Whole grain cereals are a good source of nutrients. Several cutting-edge metabolomic platforms have been deployed to identify various phenolic compounds and enhance cereal bioactive bioavailability. A diet rich in cereal phenolics may modify the microbial composition, support gut homeostasis, and increase gut health, thereby lowering the risk of non-communicable illness.In this work, we reviewed current metabolomic breakthroughs in cereal phenolic profiling and their effects on human health via gut microbiota modulation. We argue that the information presented in this paper will assist in the development of nutritionally superior cereal breeds and functional foods.Most cereal grains contain ferulic acid derivatives, caffeoyl glycerides, and feruloyl and coumaroyl esters. While there has been significant progress in discovering novel phenolic compounds in cereals, quantifying these molecules, and translating their therapeutic effects from animal model systems to humans remains a challenge. To this end, metabolomics, and other high-throughput-omics-based platforms must be integrated to further examine the structure and functionality of phenolic metabolites to breed nutritionally rich cereals as well as map their influence on human health benefits. Rare alleles must be introduced to improve bioactive content in cereal grains while maintaining yield. Following that, these exceptional varieties must be effectively processed to maximize phenolic bioavailability. 

Metabolomics based inferences to unravel phenolic compound diversity in cereals and its implications for human gut health

Rice (Oryza sativa L.) is the staple food of the majority of the population, particularly in Asia and Africa. Enriching rice with nutritional and therapeutic contents can improve its benefits for patients with lifestyle disorders. This study aimed to profile the phytochemical contents of the therapeutically known traditional rice Mappillai Samba against white rice CBMAS 14065 using non-targeted gas chromatography–mass spectrometry (GC-MS/MS). An analysis of the data using a mass spectrometry–data independent analysis (MS-DIAL) and MetaboAnalyst identified 113 metabolites belonging to 21 different classes of metabolites. A partial least square-discriminant analysis (PLS-DA) revealed 43 variable importance in projection (VIP) metabolites. This study identified therapeutically important metabolites, including phenylpropanoids, phytosterols, flavonoids, and polyamines, in the grains of Mappillai Samba. Three significant metabolic pathways, viz., phenylpropanoid biosynthesis, ubiquinone and other terpenoid-quinone biosynthesis, and steroid biosynthesis, were responsible for the grain metabolome variation between CBMAS 14065 and Mappillai Samba. Overall, the results of this study unravelled the biochemical complexity of Mappillai Samba, paving the way for the genetic mapping of the therapeutic compound accumulation in rice and the development of similar therapeutic rice varieties through molecular breeding.

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A Comparative Metabolomic Analysis Reveals the Nutritional and Therapeutic Potential of Grains of the Traditional Rice Variety Mappillai Samba

Introduction Buckwheat (Fagopyrum tataricum), an important food crop, also has medicinal uses. It is widely planted in Southwest China, overlapping with planting areas remarkably polluted by cadmium (Cd). Therefore, it is of great significance to study the response mechanism of buckwheat under Cd stress and further develop varieties with excellent Cd tolerance. Methods In this study, two critical periods of Cd stress treatment (days 7 and 14 after Cd treatment) of cultivated buckwheat (Pinku-1, named K33) and perennial species (F. tatari-cymosum Q.F. Chen) (duoku, named DK19) were analyzed using transcriptome and metabolomics. Results The results showed that Cd stress led to changes in reactive oxygen species (ROS) and the chlorophyll system. Moreover, Cd-response genes related to stress response, amino acid metabolism, and ROS scavenging were enriched or activated in DK19. Transcriptome and metabolomic analyses highlighted the important role of galactose, lipid (glycerophosphatide metabolism and glycerophosphatide metabolism), and glutathione metabolism in response to Cd stress in buckwheat, which are significantly enriched at the gene and metabolic levels in DK19. Discussion The results of the present study provide valuable information for a better understanding of the molecular mechanisms underlying Cd tolerance in buckwheat and useful clues for the genetic improvement of drought tolerance in buckwheat.

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Integrated transcriptome and metabonomic analysis of key metabolic pathways in response to cadmium stress in novel buckwheat and cultivated species

Advanced glycation end products (AGEs), the products of non-enzymatic browning reactions between the active carbonyl groups of reducing sugars and the free amines of amino acids, are largely considered oxidative derivatives resulting from diabetic hyperglycemia, which are further recognized as a potential risk for insulin resistance (IR) and type 2 diabetes (T2D). The accumulation of AGEs can trigger numerous negative effects such as oxidative stress, carbonyl stress, inflammation, autophagy dysfunction and imbalance of gut microbiota. Recently, studies have shown that cereal polyphenols have the ability to inhibit the formation of AGEs, thereby preventing and alleviating T2D. In the meanwhile, phenolics compounds could produce different biological effects due to the quantitative structure activity-relationship. This review highlights the effects of cereal polyphenols as a nonpharmacologic intervention in anti-AGEs and alleviating T2D based on the effects of oxidative stress, carbonyl stress, inflammation, autophagy, and gut microbiota, which also provides a new perspective on the etiology and treatment of diabetes.

Cereal polyphenols inhibition mechanisms on advanced glycation end products and regulation on type 2 diabetes.

To understand differences in the quality of different conventional japonica rice varieties and variations in metabolites related to rice quality, the quality of three conventional japonica varieties was determined, and the metabolites of the milled rice were investigated using nontargeted metabolomics technology. The results showed that the taste value (TV) of Yangda 4Hao (YD4) was significantly higher than that of Yangda 3Hao (YD3) and Huaidao 5Hao (HD5). The protein content (PC) of HD5 was significantly higher than that of YD3 and YD4. PC was significantly negatively correlated with TV. Ninety-one differential metabolites (59 increased and 32 decreased) were identified between YD3 and HD5. A total of 144 differential metabolites (96 upregulated and 48 downregulated) were identified between YD4 and HD5. A total of 114 differential metabolites (40 increased and 74 decreased) were identified between YD3 and YD4. The metabolites with a high correlation to rice quality were mostly involved in the amino acid metabolism pathway. Amino acid metabolites play an important role in the formation of rice quality. The key metabolites in the synthesis and regulation of metabolic pathways are sucrose, levan, and amylose, which are carbohydrates, and L-glutamine, L-aspartic acid, and L-asparagine, which are amino acid metabolites. It can be seen from this study that the metabolites of sucrose, levan, amylose, L-glutamine, L-aspartic acid, and L-asparagine may be the key metabolites in the quality formation of high-quality rice varieties.

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The Key Metabolites in Rice Quality Formation of Conventional japonica Varieties

Sorghum is one of the most important food and feed cereal crops and has been gaining industrial importance in recent years for its biofuel, nutraceutical and antioxidant values. A genetic profile variation study was undertaken for the accumulation of phytochemicals in 61 diverse sorghum accessions differing in their growth habitat and grain color through non-targeted Gas Chromatography-Mass Spectrometry (GC-MS/MS) analysis. Mass Spectrometry-Data Independent AnaLysis (MS-DIAL) and MetaboAnalyst identified 221 metabolites belonging to 27 different phytochemicals. Tropical and temperate sorghums were distinct in their metabolic profiles with minimum overlaps, and 51 different metabolites were crucial in differentiating the two groups. Temperate sorghums had the ability to accumulate more of phenolic acids, phytosterols, flavonoids, carotenoids, and tropical sorghums for stress-related amino acids, sugars and fatty acids. Grain-color-based Partial Least Square-Discriminant Analysis (PLS-DA) analysis identified 94 Variable Importance in Projections (VIP) metabolites containing majority of flavonoids, phenylpropanoids and phytosterols. This study identified two sorghum lines (IS 7748 and IS 14861) with rich amounts of antioxidants (catechins and epicatechins) belonging to the group of condensed tannins that otherwise do not accumulate commonly in sorghum. Out of 13 metabolic pathways identified, flavonoid biosynthesis showed the highest expression. This study provided new opportunities for developing biofortified sorghum with enhanced nutraceutical and therapeutics through molecular breeding and metabolic engineering.

Ajay Prasanth Ramalingam

Papers

Large-Scale Non-Targeted Metabolomics Reveals Antioxidant, Nutraceutical and Therapeutic Potentials of Sorghum.

Pilot scale genome wide association mapping identified novel loci for grain yield traits in rice