Comprehensive profiling of semi‐polar phytochemicals in whole wheat grains (Triticum aestivum) using liquid chromatography coupled with electrospray ionization quadrupole time‐of‐flight mass spectrometry

Abstract

Introduction Wheat (Triticum aestivum) it is one of the most important staple food crops worldwide and represents an important resource for human nutrition. Besides starch, proteins and micronutrients wheat grains accumulate a highly diverse set of phytochemicals. Objectives This work aimed at the development and validation of an analytical workflow for comprehensive profiling of semi-polar phytochemicals in whole wheat grains. Method Reversed-phase ultra-high performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry (UHPLC/ESI-QTOFMS) was used as analytical platform. For annotation of metabolites accurate mass collision-induced dissociation mass spectra were acquired and interpreted in conjunction with literature data, database queries and analyses of reference compounds. Results Based on reversed-phase UHPLC/ESI-QTOFMS an analytical workflow for comprehensive profiling of semi-polar phytochemicals in whole wheat grains was developed. For method development the extraction procedure and the chromatographic separation were optimized. Using whole grains of eight wheat cultivars a total of 248 metabolites were annotated and characterized by chromatographic and tandem mass spectral data. Annotated metabolites comprise hydroquinones, hydroxycinnamic acid amides, flavonoids, benzoxazinoids, lignans and other phenolics as well as numerous primary metabolites such as nucleosides, amino acids and derivatives, organic acids, saccharides and B vitamin derivatives. For method validation, recovery rates and matrix effects were determined for ten exogenous model compounds. Repeatability and linearity were assessed for 39 representative endogenous metabolites. In addition, the accuracy of relative quantification was evaluated for six exogenous model compounds. Conclusions In conjunction with non-targeted and targeted data analysis strategies the developed analytical workflow was successfully applied to discern differences in the profiles of semi-polar phytochemicals accumulating in whole grains of eight wheat cultivars.

Comprehensive profiling of chemical composition of Gleditsiae spina using ultra‐high‐performance liquid chromatography coupled with electrospray ionization quadrupole time‐of‐flight mass spectrometry

“…Lignan is a secondary plant metabolite produced by the oxidative coupling of phenylpropane compounds, derived from the shikimic acid biosynthesis pathway and widely distributed in plants as natural polyphenolic compounds. Lignans have a wide range of biological activities, such as antioxidant, antitumor, antibacterial, insecticidal, estrogen‐like, and cardioprotective 35–38 . Lignan is predominantly composed of guaiacyl (G) and syringyl (S) derived from the combinatorial radical–radical coupling of the monolignols coniferyl and sinapyl alcohol, respectively.…”

“…Lignans have a wide range of biological activities, such as antioxidant, antitumor, antibacterial, insecticidal, estrogen-like, and cardioprotective. [35][36][37][38] Lignan is predominantly composed of guaiacyl (G) and syringyl (S) derived from the combinatorial radical-radical coupling of the monolignols coniferyl and sinapyl alcohol, respectively. As radical coupling at the 8-position is favored, coupling with another monolignol radical yields, after rearomatization, a mixture of dehydrodimers with 8-8-, 8-5-, and 8-O-4-linkages.…”

Overview of the Metabolite Composition and Antioxidant Capacity of Seven Major and Minor Cereal Crops and Their Milling Fractions

“…Flavonoids were the major class of annotated metabolites found as aglycone and glycosylated forms: flavanones (isosakuranin, naringenin, narirutin 4-glucoside, 5,7,4′-trihydroxyflavanone 7-O-arabinosylglucoside, 5-O-β-D-glucosylluteoliflavan-(4 → 8)-eriodictyol), flavones (apigenin, isovitexin 2″-O-glucoside), flavanols (epicatechin, catechin, epigallocatechin 3-gallate, epicatechin 3-gallate, procyanidin B, symplocoside), chalcones (dihydroxy-4-methoxychalcone-4′-O-neohesperid), flavonols (myricetin, kaempferol), and isoflavonoids (gancaonin, isoprunetin, daidzin, ononin). 16,17,43 Hydroxycinnamic acids and their derivatives were the main phenolic acids found, despite the fact that hydroxybenzoic acids have also been detected: caffeic acid, p-coumaric acid and its isomer, sinapic acid, trans-ferulic acid and its isomer (cis-ferulic acid), dihydroxyphenylacetic acid, isomers of diferulic acids, 2,5dihydroxybenzoic acid, dihydrocaffeic, 4-hydroxybenzoic acid, sinapic acid, syringic acid, and caffeoyl glucose. Hydroxycinnamic acids were also found conjugated with quinic acid: chlorogenic acid, feruloylquinic acid, and coumaroylquinic acid.…”

“…Diferulic acids were previously reported in cereal grains, including rye, sorghum, and wheat. 17,45,47 Furthermore, the metabolomics data was submitted to multivariate data analyses to have an overview of the metabolite distribution in cereal crops and milling fractions. Unsupervised (principal component analysis, PCA; hierarchical clustering analysis, HCA) and supervised (partial least-squares-discriminant analysis, PLS-DA) methods were applied to analyze the data.…”

The Effect of Whole-Grain Diet on the Gut Microbiota of the Elderly Individuals

“…Whole grain is characterized by the retention of the endosperm, germ, and bran found in whole grain (WG). WG is a good source of dietary fiber, protein, B vitamins, vitamin E, minerals (such as selenium, copper, and magnesium), flavonoids, and polyphenols (14)(15)(16). Numerous studies have shown that they can help to reduce the risk of many diseases, such as overweight (OW)/obesity, cardiovascular disease, type 2 diabetes, intestinal disease, and certain cancers, as compared to refined grains.…”