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Profiling of Phenolic and Other Compounds from Egyptian Cultivars of Chickpea ( Cicer Arietinum L.) and Antioxidant Activity: a Comparative Study†

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Profiling of Phenolic and Other Compounds from Egyptian Cultivars of Chickpea ( Cicer Arietinum L.) and Antioxidant Activity: a Comparative Study† RSC Advances This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. This Accepted Manuscript will be replaced by the edited, formatted and paginated article as soon as this is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. www.rsc.org/advances Page 1 of 20RSC Advances RSC Advances Dynamic Article Links ► Cite this: DOI: 10.1039/c0xx00000x www.rsc.org/xxxxxx Paper Profiling of phenolic and other compounds from Egyptian cultivars of chickpea ( Cicer arietinum L.) and antioxidant activity: a comparative study† Reham Hassan Mekky, a,b,c,d María del Mar Contreras,* b,c Mohamed Roshdi El-Gindi, a Azza R. Abdel- d d b,c 5 Monem, Essam Abdel-Sattar, and Antonio Segura-Carretero Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX DOI: 10.1039/b000000x Chickpeas are basic food in many countries with several cultivars distributed all over the world. However, little is known about their secondary metabolites. Thus, this work is focused on the study of the phenolic 10 profiles of seven Egyptian cultivars of chickpea. Selecting the most appropriate extraction method and analytical conditions using reversed-phase high-performance liquid chromatography-diode array detection, with a core-shell column, and coupled with quadrupole-time-of-flight-mass spectrometry (MS), a total of 96 phenolic compounds were characterized based on their retention time, UV spectra, and Manuscript accurate MS and MS 2 data. Among them, the major phenolic subclasses were hydroxybenzoic acids and 15 flavonoids. Moreover, other minor and major metabolites including organic acids, amino acids, nucleosides, peptides and soyasaponins were characterized. Using standards, 22 compounds were unequivocally identified. Remarkably, 88 of these compounds were tentatively reported for the first time in chickpeas. The total phenol content of the cultivars was determined as well as the antioxidant activity by the trolox equivalent antioxidant capacity assay. to quadruple time-of-flight (QTOF)-MS using columns with < 2 5 6 20 µm particle sizes and core-shell columns provide enough Introduction Accepted resolution and high sensitivity detection to permit metabolic “Let food be thy medicine and medicine be thy food ” profiling of plant extracts. Hippocrates (460 BC – 377 BC). It is nearly a 2500 years 50 On the basis of the total pulse production, chickpeas (Cicer aphorism, and still a topic of current interest. In fact, the arietinum L.) are the second most important legume in the characterization of beneficial food constituents and formulation world.7 This plant is cultivated in India, Pakistan, Mexico, the 25 of novel functional foods continue to attract scientific and 8 Mediterranean basin regions, and many other countries. industrial attention. Such foods contribute to prevention and Chickpeas with respect to other legumes represent the fifth most mitigation of diseases, promotion of health and well-being with a 7 55 important product in Egypt. Their use dates from at least the reduction of health care costs. It is noteworthy that the intake of “New Kingdom” (1580-1100 BC) and they obtained the name vegetables, fruits and legumes reduces the risks of cancers, 9 1,2 “falcon-face” in that period. This pulse constitutes a well 30 diabetes mellitus, atherosclerosis, and cardiac diseases. This recognized source of dietary proteins, carbohydrates, minerals Advances may be attributed to their richness in secondary metabolites and, 10 and trace elements. To obtain functional ingredients from in particular, phenolic compounds. 1 60 chickpeas, several studies have focused on the development of To provide evidence of the connection between health and protein hydrolysates with biological activity, including food constituents, “omics” tools such as genomics, 11 3 antioxidant activity, e.g . Moreover, chickpeas contain several 35 transcriptomics, proteomics, and metabolomics have emerged. phytochemical classes, such as phenolic compounds, 12-14 RSC Among them, metabolomics is the study of the biochemical soyasaponins, 15,16 and volatile aliphatic hydrocarbons.17 In composition of living organisms making use of hyphenated 65 general, there is relatively little information about the techniques such as chromatographic separation coupled to mass 18 phytochemicals present in most of dietary legumes. This is even spectrometry (MS). more limited in the case of chickpeas. 40 In fact, the application of advanced analytical techniques and Concerning extraction procedures for phenolic compounds hybrid mass analyzers has contributed to discover and from chickpeas, many authors applied a single solid-liquid characterize new phytochemicals, especially, minor ones that 13,19 70 extraction step with solvents such as methanol and acetone, could promote human well-being. Among others, these analytical 20,21 while others used mulitple solid-liquid extractions. Solid- techniques include gas chromatography, liquid chromatography 3,4 liquid extraction combined with solid-phase extraction using a 45 (LC) and capillary electrophoresis. As an example, LC coupled This journal is © The Royal Society of Chemistry [year] RSC. Adv. [year], [vol] , 00–00 | 1 RSC Advances Page 2 of 20 silica gel column was recently applied to concentrate the extraction and solvent requirements, M3 was the method of isoflavones. 22 In the case of soyasaponins, Kerem et al. 15 applied choice in order to extract the rest of chickpea cultivars. In this microwave-assisted extraction. Among the analytical techniques sense, the selection of the extraction method is a critical step to to analyse this legume are: methods based on high-speed 60 dissolve the maximum amount of the metabolites of interest in 5 countercurrent chromatography and high-performance-LC the extraction solvent, and so achieve a successful (HPLC) coupled to ultraviolet/visible; diode array (DAD) characterization work.25,34 Using methanol/water as extraction detectors and MS using electrospray ionization (ESI).12,20,23,24 solvent constituted a reproducible protocol, allowing the selective However these studies generaly focused on a sort list of phenolic extraction of polar glycosides of phenolic compounds and as well 35,36 compounds. 65 their aglycones with more hydrophobic features. In addition, a 10 The objective of this study is to develop a global approach to wide range of other polar and semi-polar metabolites from characterize phenolic compounds from the edible seeds of seven vegetable matrices are generally co-extracted at the same time. Egyptian cultivars of chickpea, namely ‘Giza 1’, ‘Giza 2’, ‘Giza Moreover, a sonication step was introduced in order to favour the 3’, ‘Giza 4’, ‘Giza 195’, ‘Giza 531’ and ‘Solala 104’. To achieve extraction of phenolic compounds according to previous studies 34,37,38 this, solid-liquid extraction and the analytical conditions by 70 on different vegetal matrices. 15 reversed-phase (RP)-HPLC-DAD-ESI-QTOF-MS were Selection of the analytical conditions evaluated. Moreover, the total phenol content (TPC) and the antioxidant activity of the seeds using the trolox equivalent The analytical conditions and the MS parameters were antioxidant capacity (TEAC) assay were also assessed. preliminarily checked in order to further characterize the chickpea phenolic constituents. In this way, several aqueous Results and discussion 75 solutions of acetic acid from 0.25 to 1% (v/v) were tested as mobile phase A, methanol and acetonitrile as mobile phase B, 5 20 Selection of the extraction procedure and 8 µL for injection volume, flow at 0.5 and 0.8 mL/min, as Prior to the optimization of the analytical method, the well as two C18 reversed-phase columns with the same Manuscript characterization as well as the determination of the antioxidant dimension but different particle technology. In general, an potential of the chickpea cultivars, three solid-liquid extraction 80 adequate separation of the compounds from the aforementioned procedures were tested using the chickpea seeds of the cultivar ‘Giza 1’ extract was achieved in 35 min using the core–shell 25 ‘Giza 1’. In this way, the TPC was assessed according to the column, water with 0.5% acetic acid and acetonitrile as mobile Folin-Ciocalteu method and the yield was determined (Fig. 1). phases, which produces lower system back pressure than other These results showed that the TPC value was significantly higher solvents as methanol, and a flow of 0.5 mL/min. 6 The maximum using the extraction method M3 (129.4 mg of gallic acid/100 g of 85 pressure was lower than 165 bars, and so this method may be chickpea seeds). used in conventional HPLC systems. As an example, Fig. S2 30 Moreover, the comparison was also made with the total (supporting information) shows the BPC of ‘Giza 1’ chickpea integrated area of the base peak chromatogram (BPC) and UV extract using different analytical conditions, including the Accepted chromatograms at 240, 280, 330 and 350 nm, according to selected ones, and two column types. Although the co-elution of 25 Hurtado-Fernández and co-workers. These UV channels 90 the major compounds could not be avoided due to the complexity (bandwidth of 10 nm) were selected bearing in mind the phenolic of the sample, a higher number of minor peaks could be 35 classes that were previously reported on chickpeas viz. adequately separated by the core-shell column and the elution hydroxybenzoic acids, hydroxycinnamic acids and flavonoids, gradient applied (Fig.
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