Pharmacological basis and new insights of taxifolin: A comprehensive review

Hitchhiking into a cell: flavonoids may produce complexes with transition metals for transmembrane translocation

Flavonoids are a group of food polyphenols that are delivered to the human body with plant foods. In recent years, these substances have attracted the attention of researchers due to their effectiveness in preventing a wide variety of diseases, including neurodegenerative, oncological, autoimmune, and cardiovascular. Similar pathologies may also occur with a lack of some first-row transition metals, including Cu(II), Zn(II), Mn(II), Fe(II/III). It is noteworthy that flavonoids are known as transition metal chelators. When a complex with these metals is formed, the therapeutic effect of flavonoids can be enhanced, assuming the possibility of synergy. Molecular models have shown that the lipophilicity of flavonoid-metal complexes can vary significantly depending on their binding stoichiometry. Therefore, a unique process of translocation of flavonoid-metal complexes of various lipophilicity through cell membranes is assumed, based on the possibility of their sequential association and dissociation, called "hitchhiking". It is expected that studies of the interaction of flavonoids with metals will improve the effectiveness of drugs based on flavonoids.

Antiproliferative and apoptosis-inducing effects of aqueous extracts from Ecklonia maxima and Ulva rigida on HepG2 cells

This study examined the antiproliferative and apoptotic-inducing effects of Ecklonia maxima (KP) and Ulva rigida (URL) extracts in the human liver cancer (HepG2) cell line model. HepG2 cells were cultured and grown in an incubator (5% CO2 ) at 37°C. Cell viability was determined, while the effect of the extracts on apoptosis, ROS production, mitochondria membrane potential, and antioxidant enzymes were also assessed. KP and URL induced cytotoxic effects on HepG2 cells at the concentrations tested (0-1000 μg/ml). The morphological characteristics of the cells after treatment with KP and URL revealed cell shrinkage of the nucleus, cell injury, and damage compared to the control. The fluorescent micrographs from the apoptotic assay revealed induction of apoptosis and necrosis in HepG2 cells after treatment with KP and URL (200 and 400 μg/ml). The extracts also induced ROS production and reduced mitochondria membrane potential in HepG2 cells. The apoptotic-inducing effects, activation of ROS generation, and disruption of antioxidant enzymes are associated with the cytotoxic effects of the seaweed extracts. KP and URL showed good anticancer properties and could be explored as a good source of nutraceuticals, food additives, and dietary supplements to prevent uncontrolled proliferation of HepG2 cells. PRACTICAL APPLICATIONS: Seaweeds are reservoirs of nutrients and naturally occurring biologically active compounds, including sterols, phlorotannins, and polyunsaturated fatty acids. Due to the presence of these compounds, they are used as emulsifying agents, nutraceuticals, and additives in functional foods. Evidence suggests that seaweed bioactives may inhibit uncontrolled cell proliferation and induce apoptosis in cancer cells. Hence, exploring the antiproliferative and apoptotic-inducing effects of Ecklonia maxima and Ulva rigida will provide insights into their anticancer potentials as functional foods and nutraceuticals.

Ferulic Acid: A Natural Phenol That Inhibits Neoplastic Events through Modulation of Oncogenic Signaling

Despite the immense therapeutic advances in the field of health sciences, cancer is still to be found among the global leading causes of morbidity and mortality. Ethnomedicinally, natural bioactive compounds isolated from various plant sources have been used for the treatment of several cancer types and have gained notable attention. Ferulic acid, a natural compound derived from various seeds, nuts, leaves, and fruits, exhibits a variety of pharmacological effects in cancer, including its proapoptotic, cell-cycle-arresting, anti-metastatic, and anti-inflammatory activities. This review study presents a thorough overview of the molecular targets and cellular signaling pathways modulated by ferulic acid in diverse malignancies, showing high potential for this phenolic acid to be developed as a candidate agent for novel anticancer therapeutics. In addition, current investigations to develop promising synergistic formulations are also discussed.

Taxifolin Prevents Cisplatin Nephrotoxicity by Modulating Nrf2/HO-1 Pathway and Mitigating Oxidative Stress and Inflammation in Mice

Cisplatin (CIS) is an effective chemotherapeutic agent used in the treatment of several malignancies. The clinical use of CIS is associated with adverse effects, including acute kidney injury (AKI). Oxidative stress and inflammation are key events in the development of CIS-induced AKI. This study investigated the protective effect of taxifolin (TAX), a bioactive flavonoid with promising health-promoting properties, on CIS-induced nephrotoxicity in mice. TAX was orally given to mice for 10 days and a single dose of CIS was injected at day 7. Serum blood urea nitrogen (BUN) and creatinine were elevated, and multiple histopathological alterations were observed in the kidney of CIS-administered mice. CIS increased renal malondialdehyde (MDA), nitric oxide (NO), nuclear factor-kappaB (NF-κB) p65, tumor necrosis factor (TNF)-α, and interleukin (IL)-1β, and decreased cellular antioxidants in mice. TAX remarkably prevented kidney injury, ameliorated serum BUN and creatinine, and renal MDA, NO, NF-κB p65, and pro-inflammatory cytokines, and boosted antioxidant defenses in CIS-administered mice. TAX downregulated Bax and caspase-3, and upregulated Bcl-2. These effects were associated with upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2) expression and heme oxygenase (HO)-1 activity in CIS-administered mice. In conclusion, TAX prevented CIS-induced AKI by mitigating tissue injury, oxidative stress, inflammation, and cell death. The protective efficacy of TAX was associated with the upregulation of Nrf2/HO-1 signaling.

Cardioprotective Effect of Taxifolin against Isoproterenol-Induced Cardiac Injury through Decreasing Oxidative Stress, Inflammation, and Cell Death, and Activating Nrf2/HO-1 in Mice

Oxidative stress and inflammation are key components in cardiovascular diseases and heart dysfunction. Herein, we evaluated the protective effects of (+)-taxifolin (TAX), a potent flavonoid with significant antioxidant and anti-inflammatory actions, on myocardial oxidative tissue injury, inflammation, and cell death, using a mouse model of isoproterenol (ISO)-induced acute myocardial injury. Mice were given TAX (25 and 50 mg/kg, orally) for 14 days before receiving two subsequent injections of ISO (100 mg/kg, s.c.) at an interval of 24 h on the 15th and 16th days. The ISO-induced cardiac tissue injury was evidenced by increased serum creatine kinase-MB (CK-MB), cardiac troponin I (cTnI), and lactate dehydrogenase (LDH), along with several histopathological changes. The ISO also induced increased malondialdehyde (MDA) with concomitant declined myocardial glutathione level and antioxidant enzymes activities. Moreover, ISO-induced heart injury was accompained with elevated cardiac NF-κB p65, TNF-α, IL-1β, Bax, and caspase-3, as well as decreased Bcl-2, Nrf2, and HO-1. Remarkably, TAX reduced the severity of cardiac injury, oxidative stress, inflammation, and cell death, while enhancing antioxidants, Bcl-2, and Nrf2/HO-1 signaling in ISO-injected mice. In conclusion, TAX protects against ISO-induced acute myocardial injury via activating the Nrf2/HO-1 signaling pathway and attenuating the oxidative tissue injury and key regulators of inflammatory response and apoptosis. Thus, our findings imply that TAX may constitute a new cardioprotective therapy against acute MI, which undoubtedly deserves further exploration in upcoming human trials.

Engineering Saccharomyces cerevisiae for the production of dihydroquercetin from naringenin

Background

Dihydroquercetin (DHQ), a powerful bioflavonoid, has a number of health-promoting qualities and shows potential as a treatment for a number of disorders. Dihydroquercetin biosynthesis is a promising solution to meet the rising demand for dihydroquercetin. However, due to the significant accumulation of eriodietyol (ERI), naringenin (NAR), dihydrokaempferol (DHK), and other metabolites, the yield of DHQ biosynthesis is low. As a result, this is the hindrance to the biosynthesis of DHQ.

Results

In this study, we proposed several strategies to enhance the product formation and reduce the metabolites in accumulation. The flavonoid 3′-hydroxylase (F3′H) and cytochrome P450 reductase from different species were co-expressed in S. cerevisiae, and the best strain expressing the P450-reductase enzyme complex (SmF3′H/ScCPR) yielded 435.7 ± 7.6 mg/L of ERI from NAR in the deepwell microplate. The product conversion rate was improved further by mutating the predicted potential ubiquitination sites to improve SmF3′H stability, resulting in a 12.8% increase in titre using the mutant SmF3′H (K290R). Besides, different F3Hs from various sources and promoters were tested for the improved DHQ production, with the best strain producing 381.2 ± 10.7 mg/L of DHQ from 1 g/L of NAR, suggesting the temporal regulation the expression of F3H is important for maximization the function of F3′H and F3H.

Conclusion

This study offers effective strategies for improving DHQ production from NAR and could be used as a reference for related research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-022-01937-8.

Advocacy for the Medicinal Plant Artabotrys hexapetalus (Yingzhao) and Antimalarial Yingzhaosu Endoperoxides

The medicinal plant Artabotrys hexapetalus (synonyms: A.uncinatus and A. odoratissimus) is known as yingzhao in Chinese. Extracts of the plant have long been used in Asian folk medicine to treat various symptoms and diseases, including fevers, microbial infections, ulcers, hepatic disorders and other health problems. In particular, extracts from the roots and fruits of the plant are used for treating malaria. Numerous bioactive natural products have been isolated from the plant, mainly aporphine (artabonatines, artacinatine) and benzylisoquinoline (hexapetalines) alkaloids, terpenoids (artaboterpenoids), flavonoids (artabotrysides), butanolides (uncinine, artapetalins) and a small series of endoperoxides known as yingzhaosu A-to-D. These natural products confer antioxidant, anti-inflammatory and antiproliferative properties to the plant extracts. The lead compound yingzhaosu A displays marked activities against the malaria parasites Plasmodium falciparum and P. berghei. Total syntheses have been developed to access yingzhaosu compounds and analogues, such as the potent compound C14-epi-yingzhaosu A and simpler molecules with a dioxane unit. The mechanism of action of yingzhaosu A points to an iron(II)-induced degradation leading to the formation of two alkylating species, an unsaturated ketone and a cyclohexyl radical, which can then react with vital parasitic proteins. A bioreductive activation of yingzhaosu A endoperoxide can also occur with the heme iron complex. The mechanism of action of yingzhaosu endoperoxides is discussed, to promote further chemical and pharmacological studies of these neglected, but highly interesting bioactive compounds. Yingzhaosu A/C represent useful templates for designing novel antimalarial drugs.

Toxicity of Silver Nanoparticles Supported by Surface-Modified Zirconium Dioxide with Dihydroquercetin

The antibacterial performance and cytotoxic examination of in situ prepared silver nanoparticles (Ag NPs), on inorganic-organic hybrid nanopowder consisting of zirconium dioxide nanoparticles (ZrO₂ NPs) and dihydroquercetin (DHQ), was performed against Gram (-) bacteria Escherichia coli and Gram (+) bacteria Staphylococcus aureus, as well as against human cervical cancer cells HeLa and healthy MRC-5 human cells. The surface modification of ZrO₂ NPs, synthesized by the sol-gel method, with DHQ leads to the interfacial charge transfer (ICT) complex formation indicated by the appearance of absorption in the visible spectral range. The prepared samples were thoroughly characterized (TEM, XRD, reflection spectroscopy), and, in addition, the spectroscopic observations are supported by the density functional theory (DFT) calculations using a cluster model. The concentration- and time-dependent antibacterial tests indicated a complete reduction of bacterial species, E. coli and S. aureus, for all investigated concentrations of silver (0.10, 0.25, and 0.50 mg/mL) after 24 h of contact. On the other side, the functionalized ZrO₂ NPs with DHQ, before and after deposition of Ag NPs, do not display a significant decrease in the viability of HeLa MRC-5 cells in any of the used concentrations compared to the control.

Production of Taxifolin from Astilbin by Fungal Biotransformation

Taxifolin is known to have multiple biological functions. It has been widely used as a multifunctional food additive, and consequently, the global demand for taxifolin is increasing. The main method for taxifolin production is an extraction from larch wood, but the global resources of larch are limited. Astilbin, taxifolin-3-o-rhamnoside, is abundant in many plants and much more readily available, meaning taxifolin can be obtained by deglycosylation of astilbin. In this study, a fungal strain, Aspergillus fumigatus SQH4, was isolated from an enrichment culture of Smilax glabra rhizome to achieve the deglycosylation reaction. A culture of SQH4, adjusted to pH 6.5, with 5 g/L astilbin achieved a yield of taxifolin of 91.3% after biotransformation for 14 h at 35 °C. These findings offer an alternative method for the production of taxifolin.

Effects of taxifolin from enzymatic hydrolysis of Rhododendron mucrotulatum on hair growth promotion

Flavonoid aglycones possess biological activities, such as antioxidant and antidiabetic activities compared to glycosides. Taxifolin, a flavonoid aglycones, is detected only in trace amounts in nature and is not easily observed. Therefore, in this study, to investigate the hair tonic and hair loss inhibitors effect of taxifolin, high content of taxifolin aglycone extract was prepared by enzymatic hydrolysis. Taxifolin effectively regulates the apoptosis of dermal papilla cells, which is associated with hair loss, based on its strong antioxidant activities. However, inhibition of dihydrotestosterone (DHT), which is a major cause of male pattern hair loss, was significantly reduced with taxifolin treatment compared with minoxidil, as a positive control. It was also confirmed that a representative factor for promoting hair growth, IGF-1, was significantly increased, and that TGF-β1, a representative biomarker for hair loss, was significantly reduced with taxifolin treatment. These results suggest that taxifolin from enzymatic hydrolysis of RM is a potential treatment for hair loss and a hair growth enhancer.

Secondary Metabolites with Biomedical Applications from Plants of the Sarraceniaceae Family

Carnivorous plants have fascinated researchers and hobbyists for centuries because of their mode of nutrition which is unlike that of other plants. They are able to produce bioactive compounds used to attract, capture and digest prey but also as a defense mechanism against microorganisms and free radicals. The main purpose of this review is to provide an overview of the secondary metabolites with significant biological activity found in the Sarraceniaceae family. The review also underlines the necessity of future studies for the biochemical characterization of the less investigated species. Darlingtonia, Heliamphora and Sarracenia plants are rich in compounds with potential pharmaceutical and medical uses. These belong to several classes such as flavonoids, with flavonol glycosides being the most abundant, monoterpenes, triterpenes, sesquiterpenes, fatty acids, alkaloids and others. Some of them are well characterized in terms of chemical properties and biological activity and have widespread commercial applications. The review also discusses biological activity of whole extracts and commercially available products derived from Sarraceniaceae plants. In conclusion, this review underscores that Sarraceniaceae species contain numerous substances with the potential to advance health. Future perspectives should focus on the discovery of new molecules and increasing the production of known compounds using biotechnological methods.

Investigation of market herbal products regulated under different categories: How can HPTLC help to detect quality problems?

Background: Herbal products regulated under different categories were found to be of different quality. This has been demonstrated by the increasing number of reports on the quality of herbal products in the scientific literature. Proper identification is an effective way to address this concerning issue early on in a products’ manufacturing process.

Objectives: To assess the quality of milk thistle, coneflower and black cohosh herbal drugs, preparations and products commercialized under different regulatory categories, and to illustrate the usefulness of HPTLC as a tool for evaluating quality.

Methods: HPTLC methods were adapted from the European Pharmacopeia’s monographs for milk thistle fruits, black cohosh and purple coneflower. Additional detection modes beyond those described in the monographs were employed, and the entire HPTLC fingerprints were used for examination of identity and purity of the investigated samples.

Results: All products regulated as Traditional Herbal Medicinal Products were shown to be of high quality: their fingerprints were consistent and without unexpected zones. A significant number of food supplements show quality issues (mainly adulterations): 52.4% of milk thistle, 33.3% of coneflower, and 45.5% of black cohosh products. The same was observed in 66.6% of black cohosh herbal drugs and preparations.

Renoprotective and Oxidative Stress-Modulating Effects of Taxifolin against Cadmium-Induced Nephrotoxicity in Mice

Cadmium (Cd) is an inessential trace metal that accumulates in the kidney and may lead to renal toxicity by mediating oxidative stress (OS), inflammatory reactions, and apoptosis. The main objective of this experiment was to inspect the protecting potential of taxifolin (TA) on Cd-induced renal toxicity. Adult male mice were allocated into equal five groups as follows: control, TA-treated (50 mg/kg, oral), CdCl₂-treated (4 mg/kg body weight (BW), p.o.), pretreated with TA (25 mg/kg) 1 h before CdCl₂ injection (4 mg/kg BW, p.o.), and pretreated with TA (50 mg/kg) 1 h before CdCl₂ injection (4 mg/kg BW, p.o.) for 14 days. Cd-intoxicated mice revealed higher serum urea and creatinine levels and notable histopathological alterations in the renal tissues. Malondialdehyde (MDA), nitric oxide (NO), nuclear factor-kappa B (NF-κB) p65, tumor necrosis factor-α (TNF-α), and IL-1β were increased. In contrast, glutathione levels, catalase and superoxide dismutase activities, and IL-10 levels were decreased under Cd-administered effects. Conversely, the TA pre-treatment highly protected tissues from Cd-toxicity, improved renal function, decreased MDA and NO levels, attenuated inflammation, and improved redox status in the renal tissues of Cd-intoxicated mice. The TA pre-treatment of Cd-intoxicated mice showed down-regulation of both Bax and caspase-3 protein and up-regulation of Bcl-2 protein expression in the kidney. Furthermore, TA pre-treatment induced higher upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) expression in kidney cells of Cd-intoxicated mice. Therefore, TA can protect renal tissues against Cd-induced nephrotoxicity via improving redox status, modulating inflammation, diminishing cell apoptosis, and activating the Nrf2/HO-1 signaling pathway.

Gurgem-7 toxicity assessment: Regulation of cell survival or death by traditional Mongolian prescription

Surgical treatments and chemotherapy are the most commonly used methods of colorectal cancer treatment (CRC), unfortunately, these therapies have many side effects. Moreover, despite advances in primary and adjuvant treatments, the survival time in CRC patients is still unsatisfactory. Treatment options for patients with CRC continue to advance and recent research has shown that colorectal cancer is sensitive to plant-derived substances. The use of natural compounds contained in herbal extracts for the treatment of colon cancer or as adjunctive therapy for CRC gives patients a wide range of treatment options. In this study, we evaluate the potential toxicity of the Mongolian preparation - Gurgem-7 composed of Crocus sativus, Veronica officinalis, Capsella bursa-pastoris, Arctostaphylos uva-ursi, Calendula officinalis, Gentiana lutea, and Terminalia chebula. Therefore, the aim of this study was to determine its biological activities, biochemical and molecular features in vitro and composition analysis by HPLC-ESI-QTOF-MS/MS platform. We identified 18 metabolites and 8 of them were quantified. Majority of the secondary metabolites belonged to the group of phenolic constituents with taxifolin, chlorogenic acids' family, hydroxysafflor yellow A and hydroxybenzoic acid as leading compounds. In turn, our in vitro results suggest that the preparation inhibits cell metabolic activity through oxidative stress, numerous DNA damage and cell cycle arrest. Simultaneously enzymatic and non-enzymatic cell protection mechanisms mediated by TP53/Keap1 and Nrf2/HO-1 pathways may be activated in a cell-specific manner in vitro. In conclusion, we provide preliminary molecular evidence of the toxic properties of Gurgem-7 preparation to Caco-2 and CT26. WT cells related to insufficient action of their repair and adaptive mechanisms to stress conditions.

Differences in Antioxidant Potential of Allium cepa Husk of Red, Yellow, and White Varieties

The effective management of agro-industry organic waste for developing high-commercial-value products is a promising facet of the circular economy. Annually, more than 550,000 tons of waste that is potentially rich in biologically active substances is generated worldwide while processing onions (Allium cepa L.). The antioxidant potential of red, yellow, and white onion husks was studied using FRAP, ORAC, chemiluminescence, and UPLC-ESI-Q-TOF-MS analysis methods. The extraction of phenolic compounds from onion husks was more effective when using an aqueous solution of 70% ethanol as compared with water. Ethanolic extract from red onion husks exhibited the highest TAC_ORAC and TAC_FRAP values, averaging 2017.34 µmol-equiv. Trolox/g raw material and 2050.23 µmol-equiv. DQ/g raw material, respectively, while the white onion exhibited much lower levels of antioxidants. According to the chemiluminescence results, it was determined that the red and yellow onion husks contained antioxidants of three types of power, while white onion husks only contained medium and weak types. The highest content of flavonoids was found in red onion husks, averaging 1915.90 ± 9.92 µg-eq. DQ/g of raw material and 321.42 ± 2.61 µg-eq. DQ/g of raw material for ethanol and water, respectively, while yellow onion husks exhibited 544.06 ± 2.73 µg-eq. DQ/g of raw material and 89.41 ± 2.08 for ethanol and water, respectively. Quercetin and its glycosides were the most representative flavonoids, and a number of substances with different pharmacological and biological properties were also identified.

Metabolomics-Based Profiling, Antioxidant Power, and Uropathogenic Bacterial Anti-Adhesion Activity of SP4TM, a Formulation with a High Content of Type-A Proanthocyanidins

Flavonoids and proanthocyanidins (PACs) have been the subject of intense scientific investigations, both for their antioxidant properties and anti-adhesion activity against uropathogenic bacteria. We investigated the metabolomics and antioxidant capacity of SP4^TM, a patent-pending formulation based on a mixture of plant extracts with a high content of bioactive PACs and other polyphenols. The total content of polyphenols (885.51 ± 14.19 mg/g), flavonoids (135.52 ± 8.98 mg/g), anthocyanins (54.84 ± 2.97 mg/g), and PACs (379.43 ± 12.44 mg/g) was quantified using UV-Vis assays. Use of HPLC-ESI-MS/MS revealed the presence of 5 flavanols (100.77 ± 3.90 mg g⁻¹ d.wt), 11 flavonols (59.96 ± 1.83 mg g⁻¹ d.wt), and 8 anthocyanins (46.96 ± 1.59 mg g⁻¹ d.wt), whereas MALDI-TOF MS showed that SP4^TM contains PACs with one or more type-A interflavan bonds at each degree of polymerization. Regarding antioxidant properties, LUCS technology on HepG2 cells evidenced the ability of SP4^TM to neutralize intracellular free radicals, inhibit membrane lipid peroxidation, quench H₂O₂, and reduce free radicals mainly through chelating mechanism, as demonstrated by a higher FRAP value (2643.28 ± 39.86 mmol/g) compared with ABTS (139.92 ± 6.16 mmol/g) and DPPH (89.51 ± 3.91 mmol/g). Finally, the SP4^TM type-A PAC content strongly prevented bacterial adhesion of P-fimbriated uropathogenic Escherichia coli (0.23 mg/mL). In conclusion, SP4^TM has a strong antioxidant capacity involving multitarget mechanisms and is a potential supplement to fight urinary tract infections due to its ability to inhibit uropathogenic E. coli adhesion.

Metabolism, tissue distribution and excretion of taxifolin in rat

The metabolism, tissue distribution and excretion of taxifolin in rat after oral administration of taxifolin encapsulated zein-caseinate Nanoparticles (TZP) were studied. The isomerization of taxifolin in rat small intestine and colon was found. Besides isomers, 16 metabolites of taxifolin were identified in rat feces, plasma and urine by UPLC-QTOF-MS. In colon, taxifolin underwent the metabolism of hydration, dehydration and ring-fission through the gut microflora. The main metabolites of taxifolin found in plasma and urine were its sulfated, glucuronidated, and/or methylated products. The dynamic variation of taxifolin and its metabolites in tissues and urine were quantified by UPLC-QqQ-MS/MS. Taxifolin and its metabolites could be quickly absorbed and distributed in the tissues, and relatively low concentrations were found in the heart and brain. The feces excretion of taxifolin was determined by HPLC. The total excretion during 24 h was 2.83 ± 0.80% to its given does, and the maximum excretion was found during 8-10 h post administration. Compared with feces, the excretion of taxifolin and its metabolites in urine was much faster, and the total excretion was 1.96 ± 0.23% during 12 h.

Insights into the Pharmacological Effects of Flavonoids: The Systematic Review of Computer Modeling

Computer modeling is a method that is widely used in scientific investigations to predict the biological activity, toxicity, pharmacokinetics, and synthesis strategy of compounds based on the structure of the molecule. This work is a systematic review of articles performed in accordance with the recommendations of PRISMA and contains information on computer modeling of the interaction of classical flavonoids with different biological targets. The review of used computational approaches is presented. Furthermore, the affinities of flavonoids to different targets that are associated with the infection, cardiovascular, and oncological diseases are discussed. Additionally, the methodology of bias risks in molecular docking research based on principles of evidentiary medicine was suggested and discussed. Based on this data, the most active groups of flavonoids and lead compounds for different targets were determined. It was concluded that flavonoids are a promising object for drug development and further research of pharmacology by in vitro, ex vivo, and in vivo models is required.

Taxifolin Modulates Transcriptomic Response to Heat Stress in Rainbow Trout, Oncorhynchus mykiss

Taxifolin is a natural flavonoid known for its antioxidant, anti-inflammatory, and antiproliferative effects on animals. In this work, we have studied the effect of this compound on rainbow trout, Oncorhynchus mykiss, a major object of aquaculture, under slowly increasing ambient temperature and Gyrodactylus flatworm infection. Transcriptomic profiling of liver samples performed by using the Illumina HiSeq 2500 sequencing platform shows that a combined taxifolin/heat treatment, unlike heat treatment alone, downregulates the production of isopentenyl diphosphate, likely affecting the production of cholesterol and other sterols. Taxifolin treatment also modulates multiple apoptosis regulators and affects the expression of HSPs in response to increasing temperature. On the other hand, the expression of antioxidant enzymes in response to heat is not significantly affected by taxifolin. As for the Gyrodactylus infection, the parasite load is not affected by taxifolin treatment, although it was lower in the high-temperature group. Parasite load also did not induce a statistically significant transcriptomic response within the no heat/no taxifolin group.

Trapping Methylglyoxal by Taxifolin and Its Metabolites in Mice

Trapping of methylglyoxal (MGO), an important precursor of advanced glycation end products (AGEs), is considered an effective therapy for alleviating AGE-induced chronic metabolic diseases. In this paper, taxifolin (Tax) was first found to effectively trap MGO by forming mono- and di-MGO adducts under in vitro conditions. In addition, the mechanism of trapping MGO by Tax was also studied in vivo. Tax was demonstrated to efficiently trap endogenous MGO via formation of mono-MGO adducts in urine and fecal samples of C57BL/6J mice after oral administration of Tax and MGO. Mono-MGO adducts of Tax metabolites, including methylated Tax, aromadendrin, quercetin, and isorhamnetin, were identified in C57BL/6J mice urine and fecal samples by ultra-high-performance liquid chromatography coupled to quadrupole time-of-flight tandem mass spectrometry (UHPLC-QTOF-MS/MS). One mono-MGO-Tax was purified from the in vitro reaction mixture, and its structure was elucidated as 6-MGO-Tax based on the analysis of UHPLC-QTOF-MS/MS and detailed nuclear magnetic resonance (NMR) data. Quantification studies demonstrated that Tax and its metabolites trapped MGO in a dose-dependent manner in C57BL/6J mice urine and fecal samples. Furthermore, we also detected mono-MGO adducts of Tax and methylated Tax in urine and fecal samples of diabetic db/db mice after oral administration of Tax. Taken together, our results demonstrated that dietary Tax has the potential to detoxify MGO and treat AGE-associated chronic diseases.

Crystal Structure of an SSB Protein from Salmonella enterica and Its Inhibition by Flavanonol Taxifolin

Single-stranded DNA (ssDNA)-binding proteins (SSBs) play a central role in cells by participating in DNA metabolism, including replication, repair, recombination, and replication fork restart. SSBs are essential for cell survival and thus an attractive target for potential anti-pathogen chemotherapy. In this study, we determined the crystal structure and examined the size of the ssDNA-binding site of an SSB from Salmonella enterica serovar Typhimurium LT2 (SeSSB), a ubiquitous opportunistic pathogen which is highly resistant to antibiotics. The crystal structure was solved at a resolution of 2.8 Å (PDB ID 7F25), indicating that the SeSSB monomer possesses an oligonucleotide/oligosaccharide-binding (OB) fold domain at its N-terminus and a flexible tail at its C-terminus. The core of the OB-fold in the SeSSB is made of a six-stranded β-barrel capped by an α-helix. The crystal structure of the SeSSB contained two monomers per asymmetric unit, which may indicate the formation of a dimer. However, the gel-filtration chromatography analysis showed that the SeSSB forms a tetramer in solution. Through an electrophoretic mobility shift analysis, we characterized the stoichiometry of the SeSSB complexed with a series of ssDNA dA homopolymers, and the size of the ssDNA-binding site was determined to be around 22 nt. We also found the flavanonol taxifolin, also known as dihydroquercetin, capable of inhibiting the ssDNA-binding activity of the SeSSB. Thus, this result extended the SSB interactome to include taxifolin, a natural product with a wide range of promising pharmacological activities.

Taxifolin as a Major Bioactive Compound in the Vasorelaxant Effect of Different Pigmented Rice Bran Extracts

Cardiovascular disease is one of the leading causes of morbidity and mortality in recent years. The intake of polyphenol rich diets has been associated with improved cardiovascular function and reduced cardiovascular risks. Oryza sativa L. is one of the most common cereals worldwide. Rice bran, a byproduct of the rice milling process, contains many bioactive ingredients, including polyphenols, polysaccharides, proteins, and micronutrients. It is also consumed as a healthy diet in the form of rice bran oil and powder in many Asian countries like Japan, South Korea, and India for its several health benefits as a natural antioxidant. Thus, this study evaluated the vasorelaxant effect of ethanolic extracts of brown, green, red, and black rice bran and investigated its underlying vasorelaxant mechanism. Among the four rice bran extracts (RBEs) examined, the red rice bran extract (RRBE) had a strong endothelium-dependent vasorelaxant effect, which was markedly prevented by N-ω-nitro-L-arginine [endothelial nitric oxide synthase (eNOS) inhibitor], wortmannin [phosphoinositide-3 kinase (PI3K) inhibitor], and 1H-[1,2,4]oxadiazole[4,3-alpha]quinoxalin-1-one (inhibitor of guanylate cyclase). Likewise, RRBE induced the phosphorylation of eNOS and Src in cultured endothelial cells, thereby stimulating NO formation. Altogether, these findings propose that RRBE induces endothelium-dependent relaxation, involving at least in part, NO-mediated signaling through the PI3K/eNOS pathway. Further, LC-PDA analysis conducted on the four RBEs also revealed that RRBE highly contained taxifolin, which is an active flavanonol that induces endothelium-dependent vasorelaxation, compared to other RBEs. Subsequently, the underlying mechanism of taxifolin was assessed through vascular reactivity studies with pharmacological inhibitors similar to that of RRBE. These findings deciphered a distinct difference in vasorelaxant effects between RRBE and the other RBEs. We also observed that RRBE induced a potent endothelium-dependent NO-mediated relaxation in coronary artery rings, which involved the Src/PI3K pathway that activates eNOS. Additionally, taxifolin exhibited, at least in part, similar vasoprotective effects of RRBE. Therefore, we propose that RRBE may serve as natural sources of functional phytochemicals that improve cardiovascular diseases associated with disturbed NO production and endothelial dysfunction.

Targeting p-AKT/mTOR/MAP kinase signaling, NLRP3 inflammasome and apoptosis by fluvastatin with or without taxifolin mitigates gonadal dysfunction induced by bisphenol-A in male rats

Bisphenol-A (BPA) is a chemical substance that is widely used in industry for manufacturing of plastic bottles and resins. Recent reports found that BPA may mimic the effects of estrogen to a great manner that might disrupt the normal hormonal balance in the human body. Fluvastatin is an agent used for treatment of hypercholesterolemia that was proven to possess promising antioxidant ant anti-inflammatory properties. Taxifolin is a polyphenolic compound with potential antioxidant and antiestrogenic effects. The present study investigated the prospect of fluvastatin with or without taxifolin to mitigate testicular dysfunction elicited by BPA in rats. In a model of BPA-induced testicular toxicity, the hormonal profile was assessed and the testicular tissues were examined by biochemical analysis, histopathology, and immunohistochemistry. Fluvastatin with or without taxifolin improved the body weight gain, hormonal profile, testicular weight and functions, sperm characteristics, the antioxidant status, and the anti-inflammatory mechanisms together with enhancement of autophagy and suppression of the proapoptotic events induced by BPA in the testicular tissues. In addition, fluvastatin with or without taxifolin significantly mitigated the histopathological and the immunohistochemical changes induced by BPA in the testicular tissues. These desirable effects were more pronounced with fluvastatin/taxifolin combination relative to the use of each of these agents alone. In tandem, fluvastatin/taxifolin combination might counteract the pathogenic events induced by BPA in the testicular tissues which may be considered as a novel strategy for amelioration of these disorders.

Phyto-Functionalized Silver Nanoparticles Derived from Conifer Bark Extracts and Evaluation of Their Antimicrobial and Cytogenotoxic Effects

Silver nanoparticles synthesized using plant extracts as reducing and capping agents showed various biological activities. In the present study, colloidal silver nanoparticle solutions were produced from the aqueous extracts of Picea abies and Pinus nigra bark. The phenolic profile of bark extracts was analyzed by liquid chromatography coupled to mass spectrometry. The synthesis of silver nanoparticles was monitored using UV-Vis spectroscopy by measuring the Surface Plasmon Resonance band. Silver nanoparticles were characterized by attenuated total reflection Fourier transform infrared spectroscopy, Raman spectroscopy, dynamic light scattering, scanning electron microscopy, energy dispersive X-ray and transmission electron microscopy analyses. The antimicrobial and cytogenotoxic effects of silver nanoparticles were evaluated by disk diffusion and Allium cepa assays, respectively. Picea abies and Pinus nigra bark extract derived silver nanoparticles were spherical (mean hydrodynamic diameters of 78.48 and 77.66 nm, respectively) and well dispersed, having a narrow particle size distribution (polydispersity index values of 0.334 and 0.224, respectively) and good stability (zeta potential values of -10.8 and -14.6 mV, respectively). Silver nanoparticles showed stronger antibacterial, antifungal, and antimitotic effects than the bark extracts used for their synthesis. Silver nanoparticles obtained in the present study are promising candidates for the development of novel formulations with various therapeutic applications.

Chiral Flavonoids as Antitumor Agents

Flavonoids are a group of natural products with a great structural diversity, widely distributed in plant kingdom. They play an important role in plant growth, development and defense against aggressors. Flavonoids show a huge variety of biological activities such as antioxidant, anti-inflammatory, anti-mutagenic, antimicrobial and antitumor, being able to modulate a large diversity of cellular enzymatic activities. Among natural flavonoids, some classes comprise chiral molecules including flavanones, flavan-3-ols, isoflavanones, and rotenoids, which have one or more stereogenic centers. Interestingly, in some cases, individual compounds of enantiomeric pairs have shown different antitumor activity. In nature, these compounds are mainly biosynthesized as pure enantiomers. Nevertheless, they are often isolated as racemates, being necessary to carry out their chiral separation to perform enantioselectivity studies. Synthetic chiral flavonoids with promising antitumor activity have also been obtained using diverse synthetic approaches. In fact, several new chiral bioactive flavonoids have been synthesized by enantioselective synthesis. Particularly, flavopiridol was the first cyclin-dependent kinase (CDK) inhibitor which entered clinical trials. The chiral pool approaches using amino acid as chiral building blocks have also been reported to achieve small libraries of chrysin derivatives with more potent in vitro growth inhibitory effect than chrysin, reinforcing the importance of the introduction of chiral moieties to improve antitumor activity. In this work, a literature review of natural and synthetic chiral flavonoids with antitumor activity is reported for the first time.