Rhamnetin Research Articles

Rhamnetin abrogates polystyrene microplastics prompted hepatic damage by regulating Nrf-2/Keap-1 pathway

Polystyrene microplastics (PS-MPs) are environmental toxicants that exert adverse effects on organisms. Rhamnetin (RHM) is a natural flavone that shows multiple therapeutic potentials. Therefore, the present study was planned to determine the mitigative effect of RHM against PS-MPs induced liver damage. 48 rats were divided into 4 groups. Control group, PS-MPs (0.01 mg/kg) administered group, PS-MPs (0.01 mg/kg)+ RHM (50 mg/kg) co-administered group and RHM alone (50 mg/kg) administered group. PS-MPs reduced the expressions of Nrf-2 and anti-oxidant gene expressions, while increasing Keap-1 expression. PS-MPs also decreased the activities of catalase (CAT), glutathione reductase (GSR), heme oxygenase-1 (HO-1), glutathione-S-transferase (GST), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione (GSH), besides elevating the levels of MDA and ROS. Additionally, PS-MPs augmented the levels of alanine transaminase (ALT), alkaline phosphatase (ALP) and aspartate aminotransferase (AST). Furthermore, there was an upsurge in the levels of inflammatory indices in PS-MPs treated group. PS-MPs intoxication also increased Bax and Caspase-3 expressions, while lowering the Bcl-2 expression. Nevertheless, RHM mitigated all the damages due to its hepatoprotective, anti-inflammatory, anti-oxidant and anti-apoptotic potentials.

Rhamnetin Prevents Bradykinin-Induced Expression of Matrix Metalloproteinase-9 in Rat Brain Astrocytes by Suppressing Protein Kinase-Dependent AP-1 Activation.

Bradykinin (BK) has been recognized as a stimulant for matrix metalloproteinase (MMP)-9 expression, contributing to neuroinflammation. Modulating the BK/MMP-9 pathway offers potential in the treatment of neuroinflammatory disorders. Rhamnetin (RNT), a flavonoid compound known for its antioxidant and anti-inflammatory effects, has shown promise. However, the specific mechanisms through which RNT inhibits BK-induced MMP-9 expression remain unclear. Therefore, this study aims to delve into the intricate mechanisms underlying this process. Here, we initially demonstrated that RNT effectively attenuated BK-induced MMP-9 expression and its associated cell migration in rat brain astrocyte-1 (RBA-1) cells. Further investigation revealed that BK-driven MMP-9 protein, mRNA, and promoter activity linked to cell migration relied on c-Src, Pyk2, EGFR, PDGFR, PI3K/Akt, JNK1/2, and c-Jun. This was validated by the inhibition of these effects through specific inhibitors, a finding substantiated by the introduction of siRNAs targeting these signaling molecules. Notably, the phosphorylated levels of these signaling components induced by BK were significantly reduced by their respective inhibitors and RNT, underscoring the inhibitory role of RNT in this process. These findings indicate that, in RBA-1 cells, RNT diminishes the heightened induction of MMP-9 triggered by BK through the inhibition of c-Src/Pyk2/PDGFR and EGFR/PI3K/Akt/JNK1/2-dependent AP-1 activation. This suggests that RNT holds promise as a potential therapeutic approach for addressing neuroinflammation in the brain.

Rhamnetin alleviates polystyrene microplastics-induced testicular damage by restoring biochemical, steroidogenic, hormonal, apoptotic, inflammatory, spermatogenic and histological profile in male albino rats.

The current research was performed to evaluate the ameliorative effects of Rhamnetin (RHM) on polystyrene microplastics (PS-MPs)-instigated testicular dysfunction in male albino rats. 48 albino rats were distributed in four groups, i.e., control, PS-MPs treated, PS-MPs + RHM co-treated and RHM only supplemented group. PS-MPs exposure considerably reduced anti-oxidant enzymes i.e., catalase (CAT), glutathione peroxidase (GSR), superoxide dismutase (SOD) and glutathione reductase (GPx) activities. Whereas, reactive oxygen species (ROS) level along with malondialdehyde (MDA) was considerably escalated in PS-MPs treated rats as well as a potential decline was observed in sperm progressive motility. Additionally, a substantial upsurge was noticed in the count of dead sperms, deformity in the tail, mid-piece and head of sperms in PS-MPs treated rats. PS-MPs exposure also decreased steroidogenic enzymes, 17β-hydroxysteroid dehydrogenase (17β-HSD), steroidogenic acute regulatory protein (StAR) and 3β-hydroxysteroid dehydrogenase (3β-HSD) expressions. Moreover, the levels of inflammatory indices i.e., Interleukin-6 (IL-6), Nuclear factor kappa-B (NF-κB), Interleukin-1β (IL-1β), tumour necrosis factor-α (TNF-α) and cyclooxygenase-2 (COX-2) activity were also increased in PS-MPs administrated group. Besides it increased the expression of apoptotic markers (Bax and caspase-3) expression. Whereas, anti-apoptotic marker i.e., Bcl-2 expression was reduced. Moreover, luteinizing hormone (LH), follicle-stimulating hormone (FSH) as well as plasma testosterone levels were also decreased. PS-MPs exposure also led to a substantial histopathological damage in testicular tissues. However, RHM supplementation potentially reduced the damaging effects of PS-MPs in the reproductive tissues of male albino rats. Thus, the current study revealed, RHM possesses potential to prevent PS-MPs-induced testicular damage due to its anti-oxidant anti-apoptotic, anti-inflammatory as well as androgenic properties.

Exploiting DNA Ligase III addiction of multiple myeloma by flavonoid Rhamnetin

BackgroundDNA ligases are crucial for DNA repair and cell replication since they catalyze the final steps in which DNA breaks are joined. DNA Ligase III (LIG3) exerts a pivotal role in Alternative-Non-Homologous End Joining Repair (Alt-NHEJ), an error-prone DNA repair pathway often up-regulated in genomically unstable cancer, such as Multiple Myeloma (MM). Based on the three-dimensional (3D) LIG3 structure, we performed a computational screening to identify LIG3-targeting natural compounds as potential candidates to counteract Alt-NHEJ activity in MM.MethodsVirtual screening was conducted by interrogating the Phenol Explorer database. Validation of binding to LIG3 recombinant protein was performed by Saturation Transfer Difference (STD)—nuclear magnetic resonance (NMR) experiments. Cell viability was analyzed by Cell Titer-Glo assay; apoptosis was evaluated by flow cytometric analysis following Annexin V-7AAD staining. Alt-NHEJ repair modulation was evaluated using plasmid re-joining assay and Cytoscan HD. DNA Damage Response protein levels were analyzed by Western blot of whole and fractionated protein extracts and immunofluorescence analysis. The mitochondrial DNA (mtDNA) copy number was determined by qPCR. In vivo activity was evaluated in NOD-SCID mice subcutaneously engrafted with MM cells.ResultsHere, we provide evidence that a natural flavonoid Rhamnetin (RHM), selected by a computational approach, counteracts LIG3 activity and killed Alt-NHEJ-dependent MM cells. Indeed, Nuclear Magnetic Resonance (NMR) showed binding of RHM to LIG3 protein and functional experiments revealed that RHM interferes with LIG3-driven nuclear and mitochondrial DNA repair, leading to significant anti-MM activity in vitro and in vivo.ConclusionTaken together, our findings provide proof of concept that RHM targets LIG3 addiction in MM and may represent therefore a novel promising anti-tumor natural agent to be investigated in an early clinical setting.

Anti-Inflammatory Effects of Rhamnetin on Bradykinin-Induced Matrix Metalloproteinase-9 Expression and Cell Migration in Rat Brain Astrocytes.

Bradykinin (BK) has been shown to induce matrix metalloproteinase (MMP)-9 expression and participate in neuroinflammation. The BK/MMP-9 axis can be a target for managing neuroinflammation. Our previous reports have indicated that reactive oxygen species (ROS)-mediated nuclear factor-kappaB (NF-κB) activity is involved in BK-induced MMP-9 expression in rat brain astrocytes (RBA-1). Rhamnetin (RNT), a flavonoid compound, possesses antioxidant and anti-inflammatory effects. Thus, we proposed RNT could attenuate BK-induced response in RBA-1. This study aims to approach mechanisms underlying RNT regulating BK-stimulated MMP-9 expression, especially ROS and NF-κB. We used pharmacological inhibitors and siRNAs to dissect molecular mechanisms. Western blotting and gelatin zymography were used to evaluate protein and MMP-9 expression. Real-time PCR was used for gene expression. Wound healing assay was applied for cell migration. 2ʹ,7ʹ-dichlorodihydrofluorescein diacetate (H2DCF-DA) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) were used for ROS generation and NOX activity, respectively. Promoter luciferase assay and chromatin immunoprecipitation (ChIP) assay were applied to detect gene transcription. Our results showed that RNT inhibits BK-induced MMP-9 protein and mRNA expression, promoter activity, and cell migration in RBA-1 cells. Besides, the levels of phospho-PKCδ, NOX activity, ROS, phospho-ERK1/2, phospho-p65, and NF-κB p65 binding to MMP-9 promoter were attenuated by RNT. In summary, RNT attenuates BK-enhanced MMP-9 upregulation through inhibiting PKCδ/NOX/ROS/ERK1/2-dependent NF-κB activity in RBA-1.

In silico, in vitro antioxidant and density functional theory based structure activity relationship studies of plant polyphenolics as prominent natural antioxidants

In the present study, different extracts of stem bark of Shorea tumbuggaia and roots of Syzygium alternifolium were screened for total phenolic content (TPC), total flavonoid content (TFC) and in vitro DPPH radical scavenging activity to isolate the natural antioxidants. The bioassay-guided fraction of stem bark of Shorea tumbuggaia yielded three compounds, piceatannol (ST-1), resveratrol-12-C-β-d-glucopyranoside (ST-2) and hopeaphenol (ST-3). Similarly, a systematic phytochemical examination of extracts of Syzygium alternifolium roots had resulted five compounds, 5,7,8,5′-tetramethoxy-3′,4′-methylenedioxyflavone (SA-1), 5-hydroxy-4′,7-dimethoxy-6,8-di-C-methylflavone (SA-2), quercetin 7-methylether (SA-3), kaempferol 7,4′-dimethylether 3-O-β-d-glucopyranoside (SA-4) and taxifolin 3-O-α-l-rhamnopyranoside (SA-5). Structures of the isolates were established using UV, IR, Mass, 1H and 13C NMR spectral studies. Density Functional Theory (DFT) calculations, Molecular docking and Lipinski rule of five were conducted to explored the antioxidant activity of isolated compounds. SA-3 (37.52 µg/mL) and ST-1 (42.43 µg/mL) showed highest IC50 values compared to the Ascorbic acid (45.97 µg/mL) and have highest electron affinities (EA eV) along with smallest HOMO-LUMO energy gap. Molecular docking and binding affinity studies with NADPH and SPSB2 proteins, revealed the prominent antioxidant activity of SA-3 and ST-1 with molecular interaction besides promising solvation energies. Hence, the two compounds maybe useful for the treatment of oxidative damage related diseases.

Antifibrotic effect of methylated quercetin derivatives on TGFβ-induced hepatic stellate cells

Quercetin (QCT) and isorhamnetin (ISO), natural flavonoids, were both shown to possess antifibrotic activity in in vivo and in vitro models of hepatic fibrosis. Although ISO is a direct metabolite of QCT differing by a methyl group, it has been reported to be absorbed more adequately and eliminated slower than QCT after oral administration. Our aim of the study was to investigate biological effect of mono-methylated QCT derivatives against fibrosis using rat hepatic stellate cells (HSC-T6). All test derivatives were synthesized from QCT. HSC-T6 cells were induced by TGFβ and treated with derivatives followed by cell proliferation assay, immunofluorescence staining of αSMA, and gene expression analysis of fibrosis markers. All compounds showed a dose- and time-dependent antiproliferation effect. ISO, 3-O-methylquercetin (3MQ), and rhamnetin (RHA) reduced αSMA mRNA; 3MQ prevented the augmentation of collagen I mRNA; and compounds, except azaleatin and 3MQ, reduced Timp1 mRNA expression in TGFβ-induced HSCs. In conclusion, each compound had singular effect against different features of fibrosis depending on the position of methyl group although the further mechanism of action of compounds during fibrosis development remains to be investigated. These findings suggest that antifibrotic effect of quercetin can be enhanced by adding methyl group on functionally important position.

The Ability of Polyphenols to Reduce Aβ-Induced Apoptosis Associated with Alzheimer's Disease

Alzheimer's disease (AD), the most common form of dementia, is characterized by extracellular plaques in the brain created when monomeric amyloid-β (Aβ) protein aggregates into fibrillar structures. Soluble Aβ aggregates, including oligomers that form along the reaction pathway, are believed to be the more toxic species and can increase the production of reactive oxygen species (ROS). Polyphenols have been suggested as a complimentary AD therapeutic based on epidemiological evidence that polyphenol-rich diets correlate with a reduced incidence of AD. In particular, many flavonoids, a subclass of polyphenols, have the ability to inhibit Aβ aggregation. Alternatively, polyphenols can counter Aβ-induced cellular responses by neutralizing ROS through their antioxidant properties. This study sought to identify polyphenols that can reduce Aβ-induced apoptosis by inhibiting Aβ aggregation and/or reducing ROS.Polyphenols investigated include quercetin (QUE), rhamnetin (RHA), isorhamnetin (IRHA), and tamarixetin (TAM). Using SDS-PAGE and Western blot to evaluate oligomer size, only IRHA was unable to reduce Aβ oligomers 250 – 100 kDa in size, while QUE reduced these oligomers by 88.3 ± 2.4%. All compounds reduced Aβ oligomers <100 kDa in size, although IRHA was still the weakest inhibitor. Antioxidant capabilities were quantified in vitro relative to Trolox, a vitamin E analog. All compounds tested exhibited antioxidant capability similar to Trolox. To assess the effect of anti-aggregation and antioxidant properties on Aβ-induced apoptosis, human neuroblastoma cells were stained using TUNEL, which identifies breaks in the DNA strand. Polyphenols with anti-aggregation properties successfully reduced apoptosis, and it is hypothesized that antioxidant activity will also have a protective effect.

Rhamnetin and cirsiliol regulate radioresistance and EMT by suppression of Notch‐1 expression in NSCLC (794.1)

Despite optimal radiotherapy, chemotherapy and/or surgery, the majority of patients with NSCLC fail treatment. Radioresistance is a major cause of decreasing the efficiency of radiotherapy. To understand its mechanisms, we focused on radiation‐induced Notch‐1 signaling pathway. In this study, we investigated the use of Notch‐1‐regulating flavonoids, rhamnetin and cirsiliol, as novel therapeutic drugs to regulate radiosensitivity in NSCLC. Treatment with two compounds reduced the proliferation of NSCLC cells through the suppression of radiation‐induced Notch‐1 expression. Both compounds increased the expression of miR‐34a in a p53‐dependent manner, leading to inhibition of Notch‐1 expression. Consequently, reduced Notch‐1 expression promoted apoptosis through significant down‐regulation of NF‐κB pathway, resulting in a radiosensitizing effect on NSCLC cells. EMT induced by radiation was also notably attenuated by two compounds. Moreover, an in vivo xenograft mouse model confirmed the radiosensitizing effects of both flavonoids as we observed in vitro. Altogether, our findings provided evidence that rhamnetin and cirsiliol can act as novel radiosensitizers via targeting Notch‐1 expression.Grant Funding Source: Supported by the National R&amp;D Program for Cancer Control, Ministry for Health and Welfare(1320100)

Anti-inflammatory effect of O-methylated flavonol 2-(3,4-dihydroxy-phenyl)-3,5-dihydroxy-7-methoxy-chromen-4-one obtained from Cassia sophera Linn in rats

Ethnopharmacological relevanceCassia sophera Linn (Family Caesalpiniaceae), popularly known as kasundi, is used both in the Indian traditional system and folk medicine to treat several inflammatory pathologies such as asthma, arthritis and pains. The aim of the present study was to evaluate the scientific basis of anti-inflammatory activity of Cassia sophera ethanol extracts and of an isolated constituent of Cassia sophera. Materials and methodsThe anti-inflammatory activity of Cassia sophera was studied using the carrageenan, dextran induced rat paw edema, and cotton pellet induced granuloma in rats. The ethanol extract was administered at the concentrations of 200 and 400mg/kg body weight whereas rhamnetin (RN) was administered at a dose of 10 and 15mg/kg, b.w. Indomethacin was used as standard drug. ResultsThe HPLC analysis revealed that good amounts of rhamnetin (0.18%) was present in Cassia sophera.The ethanol extracts at 400mg/kg, showed maximum inhibition of inflammation induced by carrageenan (44%), dextran (40%), cotton pellets (37.47%). On the other hand rhamnetin (15mg/kg) exhibited maximum anti-inflammatory effect, that is 79 and 33% at the end of 3h with carrageenin, and dextran-induced rat paw edema, respectively. In a chronic test rhamnetin (15mg/kg) showed 43.32% reduction in granuloma weight. ConclusionThe marked inhibitory effect on paw edema and granuloma showed that Cassia sophera possess remarkable anti-inflammatory activity which may be due to rhamnetin at least in part, supporting the folkloric usage of the plant to treat various inflammatory diseases.

Inhibition of tomato ringspot virus by flavonoids

When applied in a mixed inoculum with tomato ringspot nepovirus (TomRSV), flavonoids and related compounds inhibited infectivity in Chenopodium quinoa. Compounds that showed strong anti-viral activity were: quercetin, quercetin 3-methyl ether, quercetin 7-methyl ether, quercetin 3,7,3′4′-tetramethyl ether, galangin 3-methyl ether, morin, robinin, quercetin 3,7,4′-trimethyl ether, quercetin 7,4′-dimethyl ether, 7,4′-di- O-benzol-quercetin 7-hydroxy-3,4′-dimethyl flavone, 6,3′-dihydroxy-4′-methyl aurone and fisetin 4′-methyl ether. Quercetin applied at a concentration of 5 μg ml −1 caused 70% inhibition of local lesion development. When quercetin was applied to leaves prior to inoculation, there was only slight induced resistance to infection. Quercetin at 5 μg ml −1 did not affect virus multiplication in protoplasts prepared from cucumber cotyledons and transfected with viral-RNA. In meristematic tip cultures, quercetin reduced virus titre by up to 89% over a period of 36 weeks whereas ribavirin caused a 25% reduction over the same period. It is proposed that flavonoids interfere with an early event in the virus life cycle resulting in decreased infectivity and titre in tissue culture.

Homoisoflavonoids from Caesalpinia sappan

Three new homoisoflavonoids, 7-hydroxy-3-(4′-hydroxybenzylidene)-chroman-4-one, 3,7-dihydroxy-3-(4′-hydroxybenzyl)-chroman-4-one and 3,4,7-trihydroxy-3-(4′-hydroxybenzyl)-chroman were isolated from the dried heartwood of Caesalpinia sappan, together with the known compounds 4,4′-dihydroxy-2′-methoxychalcone, 8-methoxybonducellin, quercetin, rhamnetin and ombuin.

Flavan derivatives. XX. A new glycoside and other extractives from Acacia ixiophylla: Rhamnitrin (rhamnetin 3α-L-rhamnoside)

Rhamnitrin, a new glycoside from the shrub Acacia ixiophylla, is shown to be quercetin 7-methyl ether 3α-L-rhamnoside. A quercetin diglucoside (considered to be the 3,3'-diglucoside), quercitrin, queroetin, rhamnetin, apigenin, apigenin 7,4'-dimethyl ether, and (-)-epicatechin were also isolated. The extractive consisted mainly of mixtures of condensed tannins derived from 5,7,3',4'-tetrahydroxy-flavan-3-o1 and -3,4-diol monomers, and the lower polymers appear to be responsible for the antitumour activity of the extractive.