Rakesh Jaiswal

Profiling and Characterization by LC-MSn of the Chlorogenic Acids and Hydroxycinnamoylshikimate Esters in Maté (Ilex paraguariensis)†

The chlorogenic acids of mate (Ilex paraguariensis) have been investigated qualitatively by LC-MS(n). Forty-two chlorogenic acids were detected and all characterized to regioisomeric level on the basis of their fragmentation pattern in tandem MS spectra, 24 of them for the first time from this source. Both chlorogenic acids based on trans- and cis-cinnamic acid substituents were identified. Assignment to the level of individual regioisomers was possible for eight caffeoylquinic acids (1-8), five dicaffeoylquinic acids (20-24), six feruloylquinic acids (9-14), two diferuloyl quinic acids (25 and 26), five p-coumaroylquinic acids (15-19), four caffeoyl-p-coumaroylquinic acids (34-37), seven caffeoyl-feruloylquinic acids (27-33), three caffeoyl-sinapoylquinic acids (38-40), one tricaffeoylquinic acid (41), and one dicaffeoyl-feruloylquinic acid (42). Furthermore, four caffeoylshikimates (43-46), three dicaffeoylshikimates (47-49), one tricaffeoylshikimate (51), and one feruloylshikimate (50) have been detected and shown to possess characteristic tandem MS spectra and were assigned by comparison to reference standards.

Profile and Characterization of the Chlorogenic Acids in Green Robusta Coffee Beans by LC-MSn: Identification of Seven New Classes of Compounds

LC-MS(n) (n = 2-4) has been used to detect and characterize in green Robusta coffee beans 15 quantitatively minor sinapic acid and trimethoxycinnamoylquinic acid-containing chlorogenic acids, all reported for the first time from this source, with 13 of them not previously reported in nature. These comprise 3-sinapoylquinic acid, 4-sinapoylquinic acid, and 5-sinapoylquinic acid (M(r) 398); 3-sinapoyl-5-caffeoylquinic acid, 3-sinapoyl-4-caffeoylquinic acid, and 4-sinapoyl-3-caffeoylquinic acid (M(r) 560); 3-(3,5-dihydroxy-4-methoxy)cinnamoyl-4-feruloylquinic acid (M(r) 560); 3-sinapoyl-5-feruloylquinic acid, 3-feruloyl-4-sinapoylquinic acid, and 4-sinapoyl-5-feruloylquinic acid (M(r) 574); 4-trimethoxycinnamoyl-5-caffeoylquinic acid, 3-trimethoxycinnamoyl-5-caffeoylquinic acid (M(r) 574); and 5-feruloyl-3-trimethoxycinnamoylquinic acid, 3-trimethoxycinnamoyl-4-feruloylquinic acid, and 4-trimethoxycinnamoyl-5-feruloylquinic acid (M(r) 588). Furthermore, a series of structures including nine new triacyl quinic acids have been assigned on the basis of LC-MS(n) patterns of fragmentation, relative hydrophobicity, and analogy of fragmentation patterns if compared to feruloyl, caffeoyl, and dimethoxycinnamoyl quinic acids. Sixty-nine chlorogenic acids have now been characterized in green Robusta coffee beans.

Determination of the hydroxycinnamate profile of 12 members of the Asteraceae family

The hydroxycinnamates of the leaves of 12 plants of the Astreraceae family, Achillea millefolium, Arnica montana, Artemesia dracunculus, Cichorium intybus, Cnicus benedictus, Cynara scolymus, Echinops humilis, Inula helenium, Lactuca sativa, Petasites hybridus, Solidago virgaurea, and Tanacetum parthenium were investigated qualitatively by LC-MS(n). Thirty-nine chlorogenic acids were detected and all characterized to regioisomeric level on the basis of their fragmentation pattern in the tandem MS spectra, most of them for the first time from these sources with two of them previously not reported in nature. Both chlorogenic acids based on trans and cis-cinnamic acid substituents were identified. Assignment to the level of individual regioisomers was possible for seven caffeoylquinic acids (1-7), 11 dicaffeoylquinic acids (17-27), six feruloylquinic acids (9-14), two p-coumaroylquinic acids (15-16), two caffeoyl-feruloylquinic acids (28 and 29), four caffeoyl-p-coumaroylquinic acids (30-33), three dicaffeoyl-succinoylquinic acids (34-36), two dicaffeoyl-methoxyoxaloylquinic acids (37 and 38), and one tricaffeoylquinic acid (39). Furthermore, one caffeoylshikimic acid (40), one caffeoyltartaric acid (41), three dicaffeoyltartaric acids (42-44), and three caffeoyl-feruloyltartaric acids (45-47) were detected and shown to possess characteristic tandem MS spectra and were tentatively assigned on the basis of their retention time and previously developed hierarchical keys.

Hierarchical scheme for liquid chromatography/multi‐stage spectrometric identification of 3,4,5‐triacyl chlorogenic acids in green Robusta coffee beans

Liquid chromatography/multi-stage spectrometry (LC/MS(n)) (n = 2-4) has been used to detect and characterize in green Robusta coffee beans eight quantitatively minor triacyl chlorogenic acids with seven of them not previously reported in nature. These comprise 3,4,5-tricaffeoylquinic acid (Mr 678); 3,5-dicaffeoyl-4-feruloylquinic acid, 3-feruloyl-4,5-dicaffeoylquinic acid and 3,4-dicaffeoyl-5-feruloylquinic acid (Mr 692); 3-caffeoyl-4,5-diferuloylquinic acid and 3,4-diferuloyl-5-caffeoylquinic acid (Mr 706); and 3,4-dicaffeoyl-5-sinapoylquinic acid and 3-sinapoyl-4,5-dicaffeoylquinic acid (Mr 722). Structures have been assigned on the basis of LC/MS(n) patterns of fragmentation. A new hierarchical key for the identification of triacyl quinic acids is presented, based on previously established rules of fragmentation. Fifty-two chlorogenic acids have now been characterized in green Robusta coffee beans. In this study five samples of green Robusta coffee beans and fifteen samples of Arabica coffee beans were analyzed with triacyl chlorogenic acids only found in Robusta coffee bean extracts. These triacyl chlorogenic acids could be considered as useful phytochemical markers for the identification of Robusta coffee beans.

Characterization and Quantification of Hydroxycinnamate Derivatives in Stevia rebaudiana Leaves by LC-MSn

Stevia rebaudiana leaves are used as a zero-calorie natural sweetener in a variety of food products in Asian countries, especially in Japan. In this study, the hydroxycinnamate derivatives of S. rebaudiana have been investigated qualitatively and quantitatively by LC-MSn. Twenty-four hydroxycinnamic acid derivatives of quinic and shikimic acid were detected, and 19 of them were successfully characterized to regioisomeric levels; 23 are reported for the first time from this source. These comprise three monocaffeoylquinic acids (Mr 354), seven dicaffeoylquinic acids (Mr 516), one p-coumaroylquinic acid (Mr 338), one feruloylquinic acid (Mr 368), two caffeoyl-feruloylquinic acids (Mr 530), three caffeoylshikimic acids (Mr 336), and two tricaffeoylquinic acids (Mr 678). Cis isomers of di- and tricaffeoylquinic acids were observed as well. Three tricaffeoylquinic acids identified in stevia leaves are reported for the first time in nature. These phenolic compounds identified in stevia might affect the organoleptic properties and add additional beneficial health effects to stevia-based products.

How to distinguish between feruloyl quinic acids and isoferuloyl quinic acids by liquid chromatography/tandem mass spectrometry

All four regioisomers of feruloyl quinic acid and isoferuloyl quinic acid were synthesized and a liquid chromatography/tandem mass spectrometry (LC/MS/MS) method developed that resolves all eight regioisomers. All eight regioisomers can be readily distinguished by their MS/MS spectra in the negative ion mode, illustrating the power of tandem mass spectrometry to elucidate the structures of regioisomeric compounds. Compound identification is possible, either by direct comparison of spectral fingerprints or by rational probing of diagnostic fragment ions, thus allowing the identification of these important classes of natural products and potential human metabolites.

Profiling the chlorogenic acids of Rudbeckia hirta, Helianthus tuberosus, Carlina acaulis and Symphyotrichum novae-angliae leaves by LC-MSn

INTRODUCTION Chlorogenic acids (CGAs) are a family of esters formed between quinic acid and certain cinnamic acids, most commonly caffeic, p-coumaric and ferulic acid. They show a variety of biological activities like antioxidant, anti-inflammatory, anti-HIV, anti-HBV and inhibition of mutagenesis and carcinogenesis, and are considered to be beneficial to human health. We have selected well-established plants of Asteraceae family and these are used in folk medicines as antivirals. OBJECTIVE Investigating the CGA profile of anti-viral herbal remedies, we aim at identifying selected chlorogenic acids commonly encountered in these plants in order to identify suitable candidates for anti-viral screening. It should be noted that neuroaminidase inhibitors, recently introduced into the clinical practice as Tamiflu or Relenza, bear a remarkable structural similarity to CGAs, suggesting potentially a similar mode of action. METHODOLOGY Methanolic extracts were used for LC-MS analysis. The LC equipment with DAD detector was interfaced with a high-resolution MicroTOF mass spectrometer for molecular formula assignment and an ion trap mass spectrometer for assignment of CGA regiochemistry based on characteristic fragmentation patterns. For the identification of cis cinnamoylquinic acids, extracts were treated with UV-irradiation. RESULTS A series of CGAs were identified by their tandem mass spectra and retention times. We also found that diacyl CGAs containing cis isomer of cinnamic acids have the same tandem MS spectra as those containing the trans isomer. CONCLUSION In this study, all the CGAs present in the leaves of Rudbeckia hirta, Helianthus tuberosus, Carlina acaulis and Symphyotrichum novae-angliae were identified qualitatively to their regioisomeric level without any purification or isolation, and assignment was based on their LC-MS(n) behaviour and the change in the intensity after the UV-irradiation. A series of CGAs common to these anti-viral herbal remedies was identified, which will in the future be selected for further detailed biological screening.

Identification of Phenolic Compounds in Plum Fruits (Prunus salicina L. and Prunus domestica L.) by High-Performance Liquid Chromatography/Tandem Mass Spectrometry and Characterization of Varieties by Quantitative Phenolic Fingerprints

Plums (Prunus domestica L. and Prunus salicina L.) are edible fruits mostly consumed in America, China, and Europe. We have used LC-MS(n) to detect and characterize the phenolic compounds in plum varieties. Forty-one phenolics were detected comprising caffeoylquinic acids, feruloylquinic acid, p-coumaroylquinic acids, methyl caffeoylquinates, methyl p-coumaroylquinate, caffeoylshikimic acids, catechin, epicatechin, rutin, esculin, quercetin, quercetin-3-O-hexosides, dimeric proanthocyanidins, trimeric proanthocyanidins, caffeoyl-glucoside, feruloyl-glucoside, p-coumaroyl-glucoside, vanillic acid-glucosides, 3,4-dihydroxybenzoyl-glucoside, quercetin-3-O-pentosides, quercetin-3-O-rhamnoside, quercetin-pentoside-rhamnosides, and 3-p-methoxycinnamoylquinic acid. This is the first time when 3-p-methoxycinnamoylquinic acid is reported in nature. Chlorogenic acids and proanthocyanidins were the major phenolics present in plums. Furthermore, HPLC with DAD and chemical reaction detection was used to generate quantitative phenolic fingerprints from the fruit flesh of 33 plum varieties. The predominant compound was 3-caffeoylquinic acid in nearly all varieties studied; generally, however, the qualitative and quantitative profiles showed high diversity even among closely related progenies.

The inhibition of the mammalian DNA methyltransferase 3a (Dnmt3a) by dietary black tea and coffee polyphenols

BackgroundBlack tea is, second only to water, the most consumed beverage globally. Previously, the inhibition of DNA methyltransferase 1 was shown by dietary polyphenols and epi-gallocatechin gallate (EGCG), the main polyphenolic constituent of green tea, and 5-caffeoyl quinic acid, the main phenolic constituent of the green coffee bean.ResultsWe studied the inhibition of DNA methyltransferase 3a by a series of dietary polyphenols from black tea such as theaflavins and thearubigins and chlorogenic acid derivatives from coffee. For theaflavin 3,3 digallate and thearubigins IC50 values in the lower micro molar range were observed, which when compared to pharmacokinetic data available, suggest an effect of physiological relevance.ConclusionsSince Dnnmt3a has been associated with development, cancer and brain function, these data suggest a biochemical mechanism for the beneficial health effect of black tea and coffee and a possible molecular mechanism for the improvement of brain performance and mental health by dietary polyphenols.

Profiling and characterisation by liquid chromatography/ multi-stage mass spectrometry of the chlorogenic acids in Gardeniae Fructus

The chlorogenic acids of Gardeniae Fructus used traditionally as a Chinese herbal medicine (zhizi) have been investigated qualitatively by liquid chromatography/multi-stage mass spectrometry (LC/MS(4)). Twenty-nine chlorogenic acids were detected and twenty-five characterised to regioisomer level on the basis of their fragmentation, twenty-four for the first time from this source. Assignment to the level of individual regioisomers was possible for three caffeoylquinic acids, three dicaffeoylquinic acids, three sinapoylquinic acids, four caffeoyl-sinapoylquinic acids, two feruloyl-sinapoylquinic acids, one p-coumaroyl-sinapoylquinic acid, three (3-hydroxy, 3-methyl)glutaroylquinic acids, two (3-hydroxy, 3-methyl)glutaroyl-feruloylquinic acids, one (3-hydroxy, 3-methyl)glutaroyl-dicaffeoylquinic acid, and one (3-hydroxy, 3-methyl)glutaroyl-caffeoyl-feruloylquinic acid. Six (3-hydroxy, 3-methyl)glutaroyl-caffeoylquinic acids were detected and two were tentatively assigned as 3-caffeoyl-4-(3-hydroxy, 3-methyl)glutaroylquinic acid and 3-caffeoyl-5-(3-hydroxy, 3-methyl)glutaroylquinic acid. The (3-hydroxy, 3-methyl)glutaroyl residue modifies the mass spectral fragmentation behavior and elution sequence compared with the chlorogenic acids that contain only a cinnamic acid residue(s). Fourteen of these twenty-nine chlorogenic acids have not previously been reported from any source.