Analytical and Bioanalytical Chemistry

, Volume 402, Issue 3, pp 1327–1336

New identification of proanthocyanidins in cinnamon (Cinnamomum zeylanicum L.) using MALDI-TOF/TOF mass spectrometry

Authors

  • María Luisa Mateos-Martín
    • Institute for Advanced Chemistry of Catalonia (IQAC), CSIC
    • Institute for Advanced Chemistry of Catalonia (IQAC), CSIC
    • Departament de Química AnalíticaUniversitat de Barcelona
  • Carmen Quero
    • Institute for Advanced Chemistry of Catalonia (IQAC), CSIC
  • Jara Pérez-Jiménez
    • Institute for Advanced Chemistry of Catalonia (IQAC), CSIC
  • Josep Lluís Torres
    • Institute for Advanced Chemistry of Catalonia (IQAC), CSIC
Original Paper

DOI: 10.1007/s00216-011-5557-3

Cite this article as:
Mateos-Martín, M.L., Fuguet, E., Quero, C. et al. Anal Bioanal Chem (2012) 402: 1327. doi:10.1007/s00216-011-5557-3

Abstract

The inner bark of Ceylon cinnamon (Cinnamomum zeylanicum L.) is commonly used as a spice and has also been widely employed in the treatment and prevention of disease. The positive health effects associated with the consumption of cinnamon could in part be due to its phenolic composition; proanthocyanidins (PA) are the major polyphenolic component in commercial cinnamon. We present a thorough study of the PA profile of cinnamon obtained using matrix-assisted laser desorption/ionization tandem time-of-flight (MALDI-TOF/TOF) mass spectrometry. In addition to the advantages of MALDI-TOF as a sensitive technique for the analysis of high-molecular-weight compounds, the tandem arrangement allows the identification of the compounds through their fragmentation patterns from MS/MS experiments. This is the first time that this technique has been used to analyze polymeric PA. The results show that cinnamon PA are more complex than was previously thought. We show here for the first time that they contain (epi)gallocatechin and (epi)catechingallate units. As gallates (galloyl moieties) and the pyrogallol group in gallocatechins have been related to the biological activity of grape and tea polyphenols, the presence of these substructures may explain some of the properties of cinnamon extracts. MALDI-TOF/TOF reveals that cinnamon bark PA include combinations of (epi)catechin, (epi)catechingallate, (epi)gallocatechin, and (epi)afzelechin, which results in a highly heterogeneous mixture of procyanidins, prodelphinidins, and propelargonidins.

Keywords

MALDI-TOF/TOFCinnamonPolyphenolsProanthocyanidinsMass spectrometry

Introduction

Ceylon cinnamon (Cinnamomum zeylanicum L.) has been used as a spice in several cultures for centuries. In addition to its culinary uses, cinnamon has been employed in traditional herbal medicine to treat a variety of health conditions [1]. Generally, the part used as a spice or for medical purposes is the inner bark (cinnamomi cortex). Recently, the efficacy of cinnamon in the maintenance of physiologically balanced parameters has been studied, and new properties of interest for clinical use have been discovered. In particular, the most well-documented health benefit provided by this spice is related to the prevention and treatment of type 2 diabetes [25]. In addition, other evidence suggests that cinnamon may be effective in the treatment of cancer [6, 7] and infectious diseases [8, 9], and that it also shows anti-inflammatory [10, 11], antimicrobial [1214], antioxidant [1517], hypotensive [18], and cholesterol-lowering effects [5, 19].

The positive health effects associated with the consumption of cinnamon could in part be attributed to its phenolic composition [2022]. Proanthocyanidins (PA), also known as condensed tannins, constitute the major type of polyphenols in commercial cinnamon [23]. PA are mixtures of oligomers and polymers composed of flavan-3-ol units (Fig. 1). PA consisting exclusively of (epi)catechin are named procyanidins (PC), while those containing (epi)gallocatechin and (epi)afzelechin are called prodelphinidins and propelargonidins, respectively. Additionally, PC can be esterified with gallic acid, as happens in the case of grape tannins [24, 25]. The flavan-3-ol units are linked by C4 → C8 or C4 → C6 bonds (B type) and occasionally by an additional C2 → O7 ether bond (A-type) (Fig. 2). A particular characteristic of cinnamon is that most of its PA are A type [26], in contrast to most common sources of PA, such as grape, in which most are B type [24, 25].
https://static-content.springer.com/image/art%3A10.1007%2Fs00216-011-5557-3/MediaObjects/216_2011_5557_Fig1_HTML.gif
Fig. 1

Most important structures of the flavan-3-ol units in proanthocyanidins

https://static-content.springer.com/image/art%3A10.1007%2Fs00216-011-5557-3/MediaObjects/216_2011_5557_Fig2_HTML.gif
Fig. 2

Dimeric structures of procyanidins with B-type and A-type linkages

The size of the proanthocyanidin molecules is an important feature that may influence their physiological role. The presence of polymeric PA with a high degree of polymerization is particularly interesting since in vitro and in vivo studies have suggested that large PA progressively release (epi)catechin units during their transit along the intestinal tract [27]. Most of these units, together with intact PA, reach the colon [28, 29], where they are processed by the colonic microbiota into phenolic acids and other absorbable metabolites [30, 31]. The array of compounds released and absorbed in the intestines by different physiological processes may contribute to the preventive effects of polyphenols.

Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) is a soft ionization MS technique which provides mass spectra that are mainly composed of signals corresponding to ions of intact molecules. It has the capacity to detect high-molecular-weight compounds and also to detect patterns of oligomers with small differences in mass. One of the main advantages of MALDI-TOF over other MS systems is its high sensitivity over a large mass range. However, the elucidation of complex polymeric species requires more sophisticated fragmentation analysis. MALDI-TOF/TOF provides high resolution, and in addition, MS/MS experiments can be performed on particular m/z values to obtain important information on the molecular structures of the polymeric compounds. MALDI-TOF has been widely used in the characterization of polymeric condensed tannins [32], but rarely in the analysis of cinnamon PA. Indeed, very few studies have looked at cinnamon PA at all [26, 33, 34]. MALDI-TOF/TOF, a technique widely used in proteomics, has not yet been applied to the analysis of PA. The aim of this work was to advance in the characterization of cinnamon PA and to show that MALDI-TOF/TOF is a sensitive and rapid technique suitable for detecting and characterizing new bioactive polymeric compounds in foods and natural extracts.

Experimental

Reagents and materials

Common cinnamon was purchased at a local market in Barcelona (Spain), and grape seed extract was from JF-NATURAL (Tianjin, China). The MALDI matrix, 2,5-dihydroxybenzoic acid (99%), and cesium trifluoroacetate (6 M aqueous solution) were from Sigma Chemical (Saint Louis, MO, USA); sodium chloride (99%) was from Carlo Erba Reagents (Rodano, Italy). For the extraction and fractionation of polyphenols, analytical grade hexane, acetone, and acetic acid (Merck, Darmstadt, Germany) were used. Trifluoroacetic acid (TFA; biotech grade distilled in-house) was from Fluorochem (Hadfield, UK). Water was purified using a Milli-Q plus system from Millipore (Bedford, MA, USA) to a resistivity of 18.2 MΩ cm.

Procedures

Sample extraction

Commercial cinnamon (5 g) was defatted with hexane (3 × 40 mL) and air-dried overnight. The dried extract was extracted with 4 mL of a mixture of acetone/water/acetic acid (7:2.5:0.5, v:v:v). The supernatant was decanted, filtered, and freeze-dried.

Sample preparation

Freeze-dried cinnamon extract or commercial grape extract (approximately 1 mg) was dissolved in aqueous 1% aqueous TFA (1 mL). The matrix solution was prepared by dissolving 2,5-dihydroxybenzoic acid (10 mg) and either sodium chloride or cesium trifluoroacetate (cationization reagent, 1 mg) in aqueous 1% aqueous TFA (1 mL). Aliquots of sample and matrix solutions were mixed (1:1, v:v), vortexed, and then deposited (2 μL) on the target plate. Once the solvent was dried (at room temperature), the crystals were analyzed by MALDI-TOF/TOF as detailed below.

MALDI-TOF/TOF mass spectrometry

A MALDI-TOF/TOF mass spectrometer (AutoFLEX III, Bruker Daltonics, Bremen, Germany) equipped with a pulsed N2 laser (337 nm) controlled by the Flexcontrol 1.1 software package was used to obtain MS and MS/MS data. The accelerating voltage was 20 kV and the reflectron voltage 21 kV. Spectra are the sum of 500 shots with a frequency of 200 Hz. Both positive and negative reflectron modes were tried and the positive mode finally chosen, in agreement with the literature for this type of compounds [32]. The MS/MS spectra were obtained in the collision-induced dissociation (CID) mode using argon as the collision gas.

Results and discussion

Procyanidins in cinnamon

As this was the first time that cinnamon PA were analyzed by MALDI-TOF/TOF, we first examined the behavior of grape PA, which has been widely studied using several MS techniques, including MALDI-TOF MS [24, 25, 3538]. The mass range analyzed was the same for both the cinnamon and grape extracts; to confirm the identity of the compounds, MS/MS was performed on the fragments that gave the peaks with the highest intensities.

It is known that PC are the main constituents of cinnamon extracts [26, 33]. To date, analyses performed using LC-ESI-MS have reported oligomeric structures mainly consisting of (epi)catechin units with a high proportion of A-type structures. Larger PA were only detected via doubly charged ions. Here, we report a series of oligomeric and polymeric cinnamon PA molecular ions detected by MALDI-TOF/TOF (Table 1). The masses recorded correspond to sodium ion adducts (+23 Da) in the positive ion mode. All the masses were confirmed, using cesium trifluoroacetate as the cationizing agent, to be the corresponding cesium ion adducts (+133 Da, not shown). Using this technique, we have clearly detected PA polymers with a degree of polymerization (DP) of up to 11. Figure 3 shows the spectrum of the cinnamon extract from m/z 500 to 2,000 (Fig. 3a) and from m/z 2,000 to 3,500 (Fig. 3b). Different series can be clearly identified. The first series (procyanidins) starts at [M + Na]+ 599.5, which corresponds to an A-type dimer of (epi)catechin and shows mass increments of 288 Da, which correspond to one (epi)catechin moiety. This first series corresponds, therefore, to structures composed exclusively of (epi)catechin units, where all the compounds have at least one A-type substructure.
Table 1

Calculated and observed masses of cinnamon PC by MALDI-TOF/TOF MS (all structures contain one A-type linkage)

Polymer

Galloyl units

Calculated [M + Na+]

Observed [M + Na+]

Dimer

0

599.5

599.5

1

751.7

753.7

2

903.8a

903.9

Trimer

0

887.8

887.9

1

1,039.9

1,040.1

2

1,192.0a

1,192.1

Tetramer

0

1,176.0

1,176.1

1

1,328.1

1,328.3

2

1,480.2a

1,480.4

Pentamer

0

1,464.3

1,464.4

1

1,616.4

1,616.5

2

1,768.5a

1,768.6

Hexamer

0

1,752.5

1,752.6

1

1,904.7

1,904.7

2

2,056.8a

2,056.9

Heptamer

0

2,040.8

2,040.9

1

2,192.9

2,193.0

2

2,345.0a

2,345.1

Octamer

0

2,329.1

2,329.1

1

2,481.2

2,481.2

2

2,633.3a

2,633.4

Nonamer

0

2,617.3

2,617.4

1

2,769.4

2,769.4

2

2,921.5a

2,921.5

Decamer

0

2,905.6

2,905.6

1

3,057.7

3,057.7

2

3,209.8a

3,210.0

Undecamer

0

3,193.8

3,193.8

1

3,345.9

3,341.8

am/z also compatible with a prodelphinidin one unit larger with one (epi)gallocatechin moiety and without (epi)catechingallate

https://static-content.springer.com/image/art%3A10.1007%2Fs00216-011-5557-3/MediaObjects/216_2011_5557_Fig3_HTML.gif
Fig. 3

Mass spectrum of cinnamon extract in the m/z range 500–2,000 (a) and in the m/z range 2,000–3,500 (b). c Amplification of the cinnamon extract spectrum in the m/z range 1,310—1,515

The presence of A-type linkages can easily be observed in the mass spectrum because the signals are shifted two mass units from the signals of B-type PC, corresponding to the two hydrogen atoms that are lost in the formation of the extra interflavanic linkage. While the dimeric structures present are either B type or A type, the trimers and all the species with higher DP contain at least one A-type substructure. The full mass range spectrum obtained for the grape extract was very similar to that presented in Fig. 3, with the main difference being that B-type linkages were more abundant, as described in the literature [35, 36].

MALDI-TOF/TOF allows an accurate and highly sensitive elucidation of compounds through their MS/MS spectra. The spectrum of a tetrameric procyanidin composed only of (epi)catechin units (m/z 1,176.1, [M + Na]+) is shown in Fig. 4a. Figure 5 shows the fragmentation pattern of this compound. The observed fragments agree with the typical fragmentation patterns already described in the literature for polyphenolic compounds [26, 3841]. The fragment at m/z 1,023.8 is the result of retro-Diels–Alder (RDA) cleavage of an (epi)catechin unit (−152 Da), and the fragment at m/z 1,005.8 is the corresponding loss of water (−18 Da). The fragment at m/z 1,049.9 is caused by heterocyclic ring fission (HRF) of the upper (epi)catechin unit (loss of 126 Da). The fragments at m/z 887.7 and 599.4 correspond to the trimer and the dimer PC, respectively, and are originated by quinone methide (QM) cleavages. Again, the fragmentation of the trimer (m/z 887.7) and the dimer (m/z 599.4) was observed through an RDA cleavage (m/z 735.5 and 447.4 for the trimer and the dimer, respectively), that then yields ions at m/z 717.5 and 429.4 due to the consecutive loss of a water molecule. HRF is also observed for the trimer and the dimer, generating ions at m/z 761.6 and 473.4, respectively. Finally, a QM reaction with the dimer results in the fragments at m/z 311.3 and 309.3. The two consecutive losses of 288 Da from the molecular mass, together with the presence of the ion at m/z 599.4 (A-type dimer), locate the A-type linkage in the terminal unit of the tetramer.
https://static-content.springer.com/image/art%3A10.1007%2Fs00216-011-5557-3/MediaObjects/216_2011_5557_Fig4_HTML.gif
Fig. 4

Product ion mass spectra of: an (epi)catechin tetramer (m/z 1,176.1) (a); an (epi)catechin tetramer with one (epi)catechin-O-gallate unit (m/z 1,328.2) (b); an (epi)catechin tetramer with one (epi)gallocatechin unit and/or a trimer with two (epi)catechingallate units (m/z 1,192.1) (c); and an (epi)catechin pentamer with one (epi)afzelechin unit (m/z 1,448.3) (d). All of them have one A-type linkage

https://static-content.springer.com/image/art%3A10.1007%2Fs00216-011-5557-3/MediaObjects/216_2011_5557_Fig5_HTML.gif
Fig. 5

Fragmentation pattern of an (epi)catechin tetramer with one A-type linkage (m/z 1,176)

Some of the m/z recorded and listed in Table 1 are compatible with structures composed of (epi)catechin mixed with (epi)catechingallate (one or even two galloyl units). To our knowledge, this is the first time that gallates, which are common among grape PC [42], are detected in cinnamon extracts. Galloylated PA are particularly interesting because gallates appear to be important for the biological activity of these polyphenols [43]. A second series of signals neatly identified in Fig. 3 (monogallate) corresponds to structures with one (epi)catechingallate unit. The highest degree of polymerization for this series was also 11. Mass increments of 288 Da due to the (epi)catechin moieties are observed throughout the series that is shifted 152 mass units (gallate moiety) with respect the signals of the first series (PC). The patterns of fragmentation and MS/MS experiments confirmed the presence of galloylated moieties for all the compounds listed in Table 1. An example is given in Fig. 4b which shows the spectrum corresponding to an A-type tetramer with one (epi)catechingallate unit (m/z 1,328.2). A direct comparison with Fig. 4a (same compound without the gallate moiety) reveals that, in addition to the peaks coincident with Fig. 4a (m/z 1,175.3, 887.7, 717.6, 599.6, 309.4), some new signals characteristic of the gallate moiety appear. The first peak is at m/z 463.5 and matches the sodium adduct of an (epi)catechingallate loss. In fact, this peak, together with the peak at m/z 887.7 (A-type (epi)catechin trimer), is the result of a QM reaction of the tetramer. The second characteristic peak is the one at m/z 751.6, also a QM product, now between the second and the third monomeric units of the tetramer. This peak matches a dimer composed by one (epi)catechin and one (epi)catechingallate. The presence of these peaks suggests that the gallate moiety may be located in the terminal unit of the tetramer.

A third series ((epi)gallocatechin or digallate) can also be observed in Fig. 3. The increment of 152 mass units with respect to the monogallate series suggests the presence of a digallate series. Other peaks that would match trigallate or even tetragallate oligomers have been observed, but are not included in Table 1 because the low intensity of these peaks did not allow confirmation by MS/MS experiments.

Prodelphinidins in cinnamon

By carefully examining the MS spectra of the cinnamon extract, a series of signals that are shifted 16 mass units with respect to the (epi)catechin series can be observed ((epi)gallocatechin or digallate series). This series is compatible with digallates, as suggested above, but also with species containing (epi)gallocatechin units (Fig. 1). Because MALDI spectrometers are not coupled to a separation system, experiments are performed by direct insertion of the whole sample without any previous separation, so compounds with equal mass appear together in the spectrum. MS/MS may then be used to identify each of the different species with equal mass, provided the signals are strong enough. We performed MS/MS experiments on those molecular ions that gave high-intensity signals. Figure 4c is the MS/MS spectrum corresponding to the molecular ion with m/z 1,192.1. This mass matches either a tetramer that contains one (epi)gallocatechin unit and one A-type linkage or a trimer with two (epi)catechingallate units and one A-type linkage. When examining the MS/MS spectrum, there are several pieces of evidence that support the hypothesis that we are dealing with the tetramer with one (epi)gallocatechin unit. First, the characteristic (epi)catechingallate peak at m/z 463 does not appear in the spectrum; second, a peak at m/z 887.4 corresponding to the loss of an (epi)gallocatechin unit (304 mass units) directly from the molecular ion can be clearly observed; in addition, the peaks at m/z 1,049.5 and m/z 1,005.2 could be the result of HRF and an RDA cleavage plus the loss of a water molecule, respectively, from the (epi)gallocatechin unit. Although the peaks at m/z 1,039.7 (loss of 152 mass units) and m/z 1,021.8 (consecutive loss of water) may support the hypothesis that this is a digallate series, they could also correspond to an RDA cleavage of an (epi)catechin unit in a tetramer that contains one (epi)gallocatechin. In fact, the large number of fragments observed indicates that the spectrum may come from a mixture of compounds that may include a digallate trimer and a mixture of tetramers of (epi)gallocatechin with the (epi)gallocatechin unit in different positions. For instance, the fragment at m/z 887.4 ((epi)catechin trimer) would come from a tetramer with a terminal (epi)gallocatechin moiety, and the fragments at m/z 903.6 and 615.4 (consecutive losses of 288 mass units: (epi)catechin monomers) would support the hypothesis of the (epi)gallocatechin moieties as extension units of the oligomer. The presence of prodelphinidins in the cinnamon extract is evident, which, as also noted for the galloyl moieties, has never been reported before. This may also be of biological significance since the pyrogallol moieties of (epi)gallocatechins (e.g., in tea) are more reactive than the catechol moieties of (epi)catechins (e.g., in grape). They can even promote the formation of free radicals, so-called pro-oxidant activity, which may end up stimulating endogenous antioxidant responses that result in more effective overall antioxidant activity in vivo than by direct free radical scavenging [44].

Many other low-intensity peaks attributable to prodelphinidins can be observed in the spectrum in Fig. 3. These peaks, included in Table 2, would match oligomers of (epi)catechin with two (epi)gallocatechin units or PA that contain both (epi)catechin-3-O-gallate and (epi)gallocatechin units. Amplification of a section of the cinnamon extract spectrum (Fig. 3c) reveals the presence of peaks corresponding to an (epi)catechin tetramer with one gallate unit (m/z 1,328.2) and an (epi)catechin tetramer with one gallate and one (epi)gallocatechin moieties (m/z 1,344.2) as well as pentameric PA. Other peaks that would match prodelphinidins with one (epi)gallocatehin unit and one or even two (epi)catechingallates have been observed, but are not included in Table 2 because the low intensity of these peaks did not allow a confirmation by MS/MS experiments.
Table 2

Calculated and observed masses of cinnamon prodelphinidins by MALDI-TOF/TOF MS (all structures contain one A-type linkage)

Polymer

(Epi)gallocatechin units

Calculated [M + Na+]

Observed [M + Na+]

Dimer

1

615.5

617.5

2

631.5

633.5

Trimer

1

903.7a

903.9

2

919.7

919.9

Tetramer

1

1,192.0a

1,192.1

2

1,208.0

1,208.2

Pentamer

1

1,480.4a

1,480.4

2

1,496.4

1,496.4

Hexamer

1

1,768.7a

1,768.6

2

1,784.7

1,784.6

Heptamer

1

2,056.9a

2,056.8

2

2,072.9

2,072.9

Octamer

1

2,345.2a

2,345.1

2

2,361.2

2,361.2

Nonamer

1

2,633.4a

2,633.4

2

2,649.4

2,649.4

Decamer

1

2,921.7a

2,921.5

2

2,937.7

2,937.8

am/z also compatible with a proanthocyanidin one unit shorter with two (epi)catechingallate moieties and without (epi)gallocatechin

Propelargonidins in cinnamon

In addition to PC and prodelphinidins with and without gallate moieties, MALDI-TOF/TOF enabled us to detect heteropolymers with (epi)afzelechin moieties (propelargonidins) with a DP of up to 11. Propelargonidins of lower DP have been reported before in cinnamon [33, 34]. The propelargonidins we identified in cinnamon were composed of (epi)catechin and (epi)afzelechin units, with at least one A-type linkage. The most intense peaks corresponded to oligomeric species with a single (epi)afzelechin unit. Table 3 shows the masses of the propelargonidins that yield intense MS signals. The product ion spectrum of a pentameric propelargonidin composed of four (epi)catechin units and one (epi)afzelechin unit (m/z 1,448.4, [M + Na]+) is shown in Fig. 4d. The fragment at m/z 1,159.8 corresponds to a tetramer with one (epi)afzelechin unit and one A-type linkage. The fragment at m/z 889.5 (B-type (epi)catechin trimer) implies the loss of the (epi)afzelechin unit, and the signals at m/z 601.0 and 310.4 (B-type dimer and monomer, respectively) are the result of the consecutive loss of (epi)catechin units. Several RDA reactions are also observed (m/z 1,295.9, 1,007.6, and 737.2). These fragments indicate the following structure for the compound: (epi)cat-(epi)cat-(epi)cat-A-(epi)afz-(epi)cat, although other combinations may also be present.
Table 3

Calculated and observed masses of the main propelargonidins in cinnamon by MALDI-TOF/TOF MS

Polymer

(Epi)afzelechin units

A-type linkages

Calculated [M + Na+]

Observed [M + Na+]

Dimer

1

1

583.5

583.5

2

1

567.5

567.3

Trimer

1

1

871.8

871.9

1

2

869.8

869.9

3

1

841.9

841.9

Tetramer

1

1

1,160.0

1,160.1

2

3

1,140.0

1,140.1

4

3

1,110.0

1,110.1

Pentamer

1

1

1,448.3

1,448.4

4

2

1,398.3

1,398.4

5

3

1,380.3

1,380.3

Hexamer

1

1

1,736.5

1,736.6

1

2

1,734.5

1,734.6

4

2

1,686.5

1,686.6

5

2

1,670.5

1,670.6

6

2

1,654.5

1,654.6

Heptamer

1

1

2,024.8

2,024.8

5

2

1,958.8

1,958.8

6

2

1,942.8

1,942.8

7

2

1,927.8

1,927.8

Octamer

1

1

2,313.1

2,313.1

1

2

2,311.1

2,311.1

5

3

2,245.1

2,245.1

7

5

2,209.1

2,208.9

8

5

2,193.1

2,193.0

Nonamer

1

1

2,601.3

2,601.3

7

5

2,497.3

2,497.2

8

5

2,481.3

2,481.2

9

7

2,461.3

2,461.2

Decamer

1

1

2,889.6

2,889.6

1

2

2,887.6

2,887.6

8

5

2,769.6

2,769.5

Undecamer

1

1

3,177.8

3,176.7

Conclusions

We present here the first report of cinnamon PA determined by MALDI-TOF/TOF. MALDI-TOF/TOF in CID mode is a powerful technique for the structural analysis of polyphenolic polymers. The technique combines high sensitivity for high-molecular-weight compounds with the possibility of extracting structural information via the fragmentation patterns obtained from MS/MS experiments. We show that cinnamon PA contain substructures never described before for this source. Apart from the most common flavanol (epi)catechin and (epi)afzelechin, cinnamon PA contain (epi)catechingallate and (epi)gallocatechin units. As gallates (galloyl moities) and the pyrogallol group in (epi)gallocatechins have been related to the biological activity of grape and tea polyphenols, the presence of these substructures may explain some of the properties of cinnamon extracts. MALDI-TOF/TOF reveals that cinnamon bark PA include combinations of (epi)catechin, (epi)catechingallate, (epi)gallocatechin, and (epi)afzelechin, resulting in a highly heterogeneous mixture of procyanidins, prodelphinidins, and propelargonidins.

Acknowledgments

This work was supported by the Spanish Ministry of Education and Science (research grants AGL2009-12374-C03-03/ALI). J.P-J thanks the Spanish Ministry of Science and Innovation for granting her a Sara Borrell postdoctoral contract (CD09/00068). Language revision by Christopher Evans is also appreciated.

Copyright information

© Springer-Verlag 2011