Crocus sativus Petals: Waste or Valuable Resource? The Answer of

Sep 14, 2015 - The Answer of. High-Resolution and High-Resolution Magic Angle Spinning Nuclear. Magnetic Resonance. Valeria Righi,. †. Francesca Par...
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Crocus sativus petals: waste or valuable resource? The answer of HR- and HR-MAS NMR Valeria Righi, Francesca Parenti, Vitaliano Tugnoli, Luisa Schenetti, and Adele Mucci J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.5b03284 • Publication Date (Web): 14 Sep 2015 Downloaded from http://pubs.acs.org on September 15, 2015

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Journal of Agricultural and Food Chemistry

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Crocus sativus petals: waste or valuable resource? The answer of HR- and HR-MAS NMR

2

Valeria Righi,† Francesca Parenti, ‡ Vitaliano Tugnoli,§ Luisa Schenetti,┴Adele Mucci*,‡

3 4 5 6 7 8 9 10 11



Dipartimento di Scienze per la Qualità della Vita, Università di Bologna, C.so D'Augusto 237,

47921 Rimini ‡

Dipartimento di Scienze Chimiche e Geologiche, Università di Modena e Reggio Emilia, Via G.

Campi 103, 41125 Modena §

Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Via Belmeloro 8/A,

40123 Bologna ┴

Dipartimento di Scienze della Vita, Università di Modena e Reggio Emilia, Via G. Campi 103,

41125 Modena

12 13 14 15 16

Corresponding author:

17

Prof. A. Mucci

18

Dipartimento di Scienze Chimiche e Geologiche

19

Università di Modena e Reggio Emilia

20

Via G. Campi 103

21

41125 Modena

22

tel: 00390592058636

23

e-mail: [email protected]

24

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ABSTRACT

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Intact Crocus sativus petals were studied for the first time by HR-MAS NMR spectroscopy,

27

revealing the presence of kinsenoside (2) and goodyeroside A (3), together with 3-hydroxy-γ-

28

butyrolactone (4). These findings were confirmed by HR-NMR analysis of ethanol extract of fresh

29

petals

30

glucopyranosyloxybutanolides occurs during extraction. On the other hand, kaempferol 3-O-

31

sophoroside (1) which is “NMR-silent” in intact petals, is present in extracts.

32

These results suggest to evaluate the utilization of saffron petals for phytopharmaceutical and

33

nutraceutical purposes in order to exploit a waste product of massive production of commercial

34

saffron and point to the application of HR-MAS NMR for monitoring bioactive compounds directly

35

on intact petals avoiding extraction procedure and the consequent hydrolysis reaction.

and

showed

that,

even

though

carried

out

rapidly,

partial

hydrolysis

of

36 37

Keywords: Crocus sativus, Saffron, kinsenoside, goodyeroside A, kaempferol-3-O-sophoroside,

38

HR-MAS NMR

39 40

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INTRODUCTION

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Crocus sativus (fam. Iridaceae) is cultivated in some part of Italy for the utilization of its stigmas

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(saffron) in foods and sweets for both their intense colour and strong taste. Moreover, saffron has

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also been used in preventive medicine: numerous pharmacological tests point to specific therapeutic

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actions and many studies are focused on it.1

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Crocus sativus petals represent the main by-product of saffron production. Considering that saffron

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is one of the most commercialized spices, and that 1 kg of saffron is obtained from more than

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160000 flowers, it is fair to ask whether it is possible to directly use the petals for

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phytopharmaceutical or nutraceutical purposes or as raw material to obtain substances with

50

pharmacological activity.2 Very recently, a paper proposing the use of petals of Crocus sativus as

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source of crocin and and kaempferol, appeared.3

52

A number of studies on hepatoprotective, anti-nociceptive, anti-inflammatory, anti-depressant

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effects of saffron petal extracts are reported in the literature.3-5 It is also known that petals of Crocus

54

sativus contain kaempferol,6,7 which has been reported to be a tyrosinase inhibitor,7 and its

55

glycosides, especially kaempferol-3-O-sophoroside 1 (Fig. 1), which exhibit antioxidant and anti-

56

infammatory activity.8,9

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Hence, the properties reported for petal extracts could be simply due to kaempferol derivatives, but

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they could also be due to other bioactive species. Sprouts of Crocus sativus contain 3-(R)-3-β-D-

59

glucopyranosyloxybutanolide (kinsenoside 2, Fig. 1) and 3-(S)-3-β-D-glucopyranosyloxybutanolide

60

(goodyeroside A 3, Fig. 1),10 that derive from 3-hydroxy-γ-butyrolactone (4, Fig. 1) and have been

61

isolated also from other plants such as Anoectochilus and Goodyera species (Orchidaceae).11-14

62 63

Figure 1 near here

64 65

Both 2 and 3 exhibit hepatoprotective effects;14,15 2 is also antihyperglycemic,12 anti-

66

inflammatory,16 antihyperliposis,17 vascular protective,18 ovariectomy-induced bone loss preventive 3 ACS Paragon Plus Environment

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and osteoclastogenesis suppressing.19 For these reasons efforts towards efficient synthesis of 2 and

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3 by a chemo-enzymatic approach have recently been reported.20

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In order to gain a deeper insight into this subject, and to establish which are the main metabolites

70

present in Crocus sativus petals, we analysed them by high-resolution magic-angle-spinning NMR

71

(HR-MAS NMR) and their ethanol (95%) extract by high-resolution (HR-) NMR. HR-MAS NMR

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spectroscopy allows to derive the biochemical profile of intact (human, animal or plant) tissues,21

73

formed by fast moving small metabolites, that give rise to narrow resonances. Through HR-MAS

74

NMR we tried to have a look inside a complex row matrix without disrupting its structure and

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avoiding hydrolytic processes that can flank extraction. The purpose of this paper is to contribute to

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the utilization of Crocus Sativus petals directly after the separation from saffron. To the best of our

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knowledge, this is the first HR-MAS NMR study of petals.

78 79

EXPERIMENTAL SECTION

80 81

Plant Materials

82 83

Crocus sativus flowers were collected in Abruzzo (Italy), in the Aquila Saffron Protected

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Designation of Origin (PDO) status, at the Farm "Vigna di More" located in Tione degli Abruzzi, in

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autumn 2011. The flowers grew at 700 m above sea level. The bulbs were planted in August on a

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ground prepared a year before (the soil is employed every five years) and the flowers were

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harvested in October. The bulbs were put at 2-3 cm distance from each other, at least 8 cm depth

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in rows of two or three, according to the space and land available. Flowers were hand-picked early

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in the morning, before sunrise before perianth opening, and were placed in traditional wicker

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baskets. After collection, they were stored at 5 °C and send to the lab, where intact petals were used

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for HR-MAS NMR measurements within three days after collection. 4 ACS Paragon Plus Environment

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Extraction

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Fresh petals (10 g) were extracted with 95% ethanol (Sigma Aldrich) and the extract vacuum

95

evaporated (150 mg). The whole process was carried out quickly at room temperature (about 1

96

hour). The extracts were analysed in high resolution NMR and in MS.

97 98 99

NMR measurements 1

H HR-MAS NMR spectra were recorded with a Bruker Avance400 (Bruker BioSpin) spectrometer

100

operating at a frequency of 400.13 MHz. The instrument was equipped with a 1H,13C HR-MAS

101

probe for semisolids and with a BBI probe for liquids. Before HR-MAS examination, intact saffron

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petals were introduced in a MAS zirconia rotor (4 mm OD), 10 µL of D2O were added to provide

103

deuterium for the lock system, fitted with a 50 µl cylindrical insert to increase sample homogeneity,

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and then transferred into the probe cooled to 5 ˚C. Experiments were performed at a temperature of

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5˚C controlled by a Bruker cooling unit.

106

Samples were spun at 4000 Hz and one- (1D) and two-dimensional (2D) spectra were acquired by

107

using the sequences implemented in the Bruker software. The same experiments were carried out on

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D2O extract solution at 25 °C, with a lower number of scans. To record 1H water-presaturated

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spectrum, a composite pulse sequence (zgcppr) with 2 s water presaturation during the relaxation

110

delay, 8 kHz spectral width, 32k data points, 16-8 scans were used. 2D COSY (COrrelation

111

SpectroscopY) spectra were acquired using a standard pulse sequence (cosygpprqf) and 1 s water

112

presaturation during relaxation delay, 2-4 kHz spectral width, 2 k data points, 4 scans per

113

increment, 128 increments. 2D TOCSY (TOtal Correlation SpectroscopY) spectra were acquired

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using a standard pulse sequence (mlevgpph19) and 1 s water presaturation during relaxation delay,

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100 ms mixing (spin-lock) time, 2-4 kHz (spectral width, 4 k data points, 4 scans per increment,

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512 increments. 2D HSQC (Heteronuclear Single Quantum Coherence) edited spectra were 5 ACS Paragon Plus Environment

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acquired using a standard pulse sequence echo-antiecho phase sensitive (hsqcedetgp) and 0.5 s

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relaxation delay, 1.725 ms evolution time, 2-4 kHz spectral width in f2, 2 k data points, 16-8 scans

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per increment, 15 kHz spectral width in f1, 256 increments. 2D HMBC (Heteronuclear Multiple

120

Quantum Coherence) spectra were acquired using a standard pulse sequence (hmbcgplpndqf) and

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0.5 s relaxation delay, 50 ms evolution time, 2-4 kHz spectral width in f2, 2 k data points, 128-32

122

scans per increment, 22 kHz spectral width in f1, 256 increments.

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Deconvolution of 1H NMR selected signals was run with MestReNova 9.1 (2014 Mestrelab

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Research S.L.).

125 126

ESI ion-trap MS measurements

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The negative ion ESI mass spectra and ESI-MS/MS data (collision energies: 10, 15, 20 or 35 eV)

128

were acquired with a LC-MS(n) Ion Trap 6310A (Agilent Technologies) coupled with a HPLC

129

Agilent Series 1200 equipped with a Zorbax SB-C18 column, 30x2.1mm ID, 3.5 µm particle size

130

(Agilent). Eluents: acetonitrile and H2O, 1% formic acid. Chromatographic runs were performed

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using a gradient of 1% formic acid in acetonitrile (98 →10) in 1% formic acid in water (2 → 90).

132

The solvent flow rate was 0.2 ml/min, the temperature kept at 25°C and the injector volume

133

selected was 2 µl. Total ion current (TIC) chromatograms were acquired in both positive and

134

negative mode in the mass range between 100 and 1400 m/z. He was used as collision gas in MS2

135

experiments.

136 137

RESULTS & DISCUSSION

138

The water-presaturated 1H HR-MAS NMR spectrum of saffron petals, Fig. 2a, shows the

139

overlapped signals from a number of metabolites, mainly in the carbohydrate region, whereas only

140

broad and weak signals are found in the aromatic region, at about 6.9 and 7.7 ppm, where multiplets

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from kaempferol derivatives are expected. These two broad resonances are sometimes assigned to 6 ACS Paragon Plus Environment

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polyphenols but they have also been attributed to NH protons.22 On the other hand, some multiplets

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in the range 3.1-2.5 ppm, outside the common carbohydrate region, are detected and other low

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signals mainly attributable to free aminoacids and lipids are present at lower ppm.

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To disentangle the complex spectral pattern it was necessary to use 2D NMR homo- and hetero-

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correlated experiments, such as COSY, TOCSY, HSQC and HMBC. We were thus able to

147

reconstruct molecular skeletons and to compare the chemical shifts and the correlation patterns to

148

those reported in the literature and in NMR databanks, such as HMDB (http://www.hmdb.ca/).

149

Using this approach, we found that the majority of signals in 1H spectrum are due to sucrose (Suc),

150

glucose (Glc) and fructose (Fru), as can be better seen observing HSQC correlations (Fig. 3). Apart

151

those of sugars, other resonances due to 2-4 are detected and assigned, through 2D experiments, as

152

reported in Table 1. The chemical shifts determined by us on intact petals parallel those reported in

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pyridine-d5 by Zhang et al.20 Remarkably, even 2D NMR spectra did not highlight signals from

154

kaempferol or its derivatives in the aromatic region, meaning that, in the cell environment of fresh

155

petals, these molecules are not freely tumbling, but are probably associated with rigid structures

156

within the cell. Other minor resonances were confirmed to derive from free aminoacids (mainly

157

alanine, Ala, glutamine, Gln, and valine, Val).

158

The molar ratio of total 2-4 derivatives relative to water signal, estimated through deconvolution of

159

2-H signals of 2-4 at 2.8-2.5 ppm and of H2O at 4.97 ppm in the not-presaturated 1H NMR

160

spectrum, resulted around 0.3 mol %. It can be roughly converted to 0.8 % in weight with respect

161

water and then, considering a 75 % of water in petals, to 0.6 % of 2-4 in intact petals.

162 163

Figure 2 and 3 near here

164 165

Fresh petals were then extracted rapidly with 95 % ethanol, the vacuum evaporated residue was

166

solubilized in D2O and 1D, 2D NMR and ESI MS/MS spectra were acquired.

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1

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H NMR spectrum of extract is reported in Fig. 2b, and it clearly displays signals in the aromatic

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region that compare well with those reported by Wolfram et al.23 and were assigned, together with

169

other resonances in the carbohydrate region, to kaempferol 3-O-sophoroside 1 (Table 1), and to a

170

minor derivative that differs mainly for the 2',6'-H signals that are found at 8.09 ppm, 8-H at 6.78

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(d, 2.2 Hz) and 6-H at 6.50 (d, 2.2 Hz) ppm and 1-HGlc 5.48 ppm (d, 7.6 Hz) and could be a 7-

172

substituted derivative of 1.

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Apart from differences in the chemical shifts, due to a change from the cell environment to D2O

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solution, resonances from 2-4 were detected also in the ethanol extract, even though in a ratio

175

different with respect to that observed in intact petals: the (2+3)/4 molar ratio passes from 2.5:1 in

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intact petals to less that 1:1 in the extracts and at the same time the free glucose signals enhance

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with respect to those of sucrose (1-HαGlc/1-Hsuc passes from 0.4 to 1.2). Hence, the extraction

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process, even though carried out rapidly and without acidic conditions, promoted hydrolysis of 2

179

and 3 to 4 and free Glc.

180

ElectroSpray Ionization Ion Trap Mass Spectrometry (ESI-IT MS) was finally employed to confirm

181

the presence of 1 and to clarify the structure of the minor flavonol detected in ethanol extract (Fig.

182

4). The two major peaks detected in negative mode correspond to 609 and 771 m/z [M-H]- pseudo-

183

molecular ions. The collision induced fragmentation (CID) with He gas of 609 (highest) peak gave

184

429 m/z [M-C6H12O6-H]-and 285 m/z [kaempferol-H]- as expected for two subsequent hexose losses

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starting from 1. On the other hand, CID of 771 m/z gave 609 m/z, corresponding to a loss of

186

C6H10O5 demonstrating that this derivative contains a further hexose unit. Minor peaks,

187

corresponding to pseudomolecular species of 625 m/z (which decomposes to 463 m/z through

188

hexose loss) and 651 m/z (which gives 471 m/z and 285 m/z under CID) were also detected. The

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former could be due to quercetin sophoroside, the latter is probably an acetylated derivative.

190 191

Figure 4 near here 8 ACS Paragon Plus Environment

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In conclusion, this work shows that HR-MAS NMR can be employed to monitor bioactive

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compounds freely tumbling in the cell environment, directly on intact petals. HR-MAS NMR

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allows detecting the presence of 2, 3 and 4 directly on intact Crocus sativus petals, without the need

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of extraction processes. Their content was estimated by HR-MAS NMR to be roughly 0.6 %. HR-

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MAS NMR does not detect instead flavonols, especially 1, that are still contained in petals in a not

198

negligible amount, as demonstrated by 1H NMR analysis of ethanol extract. This implies that

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flavonol derivatives in saffron petals have low tumbling rates, that could be due to their close

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association to macromolecular species in cell walls.24

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The 3-hydroxybutyrolactone derivatives 2-4 contained in Crocus sativus petals are biologically

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active species that, together with 1, probably contribute to confer hepatoprotective,

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antihyperglycemic, anti-inflammatory and other effects to petal extracts. The extraction process

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leads to partial hydrolysis of petal constituents, hence it could be useful to evaluate the direct

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employment of saffron petals for phytopharmaceutical and nutraceutical purposes, in order to better

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exploit a waste product of massive production of commercial saffron.

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The data presented in this study strongly support the idea that petals of Crocus sativus, are not a

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waste, but they can be used for their biological activity in specific foods, as well as in herbalist

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products. This can have a major impact for the community of saffron, the cultivation of which

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represents an opportunity to improve and develop the economy of the agricultural sector in poor

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European regions. The exploitation not only of stigmas but also of petals as raw material for health

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enhancing products would further enhance the economical value of this activity and reduce waste

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production.

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Acknowledgments

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We are very grateful to Prof. Dario Iarossi and to "Vigna di More" farm, located in Tione degli

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Abruzzi, for the supply of Crocus Sativus petals. http://www.valleaterno.it/vignadimore/

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Figure Legends

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Fig. 1. Structures of identified compounds in Crocus sativus petals and ethanol extract.

222

Fig. 2. Water-presaturated 1H HR-MAS NMR spectrum of fresh saffron petals (a) and 1H NMR

223

spectrum of ethanol (95%) extract of fresh saffron petals in D2O solution (b).

224

Fig. 3. Enlarged carbohydrate (a) and aliphatic (b) regions of HSQC HR-MAS NMR spectrum of

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fresh saffron petals. ChoCC =choline containing compounds.

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Fig. 4. ESI-IT MS/MS spectra of 1 (left) and of minor kaempferol derivative (right).

227

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References

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Quantitative Determination of Flavonoids from Crocus sativus L. Petals by LC-MS/MS. Nat. Prod.

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(3) Zeka, K.; Ruparelia, K.C.; Continenza, M.A.; Stagos, D.; Vegliò, F.; Arroo, R.R.J. Petals of

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Crocus sativus L. as a potential source of the antioxidants crocin and kaempferol. Fitoterapia 2015.

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petals of Carthamus tinctorius. J. Appl. Biol. Chem. 2007, 50, 175-178.

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sprouts of Crocus sativus. Planta Med. 1999, 65, 425-427.

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(11) Ito, A.; Kasa, R. Aliphatic and aromatic glucosides from Anoectochilus koshunensis.

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Phytochemistry 1993, 33, 1133-1137.

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(12) Du, X.M.; Yoshizawa, T.; Shoyama, Y. Butanoic acid glucoside composition of whole body

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and in vitro plantlets of Anoectochilus formosanus. Phytochemistry 1998, 49, 1925-1928.

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(13) Zhang, Y.H.; Cai, J.Y.; Ruan, H.L. Antihyperglycemic activity of kinsenoside, a high yielding

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constituent from Anoectochilus roxburghii in streptozotocin diabetic rats. J. Ethnopharmacol. 2007,

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formosanus suppresses LPS-stimulated inflammatory reactions inmacrophages and endotoxin shock

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its antihyperliposis effect. Biol. Pharm. Bull. 2001, 24, 65-69.

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from Anoectochilus roxburghii under high glucose condition. Fitoterapia 2013, 86, 163-170.

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Table 1 1 H and 13C NMR data of 2-4 (ppma) in Crocus sativus petals as obtained by HR-MAS NMR and of 1-4 extracted with ethanol (95%) (D2O). 2b

2c

3b 1

C

1

179.7

-

C

1

1

-

182.5

-

180.3

-

-

2

2.99, 38.2 2.71 dd, 18.1, 6.1 Hz; d, 18.1 Hz)

2.87, 37.2 2.65 (dd, 18.0, 6.4 Hz; ddd, 18.0, 1.9, 0.8 Hz)

3.03, 38.5 2.78 dd, 18.6, 6.1 Hz; d, 18.6 Hz)

2.89, 38.1 2.73 (dd, 18.2, 1.4 Hz; dd, 18.2, 6.4 Hz)

2.97, 40.1 2.51 (dd, 18.1, 6.1 Hz; d, 18.1 Hz)

2.83, 39.7 2.37 (dd, 17.7, 5.8 Hz; dt, 17.7, 1.3 Hz)

-

160.3

3

4.86

77.9

4.72

77.2

4.86

77.9

4.73

77.4

4.71 70.0 (t, 4.6 Hz)

4.57 69.5 (ddt, 4.3, 5.8, 1.3 Hz)

-

136.1

4

4.55

77.4

4.54,d 4.49

77.3

4.59

77.9

4.47d

76.4

4.54, 79.8 4.36 (d, 10.3 Hz)

4.42, 78.9 4.22d (dd, 10.0, 4.3 Hz; dt, 10.0, 1.2 Hz)

-

nd

4a

-

106.9

5

-

164.2

6

6.22

101.0

7

-

167.2

8

6.42

95.9

8a

-

159.6

e

C

1

182.5

-

13

H

C

1

13

C

1

180.1

-

183.0

-

1c 13

H

13

4c

13

H

C

4b

1

H

13

3c

H

e

H

H

13

C

1'

4.55

103.9

4.40 104.8 (d, 7.8 Hz)

4.58

103.7

4.38 105.1 (d, 7.8 Hz)

-

123.9

2'

3.27

75.6

3.19

3.27

75.6

3.19

8.05

133.5

75.9

75.9

3'

3.49

78.4

3.36

79.2

3.49

78.4

3.36

79.2

6.92

117.5

4'

f

f

3.29

72.8

f

f

3.29

72.8

-

162.8

5'

f

f

79.2

f

f

3.29

79.2

6.92

117.5

6'

f

f

63.9

f

f

3.67, 3.88

63.9

8.05

133.5

5.43g

102.2

3.29 3.67, 3.88

1”

15 ACS Paragon Plus Environment

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Page 16 of 22

2”

3.74h

84.3

3”

3.61

79.0

4”

3.36

5”

3.20

79.5

6”

3.49, 3.69

63.7

1”'

4.78

106.0

2”'

3.37

76.8

3”',4”',5”'

3.413.30

6”'

3.69, 3.80

63.5

a

chemical shifts refer to sucrose 1-H at 5.40 and 94.8 ppm, respectively; intact petals; c petals extracted with ethanol (95%); d long range correlation with C=O. e long range correlations at 4.40/77.2 ppm and 4.38/77.4 in HMBC spectrum. f overlapped to β-Glc. g long range correlations with 136.0 ppm carbon in HMBC spectrum h long range correlations with 102.2 and 106.0 ppm carbons in HMBC spectrum. b

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339 340 341

Fig. 1. Structures of identified compounds in Crocus sativus petals and ethanol extract.

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354 355

Fig. 2. Water-presaturated 1H HR-MAS NMR spectrum of fresh saffron petals (a) and 1H NMR

356

spectrum of ethanol (95%) extract of fresh saffron petals in D2O solution (b).

357 358 359 360 361 362

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Fig. 3. Enlarged carbohydrate (a) and aliphatic (b) regions of HSQC HR-MAS NMR spectrum of

367

fresh saffron petals. ChoCC =choline containing compounds.

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Fig. 4. ESI-IT MS/MS spectra of 1 (left) and of minor kaempferol derivative (right).

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Journal of Agricultural and Food Chemistry

TOC image

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kinsenoside

goodyeroside A

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