Dihydroxyflavone Research Articles

Bioactivity of a dihydroxy flavone produced by Penicillium EU0013 against the wilt pathogen of tomato

Bioassay-guided isolation of a dihydroxy flavone from the cell extract of Penicillium EU0013 was carried out using preparative LCMS and the structure was interpreted using 1D and 2D NMR spectra. The fungus was fermented in three different nutrient media i.e. Glucose Nutrient Broth, Glucose Peptone Yeast Broth, and Yeast Extract Broth and the cell extract was obtained using organics. Comparative LCMS profiles of the fungus confirmed the enhanced production of dihydroxy flavone in GPYB media. In this study, the pathogenicity of the dihydroxy flavone is reported for the first time against Fusarium oxysporum f.sp. lycopersici, wilt causing pathogen of a tomato plant. In MIC experiments, the compound inhibited the pathogen at 80 µg mL−1. Molecular docking studies of the compound with Fol tomatinase showed five binding interactions. These docking studies may help explore dihydroxy flavones as a lead for developing new fungicides to prevent wilt disease in tomatoes.

Down-regulation of iron/zinc ion transport and toxin synthesis in Microcystis aeruginosa exposed to 5,4′-dihydroxyflavone

Flavonoids, common natural polyphenolic compounds from plants, have been proposed as highly effective and safe algicides. However, the molecular mechanism of flavonoids inhibiting Microcystis aeruginosa remains unclear. This study aims in exploring the global transcriptional changes and molecular docking in cyanobacterial cells in response to flavonoids. Transcriptomic analysis revealed that 5,4′-dihydroxyflavone (DHF) primarily affected the genes transcription of iron and zinc ion transport, resulting in the blockage of transport for iron (II), iron (III) and zinc (II), which eventually led to a decrease in intracellular iron and zinc content. 5,4′-DHF can also interfere with iron and zinc transport by binding to metal ion transport-related proteins, leading to eliminated biological activities in M. aeruginosa. Meanwhile, 5,4′-DHF inhibit microcystin synthesis and reduce the content of intercellular toxin by inhibiting the transcription of mcyC and binding with McyC protein, implying that 5,4′-DHF have potential to reduce the risk of microcystins in the environment. Moreover, iron starvation and down-regulation of photosynthesis-related genes transcription led to the inhibition of electron transport in photosynthetic system. These results provide more information for the inhibitory mechanism of flavonoids, and the inhibition of flavonoids on metal ion transmembrane transport provides a new perspective for the development of allelochemical algicides.

Ameliorative Effects of 5-7, Dihydroxy Flavone (Chrysin) on Hippocampus of Wistar Rats with Doxorubicin-induced Cognitive Impairment

Concern is increasing regarding the effect of chemotherapy induced cognitive impairment on oncology patients. This sought to investigate the effect of 5-7, dihydroxyflavone on the hippocampus of wistar rats with Doxorubicin induced cognitive impairment. 30 male Wistar rats were procured and acclimatized for 14 days with feed and water, they were divided into six (6) experimental groups of five (5) animals each. Group 1 served as normal control. Group 2 was induced with 2mg/kg of DOX and was untreated. Group 3 received 150mg/kg of Chrysin. Groups 4, 5 and 6 were induced with 2mg/kg of doxorubicin and treated with Chrysin at doses of 50mg/kg, 100mg/kg, and 150mg/kg respectively. The study lasted for 21 days. The body weight of the animals were recorded three (3) times before and after induction and then recorded again at the end of the 21 days treatment. At the end of the experiment, there were significantly increase in body weight. The increase was more pronounce in group 1 and group 2. In the oxidative stress analysis and ELISA analysis on the levels of inflammatory cytokines (IL-1 & IL-6), there was a significant increase in the levels compared to the control group 1. In the neurobehavioural test, group 6 had a high spontaneous alternation percentage compared to other groups. The treatment with Chrysin significantly had an ameliorative effect on the treated animal groups and in group 3. The result from this work suggest that Chrysin extract had an ameliorative effect on cognitive impairment of the hippocampus.

Computational analysis to define efficacy & molecular mechanisms of 7, 4'- Dihydroxyflavone on eosinophilic esophagitis: Ex-vivo validation in human esophagus biopsies.

Eosinophilic Esophagitis (EoE) is a chronic condition characterized by eosinophilic inflammation of the esophagus which leads to esophageal dysfunction with common symptoms including vomiting, feeding difficulty, dysphagia, abdominal pain. Current main treatment options of EoE include dietary elimination and swallowed steroids. Diet elimination approach could lead to identifying the trigger food(s), but it often requires repeated upper endoscopy with general anesthesia and potentially could negatively affect nutrition intake and growth of the child and individuals' quality of life. Although the swallowed steroid treatment of effective, the EoE will universally recur after discontinuation of the treatment. Digestive Tea formula (DTF) has been used by the Traditional Chinese Medicine (TCM) practice to improve GI symptoms in EoE patients, including abdominal pain, GE reflux, and abnormal bowel movement. Previously, a flavonoid small molecule compound 7, 4 dihydroxy flavone (DHF) from Glycyrrhiza uralensis in DTF inhibited eotaxin, Th2 cytokine and IgE production in vitro and in vivo. This study comprehensively evaluates the potential therapeutic and immunological mechanisms underlying DHF improvement of symptoms related to EoE using computational modeling, including target mining, gene ontology enrichment, pathway analyses, protein-protein interaction analyses, in silico molecular docking and dynamic simulation followed by ex-vivo target validation by qRT-PCR using cultured human esophagus biopsy specimen with or without DHF from patients with EoE. Computational analyses defined 29 common targets of DHF on EoE, among which TNF-α, IL-6, IL1β, MAPK1, MAPK3 and AKT1 were most important. Docking analysis and dynamic simulation revealed that DHF directly binds TNF-α with a free binding energy of -7.7 kcal/mol with greater stability and flexibility. Subsequently, in the human esophagus biopsy culture system, significant reduction in levels of TNF-α, IL-6, IL-8 and IL1-β was found in the supernatant of biopsy sample cultured with DHF. Furthermore, the gene expression profile showed significant reduction in levels of TNF-α, IL1-β, IL-6, CCND and MAPK1 in the esophagus biopsy sample cultured with DHF. Taken together, the current study provides us an insight into the molecular mechanisms underlying multi-targeted benefits of DHF in the treatment of EoE and paves the way for facilitating more effective EoE therapies.

Preliminary trials of the gold nanoparticles conjugated chrysin: An assessment of anti-oxidant, anti-microbial, and in vitro cytotoxic activities of a nanoformulated flavonoid

Abstract Chrysin (CHR), a dihydroxy flavone, exhibits several bioactivities, i.e., anti-oxidant, anti-inflammatory, and anti-cancer, and is known to possess limited aqueous solubility causing lowered bioavailability, and compromised therapeutic efficacy. Gold nanoparticles (AuNPs) conjugated chrysin (CHR–AuNPs) were prepared and characterized by UV-Vis, Fourier transform infra-red, X-ray diffraction, energy dispersive X-ray (EDX), and zeta potential analyses. The nanoformulated CHR–AuNPs were primarily examined on trial scale for their cytotoxic, anti-oxidant, and anti-microbial activity in comparison to the unformulated CHR. The CHR–AuNPs effectively scavenged the 2,2-diphenyl-1-picrylhydrazyl free radicals, also in comparison to CHR and AuNPs. The CHR–AuNPs also exhibited potential cytotoxic effects in a dose-dependent manner and demonstrated significant reduction (P = 0.05) of the cells proliferation, and growth of the human breast cancer cell lines, AMJ13, which were measured by 3-(4,5-dimethylthiazal-z-yl)-2,5-diphenyltetrazolium, and crystal violet assays, respectively. When compared with the pure CHR and free-AuNPs, the CHR–AuNPs exerted highest anti-microbial bioactivity against Staphylococcus aureus and Escherichia coli. The strong anti-oxidant, anti-microbial, as well as cytotoxic activity of the CHR–AuNPs preparation has the potential for clinical use after considerable appropriate developments.

A Flavonoid Compound 7, 4 Dihydroxy Flavone as a Potential Therapeutic for the Treatment and Management of EoE

Eosinophilic Esophagitis (EoE) is a chronic condition characterized by esophageal dysfunction including dysphagia, abdominal pain and eosinophilic inflammation (>15/HPF) of the esophagus. At present, the most commonly used treatment for the management of EoE are steroids, both systemic as well as tropical, and dietary elimination. The advantage of the systemic steroids include ease of administration, rapid response, and very high response rate. However, poor solubility and the adverse effect related to prolonged steroid use are well documented. Moreover, there is a high relapse rate of EoE after the treatment is discontinued which limit the use of oral steroids as a maintenance therapy. Similarly, Ranitidine (Zantac), histamin‐2 blocker, used to treat gastrointestinal reflux and heart burns, has been recently withdrawn from the market by FDA due to increased risk of cancer. Digestive Tea has been used at the Traditional Chinese Medicine (TCM) practice to improve gastrointestinal (GI) symptoms such as stomach pain, constipation and abnormal bowel movement. Different versions of Digestion Teas are further developed to address specific clinical GI symptoms. Compound 7, 4 Dihydroxy flavone (DHF) is a flavonoid purified from Glycyrrhiza uralensis from Digestive Tea. Previously our group has shown inhibition of Eotaxin, Th2 cytokines and IgE in‐vitrousing DHF. The objective of this study is to reveal potential mechanisms underlying DHF improving symptoms related to EoE using computational modeling, including target mining, gene ontology enrichment, pathway analyses, protein‐protein interaction analyses, and in silico molecular docking. Based on the pathway analyses, the most important targets identified were TNF‐ α, IL‐6, IL1β, MAPK1, MAPK3, AKT1, CASP3 and CCND in AGE‐RAGE pathway. We further validated the targets of our computational modeling in human esophagus biopsy sample by ELISA and qRT‐PCR. We found significant reduction in levels of TNF‐α (p<0.001), IL‐6 (p<0.001), IL‐8 (p<0.001) and IL1‐β (p<0.05) in the supernatant of biopsy sample cultured with DHF. Moreover, gene expression profile showed significant reduction in level of TNF‐ α (p<0.01), IL1‐β (p<0.05), IL‐6 (p<0.01) and CCND (p<0.05) in the biopsy sample cultured with DHF. Furthermore, our molecular docking analysis revealed that DHF can directly bind TNF‐ α with free binding energies of ‐7.7 kcal/mol. Taken together, the current study may lead to development of DHF as an active therapeutic candidate in treatment of EoE.

7,8-Dihydroxyflavone improves neuropathological changes in the brain of Tg26 mice, a model for HIV-associated neurocognitive disorder

The combined antiretroviral therapy era has significantly increased the lifespan of people with HIV (PWH), turning a fatal disease to a chronic one. However, this lower but persistent level of HIV infection increases the susceptibility of HIV-associated neurocognitive disorder (HAND). Therefore, research is currently seeking improved treatment for this complication of HIV. In PWH, low levels of brain derived neurotrophic factor (BDNF) has been associated with worse neurocognitive impairment. Hence, BDNF administration has been gaining relevance as a possible adjunct therapy for HAND. However, systemic administration of BDNF is impractical because of poor pharmacological profile. Therefore, we investigated the neuroprotective effects of BDNF-mimicking 7,8 dihydroxyflavone (DHF), a bioactive high-affinity TrkB agonist, in the memory-involved hippocampus and brain cortex of Tg26 mice, a murine model for HAND. In these brain regions, we observed astrogliosis, increased expression of chemokine HIV-1 coreceptors CXCR4 and CCR5, neuroinflammation, and mitochondrial damage. Hippocampi and cortices of DHF treated mice exhibited a reversal of these pathological changes, suggesting the therapeutic potential of DHF in HAND. Moreover, our data indicates that DHF increases the phosphorylation of TrkB, providing new insights about the role of the TrkB–Akt–NFkB signaling pathway in mediating these pathological hallmarks. These findings guide future research as DHF shows promise as a TrkB agonist treatment for HAND patients in adjunction to the current antiviral therapies.

Indian red rice phenolic metabolites as potential natural inhibitors of SARS-CoV-2 main protease: A metabolomic and in silico study

COVID-19 is a viral respiratory infectious disease caused by the novel strain of SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2). SARS-CoV-2 main protease (M-pro) is associated with viral replication and transcription, thereby making it a potent target for combating COVID-19. Natural compounds from plants are being widely explored for viral inhibitors due to their safety aspect. Therefore, the present study aimed at predicting the antiviral property of red rice phenolic metabolites (RRPM) from three Indian rice varieties against SARS-CoV-2 M-pro through metabolomics and in silico studies. The Indian red rice cultivars, i.e., Veethi vadankan, Samba mosanam and Kuzhiadichan, were subjected to Q-TOF-LC-MS analysis and eighteen abundant polyphenols were selected using hierarchical cluster analysis. The abundant RRPM were virtually screened using Swiss ADME, a web-based tool. All the abundant polyphenols obeyed the Lipinski's rule except for hesperetin 3'-O-glucuronide, thereby exhibiting drug likeliness. Based on ADME analysis, fifteen of the RRPM showed good oral bioavailability, high GI absorption and acceptable overall bioavailability score. The 15 RRPM were further subjected to molecular docking analysis using Auto dock 1.5.6 against SARS-CoV-2M(pro). The analysis revealed 7, 4'-dihydroxy flavone and eriodictyol to have strong binding affinity (>10 kcal/mol) higher than nelfinavir (-8.53 kcal/mol). Eight other compounds also proved to be potential natural inhibitors of SARS-CoV-2 M-pro. The present study has revealed Kuzhiadichan as a good source of eight potent natural inhibitors of SARS-CoV-2 M-pro and as a potential functional food for COVID-19 management.

Formulation and Evaluation of 7, 8- Dihydroxy Flavone Loaded Topical Hydrogel Scaffold

Burnt skin tissue defects pose a significant challenge for physicians to manage owing to the limited skin regeneration potential. Various conventional approaches (i.e. autografts and allografts) have been endorsed for the restoration of tissue defects with inadequate results. However, skin tissue engineering techniques were appeared as an optimistic approach to improve the skin tissue regeneration. Hydrogels offering advantages over the current treatment modalities of the damaged skin tissue were proposed as an advanced and promising therapeutic approach for effective skin tissue regeneration. In general, an ideal hydrogel scaffold used for burnt skin tissue regeneration must show excellent biodegradability, biocompatibility and bioadhesive characteristics. Moreover, among the variety of several hydrogel scaffolds for skin tissue regeneration, topical hydrogels developed from both natural and synthetic polymers are likely to fulfil these above characteristics. In this study Novel 7, 8- Dihydroxy flavone loaded PVA/Agar hydrogel was developed using the facile physical cross-linking technique. Further, the characterization studies confirmed that this hydrogel scaffold possess an ideal porous cross linked structure along with excellent Hemocompatibility, cellular proliferation and controlled drug release. Histopathological staining’s provided further evidence for the reepithelization, and revascularization potential of the developed hydrogel scaffold. Moreover, our research findings revealed that the 7, 8- Dihydroxy flavone loaded PVA/Agar hydrogel is hemocomapatible and capable of burnt skin tissue repair and also possesses significant potential for skin tissue engineering.

Formulation and Evaluation of 7, 8- Dihydroxy Flavone Loaded Topical Hydrogel Scaffold

Burnt skin tissue defects pose a significant challenge for physicians to manage owing to the limited skin regeneration potential. Various conventional approaches (i.e. autografts and allografts) have been endorsed for the restoration of tissue defects with inadequate results. However, skin tissue engineering techniques were appeared as an optimistic approach to improve the skin tissue regeneration. Hydrogels offering advantages over the current treatment modalities of the damaged skin tissue were proposed as an advanced and promising therapeutic approach for effective skin tissue regeneration. In general, an ideal hydrogel scaffold used for burnt skin tissue regeneration must show excellent biodegradability, biocompatibility and bioadhesive characteristics. Moreover, among the variety of several hydrogel scaffolds for skin tissue regeneration, topical hydrogels developed from both natural and synthetic polymers are likely to fulfil these above characteristics. In this study Novel 7, 8- Dihydroxy flavone loaded PVA/Agar hydrogel was developed using the facile physical cross-linking technique. Further, the characterization studies confirmed that this hydrogel scaffold possess an ideal porous cross linked structure along with excellent Hemocompatibility, cellular proliferation and controlled drug release. Histopathological staining’s provided further evidence for the reepithelization, and revascularization potential of the developed hydrogel scaffold. Moreover, our research findings revealed that the 7, 8- Dihydroxy flavone loaded PVA/Agar hydrogel is hemocomapatible and capable of burnt skin tissue repair and also possesses significant potential for skin tissue engineering.

7, 8- Dihydroxyflavone, An Effective Natural Product Reduce Ralstonia solanacearum Populations and Control Tomato Bacterial Wilt

In this study, 7, 8- dihydroxyflavone (DHF) was isolated first time from medicinal plant Oroxylum indicum and its antibacterial potential against plant pathogen Ralstonia solanacearum was determined. The minimum inhibitory and bactericidal concentrations of DHF were 20 µg/mL and 80 µg/mL respectively. The biofilm formation and inhibition of DHF against R.solanacearum was investigated via scanning electron microscopy indicated that destruction of the cell wall. The inhibition of biofilm formation and molecular assays revealed that DHF binds lumen periplasm side of the outer membrane protein (EpsA) was identified. Moreover, DHF effectively reduced the bacterial wilt disease and control efficiency is as high as 89.10% at nine days after inoculation. Altogether, the antibacterial potential of DHF against R.solanacearum displayed effective agent can attenuates bacterial wilt disease in tomato plant.

Role of Some Food-Grade Synthesized Flavonoids on the Control of Ochratoxin A in Aspergillus carbonarius.

Ochratoxin A (OTA) is a mycotoxin with a serious impact on human health. In Mediterranean countries, the black Aspergilli group, in particular Aspergillus carbonarius, causes the highest OTA contamination. Here we describe the synthesis of three polyphenolic flavonoids: 5-hydroxy-6,7-dimethoxy-flavone (MOS), 5,6-dihydroxy-7-methoxy-flavone (NEG), and 5,6 dihydroxy-flavone (DHF), as well as their effect on the prevention of OTA biosynthesis and lipoxygenase (LOX) activity in A. carbonarius cultured in a conducive liquid medium. The best control effect on OTA biosynthesis was achieved using NEG and DHF. In fungal cultures treated with these compounds at 5, 25, and 50 μg/mL, OTA biosynthesis significantly decreased throughout the 8-day experiment. NEG and DHF appear to have an inhibiting effect also on the activity of LOX, whereas MOS, which did not significantly inhibit OTA production, had no effect on LOX activity. The presence of free hydroxyls in catecholic position in the molecule appears to be a determining factor for significantly inhibiting OTA biosynthesis. However, the presence of a methoxy group in C-7 in NEG could slightly lower the molecule’s reactivity increasing OTA inhibition by this molecule at 5 μg/mL. Polyphenolic flavonoids present in edible plants may be easily synthesized and used to control OTA biosynthesis.

PB-1 7, 8 Dihydroxyflavone reduces mitochondrial dysregulation in the HIV-1 transgenic mouse model as a treatment for HIV associated Neurocognitive disorder (HAND)

The introduction of combined antiretroviral therapy (cART) significantly increased the lifespan of HIV patients, turning a fatal disease to a chronic one. However, as a lower but persistent level of HIV infection remains, the susceptibility of HIV-associated neurocognitive disorder (HAND) is increased. Therefore, research is currently seeking improved treatment for this complication of HIV. 7, 8 Dihydroxyflavone (DHF) is a TrkB agonist that can cross the blood brain barrier and mimic the effect of Brain Derived Neurotrophic Factor (BDNF). Previous studies have described its potential as a treatment in a myriad of neurological diseases including Alzheimer's disease, peripheral sensory neuropathies, amyotrophic lateral sclerosis, Parkinson's disease, and Multiple Sclerosis. This study investigates mitochondrial dysregulation in the brain of HIV-1 Tg26 mice, a murine model of HIV, and the potential therapeutic effects of DHF treatment on this dysregulation in HAND. The mice were divided into 3 groups: wild type, untreated-Tg26, and DHF-treated Tg26 (Tg+DHF). Mice were sacrificed after 28 days and 7 µm thick paraffin sections of the brain of each mice were prepared. Tissues were immunohistochemically stained to detect the expression of mitochondria regulating proteins—SIRT3, PGC1-a, FIS-1, MFN-2, Citrate Synthase, SUR1, TRPM4—in the hippocampal and cortex regions. Our results show, that in these regions of Tg26 mice, SIRT3, PGC1-a, FIS-1, MFN-2, and Citrate Synthase were present in decreased levels, implicating the extensive role of mitochondrial dysfunction in HAND pathology. However, following DHF treatment, Tg26 mice expressed these cells at greater levels, suggesting a possible mechanism of DHF. Furthermore, both SUR1 and TRPM4 were upregulated in Tg26 mice. Previous studies have shown that SUR1 and TRPM4 often co-assemble to form an ion channel that plays a significant role in central nervous system injury and calcium homeostasis. Calcium is a regulator of mitochondrial dynamics, suggesting that the upregulation of SUR1 and TRPM4 may contribute to the mitochondrial changes that are characteristic to HAND. Interestingly, administration of DHF resulted in decreased expression of SUR1 and TRPM4. Therefore, the present study suggests that DHF treatment in the hippocampal and cortex regions of the TG26 model plays a role in reducing mitochondrial dysfunction by regulating calcium balance via the SUR1-TRPM4 ion channels, indicating its therapeutic potential as a treatment for HIV-associated neurocognitive disorder.

Fabrication of dihydroxyflavone-conjugated hyaluronic acid nanogels for targeted antitumoral effect.

We prepared hyaluronic acid (HA)-based nanogels conjugated with dihydroxyflavone (DHF) and evaluated their cellular uptake and antitumoral efficiency. 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM) was used as a conjugation agent for esterification between DHF and HA as well as crosslinking among HA. The conjugations were confirmed by nuclear magnetic resonance spectroscopy, UV/vis spectroscopy, and high-performance liquid chromatography. The size and Zeta-potential of the DHF/HA nanogels were reduced with an increase in the concentration of DMTMM due to the involvement of more HA molecules for the conjugation reactions. The DHF/HA nanogel with a smaller size was greatly taken up by two kinds of tumor cells (HeLa and HepG2), compared to NIH3T3. The cell viabilities were reduced to approximately 60% for HeLa and HepG2 cells after 48 h post treatment with DHF/HA nanogels.

A study on antidepressant-like effect of dihydroxy flavones in mice and their mechanisms involved

Background: In the treatment of depression, drugs with a quick onset of action and high margin of safety are intensely being searched. Previous studies indicate flavonoids as a potential source for such drugs. Hence, in the present study, four dihydroxy flavones have been selected for investigation. Aims and Objectives: The aim of this study is to investigate the potential antidepressant effect and the mechanism of action of dihydroxy flavone derivatives in mice. Materials and Methods: Mice were subjected to forced swim test and tail suspension test for 6 min. The period of immobility in these animals was recorded after treatment with different doses of 3,7-dihydroxy flavone, 3,3’-dihydroxy flavone, 6,3’-dihydroxy flavone, and 5,6–dihydroxy flavone. Interacting drugs such as para chlorophenylalanine, alpha-methyl-para-tyrosine, L-arginine, and naloxone were employed to delineate the role of various mechanisms involved in the action of these dihydroxy flavones in forced swim test. Results: A dose-dependent reduction in the immobility period of mice was recorded in both forced swim test and tail suspension test for dihydroxy flavones indicating the antidepressant-like effect of these compounds. However, 6,3’-dihydroxy flavone was found to be less effective than the other three compounds. Various interacting drugs differentially modulated the reduction of immobility period produced by dihydroxy flavones in forced swim test. Monoaminergic, opioid, and nitric oxide pathways were evident in the action of dihydroxy flavones. Conclusion: The present study identified the potential antidepressant effect of a few dihydroxy flavone derivatives involving novel mechanisms.

Intermittent Hypoxia during Gestation Disrupts Respiratory Rhythm and Neuroplasticity in Newborn Rat Brainstem‐spinal cord Preparations In Vitro

Pregnant women with sleep‐disordered breathing experience intermittent hypoxia, especially during late pregnancy. To test whether intermittent hypoxia exposures during pregnancy (G‐IH; gestational intermittent hypoxia) alter breathing in newborn rats, pregnant rats were exposed to intermittent hypoxia (2 min 10.5% oxygen / 2 min normoxia for 8 h) from gestational day 10 to 21 (exposures completed prior to birth). Newborn rats (P0–P3) were anesthetized and their brainstem‐spinal cords isolated under in vitro conditions. Spontaneous respiratory motor bursts were recorded on cervical spinal roots (C4–C5). G‐IH preparations from P0–P1 rats had a lower baseline burst frequency (8.2 +/− 0.6 bursts/min; n=10) compared to normoxic controls (11.0 +/− 0.3 bursts/min; n=21). After 90 min, burst frequency decreased with time nearly 2× times greater in G‐IH preparations compared to controls. In most G‐IH preparations, there were frequent “pauses” in the rhythm, which resembled spontaneous apneas. With respect to respiratory neuroplasticity, dihydroxyflavone (DHF) application (5 micromolar, 9 min; TrkB receptor agonist) induced long‐lasting 19% increase in respiratory motor burst amplitude in control preparations (n=5) after 90 min. However, only 2/4 G‐IH preparations expressed a DHF‐dependent increase in motor burst amplitude. Also, episodic substance‐P application (100 nanomolar, 3 min on / 7 min wash ×3) induced a long‐lasting (60‐min) increase in respiratory burst frequency in control preparations. However, there was no substance‐P induced frequency plasticity in any G‐IH preparations (n=4). These data suggest that gestational intermittent hypoxia disrupts respiratory rhythm generation and reduces the capacity for expressing respiratory neuroplasticity in newborn rats.Support or Funding InformationNIH Grant: NS085226

Continuous-release beads of natural allelochemicals for the long-term control of cyanobacterial growth: Preparation, release dynamics and inhibitory effects

The effects of allelochemicals on cyanobacterial blooms have been observed for more than 20 years; however, the use of these compounds, usually involving a "direct-added" mode, has clear disadvantages, such as a short activity period or temporarily excessive localized concentration. Here, a simulated-allelopathy mode to facilitate the application of allelochemicals was proposed and tested on Microcystis aeruginosa. The continuous-release beads of 5,4'-dihydroxyflavone (DHF) were constitutive of a polymer matrix and showed a high drug-loading rate (47.18%) and encapsulation efficiency (67.65%) with a theoretical release time of approximately 120d. Cyanobacterial growth tests showed that the DHF beads had long-term inhibition effects (>30d), whereas those of "direct-added" DHF to cells lasted a maximum of 10d. The beads also continuously affected the superoxide dismutase, catalase, and lipid peroxidation of M.aeruginosa. The inhibitory effects of DHF beads on cyanobacterial growth increased as initial cell densities of M.aeruginosa decreased, suggesting that the beads inhibit cyanobacterial activity more effectively in the early bloom phase. Consequently, the anti-cyanobacterial beads represent a novel application mode of allelochemicals with long-term inhibitory effects on cyanobacterial growth. Our study demonstrates that the successful application of allelochemicals offers great potential to control harmful cyanobacterial blooms, especially at the initial stage of development.

Fine control of drug delivery for cochlear implant applications

Cochlear implants are neuroprostheses that are inserted into the inner ear to directly electrically stimulate the auditory nerve, thus replacing lost cochlear receptors, the hair cells. The reduction of the gap between electrodes and nerve cells will contribute to technological solutions simultaneously increasing the frequency resolution, the sound quality and the amplification of the signal. Recent findings indicate that neurotrophins (NTs) such as brain derived neurotrophic factor (BDNF) stimulate the neurite outgrowth of auditory nerve cells by activating Trk receptors on the cellular surface (1–3). Furthermore, small-size TrkB receptor agonists such as di-hydroxyflavone (DHF) are now available, which activate the TrkB receptor with similar efficiency as BDNF, but are much more stable (4). Experimentally, such molecules are currently used to attract nerve cells towards, for example, the electrodes of cochlear implants. This paper analyses the scenarios of low dose aspects of controlled release of small-size Trk receptor agonists from the coated CI electrode array into the inner ear. The control must first ensure a sufficient dose for the onset of neurite growth. Secondly, a gradient in concentration needs to be maintained to allow directive growth of neurites through the perilymph-filled gap towards the electrodes of the implant. We used fluorescein as a test molecule for its molecular size similarity to DHF and investigated two different transport mechanisms of drug dispensing, which both have the potential to fulfil controlled low-throughput drug-deliverable requirements. The first is based on the release of aqueous fluorescein into water through well-defined 60-μm size holes arrays in a membrane by pure osmosis. The release was both simulated using the software COMSOL and observed experimentally. In the second approach, solid fluorescein crystals were encapsulated in a thin layer of parylene (PPX), hence creating random nanometer-sized pinholes. In this approach, the release occurred due to subsequent water diffusion through the pinholes, dissolution of the fluorescein and then release by out-diffusion. Surprisingly, the release rate of solid fluorescein through the nanoscopic scale holes was found to be in the same order of magnitude as for liquid fluorescein release through microscopic holes.

Effects of natural flavonoids on photosynthetic activity and cell integrity in Microcystis aeruginosa.

Flavonoids are natural polyphenolic compounds produced by many aquatic plants and released in their environments. In this study, the effects of several aquatic flavonoids on cyanobacterial Microcystis aeruginosa, especially in relation to the cell growth, photosynthetic activity, cell morphology, and cell membrane integrity, were investigated. Significant growth inhibition was observed when the cyanobacteria were exposed to three flavonoids, namely, 5,4'-dihydroxyflavone (DHF), apigenin, and luteolin. Luteolin reduced the effective quantum yield, photosynthetic efficiency, and maximal electron transport rate by 70%, 59% and 44%, respectively, whereas 5,4'-DHF and apigenin slightly affected these parameters, which implies that luteolin disrupts the photosynthetic system. Moreover, 5,4'-DHF and apigenin compromised the membrane integrity, and induced membrane depolarization in 52% and 38%, and permeabilization in 30% and 44% of the cells, respectively. The 5,4'-DHF and apigenin showed more pronounced effects on M. aeruginosa morphology and membrane integrity, compared to the luteolin. These results suggest that flavonoids could have significant effects on growth and physiological functions in cyanobacterial species.

A comparative photochemical study on the behavior of 3,3′-dihydroxyflavone and its complex with La(III) as generators and quenchers of reactive oxygen species

A 1:1 complex between 3,3′-dihydroxyflavone (DHF) and La(III) (DHF–La(III)) is formed in methanolic solution with the relatively high apparent stability constant value of 2.3×106 and a calculated standard entropy change of 88.2Jmol−1K−1, both at 25°C.The photophysical properties of the complex and the free flavonoid are discussed in comparison to the well known related compound 3-hydroxyflavone. The ligand photogenerates O2(1Δg) by energy transfer from its excited triplet state (3DHF*) to dissolved ground state oxygen, with a quantum yield of 0.13. 3DHF* is quenched by La(III) with a rate constant close to the diffusion-controlled value.The respective abilities of the free flavonoid and DHF–La(III) as quenchers of the riboflavin-photogenerated reactive oxygen species singlet molecular oxygen (O2(1Δg)) and superoxide radical anion (O2-) have been investigated. Both individual compounds were photoirradiated with visible light in the presence of the flavin as the only light-absorbing compound. A detailed kinetics and mechanistic study employing polarographic monitoring of oxygen uptake and time resolved detection of O2(1Δg) phosphorescence indicates that DHF and the complex react with O2(1Δg) and O2- by a non simple mechanism. The former deactivates O2(1Δg) in a predominant physical fashion, a fact that constitutes a desirable property for antioxidants. It was found that metal chelation greatly enhances the ability of DHF as an overall O2(1Δg) quencher.