Synergistic effects of diosmetin with erythromycin against ABC transporter over-expressed methicillin-resistant Staphylococcus aureus (MRSA) RN4220/pUL5054 and inhibition of MRSA pyruvate kinase

Plant Flavonoids with Antimicrobial Activity against Methicillin-Resistant Staphylococcus aureus (MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA) has become a serious threat to human public health and global economic development, and there is an urgent need to develop new antimicrobial agents. Flavonoids are the largest group of plant secondary metabolites, and the anti-S. aureus and anti-MRSA activities of flavonoids have now been widely reported. The aim of this Review is to describe plant-derived flavonoid active ingredients and their effects and mechanisms of inhibitory activity against MRSA in order to provide insights for screening novel antimicrobial agents. Here, 85 plant-derived flavonoids (14 flavones, 21 flavonols, 26 flavanones, 9 isoflavones, 12 chalcones, and 3 other classes) with anti-MRSA activity are reviewed. Among these flavonoids, flavones and isoflavones generally showed the most significant anti-MRSA activity (MICs: 1-8 μg/mL). The results of the present Review display that most of the flavonoids with excellent anti-MRSA activity were derived from Morus alba L. and Paulownia tomentosa (Thunb.) Steud. The antibacterial mechanism of flavonoids against MRSA is mainly achieved by disruption of membrane structures, inhibition of efflux pumps, and inhibition of β-lactamases and bacterial virulence factors. We hope this Review can provide insights into the development of novel antimicrobials based on natural products for treating MRSA infections.

Antibacterial and antibiofilm potentials of Rumex dentatus root extract characterized by HPLC-ESI-Q-TOF-MS

The control of infections is one of the key strategies to treat cuts, wounds, lung, and skin infections. In this study the folkloric use of Rumex dentatus (R. dentatus) roots in the mentioned conditions was scientifically investigated. The methanolic (MeOH) crude extract of R. dentatus root was fractionated (n-hexane, ethyl acetate and water) via bioassay-guided method, and its antibacterial activity was evaluated using the agar well diffusion and Minimum inhibitory concentration (MIC) assays against clinical isolate of Pseudomonas aeruginosa (P. aeruginosa). The antibiofilm activity was measured using the crystal violet staining method. The crude extract, fractions and sub-fractions tested showed the MICs values ranging from 200 to 1000 μg/mL respectively. Among the fractions, notably, the water fraction exhibited the highest activity against P. aeruginosa. The water fraction was then subjected to thin layer chromatography (TLC). Following spectrometric analysis using HPLC-ESI-Q-TOF-MS, gallic acid and emodin were identified as the primary components within the same fraction, responsible for eliciting antibacterial and antibiofilm effects. The in-silico studies conducted with AutoDock Vina on the LasR protein, using both isolated gallic acid and emodin, confirm the binding affinity of these molecules to the active sites of the LasR protein that has regulatory role in building of biofilm formation and its pathogenicity. By scientifically validating the infection-controlling properties of R. dentatus, this research provides compelling evidence that supports its traditional use as reported in folklore. Moreover, this study contributes to our understanding of the plant's potential in managing infections, thereby substantiating its traditional therapeutic application in a scientific context.

Use of 3-Deoxy-D-arabino-heptulosonic acid 7-phosphate Synthase (DAHP Synthase) to Enhance the Heterologous Biosynthesis of Diosmetin and Chrysoeriol in an Engineered Strain of Streptomyces albidoflavus

Flavonoids are a large family of polyphenolic compounds with important agro-industrial, nutraceutical, and pharmaceutical applications. Among the structural diversity found in the flavonoid family, methylated flavonoids show interesting characteristics such as greater stability and improved oral bioavailability. This work is focused on the reconstruction of the entire biosynthetic pathway of the methylated flavones diosmetin and chrysoeriol in Streptomyces albidoflavus. A total of eight different genes (TAL, 4CL, CHS, CHI, FNS1, F3'H/CPR, 3'-OMT, 4'-OMT) are necessary for the heterologous biosynthesis of these two flavonoids, and all of them have been integrated along the chromosome of the bacterial host. The biosynthesis of diosmetin and chrysoeriol has been achieved, reaching titers of 2.44 mg/L and 2.34 mg/L, respectively. Furthermore, an additional compound, putatively identified as luteolin 3',4'-dimethyl ether, was produced in both diosmetin and chrysoeriol-producing strains. With the purpose of increasing flavonoid titers, a 3-Deoxy-D-arabino-heptulosonic acid 7-phosphate synthase (DAHP synthase) from an antibiotic biosynthetic gene cluster (BGC) from Amycolatopsis balhimycina was heterologously expressed in S. albidoflavus, enhancing diosmetin and chrysoeriol production titers of 4.03 mg/L and 3.13 mg/L, which is an increase of 65% and 34%, respectively. To the best of our knowledge, this is the first report on the de novo biosynthesis of diosmetin and chrysoeriol in a heterologous host.

Interactions of naturally occurring compounds with antimicrobials

Antibiotics are among the most often used medications in human healthcare and agriculture. Overusing these substances can lead to complications such as increasing antibiotic resistance in bacteria or a toxic effect when administering large amounts. To solve these problems, new solutions in antibacterial therapy are needed. The use of natural products in medicine has been known for centuries. Some of them have antibacterial activity, hence the idea to combine their activity with commercial antibiotics to reduce the latter's use. This review presents collected information on natural compounds (terpenes, alkaloids, flavonoids, tannins, sulfoxides, and mycotoxins), of which various drug interactions have been observed. Many of the indicated compounds show synergistic or additive interactions with antibiotics, which suggests their potential for use in antibacterial therapy, reducing the toxicity of the antibiotics used and the risk of further development of bacterial resistance. Unfortunately, there are also compounds which interact antagonistically, potentially hindering the therapy of bacterial infection. Depending on its mechanism of action, each compound can behave differently in combination with different antibiotics and when acting against various bacterial strains.

Intramammary Infusion of Micronised Purified Flavonoid Fraction (MPFF) in Mastitis-Diagnosed Dairy Cows Naturally Infected by Staphylococcus spp. in the Late Lactation

Infectious mastitis is the most prevalent health problem in dairy cattle that can result in permanent economic losses on dairy farms. The micronised purified flavonoid fraction (MPFF) is a biocompatible active polyphenolic compound derived from flavonoid glycosides which exhibits several antimicrobial, anti-inflammatory, and phlebotonic properties. The goal was to assess the effects of an alternative therapy for mastitis based on MPFF intramammary infusions in late lactation in dairy cows naturally infected by Staphylococcus spp. The California Mastitis Test (CMT scores) was performed to detect mastitis-positive quarters in twelve dairy farms. All cows were screened for immune response by measuring somatic cell counts (SCCs; cells/mL) in milk samples from each quarter. In addition, bacteriological identification, pathogenic bacterial isolates, and total bacterial counts (TBCs; CFU/mL) were assessed before (day 0, last milking day) and after (day 3 post-calving) MPFF application. Antimicrobial sensitivity patterns of the pathogenic isolated bacteria were evaluated. Finally, cure rates (%) were determined for each MPFF treatment. Around 15 mastitis-related genera were isolated. Staphylococcus aureus (25.2%) and coagulase-negative Staphylococci (CNS; 22.4%) were the most prevalent pathogens. No statistical differences were observed in SCCs and TBCs after low, medium, and high MPFF dose administration in S. aureus-positive mastitis cases (p > 0.05). However, differences were observed in SCCs and TBCs after medium and high MPFF dose administration in CNS-positive quarters (p < 0.05). The pathogenic bacteria isolate reduction after MPFF applications showed a dose-response fashion (p < 0.01) while isolates obtained from controls and low MPFF-treated quarters remained similar, irrespective of the pathogen (p > 0.05). Sensitivity patterns were variable, although S. aureus remained resistant, irrespective of the MPFF dose. However, CNS showed a dose-response sensitivity pattern. Finally, the cure rate (%) on day 3 post-partum improved significantly using medium and higher MPFF doses in CNS-positive quarters (p < 0.05). In conclusion, MPFF treatment was found to be more effective for CNS-positive cases in the late lactation due to noticeable dose-specific responses regarding somatic cells, bacterial counts, sensitivity patterns, and cure rates in dairy cattle.

Formulation and Biomedical Activity of Oil-in-Water Nanoemulsion Combining Tinospora smilacina Water Extract and Calophyllum inophyllum Seeds Oil

Introduction

Tinospora smilacina is a native plant used in traditional medicine by First Nations peoples in Australia to treat inflammation. In our previous study, an optimised Calophyllum inophyllum seed oil (CSO) nanoemulsion (NE) showed improved biomedical activities such as antimicrobial, antioxidant activity, cell viability and in vitro wound healing efficacy compared to CSO.

Methods

In this study, a stable NE formulation combining T. smilacina water extract (TSWE) and CSO in a nanoemulsion (CTNE) was prepared to integrate the bioactive compounds in both native plants and improve wound healing efficacy. D-optimal mixture design was used to optimise the physicochemical characteristics of the CTNE, including droplet size and polydispersity index (PDI). Cell viability and in vitro wound healing studies were done in the presence of CTNE, TSWE and CSO against a clone of baby hamster kidney fibroblasts (BHK-21 cell clone BSR-T7/5).

Results

The optimised CTNE had a 24 ± 5 nm particle size and 0.21± 0.02 PDI value and was stable after four weeks each at 4 °C and room temperature. According to the results, incorporating TSWE into CTNE improved its antioxidant activity, cell viability, and ability to promote wound healing. The study also revealed that TSWE has >6% higher antioxidant activity than CSO. While CTNE did not significantly impact mammalian cell viability, it exhibited wound-healing properties in the BSR cell line during in vitro testing. These findings suggest that adding TSWE may enhance CTNE's potential as a wound-healing treatment.

Conclusion

This is the first study demonstrating NE formulation in which two different plant extracts were used in the aqueous and oil phases with improved biomedical activities.

Diosmin prophylaxis reduces gentamicin-induced kidney damage in rats

Gentamicin is an essential aminoglycoside antibiotic, but it is only used to treat severe bacterial infections due to its high nephrotoxicity in patients. We evaluated the preventive effects of diosmin (as a natural ingredient) on gentamicin-related kidney damage in rats. In this research, 28 male Wistar rats were divided into four groups: control, gentamicin (100 mg/kg (i.p.), daily for 1 week), gentamicin plus diosmin (50 mg/kg, p.o., daily for 2 weeks), and diosmin (50 mg/kg/day, p.o. for 2 weeks). After the final gavage, blood samples were collected for the determination of blood urea nitrogen (BUN) and creatinine. Kidneys are used for biochemical, inflammatory, and histological tests. The concentrations of creatinine, BUN, nitric oxide, malondialdehyde, tumor necrosis factor α (TNF-α), and interleukin 1 beta (IL-1β) were significantly increased. But, the level of glutathione and activities of catalase, glutathione peroxidase, and superoxide dismutase decreased during treatment with gentamicin. On the other hand, the concentrations of creatinine, BUN, nitric oxide, malondialdehyde, TNF-α, and IL-1β were significantly reduced, and the glutathione level, activities of catalase, and glutathione peroxidase were significantly increased via co-administration with diosmin. Diosmin had ameliorative impacts against gentamicin-related kidney injury due to its antioxidant and anti-inflammatory activities.

A toxicological evaluation for safety assessment of ruthenium-based diosmetin complex in rats

The flavonoid-based organometallic complexes have been identified as novel bioactive compounds with enhanced pharmacological and therapeutic activity. In this study, the ruthenium-p-cymene diosmetin complex was synthesized, characterized, and investigated for toxicological profiling through different toxicological and genotoxicological studies which include acute and sub-acute toxicity, chromosomal aberration, and bone marrow micronucleus study. The acute oral toxicity study demonstrated the LD₅₀ dose of the complex at 500 mg/kg body weight which further instigated the sub-acute doses i.e. 50, 100, and 200 mg/kg. The histopathological analysis demonstrated that the 400 mg/kg dose was associated with severe toxicological incidences of the vital organs (liver, kidney, pancreas, testis, and stomach) except the ovary with increased levels of ALP, AST, ALT, and WBC count. However, 50, 100, and 200 mg/kg doses did not show any toxicological alteration and maintained the normal levels of hematological and serum biochemical parameters. The genotoxicological assessment of the complex depicted no such genetic damage or mutagenicity in any complex treated groups. In conclusion, the 50, 100, and 200 mg/kg doses were determined as therapeutic dose of the novel ruthenium-p-cymene diosmetin complex without any genotoxic and mutagenic potential which can be further implemented in the investigation of various pharmacological and therapeutic interventions.

New Chalcone-Triazole Hybrids with Promising Antimicrobial Activity in Multidrug Resistance Strains

Resistance to antibiotics is an emerging problem worldwide, which leads to an increase in morbidity and mortality rates. Several mechanisms are attributed to bacterial resistance, overexpression of efflux pumps being one of the most prominent. As an attempt to develop new effective antimicrobial drugs, which could be able to act against resistant bacterial strains and considering the antimicrobial potential of flavonoids and triazolyl flavonoid derivatives, in particular chalcones, a small library of chalcone derivatives was synthesized and evaluated for its potential to act as antimicrobials and/or adjuvants in combination with antibiotics towards resistant bacteria. Although only compound 7 was able to act as antibacterial, compounds 1, 2, 4, 5, 7, and 9 revealed to be able to potentiate the activity of antibiotics in resistant bacteria. Moreover, five compounds (3, 5-8) demonstrated to be effective inhibitors of efflux pumps in Salmonella enterica serovar Typhimurium SL1344, and four compounds (1, 3, 7, and 10) showed higher ability than reserpine to inhibit biofilm formation of resistant Staphylococcus aureus 272123. Together, our results showed the potential of these compounds regarding reversion of bacterial resistance.

Amazonian Guarana- and Açai-Conjugated Extracts Improve Scratched Fibroblast Healing and Eisenia fetida Surgical Tail Amputation by Modulating Oxidative Metabolism

Background

Previous studies have suggested that guarana (Paullinia cupana) and açai (Euterpe oleracea) have antioxidant, anti-inflammatory, and proliferative properties, indicating their potential therapeutic action in wound healing. We produced a conjugated guarana-açai (GA) extract and tested its healing action on earthworms (Eisenia fetida) subjected to tail amputation by surgical incision.

Methods

Extract from roasted guarana seeds and fresh açai seed berries was produced. The antioxidant and genoprotective capacity of GA extract was tested. The concentration with the most remarkable healing potential was used in subsequent tests. The last three posterior segments of the clitellate earthworm tail reared under standardized conditions were surgically amputated. Next, topical PBS or GA extract was applied to the surgical wound. The rate of cell migration and tissue regeneration at the local wound site was histologically evaluated after the procedure. Expression of the SOX4 gene that acts in epithelial-to-mesenchymal transition was determined by RT-qPCR.

Results

Sixteen bioactive molecules, including some previously described substances, were identified. All tested concentrations exhibited antioxidant and genoprotective effects. The GA extract accelerated the healing processes as observed through macroscopic and histological analyses and increased expression of SOX4.

Conclusion

The GA extract has a potential role in the healing of surgically induced wounds.

The role of dietary flavonoids for modulation of ATP binding cassette transporter mediated multidrug resistance

Flavonoids are widely existing compounds with enormous pharmacological effects from food and medicine. However, the low bioavailability in intestinal absorption and metabolism limits their clinical application. Intestinal efflux ABC (ATP binding cassette) transporters, including P-glycoprotein (P-gp), breast cancer resistance protein (BCRP) and multidrug resistance-associated proteins (MRPs), act as "pumping doors" to regulate the efflux of flavonoids from intestinal epithelial cells into the intestinal cavity or the systemic circulation. The present review describes the critical effect of ABC transporters involved in the efflux of flavonoids which depend on its efflux direction. And the role of flavonoids for modulation of intestinal ABC transporters was emphasized and several examples were given. We summarized that the resistance effect of flavonoid-mediated multidrug on ABC transporters may influence the bioavailability of drugs, bioactive ingredients and/or toxic compounds upon dietary uptake. Meanwhile, flavonoids functionalized as reversing agents of the ABC transporter may be an important mechanism for unexpected food-drug, food-toxin or food-food interactions. The overview also indicates that elucidation of the action and mechanism of the intestinal metabolic enzymes-efflux transporters coupling will lay a foundation for improving the bioavailability of flavonoids <i>in vivo</i> and increasing their clinical efficacy.

Flavonoids as Inhibitors of Bacterial Efflux Pumps

Flavonoids are widely occurring secondary plant constituents, and are abundant in vegetable and fruit diets as well as herbal medicines. Therapeutic treatment options for bacterial infections are limited due to the spread of antimicrobial resistances. Hence, in a number of studies during the last few years, different classes of plant secondary metabolites as resistance-modifying agents have been carried out. In this review, we present the role of flavonoids as inhibitors of bacterial efflux pumps. Active compounds could be identified in the subclasses of chalcones, flavan-3-ols, flavanones, flavones, flavonols, flavonolignans and isoflavones; by far the majority of compounds were aglycones, although some glycosides like kaempferol glycosides with p-coumaroyl acylation showed remarkable results. Staphylococcus aureus NorA pump was the focus of many studies, followed by mycobacteria, whereas Gram-negative bacteria are still under-investigated.

Novel ocotillol-derived lactone derivatives: design, synthesis, bioactive evaluation, SARs and preliminary antibacterial mechanism

A new series of ocotillol-derived lactone derivatives were designed and synthesized to consider their antibacterial activity, structure-activity relationships (SARs), antibacterial mechanism and in vivo antibacterial efficacy. Compound 6d, which exhibited broad antibacterial spectrum, was found to be the most active with minimum inhibitory concentrations (MICs) of 1-2 μg/mL against Gram-positive bacteria and 8-16 μg/mL against Gram-negative bacteria. The subsequent synergistic antibacterial tests displayed that 6d had the ability to improve the susceptibility of MRSA USA300, B. subtilis 168, and E. coli DH5α to kanamycin and chloramphenicol. This active molecule 6d also induced bacterial resistance more slowly than norfloxacin and kanamycin. Furthermore, compound 6d was membrane active and low toxic against mammalian cells, and it could rapidly inhibit the growth of MRSA and E. coli and did not obviously trigger bacterial resistance. Compound 6d also displayed strong in vivo antibacterial activity against S. aureus RN4220 in murine corneal infection models. Additionally, absorption, distribution, metabolism, and excretion properties of this type of compounds have shown drug-likeness with good oral absorption and moderate blood-brain barrier permeability. The obtained results demonstrated that ocotillol-derived compounds are a promising class of antibacterial agents worthy of further study.

Polyphenolic Antibacterials for Food Preservation: Review, Challenges, and Current Applications

Natural alternatives replacing artificial additives have gained much attention in the consumer’s view because of the growing search for clean label products that are devoid of carcinogenic and toxic effects. Plant polyphenols are considered as suitable alternative natural preservatives with antioxidant and antimicrobial properties. However, their uses in the food industry are undermined by a series of limitations such as low solubility and stability during food processing and storage, lack of standardization, and undesirable organoleptic properties. Different approaches in the use of polyphenols have been proposed in order to overcome the current hurdles related to food preservation. This review article specifically focuses on the antibacterial activity of plant-derived polyphenols as well as their applications as food preservatives, main challenges, and other trends in the food industry.

A synergy interaction of artocarpin and tetracycline against Pseudomonas aeruginosa and its mechanism of action on membrane permeability

The emergence of antibacterial resistance has significantly increased. Pseudomonas aeruginosa is associated with nosocomial infection and difficult to control. Artocarpin, a flavonoid from Artocarpus heterophyllus Lam. exhibits several pharmacological properties including antibacterial. The study was performed to evaluate interaction between artocarpin and antibiotics including tetracycline against P. aeruginosa. Its mechanism of action on membrane permeability was also investigated. Broth microdilution was conducted for the susceptibility assay. The interaction of artocarpin and antibiotics was evaluated using checkerboard method, the effect on alteration of membrane cell was investigated using bacteriolysis and the released of 260 nm materials. Artocarpin showed moderate to weak activity against the Gram-negative bacteria including P. aeruginosa with MIC values in the range of 31.25-250 μg/mL. A synergistic effect against P. aeruginosa was produced by the combination of artocarpin (31.25 μg/mL) and tetracycline (1.95 μg/mL) with FICI of 0.37. The time-killing assay showed that artocarpin enhance the antibacterial activity of tetracycline against P. aeruginosa by completely inhibiting the bacterial growth. Additionally, the mixture of artocarpin (31.25 μg/mL) and tetracycline (1.95 μg/mL) disrupted membrane permeability and lead to cell death. These results proposed that the combination of artocarpin and tetracycline may be used to overcome P. aeruginosa infection.

Design, synthesis and antibacterial evaluation of ocotillol derivatives with polycyclic nitrogen-containing groups

Aim: With the increasing abuse of antibacterial drugs, multidrug-resistant bacteria have become a burden on human health and the healthcare system. To find alternative compounds effective against hospital-acquired methicillin-resistant Staphylococcus aureus (HA-MRSA), novel derivatives of ocotillol were synthesized. Methods & Results: Ocotillol derivatives with polycyclic nitrogen-containing groups were synthesized and evaluated for in vitro antibacterial activity. Compounds 36-39 exhibited potent antibacterial activity against HA-MRSA, with MIC = 8-64 μg/ml. Additionally, a combination of compound 37 and the commercially available antibiotic kanamycin showed synergistic inhibitory effects, with a fractional inhibitory concentration index of ≤0.375. Conclusion: Compound 37 has a strong inhibitory effect, and this derivative has potential for use as a pharmacological tool to explore antibacterial mechanisms.

Methicillin-resistance Staphylococcus aureus (MRSA) Pyruvate kinase (PK) inhibitors and Their Antimicrobial Activities

Resistance to antibiotics has been widely existed in the health care and community setting, thus developing a novel aspect of new antibiotics is urgently necessary. Methicillin-resistance Staphylococcus aureus (MRSA) Pyruvate kinase (PK) is crucial to the survive of bacterial, making it a novel antimicrobial target. In the past decade, most reported PK inhibitors including indole, flavonoid, phenazine derivative from natural product small molecules or their analogues, or virtual screening from small molecule compound library. This review covers the PK inhibitors and their antimicrobial activities reported from the beginning of 2011 through the middle of 2020. The Structure Activity Relationships (SARs) was discussed briefly as well.

Enhancement of the antibiotic activity by quercetin against Staphylococcus aureus efflux pumps

The objective of this work was to evaluate the inhibitory effect of quercetin on S. aureus Efflux Pumps. The MIC of Quercetin was evaluated through the broth microdilution method, as well as the Efflux Pump inhibition assay through the method of reducing the antibiotic minimum inhibitory concentration as well as that of ethidium bromide. The in silico approach through bioinformatics was performed to demonstrate the molecular mechanism of interaction of the substrate and the binding cavity. The Quercetin inhibition concentration was not clinically relevant. With respect to the reversal of bacterial resistance effect by efflux pump inhibition, this effect was observed with the strains carrying the TetK and NorA pumps. Regarding the interaction between the Quercetin complex and the NorA pump, the extra stability was provided by hydrogen bonds produced by the hydroxyl group.

Diosmetin Induces Apoptosis by Downregulating AKT Phosphorylation via P53 Activation in Human Renal Carcinoma ACHN Cells

Background:

Diosmetin (DIOS) is the aglycone of the flavonoid glycoside, diosmin, derived naturally from the leaves of the legume, Olea europaea, and Acacia farnesiana. It has potent anticancer activity against multiple forms of cancers. However, the role of DIOS in renal carcinoma and its mechanism of action remain unclear.

Objective:

The purpose of this study is to investigate the effect of DIOS on cell viability and apoptosis in renal carcinoma cells and explore the possible mechanism of action.

Methods:

Cell viability, cytotoxicity, caspase activity, apoptosis, and expression of apoptotic related proteins were analyzed in renal carcinoma ACHN cells.

Results:

The results showed that DIOS inhibited the cell viability, and induced cytotoxicity and apoptosis in ACHN cells. Furthermore, DIOS increased expression of p53 mRNA and proteins, and downregulated phosphorylation of the phosphoinositide 3-kinase and protein B kinase (PI3K/AKT). In addition, it was observed that the anticancer effect of DIOS was significantly enhanced by the p53 activator, but inhibited by the p53 inhibitor.

Conclusion:

Our data suggested that DIOS induced apoptosis in renal carcinoma ACHN cells by reducing AKT phosphorylation through p53 upregulation.

Anti-inflammatory effects of natural flavonoid diosmetin in IL-4 and LPS-induced macrophage activation and atopic dermatitis model

Diosmetin, a citrus flavonoid, has a variety of therapeutic properties such as antibacterial, anti-inflammatory and antioxidant effects. However, the effect of diosmetin on atopic dermatitis (AD) development has not been reported. This study thus aims to investigate whether diosmetin possesses inhibitory effects on AD development. A dinitrochlorobenzene (DNCB)-induced AD mouse model was used to evaluate the effects of diosmetin on AD development. Treatment with diosmetin significantly reduced the dermatitis score, thickness of epidermis and dermis and number of mast cells in comparison with the untreated group. Furthermore, immunohistochemical analysis using an anti-F4/80 antibody demonstrated that diosmetin significantly suppressed macrophage infiltration into the AD lesion. It was observed that the levels of pro-inflammatory cytokines (TNF-α, IL-4 and IL-1β) in skin lesion decreased in response to treatment with diosmetin. In addition, the anti-inflammatory effect of diosmetin was evaluated in LPS- or IL-4-induced a mouse macrophage cell line (raw 264.7). Diosmetin inhibited the production of nitric oxide and decreased the expression of inducible nitric oxide synthase (iNOS). Diosmetin not only suppressed the phosphorylation of MAP kinase (ERK 1/2, p38 and JNK) but the activation of JAK/STAT signaling. The mRNA analysis demonstrated that diosmetin also reduced the level of inflammatory cytokines such as IL-1β and IL-6. Collectively, these results demonstrate that diosmetin exhibits the inhibitory effect on AD, suggesting that diosmetin may be a potential therapeutic agent for this atopic disorder.

Efflux pumps as interventions to control infection caused by drug-resistance bacteria

Antibiotic resistance has become a global concern for healthcare workers and physicians. Efflux pumps are one of the major mechanisms of resistance. Hence, we describe examples of natural efflux pump inhibitors used to combat antibiotic resistance.

Prenylated phenolics as promising candidates for combination antibacterial therapy: Morusin and kuwanon G

Combination of antibiotics with natural products is a promising strategy for potentiating antibiotic activity and overcoming antibiotic resistance. The purpose of the present study was to investigate whether morusin and kuwanon G, prenylated phenolics in Morus species, have the ability to enhance antibiotic activity and reverse antibiotic resistance in Staphylococcus aureus and Staphylococcus epidermidis. Commonly used antibiotics (oxacillin, erythromycin, gentamicin, ciprofloxacin, tetracycline, clindamycin) were selected for the combination studies. Checkerboard and time-kill assays were used to investigate potential bacteriostatic and bactericidal synergistic interactions, respectively between morusin or kuwanon G and antibiotics. According to both fractional inhibitory concentration index and response surface models, twenty combinations (14 morusin-antibiotic combinations, six kuwanon G-antibiotic combinations) displaying bacteriostatic synergy were identified, with 4–512-fold reduction in the minimum inhibitory concentration values of antibiotics in combination. Both morusin and kuwanon G reversed oxacillin resistance of methicillin-resistant Staphylococcus aureus. In addition, morusin reversed tetracycline resistance of Staphylococcus epidermidis. At half of the minimum inhibitory concentrations, combinations of morusin with oxacillin or gentamicin showed bactericidal synergy against methicillin-resistant Staphylococcus aureus. Fluorescence and differential interference contrast microscopy and scanning electron microscopy showed an increase in the membrane permeability and massive leakage of cellular content in methicillin-resistant Staphylococcus aureus exposed to morusin or kuwanon G. Overall, our findings strongly indicate that both prenylated compounds are good candidates for the development of novel antibacterial combination therapies.

Targeting SKP2/Bcr-Abl pathway with Diosmetin suppresses chronic myeloid leukemia proliferation

Bcr-Abl is the primary cause as well as currently key therapeutic target of chronic myeloid leukemia (CML). SKP2, an E3 ligase, is a downstream factor of Bcr-Abl to motivate the cell cycle transition of CML and also found to bind and activate Bcr-Abl in reverse. Therefore, SKP2/Bcr-Abl pathway is an attractive target for CML treatment. This study aims to identify an inhibitor of the SKP2/Bcr-Abl pathway based on a large screening of the natural products. We demonstrate that Diosmetin, a kind of phytoestrogens, notably downregulates the expression of SKP2, Bcr-Abl phosphorylation, and moderately downregulates the Bcr-Abl level. Furthermore, Diosmetin displays a favorable anti-tumor activity in CML cells and xenograft models. Collectively, our study reveals a natural compound in the treatment of CML on the basis of SKP2/Bcr-Abl signaling pathway.

Diosmetin alleviates hypoxia‑induced myocardial apoptosis by inducing autophagy through AMPK activation

Diosmetin has shown great potential in the control of several diseases. The aim of the present study was to evaluate the role of diosmetin as a candidate agent for the treatment of myocardial infarction which was mainly caused by hypoxia. The model of hypoxia‑injured myocardial cells was established using the H9c2 cell line. Cell viability was determined using Cell Counting Kit‑8, cell apoptosis was determined by Annexin V‑FITC Apoptosis Detection Kit and cleaved caspase‑3 level was assessed by western blot analysis. Autophagy was monitored using a commercial kit, and a well‑established reporter system was used to confirm the role of diosmetin in autophagy. The activity of adenosine 5'‑monophosphate‑activated protein kinase (AMPK) signaling was detected by western blot analysis. Cell viability assay indicated that diosmetin alleviated hypoxia‑induced cell death of H9c2 cells in a dose‑dependent manner. Data of the apoptosis assay revealed that diosmetin reduced the proportion of apoptotic cells in the hypoxia‑injured H9c2 cells. It was also found that the occurrence of autophagy was promoted when hypoxia‑injured cells were treated with diosmetin alone, and results of the western blot analysis revealed that AMPK signaling was activated by diosmetin. Administration of diosmetin together with an inhibitor of autophagy (3‑methyladenine, 3‑MA) or AMPK (Compound C) was able to decrease the diosmetin‑induced autophagy as well as the cytoprotective effects in the hypoxia‑injured cells. Our study concluded that diosmetin exhibits a cytoprotective effect on hypoxia‑injured myocardial cells by inducing autophagy and alleviating apoptosis. AMPK was demonstrated to regulate the observed effects caused by diosmetin. This investigation confirmed diosmetin as a promising drug candidate for myocardial infarction treatment. The present findings regarding the inherent molecular mechanisms involved in the protective effects of diosmetin promote the clinical application of diosmetin.

Antibacterial activity of the structurally novel ocotillol-type lactone and its analogues

A novel series of ocotillol-type lactone derivatives were designed and synthesized in order to study their antibacterial activity and structure-activity relationships. Among which, compounds 4j and 4 m were found to be the most active with minimum inhibitory concentrations (MICs) of 1-4 μg/mL against Gram-positive bacteria and showed low cytotoxicity against MCF-7, HEK-293 and HK-2 cells at their MICs. The antibacterial effect of compound 4 m was characterized further by scanning electron microscopy, cytoplasmic β-galactosidase leakage assay and UV-visible analysis. The results showed that 4 m may exert its antibacterial effect by damaging bacterial cell membranes and disrupting the function of DNA, both of which could lead to rapid cell death.

Citrus Flavones: An Update on Sources, Biological Functions, and Health Promoting Properties

Citrus spp. are among the most widespread plants cultivated worldwide and every year millions of tons of fruit, juices, or processed compounds are produced and consumed, representing one of the main sources of nutrients in human diet. Among these, the flavonoids play a key role in providing a wide range of health beneficial effects. Apigenin, diosmetin, luteolin, acacetin, chrysoeriol, and their respective glycosides, that occur in concentrations up to 60 mg/L, are the most common flavones found in Citrus fruits and juices. The unique characteristics of their basic skeleton and the nature and position of the substituents have attracted and stimulated vigorous investigations as a consequence of an enormous biological potential, that manifests itself as (among other properties) antioxidant, anti-inflammatory, antiviral, antimicrobial, and anticancer activities. This review analyzes the biochemical, pharmacological, and biological properties of Citrus flavones, emphasizing their occurrence in Citrus spp. fruits and juices, on their bioavailability, and their ability to modulate signal cascades and key metabolic enzymes both in vitro and in vivo. Electronic databases including PubMed, Scopus, Web of Science, and SciFinder were used to investigate recent published articles on Citrus spp. in terms of components and bioactivity potentials.

Metabolism and pharmacological activities of the natural health-benefiting compound diosmin

Diosmin is a famous natural flavonoid for treating chronic venous insufficiency and varicose veins.

Baicalin Inhibits Biofilm Formation and the Quorum-Sensing System by Regulating the MsrA Drug Efflux Pump in Staphylococcus saprophyticus

Staphylococcus saprophyticus (S. saprophyticus) is one of the main pathogens that cause serious infection due to its acquisition of antibiotic resistance. The efflux pump decreases antibiotic abundance, and biofilm compromises the penetration of antibiotics. It has been reported that baicalin is a potential agent to inhibit efflux pumps, biofilm formation, and quorum-sensing systems. The purpose of this study was to investigate whether baicalin can inhibit S. saprophyticus biofilm formation and the quorum-sensing system by inhibiting the MsrA efflux pump. First, the mechanism of baicalin inhibiting efflux was investigated by the ethidium bromide (EtBr) efflux assay, measurement of ATP content, and pyruvate kinase (PK) activities. These results revealed that baicalin significantly reduced the efflux of EtBr, the ATP content, and the activity of PK. Moreover, its role in biofilm formation and the agr system was studied by crystal violet staining, confocal laser scanning microscopy, scanning electron microscopy, and real-time polymerase chain reaction. These results showed that baicalin decreased biofilm formation, inhibited bacterial aggregation, and downregulated mRNA transcription levels of the quorum-sensing system regulators agrA, agrC, RNAIII, and sarA. Correlation analysis indicated that there was a strong positive correlation between the efflux pump and biofilm formation and the agr system. We demonstrate for the first time that baicalin inhibits biofilm formation and the agr quorum-sensing system by inhibiting the efflux pump in S. saprophyticus. Therefore, baicalin is a potential therapeutic agent for S. saprophyticus biofilm-associated infections.

Efflux pump inhibitors for bacterial pathogens: From bench to bedside

With the advent of antibiotics, bacterial infections were supposed to be a thing of past. However, this instead led to the selection and evolution of bacteria with mechanisms to counter the action of antibiotics. Antibiotic efflux is one of the major mechanisms, whereby bacteria pump out the antibiotics from their cellular interior to the external environment using special transporter proteins called efflux pumps. Inhibiting these pumps seems to be an attractive strategy at a time when novel antibiotic supplies are dwindling. Molecules capable of inhibiting these pumps, known as efflux pump inhibitors (EPIs), have been viewed as potential therapeutic agents that can rejuvenate the activity of antibiotics that are no longer effective against bacterial pathogens. EPIs follow some general mechanisms of efflux inhibition and are derived from various natural as well as synthetic sources. This review focuses on EPIs and identifies the challenges that have kept these futuristic therapeutics away from the commercial realm so far.

Investigations on the structural, vibrational, computational, and molecular docking studies on potential antidiabetic chemical agent Diosmetin

In the present study, the harmonic vibrational frequencies of Diosmetin(5, 7 dihydroxy-2(3-hydroxy-4 methoxyphenyl) chromen-4-one) have been investigated by both experimental (FTIR and FT-Raman) and theoretical (HF and DFT/B3LYP) method. The calculated harmonic vibrational frequencies were compared with experimental data. A detailed interpretation of the vibrational spectra of the compound has been made on the basis of the calculated potential energy distribution (PED). The ¹ H, ¹³ C NMR chemical shifts and TD-DFT calculations of the molecule were calculated and compared with the available experimental observations. A study on the molecular electrostatic potential surface (MEP) of the compound was performed, and the electrophilic and nucleophilic reactive sites were identified. Furthermore, the inhibition effect of compound against aldose reductase enzyme has been analyzed by molecular docking method, and the results were compared with the standard drug. The docking study indicates that the investigated compound shows better inhibitory activity toward aldose reductase enzyme than the standard drug, and hence this study may be supportive in the field of drug discovery to design more potential antidiabetic agents.

Combination of Repurposed Drug Diosmin with Amoxicillin-Clavulanic acid Causes Synergistic Inhibition of Mycobacterial Growth

Effective therapeutic regimens for the treatment of tuberculosis (TB) are limited. They are comprised of multiple drugs that inhibit the essential cellular pathways in Mycobacterium tuberculosis (Mtb). The present study investigates an approach which enables a combination of Amoxicillin-Clavulanic acid (AMC) and a repurposed drug for its synergistic effect towards TB treatment. We identified Diosmin (DIO), by targeting the active site residues of L,D-transpeptidase (Ldt) enzymes involved in Mtb cell wall biosynthesis by using a structure-based drug design method. DIO is rapidly converted into aglycone form Diosmetin (DMT) after oral administration. Binding of DIO or DMT towards Ldt enzymes was studied using molecular docking and bioassay techniques. Combination of DIO (or DMT) and AMC exhibited higher mycobactericidal activity against Mycobacterium marinum as compared to individual drugs. Scanning electron microscopy study of M. marinum treated with AMC-DIO and AMC-DMT showed marked cellular leakage. M. marinum infected Drosophila melanogaster fly model showed an increased fly survival of ~60% upon treatment with a combination of AMC and DIO (or DMT). Finally, the enhanced in vitro antimicrobial activity of AMC-DIO was validated against Mtb H37Ra and a MDR clinical isolate. Our results demonstrate the potential for AMC and DIO (or DMT) as a synergistic combination for the treatment of TB.

Microbial Biosynthesis of Antibacterial Chrysoeriol in Recombinant Escherichia coli and Bioactivity Assessment

Various flavonoid derivatives including methoxylated flavones display remarkable biological activities. Chrysoeriol is a methoxylated flavone of great scientific interest because of its promising anti-microbial activities against various Gram-negative and Gram-positive bacteria. Sustainable production of such compounds is therefore of pronounced interest to biotechnologists in the pharmaceutical and nutraceutical industries. Here, we used a sugar O-methyltransferase enzyme from a spinosyn biosynthesis gene cluster of Saccharopolyspora spinosa to regioselectively produce chrysoeriol (15% conversion of luteolin; 30 µM) in a microbial host. The biosynthesized chrysoeriol was structurally characterized using high-resolution mass spectrometry and various nuclear magnetic resonance analyses. Moreover, the molecule was investigated against 17 superbugs, including thirteen Gram-positive and four Gram-negative pathogens, for anti-microbial effects. Chrysoeriol exhibited antimicrobial activity against nine pathogens in a disc diffusion assay at the concentration of 40 µg per disc. It has minimum inhibitory concentration (MIC) values of 1.25 µg/mL against a methicillin-resistant Staphylococcus aureus 3640 (MRSA) for which the parent luteolin has an MIC value of sixteen-fold higher concentration (i.e., 20 µg/mL). Similarly, chrysoeriol showed better anti-microbial activity (~1.7-fold lower MIC value) than luteolin against Proteus hauseri, a Gram-negative pathogen. In contrast, a luteolin 4′-O-methylated derivative, diosmetin, did not exhibit any anti-microbial activities against any tested pathogen.

Novel antibacterial modalities against methicillin resistant Staphylococcus aureus derived from plants

Methicillin-resistant Staphylococcus aureus (MRSA) is a notorious bacterial pathogen that induces high mortality and morbidity. Due to the emergence of multiple resistance, antibiotic treatments are rapidly becoming ineffective for the related infections. Natural products, especially those derived from plants, have been proven to be effective agents with unique antibacterial properties through different mechanisms. This review interprets the resistance mechanisms of MRSA with the aim to conquer public health threat. Further, recent researches about plant antimicrobials that showed remarkable antibacterial activity against MRSA are recorded, including the crude plant extracts and purified plant-derived bioactive compounds. Novel anti-MRSA modalities of plant antimicrobials such as alteration in efflux pump, inhibition of pyruvate kinase, and disturbance of quorum sensing in MRSA are also summarized which may be promising alternatives to antibacterial drug development in future.

Diosmetin Alleviates Lipopolysaccharide-Induced Acute Lung Injury through Activating the Nrf2 Pathway and Inhibiting the NLRP3 Inflammasome

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a common clinical syndrome of diffuse lung inflammation with high mortality rates and limited therapeutic methods. Diosmetin, an active component from Chinese herbs, has long been noticed because of its antioxidant and anti-inflammatory activities. The aim of this study was to evaluate the effects of diosmetin on LPS-induced ALI model and unveil the possible mechanisms. Our results revealed that pretreatment with diosmetin effectively alleviated lung histopathological changes, which were further evaluated by lung injury scores. Diosmetin also decreased lung wet/dry ratios, as well as total protein levels, inflammatory cell infiltration and proinflammatory cytokine (eg. TNF-α, IL-1β and IL-6) overproduction in bronchoalveolar lavage fluid (BALF). Additionally, increased MPO, MDA and ROS levels induced by LPS were also markly suppressed by diosmetin. Furthermore, diosmetin significantly increased the expression of Nrf2 along with its target gene HO-1 and blocked the activation of NLRP3 inflammasome in the lung tissues, which might be central to the protective effects of diosmetin. Further supporting these results, in vitro experiments also showed that diosmetin activated Nrf2 and HO-1, as well as inhibited the NLRP3 inflammasome in both RAW264.7 and A549 cells. The present study highlights the protective effects of diosmetin on LPS-induced ALI via activation of Nrf2 and inhibition of NLRP3 inflammasome, bringing up the hope of its application as a therapeutic drug towards LPS-induced ALI.

Combination of Erythromycin and Curcumin Alleviates Staphylococcus aureus Induced Osteomyelitis in Rats

Osteomyelitis is commonly caused by Staphylococcus aureus. Both erythromycin and curcumin can suppress S. aureus growth, but their roles in osteomyelitis are barely studied. We aim to explore the activities of erythromycin and curcumin against chronical osteomyelitis induced by methicillin-resistant S. aureus (MRSA). Chronicle implant-induced osteomyelitis was established by MRSA infection in male Wistar rats. Four weeks after bacterial inoculation, rats received no treatment, erythromycin monotherapy, curcumin monotherapy, or erythromycin plus curcumin twice daily for 2 weeks. Bacterial levels, bone infection status, inflammatory signals and side effects were evaluated. Rats tolerated all treatments well, with no death or side effects such as, diarrhea and weight loss. Two days after treatment completion, erythromycin monotherapy did not suppress bacterial growth and had no effect in bone infection, although it reduced serum pro-inflammatory cytokines tumor necrosis factor (TNF)-α and interleukin (IL)-6. Curcumin monotherapy slightly suppressed bacterial growth, alleviated bone infection and reduced TNF-α and IL-6. Erythromycin and curcumin combined treatment markedly suppressed bacterial growth, substantially alleviated bone infection and reduced TNF-α and IL-6. Combination of erythromycin and curcumin lead a much stronger efficiency against MRSA induced osteomyelitis in rats than monotherapy. Our study suggests that erythromycin and curcumin could be a new combination for treating MRSA induced osteomyelitis.

Synthesis and Antibacterial Evaluation of Novel 3-Substituted Ocotillol-Type Derivatives as Leads

Due to the rapidly growing bacterial antibiotic-resistance and the scarcity of novel agents in development, bacterial infection is still a global problem. Therefore, new types of antibacterial agents, which are effective both alone and in combination with traditional antibiotics, are urgently needed. In this paper, a series of antibacterial ocotillol-type C-24 epimers modified from natural 20(S)-protopanaxadiol were synthesized and evaluated for their antibacterial activity. According to the screening results of Gram-positive bacteria (B. subtilis 168 and MRSA USA300) and Gram-negative bacteria (P. aer PAO1 and A. baum ATCC19606) in vitro, the derivatives exhibited good antibacterial activity, particularly against Gram-positive bacteria with an minimum inhibitory concentrations (MIC) value of 2–16 µg/mL. The subsequent synergistic antibacterial assay showed that derivatives 5c and 6c enhanced the susceptibility of B. subtilis 168 and MRSA USA300 to chloramphenicol (CHL) and kanamycin (KAN) (FICI < 0.5). Our data showed that ocotillol-type derivatives with long-chain amino acid substituents at C-3 were good leads against antibiotic-resistant pathogens MRSA USA300, which could improve the ability of KAN and CHL to exhibit antibacterial activity at much lower concentrations with reduced toxicity.

A synergistic effect of artocarpanone from Artocarpus heterophyllus L. (Moraceae) on the antibacterial activity of selected antibiotics and cell membrane permeability

Aim/Backgrounds:

Artocarpanone isolated from Artocarpus heterophyllus L. (Moraceae) exhibits antibacterial activity. The present study investigated synergistic activity between artocarpanone and tetracycline, ampicillin, and norfloxacin, respectively, against methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Escherichia coli.

Materials and Methods:

A broth microdilution method was used for evaluating antibacterial susceptibility. Synergistic effects were identified using a checkerboard method, and a bacterial cell membrane disruption was investigated by assay of released 260 nm absorbing materials following bacteriolysis.

Results and Discussion:

Artocarpanone exhibited weak antibacterial activity against MRSA and P. aeruginosa with minimum inhibitory concentrations values of 125 and 500 μg/mL, respectively. However, the compound showed strong antibacterial activity against E. coli (7.8 μg/mL). The interaction between artocarpanone and all tested antibiotics revealed indifference and additive effects against P. aeruginosa and E. coli (fractional inhibitory concentration index [FICI] values of 0.75-1.25). The combination of artocarpanone (31.2 μg/mL) and norfloxacin (3.9 μg/mL) resulted in synergistic antibacterial activity against MRSA, with an FICI of 0.28, while the interaction between artocarpanone and tetracycline, and ampicillin showed an additive effect, with an FICI value of 0.5. A time-kill assay also indicated that artocarpanone had a synergistic effect on the antibacterial activity of norfloxacin. In addition, the combination of artocarpanone and norfloxacin altered the membrane permeability of MRSA.

Conclusion:

These findings suggest that artocarpanone may be used to enhance the antibacterial activity of norfloxacin against MRSA.

Metabolic Disposition of Luteolin Is Mediated by the Interplay of UDP-Glucuronosyltransferases and Catechol-O-Methyltransferases in Rats

Luteolin partially exerts its biologic effects via its metabolites catalyzed by UDP-glucuronosyltransferases (UGTs) and catechol-O-methyltransferases (COMTs). However, the interplay of UGTs and COMTs in mediating luteolin disposition has not been well clarified. In this study, we investigated the glucuronidation and methylation pathways of luteolin mediated by the interplay of UGTs and COMTs in vivo and in vitro. A total of nine luteolin metabolites was detected in rat plasma and bile by liquid chromatography-tandem mass spectrometry, namely, three glucuronides, two methylated metabolites, and four methylated glucuronides. Luteolin-3'-glucuronide (Lut-3'-G) exhibited the highest systemic exposure among these metabolites. Kinetics studies in rat liver S9 fractions suggested two pathways, as follows: 1) Luteolin was glucuronidated to luteolin-7-glucuronide, luteolin-4'-glucuronide, and Lut-3'-G by UGTs, and then Lut-7-G was methylated to chrysoeriol-7-glucuronide and diosmetin-7-glucuronide by COMTs. 2) Alternatively, luteolin was methylated to chrysoeriol and diosmetin by COMTs, and then chrysoeriol and diosmetin were glucuronidated by UGTs to their respective glucuronides. The methylation rate of luteolin was significantly increased by the absence of glucuronidation, whereas the glucuronidation rate was increased by the absence of methylation, but to a lesser extent. In conclusion, two pathways mediated by the interplay of UGTs and COMTs are probably involved in the metabolic disposition of luteolin. The glucuronidation and methylation of luteolin compensate for each other, although glucuronidation is the predominant pathway.

Regioselective Glucuronidation of Diosmetin and Chrysoeriol by the Interplay of Glucuronidation and Transport in UGT1A9-Overexpressing HeLa Cells

This study aimed to determine the reaction kinetics of the regioselective glucuronidation of diosmetin and chrysoeriol, two important methylated metabolites of luteolin, by human liver microsomes (HLMs) and uridine-5′-diphosphate glucuronosyltransferase (UGTs) enzymes. This study also investigated the effects of breast cancer resistance protein (BCRP) on the efflux of diosmetin and chrysoeriol glucuronides in HeLa cells overexpressing UGT1A9 (HeLa—UGT1A9). After incubation with HLMs in the presence of UDP-glucuronic acid, diosmetin and chrysoeriol gained two glucuronides each, and the OH—in each B ring of diosmetin and chrysoeriol was the preferable site for glucuronidation. Screening assays with 12 human expressed UGT enzymes and chemical-inhibition assays demonstrated that glucuronide formation was almost exclusively catalyzed by UGT1A1, UGT1A6, and UGT1A9. Importantly, in HeLa—UGT1A9, Ko143 significantly inhibited the efflux of diosmetin and chrysoeriol glucuronides and increased their intracellular levels in a dose-dependent manner. This observation suggested that BCRP-mediated excretion was the predominant pathway for diosmetin and chrysoeriol disposition. In conclusion, UGT1A1, UGT1A6, and UGT1A9 were the chief contributors to the regioselective glucuronidation of diosmetin and chrysoeriol in the liver. Moreover, cellular glucuronidation was significantly altered by inhibiting BCRP, revealing a notable interplay between glucuronidation and efflux transport. Diosmetin and chrysoeriol possibly have different effects on anti-cancer due to the difference of UGT isoforms in different cancer cells.

Diosmetin inhibits cell proliferation and induces apoptosis by regulating autophagy via the mammalian target of rapamycin pathway in hepatocellular carcinoma HepG2 cells

Hepatocellular carcinoma (HCC), which is a type of malignant tumor, is the fifth most common cancer in men and ninth in women worldwide. The aim of the present study was to investigate the antitumor effect of diosmetin (DIOS) in hepatocellular carcinoma HepG2 cells. The proliferation, apoptosis and autophagy rates of HepG2 cells were measured following treatment with DIOS. The effects of DIOS treatment on HepG2 cell proliferation and apoptosis rates were analyzed using MTT assays and Annexin V staining, respectively. The effect of DIOS treatment on autophagy levels was assessed using transmission electron microscopy, green fluorescent protein (GFP)-microtubule-associated protein 1 light chain (LC3) transfection and LysoTracker Red staining. Furthermore, bafilomycin A1 (BA1), an autophagy inhibitor, was used to assess the association between DIOS and cell autophagy, proliferation and apoptosis. In addition, the expression of autophagy-related proteins [mammalian target of rapamycin (mTOR), phosphatidylinositol 3-kinase, P70S6K, phosphoinositide-dependent kinase-1, extracellular signal-regulated kinase, 5′-AMP-activated protein kinase and Akt] and apoptosis-related proteins [B-cell lymphoma (Bcl)-2-associated X protein, Bak, p53, Bcl-2 and caspase-3] were analyzed by western blotting. The results revealed that DIOS significantly inhibited proliferation (P<0.01) and induced apoptosis (P<0.001) in HepG2 cells. It was also demonstrated that DIOS triggered autophagy by regulating the mTOR pathway in HepG2 cells. Notably, following treatment of HepG2 cells with the autophagy inhibitor, BA1, the expression of apoptosis-related proteins, including Bax, Bak and p53, were significantly decreased (P<0.05), and cell viability was recovered to a certain extent. In conclusion, DIOS inhibits cell proliferation and induces apoptosis in HepG2 cells via regulation of the mTOR pathway. Thus, the results of the current study indicate that DIOS may present a potential therapeutic agent for HCC treatment.

Diosmetin prevents TGF-β1-induced epithelial-mesenchymal transition via ROS/MAPK signaling pathways

AIMS

Epithelial-mesenchymal transition (EMT) plays a critical role in airway repair and remodeling in many respiratory diseases such as asthma and pulmonary fibrosis. The flavone aglycone, diosmetin, possesses anti-remodeling activity in a murine model of chronic asthma, but little is known about its effects on EMT. Herein, we investigated whether diosmetin inhibits transforming growth factor-β1 (TGF-β1)-induced EMT with underlying mechanisms in human bronchial epithelial (HBE) cells.

MAIN METHODS

HBE cells were incubated with TGF-β1 (10ng/ml), either alone or in combination with diosmetin for indicated times. We measured reactive oxygen species (ROS) levels using FACScan and immunofluorescent assays. We assessed protein expression of NADPH oxidase 4 (NOX4), superoxide dismutase (SOD), catalase, Akt, Erk, p38, and phosphorylation levels of Akt, Erk and p38 by Western blot analysis.

KEY FINDINGS

TGF-β1 promoted EMT and ROS generation in HBE cells. Diosmetin significantly suppressed TGF-β1-induced increases in cell migration and altered N-cadherin, E-cadherin, and α-smooth muscle actin expression. In addition, diosmetin prevented TGF-β1-induced intracellular ROS generation, down-regulated NOX4, and up-regulated SOD and catalase expression. Furthermore, diosmetin remarkably inhibited TGF-β1-induced phosphorylation of phosphoinositide 3-kinase (PI3K)/Akt and mitogen activated protein kinase (MAPK) pathways in HBE cells.

SIGNIFICANCE

Our results demonstrate for the first time that diosmetin alleviates TGF-β1-induced EMT by inhibiting ROS generation and inactivating PI3K/Akt and MAPK pathways. Our findings revealed a new role for diosmetin in reducing airway remodeling and fibrogenesis.

Diosmetin inhibits the metastasis of hepatocellular carcinoma cells by downregulating the expression levels of MMP-2 and MMP-9

Hepatocellular carcinoma (HCC) is one of the most malignant types of tumor worldwide with a high rate of mortality. Diosmetin (DIOS) exhibits various activities, including anticancer activities. However, the role of DIOS in the metastasis of HCC, and its underlying molecular mechanism, remain to be fully elucidated. In the present study, the antimetastatic effects of DIOS were investigated in SK‑HEP‑1 and MHcc97H HCC cell lines. Cell proliferation, wound healing, motility, invasion and adhesion capacities were examined to evaluate the inhibitory effect of DIOS on the metastasis of HCC cells. Cell viability was detected using an MTT assay in order to verify the inhibitory effect of DIOS on the proliferation of HCC cells. Cell migration was assessed using would healing and motility assays in order to verify the inhibitory effect of DIOS on the migration of HCC cells. Cell invasion and adhesion assays were performed in order to verify the inhibitory effect of DIOS on the invasion and adhesion of HCC cells. Matrix metalloproteinase (MMP)‑2/9, proteins of the mitogen‑activated protein kinase (MAPK) pathway (c‑Jun N‑terminal kinase, extracellular signal‑regulated kinase and p38 MAPK) and protein kinase C‑δ were detected in order to verify the potential molecular mechanisms of DIOS in the inhibition of the metastasis of HCC cells. DIOS was observed to inhibit the metastasis of SK‑HEP‑1 and MHcc97H cells by downregulating the expression of MMP‑2/9 via the PKC/MAPK/MMP pathways. DIOS also inhibited the migration and invasion of the HCC cells, and may serve as a potential candidate agent for the prevention of HCC metastasis.

Effect of diosmetin on airway remodeling in a murine model of chronic asthma

Bronchial asthma, one of the most common allergic diseases, is characterized by airway hyperresponsiveness (AHR), inflammation, and remodeling. The anti-oxidant flavone aglycone diosmetin ameliorates the inflammation in pancreatitis, but little is known about its impact on asthma. In this study, the effects of diosmetin on chronic asthma were investigated with an emphasis on the modulation of airway remodeling in BALB/c mice challenged with ovalbumin (OVA). It was found that diosmetin significantly relieved inflammatory cell infiltration, goblet cell hyperplasia, and collagen deposition in the lungs of asthmatic mice and notably reduced AHR in these animals. The OVA-induced increases in total cell and eosinophil counts in bronchoalveolar lavage fluid were reversed, and the level of OVA-specific immunoglobulin E in serum was attenuated by diosmetin administration, implying an anti-Th2 activity of diosmetin. Furthermore, diosmetin remarkably suppressed the expression of smooth muscle actin alpha chain, indicating a potent anti-proliferative effect of diosmetin on airway smooth muscle cells (ASMCs). Matrix metallopeptidase-9, transforming growth factor-β1, and vascular endothelial growth factor levels were also alleviated by diosmetin, suggesting that the remission of airway remodeling might be attributed to the decline of these proteins. Taken together, our findings provided a novel profile of diosmetin with anti-remodeling therapeutic benefits, highlighting a new potential of diosmetin in remitting the ASMC proliferation in chronic asthma.