Flavones: From Biosynthesis to Health Benefits

Action pattern of Sulfolobus O-α-glycoligase for synthesis of highly water soluble resveratrol 3,4'-α-diglucoside

This study presents the enzymatic synthesis of resveratrol-3,4'-O-α-diglucoside (RDG) using a hyperactive O-α-glycoligase (MalA-D416R/Q450S) and α-glucopyranosyl fluoride as the donor substrate. The transglycosylation rate for resveratrol by MalA-D416R/Q450S was maximized in 100 mM Tris-HCl (pH 9.5) containing 20 % DMSO at 45°C. Because the pKa of the 4'-OH group of resveratrol is lower than that of the 3-OH group, the 4'-OH group is more nucleophilic at the alkaline pH, leading to a preference for glycosylation at the 4'-OH site rather than the 3-OH site. This preference makes resveratrol 3-O-α-glucoside (R3G) as the more efficient acceptor than resveratrol 4'-O-α-glucoside (R4'G), resulting in negligible production of resveratrol 3-O-α-glucoside (R3G) due to its complete consumption in the second transglycosylation reaction when using a 2:1 ratio of donor to acceptor substrates. From a preparative scale reaction, R4'G and RDG were isolated with yields of 41.2 % and 43.3 %, respectively. The water solubility of RDG exceeded 1.67 M, which represents more than a 9,800-fold improvement compared to resveratrol. In a hydrolysis experiment using intestinal α-glycosidase from rat, the α-glucosides of resveratrol (R4'G and RDG) were completely deglycosylated to the aglycone.

Chemical composition and in vitro iron bioavailability of extruded and open-pan cooked germinated and ungerminated pearl whole millet "Pennisetum glaucum (L.) R. Br."

This study aimed to evaluate the effect of extrusion and of open-pan cooking on whole germinated and non-germinated grains of pearl millet (Pennisetum glaucum L. R. Br.), on its chemical-nutritional composition and in vitro iron bioavailability. The experimental design consisted of three flours: non-germination open-pan cooked millet flour (NGOPCMF), germination open-pan cooked millet flour (GOPCMF), and extrusion cooked millet flour (ECMF). The ECMF increased the carbohydrates, iron, manganese, diosmin, and cyanidin and decreased the total dietary fiber, resistant starch, lipids, and total vitamin E, in relation to NGOPCMF. The GOPCMF increased the lysine and vitamin C and decreased the phytate, lipids, total phenolic, total vitamin E, and riboflavin concentration, in relation to NGOPCMF. Furthermore, germinated cooked millet flour and extruded millet flour improved iron availability in vitro compared to non-germinated cooked millet flour. GOPCMF and ECMF generally preserved the chemical-nutritional composition of pearl millet and improved in vitro iron bioavailability; therefore, they are nutritionally equivalent and can be used to develop pearl millet-based products.

Novel Flavonol Derivatives Containing Quinoxaline: Insights into the Antifungal Mechanism against Sclerotinia sclerotiorum

In this study, 12 pairs of tautomeric flavonol derivatives containing quinoxaline were synthesized. The results of antifungal activity showed that in the enol-keto tautomerism, the target compounds containing keto (YB series) had better inhibitory activity against Sclerotinia sclerotiorum (S.s.) than compounds containing enol (YA series). YB9 showed the strongest antifungal activity against S.s., and the median effective concentration (EC50) value was 1.0 μg/mL, which was better than azoxystrobin (Az, 35.3 μg/mL). In vivo fungal inhibition experiments showed that the protective activity of YB9 against rape leaves was 83.4% at 200 μg/mL, which was superior to that of Az (70.2%). The activity of succinate dehydrogenase and molecular docking results showed that YB9 had a stronger antifungal effect than YA9. The results of oxalic acid content determination showed that YB9 could reduce the pathogenic ability of S.s. Then, the inhibitory effect of YB9 against S.s. was further verified by scanning electron microscopy, fluorescence microscopy, cell membrane permeability, cell content leakage, and malondialdehyde content.

Physiological and differential protein expression analyses of the calcium stress response in the Drynaria roosii rhizome

High concentration Ca2+ in karst soil is harmful to agriculture. Some dominant plants can adapt well to karst soil, but how Ca2+ affect plant is unknown. Drynaria roosii is a Ca2+-tolerant fern and its dry rhizome is a common Chinese medicine of Miao nationality in Guizhou, China. This study analyzed the physiological and proteomic characteristics of the rhizome of D. roosii under calcium stress. Physiological results indicated that calcium stress may lead to osmotic stress. Proteomic results showed that 147 differentially expressed proteins (96 increased, 51decreased) were identified under calcium stress, and these proteins mainly involved in signal transduction, protein translation, material transport, antioxidant defense and secondary metabolism. This study will lay a foundation for studying the calcium adaptation mechanism of D. roosii at the molecular level.

Engineering a novel pathway for efficient biosynthesis of salicin in Escherichia coli

Salicin is a natural glycoside compound widely used to treat fever, inflammation, and analgesia. Currently, salicin is primarily extracted from willow bark, which is not only cumbersome in terms of extraction and separate steps, but also subject to seasonal and geographic limitations. In this study, a highly efficient biosynthetic pathway for salicin synthesis was designed and constructed in E. coli. The most important precursor in the synthetic pathway of salicin designed in this study is salicyl alcohol. Building on a previously constructed biosynthetic salicylic acid metabolic pathway, the production of salicyl alcohol in shake flask fermentation reached 1.7 g/L by increasing the supply of shikimic acid pathway precursor PEP and salicyl alcohol precursor chorismate. According to the principle of substrate similarity, this study identified the key enzyme OsSGT1 from Oryza sativa, which uses E. coli endogenous UDP-glucose as a glycosyl donor to glycosylate salicyl alcohol into salicin. By redefining the optimal substrate of OsSGT1, and balancing metabolic flux along with increasing the supply of UDP-glucose, salicin production in shake flasks reached 4 g/L. Finally, culturing the high-yield strain in a 3-L fermenter resulted in the synthesis of 14.62 g/L of salicin. To the best of our knowledge, this achievement marks the highest salicin production through microbial fermentation to date.

A Novel MsEOBI-MsPAL1 Module Enhances Salinity Stress Tolerance, Floral Scent Emission and Seed Yield in Alfalfa

Alfalfa (Medicago sativa L.) is an important and widely cultivated forage legume, yet its yield is constrained by salinity stress. In this study, we characterized an R2R3-MYB transcription factor MsEOBI in alfalfa. Its salt tolerance function and regulatory pathways were investigated. The nuclear-localized MsEOBI functions as a transcriptional activator, enhancing salinity tolerance by promoting the biosynthesis of flavonoids and lignin, as well as facilitating the scavenging of reactive oxygen species (ROS). Additionally, MsEOBI promotes pollinator attraction and increases seed yield by activating the biosynthesis of volatile phenylpropanoids. Yeast one-hybrid (Y1H), dual-luciferase reporter and chromatin immunoprecipitation coupled with quantitative PCR (ChIP-qPCR) assays demonstrated that MsEOBI directly binds to the promoter regions of MsPAL1, a key gene in the phenylpropanoid pathway, thereby activating its expression. Overexpression of MsPAL1 enhances salinity tolerance in alfalfa. These findings elucidate the role of the MsEOBI-MsPAL1 regulatory module and provide valuable genetic resources for the future breeding of salt-tolerant alfalfa varieties.

Conserved amino acid residues and gene expression patterns associated with the substrate preferences of the competing enzymes FLS and DFR

BACKGROUND

Flavonoids, an important class of specialized metabolites, are synthesized from phenylalanine and present in almost all plant species. Different branches of flavonoid biosynthesis lead to products like flavones, flavonols, anthocyanins, and proanthocyanidins. Dihydroflavonols form the branching point towards the production of non-colored flavonols via flavonol synthase (FLS) and colored anthocyanins via dihydroflavonol 4-reductase (DFR). Despite the wealth of publicly accessible data, there remains a gap in understanding the mechanisms that mitigate competition between FLS and DFR for the shared substrate, dihydroflavonols.

RESULTS

An angiosperm-wide comparison of FLS and DFR sequences revealed the amino acids at positions associated with the substrate specificity in both enzymes. A global analysis of the phylogenetic distribution of these amino acid residues revealed that monocots generally possess FLS with Y132 (FLSY) and DFR with N133 (DFRN). In contrast, dicots generally possess FLSH and DFRN, DFRD, and DFRA. DFRA, which restricts substrate preference to dihydrokaempferol, previously believed to be unique to strawberry species, is found to be more widespread in angiosperms and has evolved independently multiple times. Generally, angiosperm FLS appears to prefer dihydrokaempferol, whereas DFR appears to favor dihydroquercetin or dihydromyricetin. Moreover, in the FLS-DFR competition, the dominance of one over the other is observed, with typically only one gene being expressed at any given time.

CONCLUSION

This study illustrates how almost mutually exclusive gene expression and substrate-preference determining residues could mitigate competition between FLS and DFR, delineates the evolution of these enzymes, and provides insights into mechanisms directing the metabolic flux of the flavonoid biosynthesis, with potential implications for ornamental plants and molecular breeding strategies.

Metabolic characterization and transcriptional profiling of polyphenols in Cannabis sativa L. inflorescences with different chemical phenotypes

MAIN CONCLUSION

After the most comprehensive analysis of the phenolic composition in Cannabis reported to date, a total of 211 compounds were identified, phenolic profiles were able to discriminate cannabis varieties and a complex regulatory network for phenolics accumulation in Cannabis chemovars was highlighted. Female inflorescences of Cannabis sativa L. are plenty of secondary metabolites, of which flavonoids and phenolic acids have been investigated by far less than phytocannabinoids and terpenoids. Understanding the biochemical composition in phenylpropanoids of Cannabis inflorescences, the molecular basis of flavonoid synthesis and how their content can be modulated by specific transcription factors will shed light on the variability of this trait in the germplasm, allowing the identification of biologically active metabolites that can be of interest to diverse industries. In this work, an untargeted metabolomic approach via UHPLC-HRMS was adopted to investigate the composition and variability of phenylpropanoids in thirteen Cannabis genotypes differentiated for their profile in phytocannabinoids, highlighting that phenolic profiles can discriminate varieties, with characteristic, unique genotype-related patterns. Moreover, the transcription profile of candidate phenolics regulatory MYB and bHLH transcription factors, analyzed by RT-qPCR, appeared strongly genotype-related, and specific patterns were found to be correlated between biochemical and transcriptional levels. Results highlight a complex regulatory network for phenolic accumulation in Cannabis chemovars that will need further insights from the functional side.

UDP-glucosyltransferase 71C4 controls the flux of phenylpropanoid metabolism to shape cotton seed development

Seeds play a crucial role in plant reproduction, making it essential to identify genes that affect seed development. In this study, we focused on UDP-glucosyltransferase 71C4 (UGT71C4) in cotton, a member of the glycosyltransferase family that shapes seed width and length, thereby influencing seed index and seed cotton yield. Overexpression of UGT71C4 results in seed enlargement owing to its glycosyltransferase activity on flavonoids, which redirects metabolic flux from lignin to flavonoid metabolism. This shift promotes cell proliferation in the ovule via accumulation of flavonoid glycosides, significantly enhancing seed cotton yield and increasing the seed index from 10.66 g to 11.91 g. By contrast, knockout of UGT71C4 leads to smaller seeds through activation of the lignin metabolism pathway and redirection of metabolic flux back to lignin synthesis. This redirection leads to increased ectopic lignin deposition in the ovule, inhibiting ovule growth and development, and alters yield components, increasing the lint percentage from 41.42% to 43.40% and reducing the seed index from 10.66 g to 8.60 g. Our research sheds new light on seed size development and reveals potential pathways for enhancing seed yield.

Programmable Biosynthesis of Plant-Derived 4'-Deoxyflavone Glycosides by an Unconventional Yeast Consortium

Previous data established 4'-deoxyflavone glycosides (4'-DFGs) as important pharmaceutical components in the roots of rare medical plants like Scutellaria baicalensis Georgi. Extracting these compounds from plants involves land occupation and is environmentally unfriendly. Therefore, a modular ("plug-and-play") yeast-consortium platform is developed to synthesize diverse 4'-DFGs de novo. By codon-optimizing glycosyltransferase genes from different organisms for Pichia pastoris, six site-specific glycosylation chassis are generated to be capable of biosynthesizing 18 different 4'-DFGs. Cellular factories showed increased 4'-DFG production (up to 18.6-fold) due to strengthened synthesis of UDP-sugar precursors and blocked hydrolysis of endogenous glycosides. Co-culturing upstream flavone-synthesis-module cells with downstream glycoside-transformation-module cells alleviated the toxicity of 4'-deoxyflavones and enabled high-level de novo synthesis of 4'-DFGs. Baicalin is produced at the highest level (1290.0 mg L-1) in a bioreactor by controlling the consortium through carbon-source shifting. These results provide a valuable reference for biosynthesizing plant-derived 4'-DFGs and other glycosides with potential therapeutic applications.

Exploring anticancer properties of the phytoconstituents and comparative analysis of their chemical space parameters with USFDA-approved synthetic anticancer agents

The present review article thoroughly analyses natural products and their derived phytoconstituents as a rich source of plausible anticancer drugs. The study thoroughly explores the chemical components derived from various natural sources, thus emphasizing their unique structural characteristics and therapeutic potential as an anticancer agent. The review contains the critical chemical constituents' in-depth molecular mechanisms, their source's chemical structures and the categories. The review also comprises an exhaustive and comprehensive analysis of different chemical spacing parameters of the anticancer agents derived from natural products. It compares them with USFDA-approved synthetic anticancer drugs up to 2020, thus providing a meaningful understanding of the relationship between natural and synthetic compounds portraying the anticancer assets. The review also delves more deeply into the chemical analysis of the heterocyclic moieties from the natural product arena, illustrating the anticancer mechanisms. The present article is, therefore, expected to serve as a valuable resource for natural product and medicinal chemists, encouraging and promoting an integrated approach to exploit the potential of natural products in drug discovery development and translational research, which have a prerequisite of bench to bedside approach. The work could guide researchers toward innovative approaches for the ever-evolving field of anticancer drug discovery.

Exploring the effectiveness of flavone derivatives for treating liver diseases: Utilizing DFT, molecular docking, and molecular dynamics techniques

In exploring nature's potential in addressing liver-related conditions, this study investigates the therapeutic capabilities of flavonoids. Utilizing in silico methodologies, we focus on flavone and its analogs (1-14) to assess their therapeutic potential in treating liver diseases. Molecular change calculations using density functional theory (DFT) were conducted on these compounds, accompanied by an evaluation of each analog's physiochemical and biochemical properties. The study further assesses these flavonoids' binding effectiveness and locations through molecular docking studies against six target proteins associated with human cancer. Tropoflavin and taxifolin served as reference drugs. The structurally modified flavone analogs (1-14) displayed a broad range of binding affinities, ranging from -7.0 to -9.4 kcal mol⁻¹, surpassing the reference drugs. Notably, flavonoid (7) exhibited significantly higher binding affinities with proteins Nrf2 (PDB:1 × 2 J) and DCK (PDB:1 × 2 J) (-9.4 and -8.1 kcal mol⁻¹) compared to tropoflavin (-9.3 and -8.0 kcal mol⁻¹) and taxifolin (-9.4 and -7.1 kcal mol⁻¹), respectively. Molecular dynamics (MD) simulations revealed that the docked complexes had a root mean square deviation (RMSD) value ranging from 0.05 to 0.2 nm and a root mean square fluctuation (RMSF) value between 0.35 and 1.3 nm during perturbation. The study concludes that 5,7-dihydroxyflavone (7) shows substantial promise as a potential therapeutic agent for liver-related conditions. However, further validation through in vitro and in vivo studies is necessary. Key insights from this study include:•Screening of flavanols and their derivatives to determine pharmacological and bioactive properties using ADMET, molinspiration, and pass prediction analysis.•Docking of shortlisted flavone derivatives with proteins having essential functions.•Analysis of the best protein-flavonoid docked complexes using molecular dynamics simulation to determine the flavonoid's efficiency and stability within a system.

Extensive targeted metabolomics analysis reveals the identification of major metabolites, antioxidants, and disease-resistant active pharmaceutical components in Camellia tuberculata (Camellia L.) seeds

Sect. tuberculata plant belongs to the Camellia genus and is named for the "tuberculiform protuberance on the surface of the ovary and fruit". It is a species of great ornamental value and potential medicinal value. However, little has been reported on the metabolites of C. tuberculata seeds. Therefore, this study was conducted to investigate the metabolites of C. tuberculata seeds based on UPLC/ESI-Q TRAP-MS/MS with extensively targeted metabolomics. A total of 1611 metabolites were identified, including 107 alkaloids, 276 amino acids and derivatives, 283 flavonoids, 86 lignans and coumarins, 181 lipids, 68 nucleotides and derivatives, 101 organic acids, 190 phenolic acids, 10 quinones, 4 steroids, 17 tannins, 111 terpenoids, and 177 other metabolites. We compared the different metabolites in seeds between HKH, ZM, ZY, and LY. The 1311 identified different metabolites were classified into three categories. Sixty-three overlapping significant different metabolites were found, of which lignans and coumarins accounted for the largest proportion. The differentially accumulated metabolites were enriched in different metabolic pathways between HKH vs. LY, HKH vs. ZM, HKH vs. ZY, LY vs. ZY, ZM vs. LY and ZM vs. ZY, with the most abundant metabolic pathways being 4, 2, 4, 7, 7 and 5, respectively (p < 0.05). Moreover, among the top 20 metabolites in each subgroup comparison in terms of difference multiplicity 7, 8 and 13. ZM and ZY had the highest phenolic acid content. Ninety-six disease-resistant metabolites and 48 major traditional Chinese medicine agents were identified based on seven diseases. The results of this study will not only lead to a more comprehensive and in-depth understanding of the metabolic properties of C. tuberculata seeds, but also provide a scientific basis for the excavation and further development of its medicinal value.

Cloning and functional characterization of a cinnamate 4-hydroxylase gene from the hornwort Anthoceros angustus

Hornworts, as the sister group to liverworts and mosses, comprise bryophytes, which are critical in understanding the evolution of key land plant traits. Cinnamate 4-hydroxylase (C4H) catalyzes the second step of the phenylpropanoid pathway to synthesize the precursor of numerous phenolic compounds, such as lignin and flavonoids. However, C4H in the hornwort Anthoceros angustus has not yet been cloned and functionally characterized. In this work, we screened the transcriptome database of A. angustus and identified one C4H gene, AnanC4H. AnanC4H maintained conserved cytochrome P450 domains with other typical plant C4Hs. Ultraviolet B irradiation and exogenous application of methyl jasmonate (MeJA) induced the expression of AnanC4H to varying degrees. The coding sequence of AnanC4H was expressed in yeast, and the recombinant proteins were isolated. The recombinant proteins of AnanC4H catalyzed the conversion of trans-cinnamic acid to p-coumaric acid and catalyzed the conversion of 3-hydroxycinnamic acid to caffeic acid. AnanC4H showed higher affinity for trans-cinnamic acid than for 3-hydroxycinnamic acid, but there was no significant difference in the catalytic efficiency of AnanC4H for the two substrates in vitro. Moreover, the expression of AnanC4H in Arabidopsis thaliana led to an increase in both the lignin content and the number of lignified cells in stems. However, there was no significant change in flavonoid content in transgenic Arabidopsis plants.

Integrative Analysis of Transcriptome and Metabolome Sheds Light on Flavonoid Biosynthesis in the Fruiting Body of Stropharia rugosoannulata

Flavonoids are a diverse family of natural compounds that are widely distributed in plants and play a critical role in plant growth, development, and stress adaptation. In recent years, the biosynthesis of flavonoids in plants has been well-researched, with the successive discovery of key genes driving this process. However, the regulation of flavonoid biosynthesis in fungi remains unclear. Stropharia rugosoannulata is an edible mushroom known for its high nutritional and pharmacological value, with flavonoids being one of its main active components. To investigate the flavonoid content of S. rugosoannulata, a study was conducted to extract and determine the total flavonoids at four stages: young mushroom (Ym), gill (Gi), maturation (Ma), and parachute-opening (Po). The findings revealed a gradual increase in total flavonoid concentration as the fruiting body developed, with significant variations observed between the Ym, Gi, and Ma stages. Subsequently, we used UPLC-MS/MS and transcriptome sequencing (RNA-seq) to quantify the flavonoids and identify regulatory genes of Ym, Gi, and Ma. In total, 53 flavonoid-related metabolites and 6726 differentially expressed genes (DEGs) were identified. Through KEGG pathway enrichment analysis, we identified 59 structural genes encoding flavonoid biosynthesis-related enzymes, most of which were up-regulated during the development of the fruiting body, consistent with the accumulation of flavonoids. This research led to the establishment of a comprehensive transcriptional metabolic regulatory network encompassing flavonoids, flavonoid synthases, and transcription factors (TFs). This represents the first systematic exploration of the molecular mechanism of flavonoids in the fruiting of fungi, offering a foundation for further research on flavonoid mechanisms and the breeding of high-quality S. rugosoannulata.

A decade of advances in the study of buckwheat for organic farming and agroecology (2013-2023)

During the last decade, research has shown the environment and human health benefits of growing buckwheat (Fagopyrum spp.). This comprehensive review aims to summarize the major advancements made in the study of buckwheat from 2013 to 2023, focusing on its agronomic characteristics, nutritional value, and potential applications in sustainable agriculture. The review examines the diverse applications of buckwheat in organic and agroecological farming systems, and discusses the ability of buckwheat to control weeds through allelopathy, competition, and other sustainable farming methods, such as crop rotation, intercropping and green manure, while improving soil health and biodiversity. The review also explores the nutritional value of buckwheat. It delves into the composition of buckwheat grains, emphasizing their high protein content, and the presence of essential amino acids and valuable micronutrients, which is linked to health benefits such as lowering cholesterol levels, controlling diabetes and acting against different types of cancer, among others. Finally, the review concludes by highlighting the gaps in current knowledge, and proposing future research directions to further optimize buckwheat production in organic or agroecological farming systems. It emphasizes the need for interdisciplinary collaboration, and the integration of traditional knowledge with modern scientific approaches to unlock the full potential of buckwheat as a sustainable crop.

Grass lignin: biosynthesis, biological roles, and industrial applications

Lignin is a phenolic heteropolymer found in most terrestrial plants that contributes an essential role in plant growth, abiotic stress tolerance, and biotic stress resistance. Recent research in grass lignin biosynthesis has found differences compared to dicots such as Arabidopsis thaliana. For example, the prolific incorporation of hydroxycinnamic acids into grass secondary cell walls improve the structural integrity of vascular and structural elements via covalent crosslinking. Conversely, fundamental monolignol chemistry conserves the mechanisms of monolignol translocation and polymerization across the plant phylum. Emerging evidence suggests grass lignin compositions contribute to abiotic stress tolerance, and periods of biotic stress often alter cereal lignin compositions to hinder pathogenesis. This same recalcitrance also inhibits industrial valorization of plant biomass, making lignin alterations and reductions a prolific field of research. This review presents an update of grass lignin biosynthesis, translocation, and polymerization, highlights how lignified grass cell walls contribute to plant development and stress responses, and briefly addresses genetic engineering strategies that may benefit industrial applications.

Synthetic Studies toward 5,6,7,3',4'-Monomethoxytetrahydroxyflavones: Synthesis of Pedalitin

During the synthetic studies toward 5,6,7,3',4'-monomethoxytetrahydroxyflavones, a concise pedalitin synthesis procedure was achieved. As previously reported, 6-hydroxy-2,3,4-trimethoxyacetophenone was prepared by Friedel-Crafts acylation of 1,4-dihydroxy-2,6-dimethoxybenzene with boron trifluoride diethyl etherate in acetic acid. When aldol condensation of 6-hydroxy-2,3,4-trimethoxyacetophenone 2b with vanillin was performed in basic conditions, it produced 2'-hydroxychalcone 3b, and, surprisingly, along with 3-hydroxyflavone 4 in a considerable amount. We propose that this oxidative cyclization is presumably due to the contribution of a quinone methide, likely to be subjected to aerobic oxidation. The chalcone was then subjected to oxidative cyclization with iodine in dimethyl sulfoxide to afford flavone 5 in good yield. To our delight, serial demethylation of the three methoxy groups at the 5-, 6-, and 3'-positions of 5 proceeded smoothly to produce pedalitin 1, under hydrogen bromide solution (30% in acetic acid). The crystal structures of 3-hydroxyflavone 4 and pedalitin tetraacetate 6 were unambiguously determined by X-ray crystallography.

Integrative metabolome and transcriptome analyses reveal the differences in flavonoid and terpenoid synthesis between Glycyrrhiza uralensis (licorice) leaves and roots

Licorice from Glycyrrhiza uralensis roots is used in foods and medicines. Although we are aware that licorice roots and leaves have distinct material compositions, the specific reasons for these differences remain unknown. Comparison of the metabolomes and transcriptomes between the leaves and roots revealed flavonoids and triterpenoid saponins were significantly different. Isoflavones were enriched in roots because of upregulation of genes encoding chalcone isomerase and flavone synthase, which are involved in isoflavone synthesis. Six triterpenoid saponins were significantly enriched only in the roots. The leaves did not accumulate glycyrrhetinic acid because of low expression levels of genes involved in its synthesis. A gene encoding a UDP glycosyltransferase, which likely catalyzes the key step in the transformation of glycyrrhetinic acid to glycyrrhizin, was screened. Our results provide information about the differences in flavonoid and triterpenoid synthesis between roots and leaves, and highlight targets for genetic engineering.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01467-y.

Synthesis and Biological Evaluation of 2-Azolylmethylene-3-(2H)-benzofuranone Derivatives as Potent Monoamine Oxidases Inhibitors

A series of 2-azolylmethylene-3-(2H)-benzofuranone derivatives, 2-indolylmethylene-3-(2H)-benzofuranone and 2-pyrrolylmethylene-3-(2H)-benzofuranone derivatives, were synthesized, and their monoamine oxidase (MAO) A and B inhibitory activities were evaluated. Compounds 1b, 3b, 6b, 7b, and 10b showed strong inhibitory activity against MAO-A, and compound 3b showed the highest potency and selectivity, with an IC50 value of 21 nM and a MAO-A selectivity index of 48. Compounds 3c, 4c, 9a, 9c, 10c, 11a, and 11c showed strong inhibitory activity against MAO-B, and compound 4c showed the highest potency and selectivity, with an IC50 value of 16 nM and a MAO-B selectivity index of >1100. Further analysis of these compounds indicated that compound 3b for MAO-A and compound 4c for MAO-B were competitive inhibitors, with Ki values of 10 and 6.1 nM, respectively. Furthermore, computational analyses, such as quantitative structure-activity relationship (QSAR) analysis of the 2-azolylmethylene-3-(2H)-benzofuranone derivatives conducting their pIC50 values with the Molecular Operating Environment (MOE) and Mordred, and molecular docking analysis using MOE-Dock supported that the 2-azolylmethylene-3-(2H)-benzofuranone derivatives are a privileged scaffold for the design and development of novel MAO inhibitors.

Enhancing Glycosylation of Flavonoids by Engineering the Uridine Diphosphate Glucose Supply in Escherichia coli

Glycosylation can enhance the solubility and stability of flavonoids. The main limitation of the glycosylation process is low intracellular uridine diphosphate glucose (UDPG) availability. This study aimed to create a glycosylation platform strain in Escherichia coli BL21(DE3) by multiple metabolic engineering of the UDPG supply. Glycosyltransferase TcCGT1 was introduced to synthesize vitexin and orientin from apigenin and luteolin, respectively. To further expand this glycosylation platform strain, not only were UDP rhamnose and UDP galactose synthesis pathways constructed, but rhamnosyltransferase (GtfC) and galactosyltransferase (PhUGT) were also introduced, respectively. In a 5 L bioreactor with apigenin, luteolin, kaempferol, and quercetin as glycosyl acceptors, vitexin, orientin, afzelin, quercitrin, hyperoside, and trifolin glycosylation products reached 17.2, 36.5, 5.2, 14.1, 6.4, and 11.4 g/L, respectively, the highest titers reported to date for all. The platform strain has great potential for large-scale production of glycosylated flavonoids.

NRTPredictor: identifying rice root cell state in single-cell RNA-seq via ensemble learning

BACKGROUND

Single-cell RNA sequencing (scRNA-seq) measurements of gene expression show great promise for studying the cellular heterogeneity of rice roots. How precisely annotating cell identity is a major unresolved problem in plant scRNA-seq analysis due to the inherent high dimensionality and sparsity.

RESULTS

To address this challenge, we present NRTPredictor, an ensemble-learning system, to predict rice root cell stage and mine biomarkers through complete model interpretability. The performance of NRTPredictor was evaluated using a test dataset, with 98.01% accuracy and 95.45% recall. With the power of interpretability provided by NRTPredictor, our model recognizes 110 marker genes partially involved in phenylpropanoid biosynthesis. Expression patterns of rice root could be mapped by the above-mentioned candidate genes, showing the superiority of NRTPredictor. Integrated analysis of scRNA and bulk RNA-seq data revealed aberrant expression of Epidermis cell subpopulations in flooding, Pi, and salt stresses.

CONCLUSION

Taken together, our results demonstrate that NRTPredictor is a useful tool for automated prediction of rice root cell stage and provides a valuable resource for deciphering the rice root cellular heterogeneity and the molecular mechanisms of flooding, Pi, and salt stresses. Based on the proposed model, a free webserver has been established, which is available at https://www.cgris.net/nrtp .

Binding mechanism and biological effects of flavone DYRK1A inhibitors for the design of new antidiabetics

The selective inhibition of kinases from the diabetic kinome is known to promote the regeneration of beta cells and provide an opportunity for the curative treatment of diabetes. The effect can be achieved by carefully tailoring the selectivity of inhibitor toward a particular kinase, especially DYRK1A, previously associated with Down syndrome and Alzheimer's disease. Recently DYRK1A inhibition has been shown to promote both insulin secretion and beta cells proliferation. Here, we show that commonly available flavones are effective inhibitors of DYRK1A. The observed biochemical activity of flavone compounds is confirmed by crystal structures solved at 2.06 Å and 2.32 Å resolution, deciphering the way inhibitors bind in the ATP-binding pocket of the kinase, which is driven by the arrangement of hydroxyl moieties. We also demonstrate antidiabetic properties of these biomolecules and prove that they could be further improved by therapy combined with TGF-β inhibitors. Our data will allow future structure-based optimization of the presented scaffolds toward potent, bioavailable and selective anti-diabetic drugs.

Phenylpropanoid Derivatives and Their Role in Plants' Health and as antimicrobials

Phenylpropanoids belong to a wide group of compounds commonly secreted by plants and involved in different roles related with plant growth and development and the defense against plant pathogens. Some key intermediates from shikimate pathway are used to synthesize these compounds. In this way, by the phenylpropanoid pathway several building blocks are achieved to obtain flavonoids, isoflavonoids, coumarins, monolignols, phenylpropenes, phenolic acids, stilbenes and stilbenoids, and lignin, suberin and sporopollenin for plant-microbe interactions, structural support and mechanical strength, organ pigmentation, UV protection and acting against pathogens. Some reviews have revised phenylpropanoid biosynthesis and regulation of the biosynthetic pathways. In this review, the most important chemical structures about phenylpropanoid derivatives are summarized grouping them in different sections according to their structure. We have put special attention on their different roles in plants especially in plant health, growth and development and plant-environment interactions. Their interaction with microorganisms is discussed including their role as antimicrobials. We summarize all new findings about new developed structures and their involvement in plants health.

[Development progress of stationary phase for supercritical fluid chromatography and related application in natural products]

Supercritical fluid chromatography (SFC) is an environment-friendly and efficient column chromatography technology that was developed to expand the application range of high performance liquid chromatography (HPLC) using a supercritical fluid as the mobile phase. A supercritical fluid has a temperature and pressure that are above the critical values as well as relatively dynamic characteristics that are between those of a gas and liquid. Supercritical fluids combine the advantages of high solubility and diffusion, as their diffusion and viscosity coefficients are equivalent to those of a gas, while maintaining a density that is comparable with that of a liquid. Owing to the remarkable compressibility of supercritical fluids, analyte retention in SFC is significantly influenced by the density of the mobile phase. Thus, the column temperature and back pressure are crucial variables that regulate analyte retention in SFC. Increasing the back pressure can increase the density and solubility of the mobile phase, leading to reductions in retention time. The column temperature can affect selectivity and retention, and the degree to which different analytes are affected by this property varies. On the one hand, increasing the temperature reduces the density of the mobile phase, thereby extending the retention time of the analytes; on the other hand, it can also increase the energy of molecules, leading to a shorter retention time of the analyte on the stationary phase. CO2, the most widely employed supercritical fluid to date, presents moderate critical conditions and, more importantly, is miscible with a variety of polar organic solvents, including small quantities of water. In comparison with the mobile phases used in normal-phase liquid chromatography (NPLC) and reversed-phase liquid chromatography (RPLC), the mobile phase for SFC has a polarity that can be extended over a wide range on account of its extensive miscibility. The compatibility of the mobile phase determines the diversity of the stationary phase. Nearly all stationary phases for HPLC, including the nonpolar stationary phases commonly used for RPLC and the polar stationary phases commonly used for NPLC, can be applied to SFC. Because all stationary phases can use the same mobile-phase composition, chromatographic columns with completely different polarities can be employed in SFC. The selectivity of SFC has been effectively expanded, and the technique can be used for the separation of diverse analytes ranging from lipid compounds to polar compounds such as flavonoids, saponins, and peptides. The choice of stationary phase has a great impact on the separation effect of analytes in SFC. As new stationary phases for HPLC are constantly investigated, specialized stationary phases for SFC have also been continuously developed. Researchers have discovered that polar stationary phases containing nitrogen heterocycles such as 2-EP and PIC are highly suitable for SFC because they can effectively manage the peak shape of alkaline compounds and provide good selectivity in separating acidic and neutral compounds.The development of various stationary phases has promoted the applications of SFC in numerous fields such as pharmaceuticals, food production, environmental protection, and natural products. In particular, natural products have specific active skeletons, multiple active groups, and excellent biological activity; hence, these materials can provide many new opportunities for the discovery of novel drugs. According to reports, compounds related to natural products account for 80% of all commercial drugs. However, natural products are among the most challenging compounds to separate because of their complex composition and low concentration of active ingredients. Thus, superior chromatographic methods are required to enable the qualitative and quantitative analysis of natural products. Thanks to technological improvements and a good theoretical framework, the benefits of SFC are gradually becoming more apparent, and its use in separating natural products is expanding. Indeed, in the past 50 years, SFC has developed into a widely used and efficient separation technology. This article provides a brief overview of the characteristics, advantages, and development process of SFC; reviews the available SFC stationary phases and their applications in natural products over the last decade; and discusses prospects on the future development of SFC.

Flavonoids: Overview of Biosynthesis, Biological Activity, and Current Extraction Techniques

Recently, increased attention has been paid to natural sources as raw materials for the development of new added-value products. Flavonoids are a large family of polyphenols which include several classes based on their basic structure: flavanones, flavones, isoflavones, flavonols, flavanols, and anthocyanins. They have a multitude of biological properties, such as anti-inflammatory, antioxidant, antiviral, antimicrobial, anticancer, cardioprotective, and neuroprotective effects. Current trends of research and development on flavonoids relate to identification, extraction, isolation, physico-chemical characterization, and their applications to health benefits. This review presents an up-to-date survey of the most recent developments in the natural flavonoid classes, the biological activity of representative flavonoids, current extraction techniques, and perspectives.

Utilizing X-ray fluorescence (XRF) method to evaluate the content of metal elements in soil and their effects on the total phenolic and flavonoid contents of some medicinal plants

Soil factors, especially metal elements in the soil, play a significant role in forming and accumulating secondary metabolites, which determine the medicinal properties of medicinal herbs. In this study, the concentrations of some metal elements (K, Mn, Fe, Cu, Zn, and Cr) in Cam Mountain and Tinh Bien Town, An Giang Province, Vietnam, were determined using the XRF method. We simultaneously determined the total phenolic and flavonoid content of some medicinal herbs collected from the collected soil sample areas, thereby assessing the influence of these elements on the formation of secondary metabolites in medicinal plants. The results showed that K, Mn, and Cr were mainly concentrated in the topsoil and transition layers; Fe and Cu elements tended to concentrate in the transition layer and the subsoil when surveying the soil profile. K, Mn, Cu, and Cr concentrations were more focused in Tinh Bien area, while Fe and Zn had higher concentrations at Cam Mountain. Additionally, results from evaluating the relationship between the content of the elements in the soil and the content of two active compounds also showed the correlation regression model between Zn and flavonoid expression by level 4 at the 5% significance level. Thus, the nonlinear model is suitable for evaluating the relationship between the content of metal elements in the soil and the active compound in medicinal plants.

Elnosary M, L. Ashour M, M. Abd El-Moneam N, A. Shreadah M. Flavonoids Biosynthesis in Plants as a Defense Mechanism: Role and Function Concerning Pharmacodynamics and Pharmacokinetic Properties

Flavonoids are a major class of secondary metabolites that comprises more than 6000 compounds that have been identified. They are biosynthesized via the phenylpropanoid metabolic pathway that involves groups of enzymes such as isomerases, hydroxylases, and reductases that greatly affect the determination of the flavonoid skeleton. For example, transferase enzymes responsible for the modification of sugar result in changes in the physiological activity of the flavonoids and changes in their physical properties, such as solubility, reactivity, and interaction with cellular target molecules, which affect their pharmacodynamics and pharmacokinetic properties. In addition, flavonoids have diverse biological activities such as antioxidants, anticancer, and antiviral in managing Alzheimer’s disease. However, most marine flavonoids are still incompletely discovered because marine flavonoid biosynthesis is produced and possesses unique substitutions that are not commonly found in terrestrial bioactive compounds. The current chapter will illustrate the importance of flavonoids’ role in metabolism and the main difference between marine and terrestrial flavonoids.

A Study of GUS Expression in Arabidopsis as a Tool for the Evaluation of Gene Evolution, Function and the Role of Expression Derived from Gene Duplication

Gene duplication played a fundamental role in eukaryote evolution and different copies of a given gene can be present in extant species, often with expressions and functions differentiated during evolution. We assume that, when such differentiation occurs in a gene copy, this may be indicated by its maintenance in all the derived species. To verify this hypothesis, we compared the histological expression domains of the three β-glucuronidase genes (AtGUS) present in Arabidopsis thaliana with the GUS evolutionary tree in angiosperms. We found that AtGUS gene expression overlaps in the shoot apex, the floral bud and the root hairs. In the root apex, AtGUS3 expression differs completely from AtGUS1 and AtGUS2, whose transcripts are present in the root cap meristem and columella, in the staminal cell niche, in the epidermis and in the proximal cortex. Conversely, AtGUS3 transcripts are limited to the old border-like cells of calyptra and those found along the protodermal cell line. The GUS evolutionary tree reveals that the two main clusters (named GUS1 and GUS3) originate from a duplication event predating angiosperm radiation. AtGUS3 belongs to the GUS3 cluster, while AtGUS1 and AtGUS2, which originate from a duplication event that occurred in an ancestor of the Brassicaceae family, are found together in the GUS1 cluster. There is another, previously undescribed cluster, called GUS4, originating from a very ancient duplication event. While the copy of GUS4 has been lost in many species, copies of GUS3 and GUS1 have been conserved in all species examined.

Piriformospora indica Increases Resistance to Fusarium pseudograminearum in Wheat by Inducing Phenylpropanoid Pathway

Fusarium crown rot (FCR), mainly caused by Fusarium pseudograminearum, not only seriously threatens the yield and quality of wheat, but also endangers the health and safety of humans and livestock. Piriformospora indica is a root endophytic fungus that colonizes plant roots extensively and can effectively promote plant growth and improve plant resistance to biotic and abiotic stresses. In this study, the mechanism of FCR resistance mediated by P. indica in wheat was revealed from the phenylpropanoid metabolic pathway. The results showed that the colonization of P. indica significantly reduced the progression of wheat disease, the amount of F. pseudograminearum colonization, and the content of deoxynivalenol (DON) in wheat roots. RNA-seq suggested that P. indica colonization could reduce the number of differentially expressed genes (DEGs) in the transcriptome caused by F. pseudograminearum infection. The DEGs induced by the colonization of P. indica were partially enriched in phenylpropanoid biosynthesis. Transcriptome sequencing and qPCR indicated that the colonization of P. indica up-regulated the expression of genes involved in the phenylpropanoid biosynthesis pathway. The metabolome analysis indicated that the colonization of P. indica increased the metabolites' accumulation in the phenylpropanoid biosynthesis. Consistent with transcriptome and metabolomic analysis, microscopic observations showed enhanced lignin accumulation in the roots of the Piri and Piri+Fp lines, most likely contributing to the arrested infection by F. pseudograminearum. These results suggested that P. indica increased resistance to F. pseudograminearum in wheat by inducing the phenylpropanoid pathway.

Combined analysis of metabolome and transcriptome of wheat kernels reveals constitutive defense mechanism against maize weevils

Sitophilus zeamais (maize weevil) is one of the most destructive pests that seriously affects the quantity and quality of wheat (Triticum aestivum L.). However, little is known about the constitutive defense mechanism of wheat kernels against maize weevils. In this study, we obtained a highly resistant variety RIL-116 and a highly susceptible variety after two years of screening. The morphological observations and germination rates of wheat kernels after feeding ad libitum showed that the degree of infection in RIL-116 was far less than that in RIL-72. The combined analysis of metabolome and transcriptome of RIL-116 and RIL-72 wheat kernels revealed differentially accumulated metabolites were mainly enriched in flavonoids biosynthesis-related pathway, followed by glyoxylate and dicarboxylate metabolism, and benzoxazinoid biosynthesis. Several flavonoids metabolites were significantly up-accumulated in resistant variety RIL-116. In addition, the expression of structural genes and transcription factors (TFs) related to flavonoids biosynthesis were up-regulated to varying degrees in RIL-116 than RIL-72. Taken together, these results indicated that the biosynthesis and accumulation of flavonoids contributes the most to wheat kernels defense against maize weevils. This study not only provides insights into the constitutive defense mechanism of wheat kernels against maize weevils, but may also play an important role in the breeding of resistant varieties.

Dietary Polyphenols as a Protection against Cognitive Decline: Evidence from Animal Experiments; Mechanisms and Limitations

Emerging evidence suggests that cognitive impairments may result from various factors, such as neuroinflammation, oxidative stress, mitochondrial damage, impaired neurogenesis, synaptic plasticity, blood-brain barrier (BBB) disruption, amyloid β protein (Aβ) deposition, and gut dysbiosis. Meanwhile, dietary polyphenol intake in a recommended dosage has been suggested to reverse cognitive dysfunction via various pathways. However, excessive intake of polyphenols could trigger unwanted adverse effects. Thus, this review aims to outline possible causes of cognitive impairments and how polyphenols alleviate memory loss via various pathways based on in vivo experimental studies. Thus, to identify potentially relevant articles, the keywords (1) nutritional polyphenol intervention NOT medicine AND neuron growth OR (2) dietary polyphenol AND neurogenesis AND memory impairment OR (3) polyphenol AND neuron regeneration AND memory deterioration (Boolean operators) were used in the Nature, PubMed, Scopus, and Wiley online libraries. Based on the inclusion and exclusion criteria, 36 research papers were selected to be further reviewed. The outcome of all the studies included supports the statement of appropriate dosage by taking into consideration gender differences, underlying conditions, lifestyle, and causative factors for cognitive decline, which will significantly boost memory power. Therefore, this review recapitulates the possible causes of cognitive decline, the mechanism of polyphenols involving various signaling pathways in modulating the memory, gut dysbiosis, endogenous antioxidants, bioavailability, dosage, and safety efficacy of polyphenols. Hence, this review is expected to provide a basic understanding of therapeutic development for cognitive impairments in the future.

Advances in the study of the function and mechanism of the action of flavonoids in plants under environmental stresses

MAIN CONCLUSION

This review summarizes the anti-stress effects of flavonoids in plants and highlights its role in the regulation of polar auxin transport and free radical scavenging mechanism. As secondary metabolites widely present in plants, flavonoids play a vital function in plant growth, but also in resistance to stresses. This review introduces the classification, structure and synthetic pathways of flavonoids. The effects of flavonoids in plant stress resistance were enumerated, and the mechanism of flavonoids in plant stress resistance was discussed in detail. It is clarified that plants under stress accumulate flavonoids by regulating the expression of flavonoid synthase genes. It was also determined that the synthesized flavonoids are transported in plants through three pathways: membrane transport proteins, vesicles, and bound to glutathione S-transferase (GST). At the same time, the paper explores that flavonoids regulate polar auxin transport (PAT) by acting on the auxin export carrier PIN-FORMED (PIN) in the form of ATP-binding cassette subfamily B/P-glycoprotein (ABCB/PGP) transporter, which can help plants to respond in a more dominant form to stress. We have demonstrated that the number and location of hydroxyl groups in the structure of flavonoids can determine their free radical scavenging ability and also elucidated the mechanism by which flavonoids exert free radical removal in cells. We also identified flavonoids as signaling molecules to promote rhizobial nodulation and colonization of arbuscular mycorrhizal fungi (AMF) to enhance plant-microbial symbiosis in defense to stresses. Given all this knowledge, we can foresee that the in-depth study of flavonoids will be an essential way to reveal plant tolerance and enhance plant stress resistance.

Digital Database of Absorption Spectra of Diverse Flavonoids Enables Structural Comparisons and Quantitative Evaluations

Flavonoids play diverse roles in plants, comprise a non-negligible fraction of net primary photosynthetic production, and impart beneficial effects in human health from a plant-based diet. Absorption spectroscopy is an essential tool for quantitation of flavonoids isolated from complex plant extracts. The absorption spectra of flavonoids typically consist of two major bands, band I (300-380 nm) and band II (240-295 nm), where the former engenders a yellow color; in some flavonoids the absorption tails to 400-450 nm. The absorption spectra of 177 flavonoids and analogues of natural or synthetic origin have been assembled, including molar absorption coefficients (109 from the literature, 68 measured here). The spectral data are in digital form and can be viewed and accessed at http://www.photochemcad.com. The database enables comparison of the absorption spectral features of 12 distinct types of flavonoids including flavan-3-ols (e.g., catechin, epigallocatechin), flavanones (e.g., hesperidin, naringin), 3-hydroxyflavanones (e.g., taxifolin, silybin), isoflavones (e.g., daidzein, genistein), flavones (e.g., diosmin, luteolin), and flavonols (e.g., fisetin, myricetin). The structural features that give rise to shifts in wavelength and intensity are delineated. The availability of digital absorption spectra for diverse flavonoids facilitates analysis and quantitation of these valuable plant secondary metabolites. Four examples are provided of calculations─multicomponent analysis, solar ultraviolet photoprotection, sun protection factor (SPF), and Förster resonance energy transfer (FRET)─for which the spectra and accompanying molar absorption coefficients are sine qua non.

Integrated transcriptome and metabolome provide insight into flavonoid variation in goji berries (Lycium barbarum L.) from different areas in China

Goji berries (Lycium barbarum L.) were rich in flavonoids, showing high nutritional and medicinal value. However, a thorough evaluation and comparison of the flavonoids in goji berries from various regions and the possible biological regulation pathways with differences are scanty. Here, we investigated the flavonoid metabolites and gene expression levels of goji berries from three major production areas in China using transcriptomics sequencing and metabolomics. The total flavonoid content and total polyphenol content of goji berry in Ningxia (57.87 μg/g and 183.41 μg/g, respectively) were higher than in Qinghai (50.77 μg/g and 156.81 μg/g) and Gansu (47.86 μg/g and 111.17 μg/g). We identified the 105 differentially accumulated flavonoids (DAFs) and 1858 differentially expressed genes (DEGs) from the goji berries in three habitats. Interestingly, gossypetin-3-O-rutinoside and isorhamnetin were significantly expressed between Ningxia and Qinghai berries. The chalcone isomerase (CHI), chalcone synthase (CHS), and flavonol synthase (FLS) genes also played key roles in the regulation of flavonoid synthesis. In addition, MYB1 positively regulated the expression of quercetin-3-O-glucoside, quercetin-7-O-glucoside and isohyperoside. As a result, we speculated that CHI, CHS, FLS genes, and related transcription factors jointly controlled the variation of flavone accumulation in goji berries. These findings may provide a new perspective for understanding the accumulation and molecular mechanisms of goji flavonoids.

Integrated metabolomic and transcriptomic analysis revealed the flavonoid biosynthesis and regulation in Areca catechu

INTRODUCTION

Flavonoids are active substances in many herbal medicines, and Areca catechu fruit (AF), an important component in traditional Chinese medicine (TCM), is rich in flavonoids. Different parts of AF, Pericarpium Arecae (PA) and Semen Arecae (SA), have different medicinal effects in prescription of TCM.

OBJECTIVE

To understand flavonoid biosynthesis and regulation in AF.

METHODOLOGY

The metabolomic based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) and the transcriptome based on high-throughput sequencing technology were combined to comprehensively analyse PA and SA.

RESULTS

From the metabolite dataset, we found that 148 flavonoids showed significant differences between PA and SA. From the transcriptomic dataset, we identified 30 genes related to the flavonoid biosynthesis pathway which were differentially expressed genes in PA and SA. The genes encoding the key enzymes in the flavonoid biosynthesis pathway, chalcone synthase and chalcone isomerase (AcCHS4/6/7 and AcCHI1/2/3), were significantly higher expressed in SA than in PA, reflecting the high flavonoid concentration in SA.

CONCLUSIONS

Taken together, our research acquired the key genes, including AcCHS4/6/7 and AcCHI1/2/3, which regulated the accumulation of flavonol in AF. This new evidence may reveal different medicinal effects of PA and SA. This study lays a foundation for investigating the biosynthesis and regulation of flavonoid biosynthesis in areca and provides the reference for the production and consumption of betel nut.

Estrogenic flavonoids and their molecular mechanisms of action

Flavonoids are a major group of phytoestrogens associated with physiological effects, and ecological and social impacts. Although the estrogenic activity of flavonoids was reported by researchers in the fields of medical, environmental and food studies, their molecular mechanisms of action have not been comprehensively reviewed. The estrogenic activity of the respective classes of flavonoids, anthocyanidins/anthocyanins, 2-arylbenzofurans/3-arylcoumarins/α-methyldeoxybenzoins, aurones/chalcones/dihydrochalcones, coumaronochromones, coumestans, flavans/flavan-3-ols/flavan-4-ols, flavanones/dihydroflavonols, flavones/flavonols, homoisoflavonoids, isoflavans, isoflavanones, isoflavenes, isoflavones, neoflavonoids, oligoflavonoids, pterocarpans/pterocarpenes, and rotenone/rotenoids, was summarized through a comprehensive literature search, and their structure-activity relationship, biological activities, signaling pathways, and applications were discussed. Although the respective classes of flavonoids contained at least one chemical mimicking estrogen, the mechanisms varied, such as those with estrogenic, anti-estrogenic, non-estrogenic, and biphasic activities, and additional activities through crosstalk/bypassing, which exert biological activities through cell signaling pathways. Such mechanistic variations of estrogen action are not limited to flavonoids and are observed among other broad categories of chemicals, thus this group of chemicals can be termed as the "estrogenome". This review article focuses on the connection of estrogen action mainly between the outer and the inner environments, which represent variations of chemicals and biological activities/signaling pathways, respectively, and form the basis to understand their applications. The applications of chemicals will markedly progress due to emerging technologies, such as artificial intelligence for precision medicine, which is also true of the study of the estrogenome including estrogenic flavonoids.

Responses of flavonoids to solar UV radiation and gradual soil drying in two Medicago truncatula accessions

Ground level UV-B (290-315 nm) and UV-A (315-400 nm) radiation regulates multiple aspects of plant growth and development. In a natural environment, UV radiation interacts in a complex manner with other environmental factors (e.g., drought) to regulate plants' morphology, physiology, and growth. To assess the interactive effects of UV radiation and soil drying on plants' secondary metabolites and transcript abundance, we performed a field experiment using two different accessions of Medicago truncatula (F83005-5 French origin and Jemalong A17 Australian origin). Plants were grown for 37 days under long-pass filters to assess the effects of UV short wavelength (290-350 nm, UV_sw) and UV-A long wavelength (350-400 nm, UV-A_lw). Soil-water deficit was induced by not watering half of the plants during the last seven days of the experiment. The two accessions differed in the concentration of flavonoids in the leaf epidermis and in the whole leaf: F83005-5 had higher concentration than Jemalong A17. They also differed in the composition of the flavonoids: a greater number of apigenin derivatives than tricin derivatives in Jemalong A17 and the opposite in F83005-5. Furthermore, UV_sw and soil drying interacted positively to regulate the biosynthesis of flavonoids in Jemalong A17 through an increase in transcript abundance of CHALCONE SYNTHASE (CHS). However, in F83005-5, this enhanced CHS transcript abundance was not detected. Taken together the observed metabolite and gene transcript responses suggest differences in mechanisms for acclimation and stress tolerance between the accessions.

Analysis of anthocyanins and total flavonoids content in functional rice and its recombination inbred lines

Anthocyanin is one of the flavonoids, which has strong antioxidant properties. Functional rice rich in anthocyanins can not only improve immunity, but also anti-radiation, beauty, anti-aging effect, very popular in the market. In this study, we used Zibaoxiangnuo 1 (ZBXN 1), a functional rice variety which is rich in total flavonoids and anthocyanins, as the experimental material to construct Recombination Inbred Lines (RILs) with Minghui63 (MH63), a variety without anthocyanins. The contents of anthocyanins and total flavonoids of RILs and two parents were determined for three consecutive generations. The average anthocyanin content of parent ZBXN 1 was 319.31 mg/kg, and the anthocyanin inheritance of RIL population was relatively stable, with 10 samples higher than ZBXN 1. In addition, there was no significant difference in the total flavonoids content between the two parents, the total flavonoids content of Z25 in RIL population was 0.33%. Based on these studies, we believe that ZBXN 1 has abundant and stable anthocyanins, which can be used as an intermediate breeding material for breeding high-quality varieties with high anthocyanins, and lay a foundation for breeding more anthocyanin-rich rice varieties.

Discovery of a Unique Flavonoid Biosynthesis Mechanism in Fungi by Genome Mining

Flavonoids are important plant natural products with variable structures and bioactivities. All known plant flavonoids are generated under the catalysis of a type III polyketide synthase (PKS) followed by a chalcone isomerase (CHI) and a flavone synthase (FNS). In this study, the biosynthetic gene cluster of chlorflavonin, a fungal flavonoid with acetolactate synthase inhibitory activity, was discovered using a self-resistance-gene-directed strategy. A novel flavonoid biosynthetic pathway in fungi was revealed. A core nonribosomal peptide synthetase-polyketide synthase (NRPS-PKS) is responsible for the generation of the key precursor chalcone. Then, a new type of CHI catalyzes the conversion of a chalcone into a flavanone by a histidine-mediated oxa-Michael addition mechanism. Finally, the desaturation of flavanone to flavone is catalyzed by a new type of FNS, a flavin mononucleotide (FMN)-dependent oxidoreductase.

Transcriptome analysis of auxin transcription factor OsARF17-mediated rice stripe mosaic virus response in rice

Introduction

Plant auxin response factors (ARFs) play an irreplaceable role in regulating the expression of auxin response genes. Our previous studies have indicated that auxin response factor OsARF17 plays a crucial role in plant defense against diverse rice viruses.

Methods

Utilizing a comparative transcriptome analysis of Rice stripe mosaic virus (RSMV)-inoculated OsARF17 mutant rice plants, to further elucidate the molecular mechanism of OsARF17 in antiviral defense pathway.

Results

KEGG enrichment analyses showed that the down-regulated differentially expressed genes (DEGs) belonged to plant-pathogen interaction and plant hormone signal transduction pathways were markedly enriched in OsARF17 mutants under RSMV inoculation. Furthermore, Gene ontology (GO) analyses revealed that these genes were enriched in a variety of hormone biosynthetic process, including jasmonic acid (JA), auxin, and abscisic acid (ABA). RT-qPCR assays showed that the induction of plant defense-related genes, such as WRKY transcription factors, OsAHT2 and OsDR8, and JA-related genes, were significantly suppressed in OsARF17 mutants in response to RSMV.

Discussion

Our study reveals that OsARF17-mediated antiviral immunity may be achieved through affecting the interaction between different phytohormones and regulating defense gene expression in rice. This study provides new insights into the molecular mechanisms of auxin signaling in the rice-virus interaction.

Recent Developments in Polyphenol Applications on Human Health: A Review with Current Knowledge

Polyphenol has been used in treatment for some health disorders due to their diverse health promoting properties. These compounds can reduce the impacts of oxidation on the human body, prevent the organs and cell structure against deterioration and protect their functional integrity. The health promoting abilities are attributed to their high bioactivity imparting them high antioxidative, antihypertensive, immunomodulatory, antimicrobial, and antiviral activity, as well as anticancer properties. The application of polyphenols such as flavonoids, catechin, tannins, and phenolic acids in the food industry as bio-preservative substances for foods and beverages can exert a superb activity on the inhibition of oxidative stress via different types of mechanisms. In this review, the detailed classification of polyphenolic compunds and their important bioactivity with special focus on human health are addressed. Additionally, their ability to inhibit SARS-CoV-2 could be used as alternative therapy to treat COVID patients. Inclusions of polyphenolic compounds in various foods have demonstrated their ability to extend shelf life and they positive impacts on human health (antioxidative, antihypertensive, immunomodulatory, antimicrobial, anticancer). Additionally, their ability to inhibit the SARS-CoV-2 virus has been reported. Considering their natural occurrence and GRAS status they are highly recommended in food.

Understanding the Seasonal Effect of Metabolite Production in Terminalia catappa L. Leaves through a Concatenated MS- and NMR-Based Metabolomics Approach

Terminalia catappa L. (Combretaceae) is a medicinal plant that is part of the Brazilian biodiversity; this plant is popularly used for the treatment of a wide range of diseases. To better understand the chemical composition of T. catappa in different seasons, we conducted a thorough study using LC-MS and NMR data analysis techniques. The study helped obtain a chemical profile of the plant ethanolic extracts in different seasons of the year (spring, summer, autumn, and winter). The dereplication of LC-HRMS data allowed the annotation of 90 compounds in the extracts of T. catappa (hydrolyzable tannins, ellagic acid derivatives, and glycosylated flavonoids). Triterpenes and C-glycosyl flavones were the compounds that significantly contributed to differences observed between T. catappa plant samples harvested in autumn/winter and spring, respectively. The variations observed in the compound composition of the plant leaves may be related to processes induced by environmental stress and leaf development. Data fusion applied in the metabolomic profiling study allowed us to identify metabolites with greater confidence, and provided a better understanding regarding the production of specialized metabolites in T. catappa leaves under different environmental conditions, which may be useful to establish appropriate quality criteria for the standardization of this medicinal plant.

Carnivorous Plants from Nepenthaceae and Droseraceae as a Source of Secondary Metabolites

Carnivorous plants are able to attract small animals or protozoa and retain them in their specialized traps. Later, the captured organisms are killed and digested. The nutrients contained in the prey bodies are absorbed by the plants to use for growth and reproduction. These plants produce many secondary metabolites involved in the carnivorous syndrome. The main purpose of this review was to provide an overview of the secondary metabolites in the family Nepenthaceae and Droseraceae, which were studied using modern identification techniques, i.e., high-performance liquid chromatography or ultra-high-performance liquid chromatography with mass spectrometry and nuclear magnetic resonance spectroscopy. After literature screening, there is no doubt that tissues of species from the genera Nepenthes, Drosera, and Dionaea are rich sources of secondary metabolites that can be used in pharmacy and for medical purposes. The main types of the identified compounds include phenolic acids and their derivatives (gallic, protocatechuic, chlorogenic, ferulic, p-coumaric acids, gallic, hydroxybenzoic, vanillic, syringic caffeic acids, and vanillin), flavonoids (myricetin, quercetin, and kaempferol derivatives), including anthocyanins (delphinidin-3-O-glucoside, cyanidin-3-O-glucoside, and cyanidin), naphthoquinones (e.g., plumbagin, droserone, and 5-O-methyl droserone), and volatile organic compounds. Due to the biological activity of most of these substances, the importance of the carnivorous plant as a pharmaceutical crop will increase.

Santin (5,7-Dihydroxy-3,6,4'-Trimetoxy-Flavone) Enhances TRAIL-Mediated Apoptosis in Colon Cancer Cells

TRAIL (Tumor necrosis factor-Related Apoptosis-Inducing Ligand) has the ability to selectively kill cancer cells without being toxic to normal cells. This endogenous ligand plays an important role in surveillance and anti-tumor immunity. However, numerous tumor cells are resistant to TRAIL-induced apoptosis. In this study, the apoptotic effect of santin in combination with TRAIL on colon cancer cells was examined. Flow cytometry was used to detect the apoptosis and expression of death receptors (TRAIL-R1/DR4 and TRAIL-R2/DR5). Mitochondrial membrane potential (ΔΨm) was evaluated by DePsipher staining with the use of fluorescence microscopy. We have shown for the first time that flavonoid santin synergizes with TRAIL to induce apoptosis in colon cancer cells. Santin induced TRAIL-mediated apoptosis through increased expression of death receptors TRAIL-R1 and TRAIL-R2 and augmented disruption of the mitochondrial membrane in SW480 and SW620 cancer cells. The obtained data may indicate the potential role of santin in colon cancer chemoprevention through the enhancement of TRAIL-mediated apoptosis.

Resonance-Enhanced Multiphoton Ionization Studies of the Lower Electronically Excited States of Flavone

The spectroscopic and dynamics properties of flavone─the core chromophore of a wide variety of naturally occurring ultraviolet protecting filters─have been studied under supersonic beam conditions using (1 + 1') resonance-enhanced two-photon ionization spectroscopic techniques. Excitation spectra recorded under such conditions are found to differ significantly from previously reported spectra. Pump-probe studies find that intersystem crossing is the dominant decay pathway of the excited singlet manifold, in agreement with previous solution phase studies and quantum chemical predictions for the isolated molecule. Microsolvation studies on flavone-water clusters reveal that the addition of one and two water molecules leads to considerable shifts in excitation energies but that further complexation does not result in further noticeable shifts. The relaxation pathways of the electronically excited states, on the other hand, do not appear to be influenced by interactions with the solvent molecules. Finally, photoionization spectra have enabled the accurate determination of the adiabatic ionization energy to the ground state of the molecular ion─key to the antioxidant properties of flavone─as 65,415 cm^-1 (8.110 eV).

Mass Spectrometry-Based Untargeted Metabolomics Reveals the Importance of Glycosylated Flavones in Patterned Lentil Seed Coats

Lentil seed coats are rich in antioxidant polyphenols that are important for plant defense and have potential as valorized byproducts. Although biochemical differences among lentil seed coat colors have been previously studied, differences among seed coat patterns remain largely unexplored. This study used mass spectrometry-based untargeted metabolomics to investigate polyphenol differences among lentil seed coat patterns to search for biochemical pathways potentially responsible for seed coat pattern differences. Comparing patterned with non-patterned green lentil seed coats, 28 significantly upregulated metabolites were found in patterned seed coats; 19 of them were identified as flavones. Flavones were virtually absent in non-patterned seed coats, thereby strongly suggesting a blockage in their flavone biosynthetic pathway. Although the black pattern is not readily discernible on black seed coats, many of the same flavones found in green marbled seed coats were also found in black seed coats, indicating that black seed coats likely have a marbled pattern.

Analysis of oxidase activity and transcriptomic changes related to cutting propagation of hybrid larch

Hybrid larch is the main timber and afforestation tree species in Northeast China. To solve the problem of rooting difficulties in larch cutting propagation, enzyme activity determination and transcriptome sequencing were carried out on the rooting tissues at five timepoints after cutting. peroxidase (POD), indole acetic acid oxidase (IAAO) and polyphenol oxidase (PPO) play important roles in the larch rooting process after cutting. A total of 101.20 Gb of clean data was obtained by transcriptome sequencing, and 43,246 unigenes were obtained after further screening and assembly. According to GO analysis and KEGG enrichment analysis, we think that plant hormones play an important role in the rooting process of larch stem cuttings. in the plant hormone signal transduction pathway, a larch gene c141104.graph_c0 that is homologous to the Arabidopsis AUX1 was found to be significantly up-regulated. We suggest that AUX1 may promote IAA transport in larch, thus affecting adventitious root development. According to the results of POD, PPO IAAO indexes and GO analysis, we think s1 and s2 periods may be important periods in the rooting process of larch stem cuttings, so we built a gene regulatory network, a total of 14genes, including LBD, NAC, AP2/ERF, bHLH and etc., may be important in different stages of cutting propagation. As the rooting rate after cutting inhibits the development of larch clone propagation, identifying the genes that regulate rooting could help us to preliminarily understand the molecular mechanism of adventitious root formation and select a better treatment method for cutting propagation.

Major Phytochemicals: Recent Advances in Health Benefits and Extraction Method

Recent scientific studies have established a relationship between the consumption of phytochemicals such as carotenoids, polyphenols, isoprenoids, phytosterols, saponins, dietary fibers, polysaccharides, etc., with health benefits such as prevention of diabetes, obesity, cancer, cardiovascular diseases, etc. This has led to the popularization of phytochemicals. Nowadays, foods containing phytochemicals as a constituent (functional foods) and the concentrated form of phytochemicals (nutraceuticals) are used as a preventive measure or cure for many diseases. The health benefits of these phytochemicals depend on their purity and structural stability. The yield, purity, and structural stability of extracted phytochemicals depend on the matrix in which the phytochemical is present, the method of extraction, the solvent used, the temperature, and the time of extraction.

Flavonoid Production: Current Trends in Plant Metabolic Engineering and De Novo Microbial Production

Flavonoids are secondary metabolites that represent a heterogeneous family of plant polyphenolic compounds. Recent research has determined that the health benefits of fruits and vegetables, as well as the therapeutic potential of medicinal plants, are based on the presence of various bioactive natural products, including a high proportion of flavonoids. With current trends in plant metabolite research, flavonoids have become the center of attention due to their significant bioactivity associated with anti-cancer, antioxidant, anti-inflammatory, and anti-microbial activities. However, the use of traditional approaches, widely associated with the production of flavonoids, including plant extraction and chemical synthesis, has not been able to establish a scalable route for large-scale production on an industrial level. The renovation of biosynthetic pathways in plants and industrially significant microbes using advanced genetic engineering tools offers substantial promise for the exploration and scalable production of flavonoids. Recently, the co-culture engineering approach has emerged to prevail over the constraints and limitations of the conventional monoculture approach by harnessing the power of two or more strains of engineered microbes to reconstruct the target biosynthetic pathway. In this review, current perspectives on the biosynthesis and metabolic engineering of flavonoids in plants have been summarized. Special emphasis is placed on the most recent developments in the microbial production of major classes of flavonoids. Finally, we describe the recent achievements in genetic engineering for the combinatorial biosynthesis of flavonoids by reconstructing synthesis pathways in microorganisms via a co-culture strategy to obtain high amounts of specific bioactive compounds.