Construction of a novel flavonol fluorescent probe for copper (II) ion detection and its application in actual samples

Copper is an essential trace element in the human body, and its level is directly related to many diseases. While the source of copper in human body is mainly intake from food, then the detection of copper ions (Cu2+) in food becomes crucial. Here, we synthesized a novel probe (E)-3-hydroxy-2-styryl-4H-benzo[h]chromen-4-one (NSHF) and explored the binding ability of NSHF for Cu2+ using nuclear magnetic resonance hydrogen spectroscopy (1H NMR), high-resolution mass spectrometry (HRMS), Job's plot method and density functional theory (DFT). NSHF shows the advantages of fast response time, good selectivity and high sensitivity for Cu2+. The fluorescence intensity ratio (F/F0) of NSHF shows a good linear relationship with the concentration of Cu2+ and the detection limit is 0.061 μM. NSHF was successfully applied to the detection of Cu2+ in real samples. In addition, a simple and convenient Cu2+ detection platform was constructed by combining NSHF with a smartphone and a UV lamp, which can realize the rapid detection of Cu2+. This work provides an effective tool for the real-time detection of Cu2+.

Comparison of binding sites and affinity of flavonol-Cu(II) complexes with the same parent nucleus: Synthesis, DFT prediction, and coordination pattern

This study explores the coordination dynamics between dietary polyphenols, specifically kaempferol, quercetin, and myricetin, and Cu ions in aqueous environments. A novel synthesis method for flavonol-Cu(II) coordination compounds is introduced, effectively reducing interference from free metal ions. Our results reveal consistent binding patterns of Cu ions with flavonols (2:1 ratio of flavonol to Cu(II)), predominantly at the 4,5 sites. Various analytical techniques are used to validate these coordination ratios and sites. The binding affinity of the flavonols for Cu ions follows a descending sequence: myricetin > quercetin > kaempferol. Notably, coordination with Cu ions enhances the free-radical scavenging activities of these flavonols. These findings hold substantial importance for food chemistry, biology, and medicine, providing crucial insights into the way dietary flavonols form stable structures in environments similar to human body fluids and their interactions with metal ions, opening new possibilities for their application and understanding in diverse scientific domains.

Transcriptomic and targeted metabolomic analyses provide insights into the flavonoids biosynthesis in the flowers of Lonicera macranthoides

BACKGROUND

Flavonoids are one of the bioactive ingredients of Lonicera macranthoides (L. macranthoides), however, their biosynthesis in the flower is still unclear. In this study, combined transcriptomic and targeted metabolomic analyses were performed to clarify the flavonoids biosynthesis during flowering of L. macranthoides.

RESULTS

In the three sample groups, GB_vs_WB, GB_vs_WF and GB_vs_GF, there were 25, 22 and 18 differentially expressed genes (DEGs) in flavonoids biosynthetic pathway respectively. A total of 339 flavonoids were detected and quantified at four developmental stages of flower in L. macranthoides. In the three sample groups, 113, 155 and 163 differentially accumulated flavonoids (DAFs) were detected respectively. Among the DAFs, most apigenin derivatives in flavones and most kaempferol derivatives in flavonols were up-regulated. Correlation analysis between DEGs and DAFs showed that the down-regulated expressions of the CHS, DFR, C4H, F3'H, CCoAOMT_32 and the up-regulated expressions of the two HCTs resulted in down-regulated levels of dihydroquercetin, epigallocatechin and up-regulated level of kaempferol-3-O-(6''-O-acetyl)-glucoside, cosmosiin and apigenin-4'-O-glucoside. The down-regulated expressions of F3H and FLS decreased the contents of 7 metabolites, including naringenin chalcone, proanthocyanidin B2, B3, B4, C1, limocitrin-3,7-di-O-glucoside and limocitrin-3-O-sophoroside.

CONCLUSION

The findings are helpful for genetic improvement of varieties in L.macranthoides.

Flavonoids: A treasure house of prospective pharmacological potentials

Flavonoids are organic compounds characterized by a range of phenolic structures, which are abundantly present in various natural sources such as fruits, vegetables, cereals, bark, roots, stems, flowers, tea, and wine. The health advantages of these natural substances are renowned, and initiatives are being taken to extract the flavonoids. Apigenin, galangin, hesperetin, kaempferol, myricetin, naringenin, and quercetin are the seven most common compounds belonging to this class. A thorough analysis of bibliographic records from reliable sources including Google Scholar, Web of Science, PubMed, ScienceDirect, MEDLINE, and others was done to learn more about the biological activities of these flavonoids. These flavonoids appear to have promising anti-diabetic, anti-inflammatory, antibacterial, antioxidant, antiviral, cytotoxic, and lipid-lowering activities, according to evidence from in vitro, in vivo, and clinical research. The review contains recent trends, therapeutical interventions, and futuristic aspects of flavonoids to treat several diseases like diabetes, inflammation, bacterial and viral infections, cancers, and cardiovascular diseases. However, this manuscript should be handy in future drug discovery. Despite these encouraging findings, a notable gap exists in clinical research, hindering a comprehensive understanding of the effects of flavonoids at both high and low concentrations on human health. Future investigations should prioritize exploring bioavailability, given the potential for high inter-individual variation. As a starting point for further study on these flavonoids, this review paper may promote identifying and creating innovative therapeutic uses.

adults from NHANES database

Using updated National Health and Nutrition Examination Survey (NHANES) follow-up data, and a large nationwide representative sample of adult U.S. citizens, the aim of this study was to explore the relationship between dietary flavonol intake, all-cause and cause-specific mortality risks. In this prospective cohort study based on NHANES (2007-2008, 2009-2010, and 2017-2018), a total of 11,679 participants aged 20 years and above were evaluated. The amount and type of food taken during a 24-h dietary recall were used to estimate dietary flavonol intake, which includes total flavonol, isorhamnetin, kaempferol, myricetin, and quercetin. Each analysis of the weighted data was dealt with in accordance with the NHANES reporting requirements' intricate stratification design. The Cox proportional risk regression model or Fine and Gray competing risks regression model were applied to evaluate all-cause and cause-specific mortality risks, respectively. The follow-up period was calculated using the time interval between the baseline and the death date or December 31, 2019 (whichever occurs first). Each data analysis was performed between October 1, 2023, and October 22, 2023. Dietary flavonol intake included total flavonol, isorhamnetin, kaempferol, myricetin, and quercetin. Up to December 31, 2019, National Death Index (NDI) mortality data were used to calculate mortality from all causes as well as cause-specific causes. A total of 11,679 individuals, which represents 44,189,487 U.S. non-hospitalized citizens, were included in the study; of these participants, 49.78% were male (n = 5816), 50.22% were female (n = 5, 863); 47.56% were Non-Hispanic White (n = 5554), 18.91% were Non-Hispanic Black (n = 2209), 16.23% were Mexican American (n = 1895), and 17.30% were other ethnicity (n = 2021); The mean [SE] age of the sample was 46.93 [0.36] years, with a median follow-up of 7.80 years (interquartile range, 7.55-8.07 years). After adjusting covariates, Cox proportional hazards models and fine and gray competing risks regression models for specific-cause mortality demonstrated that total flavonol intake was associated with all-cause (HR 0.64, 95% CI 0.54-0.75), cancer-specific (HR 0.45, 95% CI 0.28-0.70) and CVD-specific (HR 0.67, 95% CI 0.47-0.96) mortality risks; isorhamnetin intake was associated with all-cause (HR 0.72, 95% CI 0.60-0.86), and cancer-specific (HR 0.62, 95% CI 0.46-0.83) mortality risks; kaempferol intake was associated with all-cause (HR 0.74, 95% CI 0.63-0.86), and cancer-specific (HR 0.62, 95% CI 0.40-0.97) mortality risks; myricetin intake was associated with all-cause (HR 0.77, 95% CI 0.67-0.88), AD-specific (HR 0.34, 95% CI 0.14-0.85), and CVD-specific (HR 0.61, 95% CI 0.47-0.80) mortality risks; quercetin intake was associated with all-cause (HR 0.66, 95% CI 0.54-0.81), cancer-specific (HR 0.54, 95% CI 0.35-0.84), and CVD-specific (HR 0.61, 95% CI 0.40-0.93) mortality risks; there was no correlation observed between dietary flavonol intake and DM-specific mortality. According to the current study, all-cause, AD, cancer, and CVD mortality risks declined with increased dietary flavonoid intake in the U.S. adults. This finding may be related to the anti-tumor, anti-inflammatory, and anti-oxidative stress properties of flavonol.

Novel flavonol derivatives containing benzoxazole as potential antiviral agents: design, synthesis, and biological evaluation

A series of flavonol derivatives containing benzoxazole were designed and synthesized, and the structures of all the target compounds were determined by nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS). The structure of X2 was further confirmed by single crystal X-ray diffraction analysis. The results of the bioactivity tests showed that some of the target compounds possessed excellent antiviral activity against tobacco mosaic virus (TMV) in vivo. In particular, the median effective concentration (EC50) values for the curative and protective activities of X17 against TMV were 127.6 and 101.2 μg/mL, respectively, which were superior to those of ningnanmycin (320.0 and 234.6 μg/mL). The results of preliminary mechanism study indicated that X17 had a strong binding affinity for TMV coat protein (TMV-CP), which might hinder the self-assembly and replication of TMV particles. In addition, X17 was able to effectively inhibit tobacco leaf membrane lipid peroxidation and facilitate the removal of O2- from the body, thereby improving the disease resistance of tobacco plants. Therefore, the design and synthesis of flavonol derivatives containing benzoxazole provides value for the development of new antiviral drugs.

natto BCRC 80517

Flavonols (3-hydroxy flavones) have been studied for their beneficial bioactivities for human health. Recently, we reported that a flavonoid phosphate synthetase (BsFPS) from Bacillus subtilis BCRC 80517 can transform several flavonoids into their phosphate conjugates, which become more water-soluble and thus increase the oral bioavailability. However, the in vivo metabolism of different flavonols has yet to be determined. Here, we investigated biotransformation of three flavonols (quercetin, kaempferol and fisetin) by B. subtilis BCRC 80517. C-ring cleavage products of quercetin and kaempferol, i.e., 2-protocatechuoyl-phloroglucinol carboxylic acid (2-PCPGCA), were produced, whereas two phosphate derivatives of fisetin (fisetin 4'-O-phosphate and fisetin 3'-O-phosphate) were generated by cultivation with B. subtilis BCRC 80517. Our results indicated that there are structure-specific metabolic pathways in B. subtilis toward different flavonols, where the 5-hydroxy group determines metabolic priority. Our findings provide new insights for developing bioproduction platform to produce flavonol phosphate derivatives for nutraceutical applications.

HaMYBA-HabHLH1 regulatory complex and HaMYBF fine-tune red flower coloration in the corolla of sunflower (Helianthus annuus L.)

Sunflowers are well-known ornamental plants, while sunflowers with red corolla are rare and the mechanisms underlying red coloration remain unclear. Here, a comprehensive analysis of metabolomics and transcriptomics on flavonoid pathway was performed to investigate the molecular mechanisms underlying the differential color formation between red sunflower Pc103 and two yellow sunflowers (Yr17 and Y35). Targeted metabolomic analysis revealed higher anthocyanin levels but lower flavonol content in Pc103 compared to the yellow cultivars. RNA-sequencing and phylogenetic analysis identified multiple genes involved in the flavonoid pathway, including series of structural genes and three MYB and bHLH genes. Specifically, HaMYBA and HabHLH1 were up-regulated in Pc103, whereas HaMYBF exhibited reduced expression. HaMYBA was found to interact with HabHLH1 in vivo and in vitro, while HaMYBF does not. Transient expression analysis further revealed that HabHLH1 and HaMYBA cooperatively regulate increased expression of dihydroflavonol 4-reductase (DFR), leading to anthocyanin accumulation. On the other hand, ectopic expression of HaMYBF independently modulates flavonol synthase (FLS) expression, but hindered anthocyanin production. Collectively, our findings suggest that the up-regulation of HaMYBA and HabHLH1, as well as the down-regulation of HaMYBF, contribute to the red coloration in Pc103. It offers a theoretical basis for improving sunflower color through genetic engineering.

Fluorescence determination of the total amount of tetracyclines by a flavonol-based supramolecular sensor

Tetracyclines (TCs) are a group of broad-spectrum antibiotics against multiplying microorganisms yet with several adverse effects on humans. Since all types of TCs have the similar chemical skeleton and mechanism of action, quantification of total amount of TCs in the environment was of particular importance. To date, dozens of fluorescent probes have been reported for TCs detection, but only very few of them enabled detection of total TCs. In this study, we report a novel supramolecular sensor constructed by human serum albumin as the recognition moiety and a flavonol fluorophore as the indicator. Under the 370 nm UV excitation, this sensor exhibits the rapid response (5 s), acceptable sensitivity (limit of detection ∼ 0.58 μM), long dynamic detection range (0-20 μM), prominent specificity, and excellent anti-interference properties for analysis of total TCs. The mechanism was carefully validated using 1H NMR, fluorescence titration experiments, molecular docking, and mass spectrometry. We expect this work can inspire more sensor design for TCs quantification.

Design of flavonol-loaded cationic gold nanoparticles with enhanced antioxidant and antibacterial activities and their interaction with proteins

In this work, four structurally similar flavonols (galangin, kaempferol, quercetin and myricetin) were coated on the surface of (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide (MUTAB)‑gold nanoparticles (AuNPs) by two-step phase transfer and self-assembly, and the cationic MUTAB- AuNPs coated with flavonols (flavonol-MUTAB-AuNPs) were designed. Free radical scavenging and antibacterial experiments show that flavonol-MUTAB-AuNPs greatly improve the scavenging effect on DPPH, hydroxyl and superoxide anion radicals, and significantly enhance the inhibition effect on Staphylococcus aureus and Escherichia coli compared with flavonols and AuNPs. Then γ-globulin, fibrinogen, trypsin and pepsin were selected as representative proteins and their interaction with flavonol-MUTAB-AuNPs were investigated by various spectroscopic techniques. The fluorescence quenching mechanism of these four proteins by flavonol-MUTAB-AuNPs is static quenching. The binding constants Ka between them are in the range of 103 to 106. The interaction between them is endothermic, entropy-driven spontaneous process, and the main non-covalent force is the hydrophobic interaction. The effect of flavonol-MUTAB-AuNPs on the structure of the four proteins were investigated using UV-vis absorption spectra, synchronous fluorescence spectra and circular dichroism spectra. These results offer important insights into the essence of the interaction between flavonol-MUTAB-AuNPs and γ-globulin/fibrinogen/trypsin/pepsin. They will contribute to the development of safe and effective flavonol-MUTAB-AuNPs in biomedical fields.

Integrated metabolome, full-length sequencing, and transcriptome analyses unveil the molecular mechanisms of color formation of the canary yellow and red bracts of Bougainvillea × buttiana 'Chitra'

Bougainvillea is a typical tropical flower of great ornamental value due to its colorful bracts. The molecular mechanism behind color formation is not well-understood. Therefore, this research conducted metabolome analysis, transcriptome analysis, and multi-flux full-length sequencing in two color bracts of Bougainvillea × buttiana 'Chitra' to investigate the significantly different metabolites (SDMs) and differentially expressed genes (DEGs). Overall, 261 SDMs, including 62 flavonoids and 26 alkaloids, were detected, and flavonols and betalains were significantly differentially accumulated among the two bracts. Furthermore, the complete-length transcriptome of Bougainvillea × buttiana was also developed, which contained 512 493 non-redundant isoforms. Among them, 341 210 (66.58%) displayed multiple annotations in the KOG, GO, NR, KEGG, Pfam, Swissprot, and NT databases. RNA-seq findings revealed that 3610 DEGs were identified between two bracts. Co-expression analysis demonstrated that the DEGs and SDMs involved in flavonol metabolism (such as CHS, CHI, F3H, FLS, CYP75B1, kaempferol, and quercetin) and betacyanin metabolism (DODA, betanidin, and betacyanins) were the main contributors for the canary yellow and red bract formation, respectively. Further investigation revealed that several putative transcription factors (TFs) might interact with the promoters of the genes mentioned above. The expression profiles of the putative TFs displayed that they may positively and negatively regulate the structural genes' expression profiles. The data revealed a potential regulatory network between important genes, putative TFs, and metabolites in the flavonol and betacyanin biosynthesis of Bougainvillea × buttiana 'Chitra' bracts. These findings will serve as a rich genetic resource for future studies that could create new color bracts.

Clinical development and informatics analysis of natural and semi-synthetic flavonoid drugs: A critical review

BACKGROUND

Flavonoids are one of the most important metabolites with vast structural diversity and a plethora of potential pharmacological applications, which have drawn considerable attention in the laboratory. Nevertheless, it remains uncertain how many candidates were progressed to clinical application.

AIM OF REVIEW

We carried out a critical review of natural and semi-synthetic flavonoid drugs and candidates undergoing different clinical phases worldwide by applying an adequate search method and conducted a brief cheminformatic and bioinformatic analysis. It was expected that the obtained results might narrow the screening scope and reduce the cost of drug research and development.

KEY SCIENTIFIC CONCEPTS OF REVIEW

To our knowledge, this is the most systematic summarization of flavonoid-based drugs and clinical candidates to date. It was found that a total of 19 flavonoid-based drugs have been approved for the market, and of these, natural flavonoids accounted for 52.6%. Besides, a total of 36 flavonoid-based clinical candidates are undergoing or suspended in different phases, and of these, natural flavonoids account for 44.4%. Thus, natural flavonoids remain the best option for finding novel agents/active templates, and when investigated in conjunction with synthetic chemicals and biologicals, they offer the potential to discover novel structures that can lead to effective agents against a variety of human diseases. Additionally, flavonoid-based marketed drugs have been successful in cardiovascular treatment, and the related drugs account for more than 30% of marketed drugs. However, the use of flavonoids as antineoplastic and immunomodulating agents is not likely for approximately 50% of the candidates suspended in the clinical stage. Interestingly, the marketed drugs covered a broader range of chemical spaces based on size, polarity, and three-dimensional structure compared to the clinical candidates. In addition, flavonoid glycosides with poor oral bioavailability account for 36.8% of the marketed drugs, and thus, they could be thoroughly investigated.

Novel Flavonoid Photoswitchable "Turn-On" Fluorescent Chemosensors: Synthesis of Bromo Flavonols for Nanomolar Aluminum Ion Detection and Cellular Imaging, among Other Applications

Aluminum (Al), a non-essential element in living systems, can potentially cause chronic toxicity. Therefore, it is crucial to have a specific and sensitive method for detecting Al3+ in order to assess its risk to life. In this study, we designed and synthesized a novel fluorescent probe (IV) based on bromoflavonol. Upon binding to Al3+, probe IV exhibits a blue shift in emission and enhanced fluorescence, making it suitable for Al3+ detection. Our UV-Vis absorption and fluorescence emission spectra demonstrate that probe IV has high selectivity and sensitivity towards Al3+ while being immune to interference from other metal ions. Through fluorescence titration, we determined that the detection limit (LOD) of probe IV for Al3+ is 1.8 × 10-8 mol/L. Job's curve and 1 H NMR titration further confirmed a 1:1 binding stoichiometry between probe IV and Al3+. Additionally, using DFT (Density Functional Theory), we calculated the energy gap difference between IV and IV + Al3+ and found that the complex formed by probe IV and Al3+ is more stable than IV alone. We successfully detected Al3+ in tap water and river water from the middle regions of the Han River, achieving recoveries of over 96% using this probe. This demonstrates its potential for quantitative detection of Al3+ in environmental water samples. Moreover, we successfully used the probe for imaging Al3+ in MG63 cells, suggesting its potential application in biological imaging.

The case for an oxidopyrylium intermediate in the mechanism of quercetin dioxygenases

The quercetin dioxygenases (QDOs) are unusual metalloenzymes in that they display ring-opening dioxygenase activity with several different first-row transition metal ions which do not undergo redox changes during turnover. The QDOs are also unique in that the substrate binds as an η1-flavonolate rather than the η2 -bidentate mode seen in all reported model complexes. The flavonol substrates were early examples of excited state intramolecular proton transfer (ESIPT) phenomena, in which photoexcitation causes an H-atom exchange between the adjacent hydroxyl and ketone, generating an oxidopyrylium emissive state. These oxidopyryliums undergo ring-opening dioxygenations analogous to the enzymatic reactions. Our hypothesis is that lability of the divalent metal ion may allow access to a reactive oxidopyrylium intermediate via coordination switching from the oxy to ketone position, which allows reaction with O2. In this report, we use a straight-forward methylation strategy to generate a panel of flavonol and thioflavonol derivatives modeling several η1- and η2-coordination modes. Methylation of 3-hydroxythioflavone generates an air stable η1 hydroxopyrylium salt, which undergoes rapid ring-opening dioxygenation by deprotonation or photoexcitation. By comparison, the η1-methoxyflavonol does not react with O2 under any condition. We find that any of the studied flavonol derivatives, η1 or η2, which demonstrates ESIPT-like oxidopyrylium emissions undergo QDO-like ring-opening reactions with dioxygen. The implications of these results concerning the mechanism of QDOs and related dioxygenases is discussed.

Kaempferol therapy improved MC903 induced-atopic dermatitis in a mouse by suppressing TSLP, oxidative stress, and type 2 inflammation

BACKGROUND

Atopic dermatitis is a common skin disease caused by genetic susceptibility, environmental factors, immune response, and skin barrier dysfunction. Kaempferol is a natural flavonoid widely found in tea, vegetables, and fruits and has been reported to have excellent anti-inflammation activity. However, the therapeutic effect of kaempferol on atopic dermatitis is unclear.

OBJECTIVE

This study aimed to elucidate the effect of kaempferol on skin inflammation in atopic dermatitis.

METHODS

The suppressive effect of kaempferol administration on skin inflammation was examined using MC903-induced atopic dermatitis-like skin inflammation mouse model. Quantification of skin dermatitis and transepidermal water loss was performed. A histopathological study was performed to examine thymic stromal lymphopoietin expression, cornified envelope proteins such as filaggrin, loricrin, and involucrin, and the numbers of infiltrating inflammatory cells, including lymphocytes, macrophages, and mast cells in the dermatitis area. The expressions of IL-4 and IL-13 were investigated by qPCR and flow cytometry analysis using skin tissues. The expression of HO-1 was investigated by western blot and qPCR.

RESULTS

Kaempferol therapy significantly suppressed MC903-induced dermatitis, TEWL, TSLP, and HO-1 expression, and infiltration of inflammatory cells. Kaempferol therapy improved the decreased expressions of filaggrin, loricrin, and involucrin in MC903-induced dermatitis skin site. The expressions of IL-4, and IL-13 were partially decreased in kaempferol-treated mice.

CONCLUSION

Kaempferol might improve MC903-induced dermatitis via suppression of type 2 inflammation and improvement of barrier dysfunction by inhibition of TSLP expression and oxidative stress. Kaempferol might have the potential to be a new treatment for atopic dermatitis.

The role of flavonols in insect resistance and stress response

Plants are sessile organisms and must adapt to various environmental changes, especially from stress conditions. Synthesis of secondary metabolites by the plant is one of the adaptive mechanisms against stress to provide resistance. Among several secondary metabolites, flavonols, a subgroup of flavonoids, are one of the most widely distributed in the plant kingdom. These molecules work as antioxidants, reduce reactive oxygen species (ROS) in plants, and cause detrimental effects on insect growth on feeding. Despite the great interest in flavonol function leading to insect tolerance and stress response, the detailed mechanisms related to these specific functions have yet to be studied. In this review, we have summarized the role of flavonols in plant defense against insects and different abiotic stresses and possible mechanisms involved in these functions.

Natural flavonols: actions, mechanisms, and potential therapeutic utility for various diseases

Background

Flavonols are phytoconstituents of biological and medicinal importance. In addition to functioning as antioxidants, flavonols may play a role in antagonizing diabetes, cancer, cardiovascular disease, and viral and bacterial diseases. Quercetin, myricetin, kaempferol, and fisetin are the major dietary flavonols. Quercetin is a potent scavenger of free radicals, providing protection from free radical damage and oxidation-associated diseases.

Main body of the abstract

An extensive literature review of specific databases (e.g., Pubmed, google scholar, science direct) were conducted using the keywords "flavonol," "quercetin," "antidiabetic," "antiviral," "anticancer," and "myricetin." Some studies concluded that quercetin is a promising antioxidant agent while kaempferol could be effective against human gastric cancer. In addition, kaempferol prevents apoptosis of pancreatic beta-cells via boosting the function and survival rate of the beta-cells, leading to increased insulin secretion. Flavonols also show potential as alternatives to conventional antibiotics, restricting viral infection by antagonizing the envelope proteins to block viral entry.

Short conclusion

There is substantial scientific evidence that high consumption of flavonols is associated with reduced risk of cancer and coronary diseases, free radical damage alleviation, tumor growth prevention, and insulin secretion improvement, among other diverse health benefits. Nevertheless, more studies are required to determine the appropriate dietary concentration, dose, and type of flavonol for a particular condition to prevent any adverse side effects.

Characterization of the color parameters and monomeric phenolic composition of 'Tempranillo' and 'Graciano' wines made by carbonic maceration

The current study aims to gather information about the color-related characteristics and the monomeric phenolic composition of carbonic maceration (CM) wines. The study was conducted over two vintages, with two different grape varieties. Color-related general parameters and wine monomeric phenolic composition were determined in both free-run and press CM fractions and were compared to conventional winemaking (CW). Overall, wines made by CM had lower phenolic content and color intensity. The analysis of wine detailed phenolic composition showed that CM wines were characterized by low contents of anthocyanins and flavonols. In contrast, free-run wine obtained by CM had the greatest concentration of flavanols and hydroxycinnamic acids, probably due to the presence of stems during the fermentation. In conclusion, vinification by CM leads to important differences in wine phenolic composition and, as consequence, on wine color properties. These differences could play an important role in wine sensorial properties and wine aging potential.

The CmMYB3 transcription factors isolated from the Chrysanthemum morifolium regulate flavonol biosynthesis in Arabidopsis thaliana

Chrysanthemum morifolium MYB3 factors are transcriptional activators for the regulation of flavonol biosynthesis. Flavonol was not only the critical secondary metabolite participating in the growth and development of plants but also the main active ingredient in medicinal chrysanthemum. However, few pieces of research revealed the transcriptional regulation of flavonol biosynthesis in Chrysanthemum morifolium. Here, we isolated two CmMYB3 transcription factors (CmMYB3a and CmMYB3b) from the capitulum of Chrysanthemum morifolium cv 'Hangju'. According to the sequence characteristics, the CmMYB3a and CmMYB3b belonged to the R2R3-MYB subgroup 7, whose members were often reported to regulate flavonol biosynthesis positively. CmMYB3a and CmMYB3b factors were identified to localize in the nucleus by subcellular localization assay. Besides, both of them have obvious transcriptional self-activation activity in their C-terminal. After the overexpression of CmMYB3 genes in Nicotiana benthamiana and Arabidopsis thaliana, the flavonol contents in plants were increased, and the expression of AtCHS, AtCHI, AtF3H, and AtFLS genes in A. thaliana was also improved. Interestingly, the CmMYB3a factor had stronger functions in improving flavonol contents and related gene expression levels than CmMYB3b. The interaction analysis between transcription factors and promoters suggested that CmMYB3 could bind and activate the promoters of CmCHI and CmFLS genes in C. morifolium, and CmMYB3a also functioned more powerfully. Overall, these results indicated that CmMYB3a and CmMYB3b work as transcriptional activators in controlling flavonol biosynthesis.

Probing the binding of morin with alpha-2-macroglobulin using multi-spectroscopic and molecular docking approach : Interaction of morin with α2M

Alpha-2-macroglobulin (α₂M) is an essential antiproteinase that is widely distributed in human plasma. The present study was aimed at investigating the binding of a potential therapeutic dietary flavonol, morin, with human α₂M using a multi-spectroscopic and molecular docking approach. Recently, flavonoid-protein interaction has gained significant attention, because a majority of dietary bioactive components interact with proteins, thereby altering their structure and function. The results of the activity assay exhibited a 48% reduction in the antiproteolytic potential of α₂M upon interaction with morin. Fluorescence quenching tests unequivocally confirmed quenching in the fluorescence of α₂M in the presence of morin, conforming complex formation and demonstrating that the binding mechanism involves a dynamic mode of interaction. Synchronous fluorescence spectra of α₂M with morin showed perturbation in the microenvironment around tryptophan residues. Furthermore, structural changes were observed through CD and FT-IR, showing alterations in the secondary structure of α₂M induced by morin. FRET further supports the results of the dynamic mode of quenching. Moderate interaction is shown by binding constant values using Stern-Volmer's fluorescence spectroscopy. Morin binds to α₂M at 298 K with a binding constant of 2.7 × 10⁴ M^-1, indicating the strength of the association. The α₂M-morin system was found to have negative ΔG values, which suggests that the binding process was spontaneous. Molecular docking also reveals the different amino acid residues involved in this binding process, revealing that the binding energy is -8.1 kcal/mol.

A flavonol-derived fluorescent probe for highly specific and sensitive detection of hydrazine in actual environmental samples and living zebrafish

Hydrazine (N₂H₄) is a significant chemical reagent and widely applied in industrial field, which can bring potential risk to environmental safety and human health due to its high toxicity and potential carcinogenicity. In this paper, a flavonol-derived fluorescent probe named TB-N₂H₄ was rationally developed for detecting N₂H₄ based on the excited intramolecular proton transfer (ESIPT) principle. TB-N₂H₄ exhibited a remarkable fluorescence turn-on response toward N₂H₄ with a large Stokes shift of 191 nm. Moreover, TB-N₂H₄ could selectively recognize N₂H₄ over other competitive analytes, and displayed high sensitivity toward N₂H₄ with a low detection limit of 0.117 μM. The sensing mechanism of the probe TB-N₂H₄ for N₂H₄ was confirmed by theoretical calculation and HRMS analysis. This probe was able to quantitatively determine N₂H₄ in environmental water and soil samples. Additionally, TB-N₂H₄ was also successfully utilized for real-time tracking of the distribution of N₂H₄ in living zebrafish.

Dysosmaflavonoid A-F, new flavonols with potent DPPH radical scavenging activity from Dysosma versipellis

Six new flavonols, including four glucosylated flavonols (dysosmaflavonoid A-D), one phenylpropanoid-substituted flavonol (dysosmaflavonoid E), and one phenyl-substituted flavonol (dysosmaflavonoid F), together with five known analogues, were isolated from the roots and rhizomes of Dysosma versipellis. Their structures were elucidated by comprehensive analysis of their NMR, IR, UV, HRESIMS, and HPLC data. The antioxidant activities of all isolated compounds were examined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. Compounds 2, 3, 5-8, and 12 exhibited significant DPPH scavenging capacity with IC₅₀ values of 33.95, 39.02, 31.17, 32.79, 31.85, 30.48, and 23.75 μM, respectively, in comparison with Trolox (IC₅₀, 15.80 μM). Compound 12 displayed more potent DPPH radical scavenging activity than prenylated and (or) glucosided derivatives (2-4, or 10). The preliminary structure-activity relationship showed that the catechol structure in flavonol is essential for DPPH radical scavenging effect.

Metabolic profile and transcriptome reveal the mystery of petal blotch formation in rose

BACKGROUND

Petal blotch is a unique ornamental trait in angiosperm families, and blotch in rose petal is rare and has great esthetic value. However, the cause of the formation of petal blotch in rose is still unclear. The influence of key enzyme genes and regulatory genes in the pigment synthesis pathways needs to be explored and clarified.

RESULTS

In this study, the rose cultivar 'Sunset Babylon Eyes' with rose-red to dark red blotch at the base of petal was selected as the experimental material. The HPLC-DAD and UPLC-TQ-MS analyses indicated that only cyanidin 3,5-O-diglucoside (Cy3G5G) contributed to the blotch pigmentation of 'Sunset Babylon Eyes', and the amounts of Cy3G5G varied at different developmental stages. Only flavonols but no flavone were found in blotch and non-blotch parts. As a consequence, kaempferol and its derivatives as well as quercetin and its derivatives may act as background colors during flower developmental stages. Despite of the differences in composition, the total content of carotenoids in blotch and non-blotch parts were similar, and carotenoids may just make the petals show a brighter color. Transcriptomic data, quantitative real-time PCR and promoter sequence analyses indicated that RC7G0058400 (F3'H), RC6G0470600 (DFR) and RC7G0212200 (ANS) may be the key enzyme genes for the early formation and color deepening of blotch at later stages. As for two transcription factor, RC7G0019000 (MYB) and RC1G0363600 (WRKY) may bind to the promoters of critical enzyme genes, or RC1G0363600 (WRKY) may bind to the promoter of RC7G0019000 (MYB) to activate the anthocyanin accumulation in blotch parts of 'Sunset Babylon Eyes'.

CONCLUSIONS

Our findings provide a theoretical basis for the understanding of the chemical and molecular mechanism for the formation of petal blotch in rose.

An efficient ethylcellulose fluorescent probe for rapid detection of Fe3+ and its multi-functional applications

Fe³⁺ is the most abundant essential transition metal ion in the human body, plays a vital role in biological and environmental systems. Ethyl cellulose is one of the derivatives of cellulose. Herein, a novel ethylcellulose fluorescent probe EC-HPCB for detecting Fe³⁺ was prepared by grafting a flavonol derivative as both fluorophore and selective recognition group. The probe exhibited a highly specific "turn-off" fluorescence response to Fe³⁺, and the fluorescence color changed from yellow to colorless in the presence of Fe³⁺. The detection limit of EC-HPCB for Fe³⁺ was 2.65 × 10^-7 mol/L, and the response time was as quick as 2 min. The detection mechanism was confirmed by ¹H NMR and DFT calculations. Based on the good solubility and processability in organic solvent, EC-HPCB was made into coating and film with favorable fluorescent performances. Furthermore, EC-HPCB probe was successfully applied to monitor Fe³⁺ in real water samples, and the EC-HPCB-loaded filter paper provided a solid-state platform for detecting Fe³⁺ by naked eye and fluorescence method.

First and second order hyperpolarizabilities of flavonol derivatives: A density functional theory study

In this study, seventeen flavonol derivatives (1-17) were evaluated with regard to their first- and second-order hyperpolarizability parameters. For this purpose, the molecular geometries of 1-17 were optimized by using B3LYP/6-311++G(d,p) level. Spectroscopic characterizations for 1-17 were executed through the calculations of IR, UV-vis, ¹H NMR and ¹³C NMR spectra. The quantum chemical parameters such as electronegativity, chemical hardness, chemical potential and electrophilicity indexes were obtained by using the frontier molecular orbital (FMO) energies. The potential energy distribution (PED) analysis was used to provide a detailed assignment of vibrational bands. Important contributions to electronic absorption bands from FMOs were also evaluated. The distribution of FMOs to the whole molecule was investigated to determine the nature of electronic charge transfers in 1-17. The static and dynamic first- and second-order hyperpolarizability parameters for 1-17 were calculated by using B3LYP/6-311++G(d,p) level. The static β and γ were calculated at the ranges of 9.8279-0.0303 × 10^-29 esu and 80.200-268.40 × 10^-36 esu. The dynamic β and γ (ω = 532 nm) were also obtained in the field of 1.0440-71.786 × 10^-29 esu and 306.20-3607.00 × 10^-36 esu. This wide range of β and γ values indicate that flavonol derivatives with rational substitution may be promising candidates for first- and second-order NLO applications.

Synthesis of new flavonoid derivatives based on 3-hydroxy-4'-dimethylamino flavone and study the activity of some of them as antifungal

Chalcone was prepared in a new route by reacting o-hydroxyacetophenone with 4-dimethylaminobenzaldehyde using piperidine as a catalyst. 3-Hydroxy-2-[4-(dimethylamino)phenyl] benzopyran-4-one were prepared by Algar-Flynn-Oyamada method by cyclization of chalcone using Hydrogen peroxide. A series of alkyl and ester derivatives of the flavonoid 3-hydroxy-2-[4-(dimethylamino)phenyl] benzopyran-4-one were prepared by reacting the above mentioned compound with different chemical reagents (Methyl iodide, Allyl bromide, Benzyl chloride, Bromoacetylcoumarin, Chloroacetamide, Chloroacetyl chloride, Phthalic anhydride, Maleic anhydride, Phthalimide, Cinnamoyl chloride) with potassium carbonate and acetone or DMF as a solvent. The physical and spectroscopic properties of the new compounds were studied by (FT-IR, ¹³C-NMR and ¹H-NMR) spectral methods. The purity of the synthesized compounds were confirmed using TLC thin layer chromatography. The biological activity of some synthetic flavonoids (A₂, A₅, A₇, A₈, A₉, A₁₂) at two different concentrations (0.5 mg/ml, 0.25 mg/ml) were studied on three types of fungi: Aspergillus flavus, Acremonium strictum, Penicillium expansum. Some of this compounds showed high activity against the tested fungi.

A novel water-soluble flavonol-based fluorescent probe for highly specific and sensitive detection of Al3+ and its application in onion and zebrafish

A novel and simple turn-on fluorescence probe (HD) for Al³⁺ detection was successfully developed based on flavonol derivatives. This probe exhibited a significantly enhanced fluorescence response toward Al³⁺ in aqueous solution which could be observed by naked-eye from poor fluorescence to strong light green emission. The probe HD displays highly specific detection for Al³⁺ over other competitive metal ions, and the detection limit of probe HD for Al³⁺ was determined to be 2.57 × 10^-8 M, which are much lower than the World Health Organization (WHO) guideline value for drinking food/water. The binding stoichiometry of probe HD with Al³⁺ was determined to be 1:1 according to Job's plot and ESI-HRMS analysis, and the binding constant was calculated to be 2.01 × 10⁴ M^-1. The probe HD exhibited high selectivity, high sensitivity, good anti-interface ability, and wide pH application range as well as the quantitative determination in the detection of Al³⁺. The coordination mechanism of probe HD with Al³⁺ was supported by density functional theory (DFT) calculations and HRMS analysis. In addition, the probe HD was found to have good cell permeability and could be applied for live-cell imaging to detect Al³⁺ in onions and zebrafish.

The flavonoid kaempferol protects the fruit fly Drosophila melanogaster against the motor impairment produced by exposure to the insecticide fipronil

Exposure to pesticides across species has been associated with cognitive and motor impairments. As the problem impacts ecosystem stability, food production, and public health, it is urgent to develop multifactorial solutions, from regulatory legislation to pharmacological alternatives that ameliorate the impairments. Fipronil, a commonly used insecticide, acts as a GABAAR antagonist and induces motor impairments in vertebrates and invertebrates. Here, we hypothesize that kaempferol, a secondary metabolite derived from plants, acting as an allosteric modulator of GABAARs would protect against the negative effects induced by the administration of fipronil in adults of the fruit fly Drosophila melanogaster. We further evaluated our hypothesis via coadministration of flumazenil, a competitive antagonist on the GABAAR, and through in silico analyses. We administered kaempferol prophylactically at three concentrations (10µM, 30µM, 50µM) and evaluated its protective effects on motor impairments induced by fipronil. We then relied on a single dose of kaempferol (50µM) to evaluate its protective effect while administering flumazenil. We found that oral administration of fipronil impaired motor control and walking ability. In contrast, kaempferol was innocuous and protected from developing the motor-impaired phenotype, whereas the co-administration of flumazenil counteracted the protective effects. These results are supported by the binding of the ligands with the receptor. Together, our results suggest that kaempferol exerts a protective effect against fipronil via positive allosteric modulation of GABAARs, probably within brain areas such as the Central complex and the Mushroom bodies. These findings further support current attempts relying on metabolites derived from plants as protectors against impairments produced by pesticides.

The Impact of Heat Treatment of Quercetin and Myricetin on their Activities to Alleviate the Acrylamide-Induced Cytotoxicity and Barrier Loss in IEC-6 Cells

Two flavonols quercetin and myricetin were assessed for their in vitro activities to attenuate the acrylamide-induced cytotoxicity and barrier loss in rat intestinal epithelial (IEC-6) cells and to identify whether heat treatment of the flavonols might cause activity changes. The results showed that the flavonols could alleviate the acrylamide-caused cell injury, resulting in higher cell viability, lower lactate dehydrogenase release, and less formation of reactive oxygen species. Meanwhile, the flavonols could antagonize the acrylamide-induced barrier dysfunction via decreasing the paracellular permeability, increasing the transepithelial resistance of cell monolayer, and enhancing the expression of three tight junction proteins namely occludin, claudin-1, and zonula occludens-1. The flavonols also could down-regulate the expression of JNK/Src proteins and thus cause lower relative protein ratios of p-JNK/JNK and p-Src/Src, resulting in a suppressed JNK/Src activation. Totally, quercetin was more potent than myricetin to exert these assessed activities, while the heated flavonols obtained lower activity than the unheated ones. It is thus concluded that the flavonols had beneficial activities towards the intestinal epithelial cells with acrylamide exposure by alleviating the acrylamide-induced cytotoxicity and barrier disruption, while heat treatment of the flavonols was unfavorable because it led to a reduced flavonol activity to the cells.

The flavonoid rutin protects against cognitive impairments by imidacloprid and fipronil

The ongoing decline of bee populations and its impact on food security demands integrating multiple strategies. Sublethal impairments associated with exposure to insecticides, affecting the individual and the colony levels, have led to insecticide moratoria and bans. However, legislation alone is not sufficient and remains a temporary solution to an evolving market of insecticides. Here, we asked whether bees can be prophylactically protected against sublethal cognitive effects of two major neurotoxic insecticides, imidacloprid and fipronil, with different mechanisms of action. We evaluated the protective effect of the prophylactic administration of the flavonoid rutin, a secondary plant metabolite, present in nectar and pollen, and known for its neuroprotective properties. Following controlled or ad libitum administration of rutin, foragers of the North American bumble bee Bombus impatiens received oral administration of the insecticides at sublethal realistic dosages. Learning acquisition, memory retention and decision speed were evaluated using olfactory absolute conditioning of the proboscis extension response. We show that the insecticides primarily impair acquisition but not retention or speed of the conditioned proboscis extension response. We further show that the administration of the flavonoid rutin successfully protects the bees against impairments produced by acute and chronic administration of insecticides. Our results suggest a new avenue for the protection of bees against sublethal cognitive effects of insecticides.

Highlighted Article: Prophylactically feeding bumble bees with rutin protects their learning and memory performance against oral exposure to insecticides with different mechanisms of action.

"Improved quality assessment of cornelian cherry (Cornus mas L.) fruit with regard to their processing potential"

The sensory properties and appropriateness of cornelian cherry (Cornus mas L.) for processing is very closely related to its ripening stage, recognizable by firmness and skin colour to some extent. Due to the non-uniform ripening on the trees the quality of the fruits offered on the market depends very much on the harvest-method. Today, processors, who usually do not buy fresh fruits but frozen fruits or puree on the market, don`t have a suitable means for the accurate quality assessment of the raw material they need for the processing of high-quality products. The results of this work show for the first time that from the selected parameters (carbohydrates, organic acids, phenols) only flavonols, especially kaempferol-3-glucoside is appropriate to determine the stage of ripeness of cornelian cherries properly independent from species, provenance and crop year. Kaempferol 3-O-glucoside of about 1.75 mg/Kg in wild genotypes and of about 0.80 mg/Kg in most big cornelian cherry species can serve as a reference for sufficient ripeness and therefore for high fruit quality.

Kaempferol rhamnoside catabolism in rosette leaves of senescing Arabidopsis and postharvest stored radish

Flavonol rhamnosides including kaempferitrin (i.e., kaempferol 3-O-α-rhamnoside-7-O-α-rhamnoside) occur throughout the plant kingdom. Mechanisms governing flavonol rhamnoside biosynthesis are established, whereas degradative processes occurring in plants are relatively unknown. Here, we investigated the catabolic events affecting kaempferitrin status in the rosette leaves of Arabidopsis thaliana L. Heynh. (Arabidopsis) and Raphanus sativus L. (radish), respectively, in response to developmental senescence and postharvest handling. On a per plant basis, losses of several kaempferol rhamnosides including kaempferitrin were apparent in senescing leaves of Arabidopsis during development and postharvest radish stored at 5 °C. Conversely, small pools of kaempferol 7-O-α-rhamnoside (K7R), kaempferol 3-O-α-rhamnoside (K3R), and kaempferol built up in senescing leaves of both species. Evidence is provided for ⍺-rhamnosidase activities targeting the 7-O-α-rhamnoside of kaempferitrin and K7R in rosette leaves of both species. An HPLC analysis of in vitro assays of clarified leaf extracts prepared from developing Arabidopsis and postharvest radish determined that these metabolic shifts were coincident with respective 237% and 645% increases in kaempferitrin 7-O-⍺-rhamnosidase activity. Lower activity rates were apparent when these ⍺-rhamnosidase assays were performed with K7R. A radish ⍺-rhamnosidase containing peak eluting from a DEAE-Sepharose Fast Flow column hydrolyzed various 7-O-rhamnosylated flavonols, as well as kaempferol 3-O-β-glucoside. Together it is apparent that the catabolism of 7-O-α-rhamnosylated kaempferol metabolites in senescing plant leaves is associated with a flavonol 7-O-α-rhamnoside-utilizing α-rhamnosidase.

A simple "turn-on" fluorescent probe capable of recognition cysteine with rapid response and high sensing in living cells and zebrafish

Cysteine (Cys), an essential biological amino acid, participates several crucial functions in various physiological and pathological processes. The sensitive and specific detection of Cys is of great significance for understanding its biological function to disease diagnosis. Herein, we designed and synthesized a simple fluorescence sensor 2-(benzothiophen-2-yl)-4-oxo-4H-chromen-3-yl acrylate (BTCA) composed of a flavonol skeleton as the fluorophore and acrylic ester group as the recognition receptor. Probe BTCA displayed high selectivity and extremely fast response toward Cys in phosphate buffer solution in the presence of other competitive species even Homocysteine (Hcy) and Glutathione (GSH) owing to a specific conjugate addition-cyclization reaction between the acrylate moiety and Cys. The photoluminescence mechanism of probe BTCA toward Cys was modulated by excited state intramolecular proton transfer (ESIPT) process. The sensing property for Cys was studied by UV-Visible, fluorescence spectrophotometric analyses and time-dependent density functional theory (TD-DFT) calculations, those results indicated that probe BTCA possessed excellent sensitivity, higher specificity, dramatically "naked-eye" fluorescence enhancement (30-fold), high anti-interference ability, especially immediate response speed (within 40 s). Additionally, the practicability of sensor BTCA in exogenous and endogenous Cys imaging in living cells and zebrafish was elucidated as well, suggesting that it has remarkedly diagnostic significance in physiological and pathological process.

Impact of covalent grafting of two flavonols (kaemperol and quercetin) to caseinate on in vitro digestibility and emulsifying properties of the caseinate-flavonol grafts

Covalent grafting of one of the two flavonols (kaemperol and quercetin) to caseinate was achieved by a reaction between the heat-oxidized flavonols and caseinate at flavonol-lysine molar ratios of 1:100 and 1:200. Grafted caseinate products (GCPs) showed - NH₂ content reduction and respective kaemperol and quercetin contents of 1.08-6.13 and 3.23-6.64 mmol/kg protein. Quercetin was more reactive than kaemperol under the same conditions, while long-time flavonol heat and higher flavonol-lysine molar ratio caused greater flavonol-grafting. GCPs subjected to 180-day storage had further flavonol-grafting, -NH₂ content decrease, and weak protein crosslinking. GCPs consistently had higher surface hydrophobicity but lower emulsification and digestibility than caseinate, while greater flavonol-grafting caused a remarkable value change. Meanwhile, the Kjeldahl method was more suitable than the UV-absorption method to evaluate protein digestibility, because the grafted flavonols in this case did not interfere with data results. Collectively, the covalent flavonol-grafting of proteins can impact the assayed protein functionalities.

In through the out door: Biochemical mechanisms affecting flavonoid glycoside catabolism in plants

Plants are the sole source of flavonoids, a chemical category that includes flavonols. For the most part, flavonols occur as glycosides with numerous postulated biological roles in plants, including photoprotection, modulation of hormone translocation, and sequestration of reactive oxygen species. Flavonol glycosides are often considered as dead-end metabolites because related flavonoids (i.e., anthocyanins) occur in terminal tissues such as flowers and fruit, but recent evidence points to their turnover in planta, including developing photosynthetic tissues. Although microbial degradation pathways for flavonol glycosides of plant origin are well described, plant catabolic pathways are little studied by comparison. This review will address our current understanding of biochemical processes leading to the loss of flavonol glycosides in plants, with a specific emphasis on the evidence for flavonol-specific β-glucosidases. Complete elucidation of these catabolic pathways is dependent on the identification of regiospecific modifying steps, including enzymes associated with the hydrolysis of rhamnosylated flavonols, as well as flavonol peroxidation and their encoding genes. Herein, we highlight challenges for the identification of hypothetical plant α-rhamnosidases and peroxidases involved in flavonol glycoside degradation, and the potential biological role of this catabolism in mitigating oxidative stress in developing and postharvest plant tissues.

A comprehensive review on chemotherapeutic potential of galangin

Galangin, a non-toxic phytochemical is known to possess several therapeutic applications. Mounting evidences have demonstrated that galangin a naturally available flavonoid exerts anticancer effects via several mechanisms. The phytocompound induces apoptosis and renders antiangiogenic property. Additionally, galangin has demonstrated significate results in combating various cancer types when administered in combination with other phytocompounds or with gold nanoparticles (GNPs). The present article is a critical review of galangin for its treatment on different types of cancer and its usability as an alternative cancer therapeutics.

Effects of substituent pattern on the intracellular target of antiproliferative benzo[b]thiophenyl chromone derivatives

A new biological scaffold was produced by replacing the 6π-electron phenyl ring-B of a natural flavone skeleton with a 10π-electron benzothiophene (BT). Since aromatic rings are important for ligand protein interactions, this expansion of the π-electron system of ring-B might change the bioactivity profile. One of the resulting novel natural product-inspired compounds, 2-(benzo[b]thiophen-3-yl)-5-hydroxy-7-isopropoxy-6-methoxyflavone (6), effectively arrested the cell cycle at the G2/M phase and displayed significant antiproliferative effects with IC₅₀ values of 0.05-0.08 μM against multiple human tumor cell lines, including a multidrug resistant line. A structure-activity relationship study revealed that a 10π-electron system with high aromaticity, juxtaposed 4-oxo and 5-hydroxy groups, and 7-alkoxy groups were important for potent antimitotic activity. Interestingly, two BT-flavonols (3-hydroxyflavone), 16 and 20, with 3-hydroxy and 5-alkoxy groups, induced distinct biological profiles affecting the cell cycle at the G1/S phase by inhibition of DNA replication through an interaction with topoisomerase I.

Impacts of leaf removal and shoot thinning on cumulative daily light intensity and thermal time and their cascading effects of grapevine (Vitis vinifera L.) berry and wine chemistry in warm climates

Leaf removal (LR), shoot thinning (ST) and their combination (LRST) are known to increase berry solar exposure affecting berry composition and consequently improving wine quality and antioxidant properties. We hypothesized that LR, ST or their combination (LRST) would affect flavonoid content during berry ripening by means of changes of the berry microclimate (light and temperature) as well as wine composition, quality, and antioxidant properties. Thermal time and sum of light intensity thresholds were different to achieve the maximum berry anthocyanin and flavonol contents. ST mostly affected wine characteristics by increasing alcoholic content, acidity, hue and phenolic substances. Wine antioxidant capacity decreased in ST wines likely by decreases in catechin and quercetin contents. ST and LRST increased proanthocyanidin polymerization and decreased monomeric flavan-3-ols, which may reduce wine bitterness and enhance astringency. Therefore, the management of canopy should take into account the warming trends in viticulture regions, rather than being applied preemptively.

Protective effect of myricetin on nonylphenol-induced testicular toxicity: biochemical, steroidogenic, hormonal, spermatogenic, and histological-based evidences

Nonylphenol (NP) is an environmental contaminant, which induces testicular toxicity through oxidative stress. Myricetin (MYR) is a naturally occurring flavonol having powerful antioxidant activity. The current research was planned to examine the ameliorative role of MYR against NP-induced testicular damage. A total of 24 adult male Sprague-Dawley rats were randomly divided into 4 equivalent groups: control (0.1% DMSO), NP group (50 mg kg-1), NP + MYR group (50 mg kg-1; 100 mg kg-1), and MYR-treated group (100 mg kg-1). NP administration significantly (p < 0.05) decreased the activity of antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GSR), and protein content while significantly (p < 0.05) elevating the thiobarbituric acid reactive substances (TBARS) and reactive oxygen species (ROS) levels. Additionally, NP significantly (p < 0.05) reduced the sperm motility, gene expression of testicular steroidogenic enzymes (3β-HSD, 3β-hydroxysteroid dehydrogenase; 17β-HSD, 17β-hydroxysteroid dehydrogenase; StAR, steroidogenic-acute regulatory protein), level of luteinizing hormone (LH), follicle-stimulating hormone (FSH), plasma testosterone, and daily sperm production (DSP). On the other hand, it raised the testicular cholesterol, dead sperms, and head, midpiece, and tail abnormalities along with abnormal histomorphometry. However, MYR remarkably abrogated NP-induced damages. In conclusion, the outcomes of the study suggest that MYR can effectively alleviate the NP-induced oxidative stress and testicular damages.

Identification and quantification of phenolic composition from different species of Jabuticaba (Plinia spp.) by HPLC-DAD-ESI/MSn

The aim of this study was to investigate phenolic compounds in peel, pulp and seeds of five different jabuticabas - Plinia trunciflora, "cabinho", P. cauliflora, cultivars "paulista" and "canaã-açu", P. jaboticaba, "sabará" and P. phitrantha, "branca-vinho". In addition to the commonly reported cyanidin-3-glucoside and delphinidin3-glucoside, it was also found the unreported cyanidin-3-coumaroylglucoside in the peels. Flavonols derived from quercetin and myricetin were also detected in jaboticaba peels, along with a wide variety of derivatives of ellagic acid and methyl ellagic acid. The latter derivatives occurred in acylated forms, which were not usually found in jabuticabas. The pulps and seeds of jabuticabas contained large amounts of ellagitannins vescalagin and castalagin, as well as gallic and ellagic acids. The jabuticabas showed small amounts of catechin and gallocatechin. P. jaboticaba showed the highest levels of anthocyanins and flavonols derived from myricetin, and P. phitrantha presented the highest concentration of ellagitannins and flavan-3-ols.

COP1 mediates light-dependent regulation of flavonol biosynthesis through HY5 in Arabidopsis

Flavonols, a class of flavonoids, accumulate as protective agents in response to various stresses. Among various environmental stimuli, light is one of the factors regulating flavonol production. MYB12/11/111, members of the R2R3 MYBs family, regulates spatio-temporal flavonol accumulation in Arabidopsis. Although various studies indicate at the involvement of an E3 ubiquitin ligase CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) and ELONGATED HYPOCOTYL 5 (HY5) in flavonoid biosynthesis in response to UV-B, the regulatory roles of these components under visible light are yet to be investigated. Here, we demonstrate that flavonol accumulation in Arabidopsis is light-regulated. Furthermore, our analysis suggests that MYB12 is a HY5-dependent light-inducible gene and plays a key role in the activation of the flavonol biosynthesis in response to light. Our results indicate the involvement of COP1 in the dark-dependent repression of MYB12 expression and flavonol accumulation. In addition, results also suggest that the effect of COP1 on MYB12 is indirect and is mediated through HY5, a direct transcriptional activator of the MYB12. Together these findings indicate that COP1 acts as a master negative regulator of flavonol biosynthesis in the dark.

New phenylpropanoid-substituted and benzyl-substituted flavonols from Alangium chinense

Two previously undescribed flavonols with phenylpropanoid or benzyl substitution, named alangsine A (1), and alangsine B (2), together with four known compounds (3-6) were isolated from the leaves of Alangium chinense. Alangsine A was a racemic mixture, which was further separated into two enantiomers via high-performance liquid chromatography on a chiral column. The absolute configurations of the enantiomer pairs were deduced from the circular dichroism (CD) spectra. The activity of the isolated compounds towards neuronal excitability was examined.

Rhamnose in plants - from biosynthesis to diverse functions

In plants, the deoxy sugar l-rhamnose is widely present as rhamnose-containing polymers in cell walls and as part of the decoration of various specialized metabolites. Here, we review the current knowledge on the distribution of rhamnose, highlighting the differences between what is known in dicotyledoneuos compared to commelinid monocotyledoneous (grasses) plants. We discuss the biosynthesis and transport of UDP-rhamnose, as well as the transfer of rhamnose from UDP-rhamnose to various primary and specialized metabolites. This is carried out by rhamnosyltransferases, enzymes that can use a large variety of substrates. Some unique characteristics of rhamnose synthases, the multifunctional enzymes responsible for the conversion of UDP-glucose into UDP-rhamnose, are considered, particularly from the perspective of their ability to convert glucose present in flavonoids. Finally, we discuss how little is still known with regards to how plants rescue rhamnose from the many compounds to which it is linked, or how rhamnose is catabolized.

Antiplasmodial and antileishmanial flavonoids from Mundulea sericea

Five known compounds (1-5) were isolated from the extract of Mundulea sericea leaves. Similar investigation of the roots of this plant afforded an additional three known compounds (6-8). The structures were elucidated using NMR spectroscopic and mass spectrometric analyses. The absolute configuration of 1 was established using ECD spectroscopy. In an antiplasmodial activity assay, compound 1 showed good activity with an IC₅₀ of 2.0 μM against chloroquine-resistant W2, and 6.6 μM against the chloroquine-sensitive 3D7 strains of Plasmodium falciparum. Some of the compounds were also tested for antileishmanial activity. Dehydrolupinifolinol (2) and sericetin (5) were active against drug-sensitive Leishmania donovani (MHOM/IN/83/AG83) with IC₅₀ values of 9.0 and 5.0 μM, respectively. In a cytotoxicity assay, lupinifolin (3) showed significant activity on BEAS-2B (IC₅₀ 4.9 μM) and HePG2 (IC₅₀ 10.8 μM) human cell lines. All the other compounds showed low cytotoxicity (IC₅₀ > 30 μM) against human lung adenocarcinoma cells (A549), human liver cancer cells (HepG2), lung/bronchus cells (epithelial virus transformed) (BEAS-2B) and immortal human hepatocytes (LO2).

In vitro and in silico assessment of DNA interaction, topoisomerase I and II inhibition properties of chrysosplenetin

Chrysosplenetin is a methoxyflavone with reported anti-cancer effect. We tested its cytotoxic effect on the MCF-7 breast cancer cell line, and determined its effect on DNA intercalation and on the activity of topoisomerases I and II. The compound inhibited proliferation MCF-7 with an IC₅₀ value of 0.29 μM. Chrysosplenetin did not initiate plasmid DNA cleavage but, in a concentration-dependent manner, protected plasmid DNA against damage induced by Fenton reagents. Furthermore, it possessed dual Topoisomerase I and II inhibitory properties. Especially, it inhibited topoisomerase II by 83-96% between the range 12.5-100 μM. In the light of these experimental findings, molecular docking studies were performed to understand binding mode, interactions and affinity of chrysosplenetin with DNA, and with topoisomerases I and II. These studies showed that of 4-chromone core and the hydroxyl and methoxy groups important for both intercalation with DNA and topoisomerase I and II inhibition.

Flavonol glycosides from Fissistigma maclurei

Two new flavonol glycosides, fissmacosides A (1) and B (2) along with two known flavonol glycosides, kaempferol 3-O-α-l-rhamnopyranosyl-(1→6)-β-d-galactopyranoside (3) and kaempferol 3-O-β-d-glucopyranosyl-(1→4)-α-l-rhamnopyranosyl-(1→6)-[4-(E)-feruloyl]-β-d-galactopyranoside (4) were isolated from the methanol extract of the leaves of Fissistigma maclurei Merr. Their structures were determined on the basis of extensive spectroscopic methods, including 1D-, 2D-NMR, and MS data.

Impacts of leaf removal and shoot thinning on cumulative daily light intensity and thermal time and their cascading effects of grapevine (Vitis vinifera L.) berry and wine chemistry in warm climates

Leaf removal (LR), shoot thinning (ST) and their combination (LRST) are known to increase berry solar exposure affecting berry composition and consequently improving wine quality and antioxidant properties. We hypothesized that LR, ST or their combination (LRST) would affect flavonoid content during berry ripening by means of changes of the berry microclimate (light and temperature) as well as wine composition, quality, and antioxidant properties. Thermal time and sum of light intensity thresholds were different to achieve the maximum berry anthocyanin and flavonol contents. ST mostly affected wine characteristics by increasing alcoholic content, acidity, hue and phenolic substances. Wine antioxidant capacity decreased in ST wines likely by decreases in catechin and quercetin contents. ST and LRST increased proanthocyanidin polymerization and decreased monomeric flavan-3-ols, which may reduce wine bitterness and enhance astringency. Therefore, the management of canopy should take into account the warming trends in viticulture regions, rather than being applied preemptively.

Extraction methods of butterfly pea (Clitoria ternatea) flower and biological activities of its phytochemicals

Clitoria ternatea or commonly known as 'Butterfly pea' has been used traditionally in Ayurvedic medicine in which various parts of the plants are used to treat health issues such as indigestion, constipation, arthritis, skin diseases, liver and intestinal problems. The flowers of C. ternatea are used worldwide as ornamental flowers and traditionally used as a food colorant. This paper reviews the recent advances in the extraction and biological activities of phytochemicals from C. ternatea flowers. The application of maceration or ultrasound assisted extraction greatly increased the yield (16-247% of increase) of phytochemicals from C. ternatea flowers. Various phytochemicals such as kaempferol, quercetin and myricetin glycosides as well as anthocyanins have been isolated from C. ternatea flowers. Clitoria ternatea flower extracts were found to possess antimicrobial, antioxidant, anti-inflammatory, cytotoxic and antidiabetic activities which are beneficial to human health. Clitoria ternatea flower is a promising candidate for functional food applications owing to its wide range of pharmacotherapeutic properties as well as its safety and effectiveness.

Foliar-sprayed manganese sulfate improves flavonoid content in grape berry skin of Cabernet Sauvignon (Vitis vinifera L.) growing on alkaline soil and wine chromatic characteristics

Flavonoids are key determinants of grape quality and wine color. Grapevines growing in alkaline soil are prone to manganese deficiency, which can decrease the contents of secondary metabolites, including flavonoids. We determined the effects of a foliar Mn treatment (MnSO₄·H₂O) of Cabernet Sauvignon grapevines (V. vinifera L.) growing in alkaline soil on the flavonoid contents in grape skin, and the quality of wine. The Mn treatments were applied in 2017 and 2018, and tended to increase the grape sugars, berry weight, and the contents of phenolic compounds from veraison until harvest. The Mn treatments increased the amounts of acetylated, methylated, and total anthocyanins, as well as the total flavonol contents in grape berry skin at harvest. The wines prepared from these grapes had a higher color intensity than those prepared from grapes from control vines. Foliar-applied MnSO₄·H₂O can promote flavonoid biosynthesis in grape berries, and improve the color of wine.

Identification of compound causing yellow bone discoloration following alpha-glycosyl isoquercitrin exposure in Sprague-Dawley rats

Previous rat toxicity studies of alpha-glycosyl isoquercitrin (AGIQ), a water-soluble flavonol glycoside derived from rutin, revealed systemic yellow bone discoloration. This investigative study was conducted to determine the AGIQ metabolite(s) responsible for the discoloration. Female Sprague-Dawley rats were administered dietary AGIQ at doses of 0%, 1.5%, 3.0%, or 5.0% (0, 1735.0, 3480.8, and 5873.7 mg/kg/day, respectively) for 14 days, followed by a 14- or 28-day recovery period. Measurements of quercetin in urine and quercetin, quercetin 3-O-glucuronide, kaempferol, and 3-o-methylquercetin metabolites of AGIQ in bone (femur), white and brown fat, and cerebrum samples were conducted following the exposure period and each recovery period. Gross examination of the femur revealed yellow discoloration that increased in intensity with dose and was still present in a dose-related manner following both recovery periods. Quercetin, at levels correlating with AGIQ dose, was measured in the urine following the 14-day exposure period and, at lower concentrations, 14 or 28 days following cessation of AGIQ exposure. All four metabolites were present in a dose-dependent manner in the femur following 14 days of dietary exposure; only quercetin, quercetin 3-O-glucuronide, and 3-o-methylquercetin were present during the recovery periods. Quercetin, quercetin 3-O-glucuronide, and 3-o-methylquercetin were detected in white fat (along with kaempferol), brown fat (excluding quercetin due to analytical interference), and cerebrum samples, indicating systemic availability of the metabolites. Collectively, these data implicate quercetin, quercetin 3-O-glucuronide, or 3-o-methylquercetin (or a combination thereof) as the most likely metabolite of AGIQ causing the yellow discoloration of bone in rats administered dietary AGIQ.