(32)MS3[433 → 301]: 301(49), 284(36), 273(12), 257(100), 229(67), 213(8), 201(6), 185(32) – Ellagic acid pentoside
38 19.41 461.2023 −0.505 C21H34O11 [M–H]− MS2[461]: 461(6), 453(9), 443(55), 430(6), 418(9), 417(15), 416(9), 415(30), 400(6), 399(16), 393(6), 376(6), 329(100), 299(10), 293(90), 233(49), 191(185), 161(13), 149(28) – Unknown
39 19.72 300.9983 −0.73 C14H6O8 [M–H]− MS2[301]: 301(34), 300(13), 284(28), 257(100), 229(64), 201(13), 185(34)MS3[301 → 257]: 229(96), 213(23), 201(11), 185(100), 173(6) 234, 252, 368 Ellagic acid*
40 20.42 447.0564 −0.499 C20H17O12 [M–H]− MS2[447]: 301(100), 300(19)MS3[447 → 301]: 301(15), 284(11), 257(100), 229(29), 185(10) 233, 365 Ellagic acid-methyl pentoside
41 21.07 473.1083 −0.142 C23H23O11 [M–2H]− MS2[473]: 269(100)MS3[473 → 269]: 241(59), 225(62), 224(8), 201(7), 199(9), 147(100) 233, 501 Pelargonidin acetyl hexoside
42 21.89 623.1247 0.414 C27H28O17 [M–H]− MS2[623]: 608(11), 477(46), 476(8), 460(100), 314(11), 313(6)MS3[623 → 460]: 445(10), 314(35), 313(100)MS4[623 → 460 → 313]: 298(100), 285(42), 283(6) – Unknown
43 22.26 503.1189 0.498 C24H24O12 [M–H]− MS2[503]: 299(100)MS3[503 → 299]: 284(100), 283(22), 255(23), 240(10), 147(11) 230, 365 Diosmetin acetylhexoside
44 22.43 549.1228 −1.022 C25H25O14 M+ MS2[549]: 301(100)MS3[549- > 301]: 286(100) 233, 515 Peonidin 3-O-malonylglucoside
45 23.05 435.0931 −0.145 C20H20O11 [M–H]− MS2[435]: 303(100), 285(34)MS3[435 → 303]: 285(100), 177(11), 125(7)MS4[435 → 303 → 285]: 257(11), 243(17), 241(100), 217(13), 199(23), 175(56) 217, 234, 289 Taxifolin 3-O-arabinofuranoside
46 23.50 463.0876 −0.609 C21H20O12 [M–H]− MS2[463]: 301(100), 300(23)MS3[463 → 301]: 283(6), 273(16), 257(15), 229(8), 179(100), 151(63) 233, 364 Quercetin 3-O-glucoside*
47 23.61 477.067 −0.444 C21H18O13 [M–H]− MS2[477]: 315(100)MS3[477 → 315]: 300(100)MS4[477 → 315 → 300]: 300(100), 283(6), 272(24), 271(21), 244(53), 243(12), 228(13), 216(17), 200(22) 217, 233, 271 Methylellagic acid hexose
48 23.73 521.2017 −1.115 C26H34O11 [M–H]− MS2[521]: 503(9), 359(100)MS3[521 → 359]: 344(100)MS4[521 → 359 → 344]: 329(34), 328(8), 313(100), 255(16), 203(14), 191(10), 189(52), 173(11), 159(41) 215, 233, 271 Tetramethylellagic acid hexose
49 24.55 491.0831 −0.014 C22H20O13 [M–H]− MS2[491]: 476(20), 328(100), 313(9)MS3[491 → 328]: 313(100)MS4[491 → 328 → 313]: 298(100), 285(54) 215, 233, 280 Dimethylellagic acid hexose
50 24.73 521.2016 −1.235 C26H34O11 [M–H]− MS2[521]: 503(9), 359(100)MS3[521 → 359]: 344(100)MS4[521 → 359 → 344]: 329(32), 328(10), 313(100), 255(16), 203(16), 191(10), 189(45), 173(11), 159(45) 216, 233, 271 Tetramethylellagic acid hexose
51 25.32 709.1252 −0.526 C30H30O20 [M–H]− MS2[709]: 709(7), 691(10), 665(84), 663(9), 625(8), 563(100), 545(13), 519(83), 477(18), 461(8), 447(7), 357(21), 315(46), 301(27), 300(13) 217, 233, 356 Unknown
52 25.60 607.1298 −0.638 C27H28O16 [M–H]− MS2[607]: 461(100)MS3[607 → 461]: 314(100), 299(6)MS4[607 → 461 → 314]: 313(31), 299(97), 286(66), 285(100), 284(21), 283(25) 215, 233 Unknown
53 26.20 567.2076 −0.674 C27H36O13 [M–H]− MS2[567]: 567(10), 558(11), 550(7), 549(14), 545(7), 523(10), 521(40), 499(7), 359(77), 341(100), 329(87) 215, 233 Unknown
54 26.28 505.0983 −0.434 C23H22O13 [M–H]− MS2[505]: 463(22), 301(100), 300(46)MS3[505 → 301]: 283(17), 273(29), 257(10), 229(7), 193(7), 179(100), 151(63) – Quercetin acetyl hexoside
55 26.51 327.1234 −0.447 C19H20O5 [M–H]− MS3[327 → 312]: 295(22), 284(47), 283(30), 281(48), 267(100), 256(12), 253(26), 240(11), 145(30) – Unknown
56 26.67 447.0563 −0.599 C20H16O12 [M–H]− MS2[447]: 315(100)MS3[447 → 315]: 300(100)MS4[447 → 315 → 300]: 300(100), 283(12), 272(24), 271(12), 244(69), 243(29), 228(33), 216(47), 200(35), 188(6), 172(10) – Methylellagic acid pentose
57 27.34 461.0724 −0.189 C21H18O12 [M–H]− MS2[461]: 328(6), 315(100)MS3[461 → 315]: 300(100)MS4[461 → 315 → 300]: 300(19), 283(59), 272(100), 271(18), 244(39), 228(40), 200(20), 172(17) – Methylellagic acid methyl pentose
58 27.68 519.0779 −0.148 C23H20O14 [M–H]− MS2[519]: 315(100)MS3[519 → 315]: 300(100)MS4[519 → 315 → 300]: 300(100), 272(24), 271(18), 244(67), 243(12), 228(12), 216(21), 200(12), 172(6), 151(6) – Methylellagic acid acetyl hexose
59 27.88 939.1095 −1.404 C41H32O26 [M–H]− MS2[939]: 787(8), 769(100), 617(9)MS3[939 → 769]: 725(16), 617(100), 601(37), 599(33), 511(7), 465(6), 447(21), 431(11), 429(14), 403(6)MS4[939 → 769 → 617]: 465(100), 447(37), 423(18), 313(8), 295(6), 211(6) – Pentagalloyl hexose
60 28.16 447.0932 −0.115 C21H20O11 [M–H]− MS2[447]: 327(18), 285(92), 284(100), 255(14)MS3[447 → 284]: 255(100), 227(13)MS4[447 → 284 → 255]: 255(12), 227(100), 211(57), 183(8), 167(6) – Kaempferol 3-O-hexoside
61 28.55 519.0779 −0.148 C23H20O14 [M–H]− MS2[519]: 315(100), 300(10)MS3[519 → 315]: 300(100)MS4[519 → 315 → 300]: 300(100), 283(11), 272(27), 271(29), 244(80), 243(17), 228(23), 216(19), 200(34), 172(10) 217, 233, 366 Methylellagic acid acetyl hexoside
62 29.22 461.0718 −0.738 C21H18O12 [M–H]− MS2[461]: 315(100), 314(6)MS3[461 → 315]: 300(100)MS4[461 → 315 → 300]: 300(100), 283(17), 272(36), 271(24), 244(74), 243(21), 228(23), 216(24), 200(39), 172(10) 243, 375 Methylellagic acid rhamnoside
63 30.00 477.1035 −0.399 C22H22O12 [M–H]− MS2[477]: 459(6), 357(23), 315(31), 314(100), 299(6), 285(8), 271(7)MS3[477 → 314]: 299(18), 286(36), 285(100), 271(72), 257(11), 243(24) – Methylellagic acid hexose
64 30.56 461.0725 −0.069 C21H18O12 [M–H]− MS2[461]: 315(100)MS3[461 → 315]: 300(100)MS4[461 → 315 → 300]: 300(100), 283(10), 272(17), 271(21), 244(65), 243(18), 228(18), 216(18), 200(24), 172(7) 217, 233, 365 Methylellagic acid hexose
65 31.81 489.1038 −0.029 C23H22O12 [M–H]− MS2[489]: 285(100), 284(7)MS3[489 → 285]: 267(43), 257(100), 256(9), 243(6), 241(29), 240(10), 239(13), 229(49), 223(10), 213(15), 211(9), 199(10), 197(20), 195(9), 163(17) – Kaempferol acetylhexoside
66 32.45 341.1393 −0.107 C20H22O5 [M–H]− MS2[341]: 326(100)MS3[341 → 326]: 311(100)MS4[341 → 326 → 311]: 293(6), 283(100), 267(12), 266(14), 252(7) – Unknown
67 34.05 519.1142 −0.214 C24H24O13 [M–H]− MS2[519]: 315(100)MS3[519 → 315]: 300(100), 287(6), 272(6)MS4[519 → 315 → 300]: 272(43), 271(100), 255(66) 215, 233, 329 Methylellagic acid acetyl hexoside
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*

Confirmed with reference standards, - weak absorbance.

3.1. Identification of anthocyanins in F. vesca var. Ruegen F7-4

Fig. 1(A) shows the HPLC-UV (520 nm) chromatogram of Ruegen F7-4 ripe fruits (stage 3). Previous reports of anthocyanins in strawberries were used to assist in the identification of the anthocyanins in Table 1 in addition to UV and HRMSn data (Aaby et al., 2007; Buendia et al., 2010; Hilt et al., 2003; Kelebek & Selli, 2011; Zhang et al., 2011).

Peak 20 with M+ at m/z 449.1071 (C21H21O11, −1.53 ppm) and a product ion at m/z 287 (−162 amu, hexose moiety) was identified as cyanidin 3-O-glucoside. Peak 24, the major peak in Ruegen F7-4 with M+ at m/z 433.1122 (C21H21O10, 1.58 ppm) and a major MS2 product ion at m/z 271(−162 amu, hexose moiety), was identified as pelargonidin 3-O-glucoside. Peak 30 with M+ at m/z 463.1228 (C22H23O11, 1.49 ppm) and a MS2 product ion at m/z 301(−162 amu, hexose moiety) was identified as peonidin 3-O-glucoside. Peak 35 with [M]+ at m/z 535.1072 (C24H23O14, −2.0 ppm) and two major product ions at m/z 449 and 287 (−86 amu, and then −162 amu, corresponding to malonyl and glucose moiety, respectively) was identified as cyanidin 3-O-malonylglucoside. Peak 41 showed the M+ ion at m/z 519.1126 (C24H23O13, −1.38 ppm) and a neutral loss of 248 amu (malonyl-hexosyl residue) for its product ion and was identified as pelargonidin 3-O-malonylglucoside. Peak 44 showed the M+ at m/z 549.1226 (C25H25O14, −1.38 ppm) and a neutral loss of 248 amu (malonyl-hexosyl residue) for its product ion and was identified as peonidin 3-O-malonylglucoside. Cyanidin and pelargonidin glycosides are commonly found in cultivated strawberry (F. × ananassa var. Fort Laramie), but peonidin 3-O-glucoside and peonidin 3-O-malonylglucoside were identified in F. vesca var. Ruegen F7-4 for the first time. However, YW5AF7 ripe fruits (stage 3) only contain pelargonidin 3-O-glucoside.

3.2. Identification of non-anthocyanin phenolic compounds in Ruegen F7-4 and YW5AF7

Fig. 1 (B) shows the HPLC-UV profiles at 280 nm of Ruegen F7-4 ripe fruits (stage 3). More than sixty non-anthocyanin phenolic compounds were identified. Unlike anthocyanins, the Ruegen F7-4 and YW5AF7 exhibited very similar profiles and all non-anthocyanin phenolic compounds were found in both genotypes (details discussed below). However, the phenolic profiles differed from those of cultivated strawberries previously reported in the literature (Bianco et al., 2009; Buendia et al., 2010; Kelebek & Selli, 2011; Zhang et al., 2011).

3.2.1. Dihydroflavonol and flavonols

Peak 45 exhibited UV/Vis absorption maxima at about 234 and 290 nm. The HRMS gave a deprotonated [M–H]− ion at m/z 435.0321, suggesting the formula of C20H19O11 (0.33 ppm). The MS2 major product ion was m/z 303 (−132 amu, pentose), the MS3 and the MS4 spectra of peak 45 were consistent with the MS2 and the MS3 spectra of taxifolin. Hence this compound was identified as taxifolin 3-O-arabinoside, a compound previously reported in cultivated strawberry roots but not in fruits (Ishimaru, Omoto, Asai, Ezaki, & Shimomura, 1995). Peak 29 with m/z at 447.0927 (C21H19O11, −1.22 ppm) and a major product ion at m/z 285 (−162 amu: hexose) was identified as kaempferol 3-O-glucoside. Peak 46 (C21H20O12) with [M–H]− ion at m/z 463, a major MS2 product ion at m/z 301, and corresponding MS3 product ions at m/z 151 and 179, was identified as quercetin 3-O-glucoside. Similarly, peak 54 (C23H22O13) was identified as quercetin-acetyl-hexoside; and peaks 65 and 68 were identified as kaempferol 3-O-acetylhexosides.

3.2.2. Flavan-3-ols and proanthocyanidins

(+) Catechin, B type proanthocyanidin dimers, B type proanthocyanidin trimers, and B type proanthocyanidin tetramers were found in these two genetically improved strawberries using HRMSn data, UV spectral data, and literature reports. Peak 14, with a deprotonated molecule ion [M–H]− at m/z 289 (C15H13O6) and characteristic MS2 ions at m/z 245, 205, 231, and 179, was identified as (+)-catechin. Peak 13 ([M–H]− at m/z 577.1346, C30H25O12, 0.95 ppm, primary MS2 ion at m/z 577, −152 amu via a characteristic fragmentation pathway by retro Diels–Alder reaction) was identified as a proanthocyanidin dimer of the B type catechin–catechin (Aaby et al., 2007). Peak 15 was identified as a B type proanthocyanidin trimer. Its [M–H]− ion was at m/z 865.1970 (C45H37O18, −1.82 ppm) and MS2 ions were at m/z 695, 739, 713, 577, 425, and 287. The MS3 ions of m/z 695 gave fragment ions at m/z 543, 451, 289, and 243. Using the fragment pattern, the sequence of this trimer was epicatechin–epicatechin–epicatechin. Peak 16 had an [M–H]− ion at m/z 1153.2596 (C60H4s9O24, −1.98 ppm) and was tentatively identified as an isomer of a B type proanthocyanidin tetramer according to its characteristic MS2 ions at m/z 865, 1135, 1027, 983, 695, 575 and 407. It was composed of four epicatechin units. Peak 19 had [M–H]– at m/z 561.1393 (C30H25O11) and MS2 ions at m/z 289, 543, and 435. The compound was identified as epiafzelechin–epicatechin. The fragmentation pathway of peak 19 was different from that of the B-catechin dimer in strawberries described in a previous study (Aaby et al., 2007). Peak 21 had [M–H]− at m/z 849.2023 (C45H37O17), characteristic MS2 ions at m/z 801, 697, 577 (base peak obtained after a loss of 272 amu), 559, 425, 407, and 287. The MS3 spectra of the MS2 base peak (m/z 577) gave ions at 425, 407, and 289 (−288 amu, epi catechin) and corresponded to B type proanthocyanidin trimer of the type epiafzele-chin−epicatechin−epicatechin (Aaby et al., 2007; Hilt et al., 2003).

3.2.3. Ellagic acid and its Derivatives

Peak 39 had [M–H]− at m/z 300.9983 (C14H5O8, −0.97 ppm) and MS2 fragmentation ions at m/z 257, 229,185, and 157. It was identified as ellagic acid. The identity was confirmed with an ellagic acid reference standard. The UV/Vis spectra of peaks 30 and 37 suggested glycosylated forms of ellagic acid (33). Peak 30 with [M–H]– at m/z 463 (C20H15O13) and the main MS2 ion at m/z 301 (−162, hexose) was tentatively identified as an ellagic acid hexoside. Peak 37 had the [M–H]– at m/z 447 (C19H13O12). Its main MS2 product ion was at m/z 301 (MS3 ions at m/z 257, 229, and 185) and corresponded to ellagic acid. Peak 37 was identified as ellagic acid methyl pentoside. A similar compound has been previously reported in strawberries (Aaby et al., 2007).

Peak 62 (m/z 461.0725, C21H17O12, −0.107 ppm) is the major compound observed in the HPLC-DAD profiles for both Ruegen and YW5AF7. The maximum UV absorptions were at 243 nm and 375 nm. The characteristic MS2 product ion at m/z 315 (−146 amu, methyl pentose) and its MS3 product ions at m/z 300 and its MS4 product ions at m/z 272, 271, 244 confirmed the identity of methylellagic acid. Hence, Peak 62 was identified as methylella-gic acid methyl pentoside. Peaks 57 and 64 had the same m/z (461.0725) and exhibited similar fragmentation behaviour to that of peak 62, except that the relative abundance of product ion at m/z 315 was different. These two compounds were tentatively identified as methylellagic acid methyl pentoside isomers. Peaks 61 and 67 had [M–H]− ions at m/z 519 (C23H19O14) with the MS2 product ions corresponding to kaempferol glucoside (m/z 315) after the loss of the acetyl and hexosyl moieties (162 + 42 amu). They were identified as methylellagic acid 3-O-acetyl-hexosides. Similarly, Peak 56 (m/z 447.0563) was identified as methylellagic acid 3-O-pentoside. Similar compounds (methylellagic acid-pen-tose conjugates) have been previously reported (Aaby et al., 2007).

Peaks 5, 6, 8, 9,17, 26, and 36 were identified as ellagitannins. Ellagitannins are hydrolysable tannins, since they are esters of hexahydroxydiphenic acid (HHDP: 6,6’-dicarbonyl-2,2′,3,3′,4,4′-hexahydroxybiphenyl moiety) and a polyol, usually glucose, and in some cases gallic acid, which are commonly found in strawberries (Aaby et al., 2007; Kelebek & Selli, 2011; Vrhovsek et al., 2012). Typical losses during fragmentation of ellagitannins are galloyl (152 amu), HHDP (302 amu), galloyl-glucose (332 amu), HHDP-glucose (482 amu), and galloyl-HHDP-glucose (634 amu). Recent research found that agrimoniin is one of the most abundant ellagitannins and sanguiin H-6 and lambertianin C are minor compounds in both F. vesca and F. ananassa D. (Vrhovsek et al., 2012). However, we did not find any of these three compounds in our two strawberry lines. Peak 8 had a [M–2H]2− ion at m/z 957.0535 (its isotopic distribution suggests it to be a double-charged ion), implying the formula of C82H52O55. Fragmentation of the double-charged ions gave single-charged MS2 product ions at m/z 1557, 1224, 1099, 1096, 943, 930, 451, and 301. Thus Peak 8 has two more oxygen atom substituted in the structures than that of sanguiin H-6/agrimoniin. Similarly, Peak 9 (C82H52O56) had three more oxygen atoms substituted in the structure in comparison to literature reports for sanguiin H-6/agrimoniin (Aaby et al., 2007; Vrhovsek et al., 2012).

Peak 5, with [M–H]− at m/z 783 (C34H23O22) and MS2 fragmentations at m/z 481 (−302 amu, loss of HHDP) and 301 (−482 amu, loss of HHDP-glucose) was identified as bis-HHDP-glucose, previously reported in strawberries (Aaby et al., 2007). Peak 36 was identified as galloyl-bis-HHDP-glucose with [M–H]− at m/z 935 and MS2 product ions at m/z 633 −02 amu, loss of HHDP) and 301 (332 amu, loss of galloyl glucose).

Peak 26 had an [M–H]− at m/z 635 (C27H23O18), and a major MS2 product ion at m/z 465 (−170 amu, gallic acid). The MS3 ion of m/z 465 was at m/z 313 (−152 amu, loss of galloyl unit). The ion at m/z 313 could be further fragmented into an MS4 product ion at m/z 169. Peak 26 was identified as tri-galloyl-glucose.

Peak 36 had a [M–H]− ion at 935.0771, and ions at m/z 633,m/z 463 and m/z 301 in the MS2 to MS3 specta, indicating the structure of galloyl-bis-HHDP-glucose.

3.2.4. Other compounds

Peak 12 (C7H8O6) was identified as benzoic acid with the main MS2 ion at m/z 143 (loss of CO2). It was reported previously (Russell, Scobbie, Labat, & Duthie, 2009). Peak 32 was identified as a ferulic acid hexose derivative with [M–H]− at m/z 449 and MS2 ions at m/z 355, 329, 287, 269, and 193 (base peak 355) (Aaby et al., 2007). The major MS3 ion of m/z 355 was at m/z 193 (loss of a hexose unit). The fragmentation patterns were in agreement with previously published data (Aaby et al., 2007). Possible composition of Peak 32 could be ferulic acid, hexose, and a C6H6O group. Peak 1 (C12H22O12) was identified as hexosyl-hexose and it is the sugar form that widely exists in fruits and vegetables (Kallio, Hakala, Pel-kkikangas, & Lapvetelainen, 2000). Peaks 2 and 3 (C6H8O7) were tentatively identified as citric acid and its isomer (Kelebek & Selli, 2011). Peak 7 (C12H18O8) was tentatively identified as furaneol glucoside, a compound previously reported in detached ripening strawberry fruits (Roscher, Bringmann, Schreier, & Schwab, 1998). Peak 11 (C11H12O2N2) was identified as tryptophan, which was reported in Chilean strawberry F. × chiloensis ssp. chiloensis (Cheel et al., 2005).

3.3. The chemical differences of F. vesca Ruegen F7-4 and YW5AF7 and F. × ananassa cv. Fort Laramie

The metabolite profiles of strawberry fruits are strongly affected by developmental, genetic, and environmental factors (Carbone et al., 2009). In previous publications, the difference between wild and cultivated strawberry species in the production of specific volatile terpenoid flavour components was studied using a combination of molecular and biochemical tools. The results suggest that domestication of strawberry has involved selection for specific alleles in the cultivated species which contribute to a strongly modified flavour profile (Aharoni et al., 2004). In this investigation, we also found a significant difference between wild and cultivated strawberry species as shown by their phenolic profiles. The constituents found in octoploid strawberry F. × ananassa cv. Fort Laramie are shown in Fig. 2 and Table 2. The two major anthocyanins of Fort Laramie, cyanidin 3-O-glucoside and pelargonidin 3-O-glucoside, accounted for almost 100% of the total peak area in its HPLC chromatogram at 520 nm; on the other hand, there are many other anthocyanins in diploid strawberry Ruegen F7-4, such as peonidin 3-O-glucoside, peonidin 3-O-malonylglucoside cyanidin 3-O-malonylglucoside, and pelargonidin 3-O-malonylglucoside.

Fig. 2.

Fig. 2

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The HPLC chromatograms of anthocyanins (A, at 520 nm) and non-anthocyanin polyphenols (B, at 280 nm) from F × ananassa cv. LAR.

Table 2.

Compounds identified from Fragaria × ananassa cv. Fort Laramie.

Peak
no.		 tR
(min)		 m/z Error
(mmu)		 Formula Adduct MS2 to MS4 data UV λmax
(nm)		 Possible
identification
1a 1.76 341.1083 −0.635 C12H22O11 [M–H]− MS2[341]: 179(100), 161(20), 143(21), 131(7), 119(15), 113(19), 101(6) – Hexosyl hexose
2a 1.89 191.0193 −0.406 C6H8O7 [M–H]− MS2[191]: 173(25), 111(100) – Citric acid or its isomer
3a 2.11 191.0194 −0.326 C6H8O7 [M–H]− MS2[191]: 173(25), 111(100) – Citric acid isomer
4a 2.59 191.0194 −0.286 C6H8O7 [M–H]− MS2[191]: 173(25), 111(100) – Citric acid isomer
5a 3.28 865.1965 −2.007 C45H38O18 [M–H]− MS2[865]: 848(11), 739(15), 713(29), 695(100), 587(8), 577(32), 575(28), 543(8), 451(10), 449(10), 425(11), 413(8), 407(12), 405(6), 363(6), 287(13)MS3[865 → 695]: 677(30), 651(11), 586(15), 585(9), 543(100), 525(15), 451(37), 407(15), 405(51), 391(12), 387(7), 363(48), 299(10), 289(27), 243(46) 234 Proanthocyanidin trimer
6a 3.33 865.196 −2.497 C45H38O18 [M–H]− – – Proanthocyanidin trimer
7a 3.98 783.0670 −1.685 C34H24O22 [M–H]− MS2[783]: 481(28), 301(100), 275(8) – bis-HHDP hexose
8a 5.39 783.0682 −0.465 C34H24O22 [M–H]− MS2[783]: 481(28), 301(100), 275(81) – bis-HHDP Hexose
9a 5.62 289.0924 −0.511 C12H18O8 [M–H]− MS2[289]: 245(6), 161(100), 101(8)MS3[289 → 161]: 143(9), 125(9), 113(61), 101(100), 99(13), 97(11), 89(9), 85(11), 73(7), 71(30) 232, 271 Furaneol hexoside
10a 6.54 285.0614 −0.211 C12H14O8 [M–H]− MS2[285]: 165(6), 153(100), 152(31), 109(7), 108(6)MS3[285 → 153]: 109(100) 231, 283 Dihydroxybenzoic acid xylose
11a 6.73 951.0743 −0.178 C41H28O27 [M–H]− MS2[951]: 907(100), 783(25) Geraniin
12a 7.91 865.1976 −0.967 C45H38O18 [M–H]− MS2[865]: 847(21), 739(64), 713(31), 695(100), 677(6), 587(31), 577(57), 575(33), 543(18), 533(7), 451(21), 449(21), 425(21), 423(8), 413(11), 407(26), 405(11), 289(10), 287(17)MS3[865 → 695]: 677(29), 585(6), 543(100), 525(27), 451(49), 407(11), 405(28), 391(7), 387(8), 363(13), 299(9), 289(14), 243(29) 234, 278 Proanthocyanidin trimer
13a 8.98 865.1976 −0.967 C45H38O18 [M–H]− MS2[865]: 847(27), 739(59), 713(49), 695(100), 587(19), 577(63), 575(33), 559(7), 557(6), 543(17), 533(7), 451(22), 449(22), 425(20), 423(8), 413(11), 407(21), 405(10), 395(6), 289(10), 287(18)MS3[865 → 695]: 678(34), 585(6), 543(100), 542(15), 525(28), 451(36), 407(8), 405(26), 391(11), 363(26), 299(9), 289(23), 243(49) 234, 278 Proanthocyanidin trimer
14a 9.25 1153.261 −1.425 C42H58O37 [M–H]− MS2[1153]: 1135(50), 1028(90), 1009(7), 1002(38), 1001(17), 983(85), 982(6), 965(8), 907(24), 865(100), 863(53), 857(7), 847(25), 846(11), 821(8), 739(50), 738(21), 701(32), 695(25), 694(7), 683(9), 588(6), 577(40), 575(55), 569(6), 560(11), 451(11), 449(18), 423(9), 407(26), 405(11), 395(7) 234, 278 Proanthocyanidin tetramer
15a 10.01 325.0929 −1.267 C15H18O8 [M–H]− MS2[325]: 265(19), 235(7), 205(7), 187(50), 163(90), 145(100), 119(9)MS3[325 → 145]: 117(100) 219, 234, 314 Coumaroyl glucose
16a 11.05 449.1074 −0.148 C21H21O11 M+ MS2[449]: 287(100) 276, 428, 500 Cyanidin 3-O-glucoside*
17a 11.57 849.2031 −0.563 C45H38O17 [M–H]− MS2[849]: 831(22), 724(90), 723(13), 714(7), 697(34), 695(30), 679(12), 577(100), 571(45), 559(74), 553(15), 543(10), 451(19), 433(14), 425(38), 407(25), 397(11), 289(15), 287(20) 234, 278 Epiafzelechin-(4β → 8)-epicatechin-(4β → 8)-epicatechin
18a 12.61 577.1343 −0.859 C30H26O12 [M–H]− MS2[577]: 559(15), 451(54), 425(100), 407(52), 299(10), 289(26), 287(13) 233, 278 Proanthocyanidin dimer
19a 13.32 433.1125 −0.463 C21H21O10 M+ MS2[433]: 271(100) 234, 276, 428, 499 Pelargonidin 3-O-glucoside*
20a 14.87 865.1970 −1.577 C45H38O18 [M–H]− MS2[865]: 847(15), 739(63), 714(34), 713(17), 695(100), 677(6), 587(28), 577(60), 575(29), 569(10), 561(11), 559(8), 543(19), 451(20), 449(12), 425(29), 413(9), 407(33), 405(7), 289(7), 287(18)MS3[865 → 695]: 677(31), 652(7), 569(23), 543(86), 525(49), 451(15), 449(11), 407(100), 405(19), 363(9), 289(12), 243(24) 233, 278 Proanthocyanidin trimer
21a 15.84 449.1089 0.015 C21H22O11 [M–H]− MS2[449]: 355(100), 329(12), 287(36), 269(29), 193(13) MS3[449 → 355]: 193(100), 192(12) 234, 330 Ferulic acid hexose
22a 18.18 935.0782 1.414 C41H28O26 [M–H]− MS2[935]: 633(100), 301(43)MS3[935 → 633]: 463(7), 301(100) 234, 278 Galloyl bis-HHDP Hexose
23a 19.40 433.0406 −0.659 C19H14O12 [M–H]− MS2[433]: 415(6), 301(100), 300(30)MS3[433 → 301]: 301(42), 284(47), 257(100), 229(70), 185(27) 216, 234, 278 Ellagic acid pentoside
24a 19.95 300.9985 −0.45 C14H6O8 [M–H]− MS2[301]: 301(43), 300(6), 284(29), 283(20), 273(15), 257(100), 245(9), 229(69), 213(8), 201(9), 185(39) 233, 366 Ellagic acid*
25a 20.44 447.0563 −0.559 C20H16O12 [M–H]− MS2[447]: 301(100), 300(30)MS3[447 → 301]: 301(13), 284(11), 257(100), 229(27), 185(12) 234, 370 Ellagic acid deoxyhexoside
26a 21.31 447.0566 −0.289 C20H16O12 [M–H]− MS2[447]: 301(100), 300(30)MS3[447 → 301]: 301(25), 300(12), 284(14), 283(40), 271(6), 257(100), 255(6), 245(7), 229(50), 185(23) – Ellagic acid deoxyhexoside
27a 22.99 477.0673 −0.204 C21H18O13 [M–H]− MS2[477]: 301(100)MS3[477 → 301]: 273(20), 257(15), 179(100), 151(69)MS4[477 → 301 → 179]: 151(100) 216, 233, 350 Quercetin 3-O-glucuronide*
28a 23.75 463.088 −0.219 C21H20O12 [M–H]− MS2[463]: 301(100), 300(21)MS3[463 → 301]: 283(8), 273(28), 257(14), 239(6), 193(8), 179(100), 151(75), 107(6) – Quercetin 3-glucoside*
29a 24.41 935.0782 −1.354 C41H28O26 [M–H]− MS2[935]: 918(6), 633(100), 463(7), 301(61) – Galloyl-bis-HHDP-glucose
30a 24.81 355.1031 −0.395 C16 H19 O9 [M–H]− MS2[355]: 337(23), 311(10), 309(100), 207(35), 147(50) 216, 233, 282 Feruloyl hexoside
31a 26.28 934.0712 −0.609 C82H52O54 [M– 2H]2− MS2[934]: 1568(100), 1567(9), 1265(25), 1085(26), 916(31), 915(93), 897(84), 783(32), 633(41), 301(86) 233 Agrimoniin
32a 27.89 461.0725 −0.039 C21H18O12 [M–H]− MS2[461]: 285(100)MS3[461 → 285]: 267(42), 257(100), 243(8), 241(23), 240(17), 239(21), 229(41), 223(11), 213(24), 211(10), 199(16), 197(16), 195(7), 185(7), 163(14), 151(8 217, 233, 265, 350 Kaempferol 3-O-glucuronide*
33a 28.40 447.0934 0.065 C21H20O11 [M–H]− MS2[447]: 327(23), 301(7), 285(90), 284(100), 255(15)MS3[447 → 284]: 255(100), 227(13) 218, 233, 350 Kaempferol 3-O-glucoside
34a 30.33 505.0983 –0.494 C23H22O13 [M–H]− MS2[505]: 487(10), 463(25), 343(6), 301(100), 300(53) – Quercetin 3-acetylglucoside
35a 32.04 489.1039 0.031 C23H22O12 [M–H]− MS2[489]: 285(100)MS3[489 → 285]: 267(59), 257(100), 256(16), 241(25), 240(12), 239(25), 229(57), 223(12), 213(26), 199(26), 197(21), 195(10), 189(6), 165(6), 163(23) – Kaempferol 3-acetylglucoside
36a 44.26 593.1299 −0.124 C30H25O13 [M–H]− MS2[593]: 447(10), 307(6), 285(100) – Kaempferol 3-coumaroylglucoside
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*

Confirmed with reference standards.

The non-anthocyanin polyphenols in Fort Laramie are mainly coumaroyl-glucose, ferulic acid hexose, quercetin, and kaempferol derivatives while in Ruegen F7-4 and YW5AF7, taxifolin 3-O-arabi-noside, methylellagic acid rhamnoside, and ellagic acid are the major constituents. Understanding the chemical differences between cultivated strawberry Fort Laramie and wild strawberry Ruegen F7-4/YW5AF7 may help target modification of strawberries for quality improvement.

4. Conclusion

This study was the first chemical investigation to describe the phenolic composition of two diploid inbred lines, Ruegen F7-4 and YW5AF7, which will facilitate genetic and biochemical studies of the enzymes catalysing the biosynthesis of these important compounds. The UHPLC-DAD-HRMS analysis identified the presence of a variety of anthocyanins, dihydroflavonols, flavonols, fla-van-3-ols, proanthocyanidins, free and conjugated forms of ellagic acid, and ellagitannins. A total of 78 phenolic compounds were identified. The results demonstrate the differences in anthocyanin composition in Ruegen F7-4 and cultivated strawberry Fort Laramie are mainly due to peonidin 3-O-glucoside and peonidin 3-O-malonylglucoside. The identification of phenolic compounds revealed some interesting compounds newly found in strawberry. Taxifolin 3-O-arabinoside and methylellagic acid glycosides in Ruegen F7-4 and YW5AF7 were reported in strawberry fruits for the first time. The high diversity of the phenolic com pounds found in wild diploid strawberry samples may have potential beneficial effects for human health. Further studies should be carried out for quantification of major compounds and biochemical and genetic characterisation of biosynthetic pathways.

Supplementary Material

1

Acknowledgments

This research is supported by the Agricultural Research Service of the U.S. Department of Agriculture and an Interagency Agreement with the Office of Dietary Supplements (ODS) of the National Institutes of Health (NIH).

Footnotes

Appendix A. Supplementary data

Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.foodchem.2013.08.089.

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Associated Data

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Supplementary Materials

1
NIHMS527035-supplement-1.pptx (1.5MB, pptx)

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