Concentration-dependent influence of quercetin on nodulation process and the main characteristics of soybean inoculated with Bradyrhizobium japonicum

Soybean plants cv. Corsoy were grown in greenhouse conditions on sterilized quartz sand. They were inoculated with Bradyrhizobium japonicum, strain 542. The plants were treated with different concentrations of quercetin (ranging from 10 nM to 1M) at regular intervals during the experiment. The experiment was terminated at flower development. The following parameters, important for symbiosis efficiency were determined: shoot, root and nodule weights, nodule number, total leghemoglobin in the nodules,total nitrogen and soluble protein concentrations in shoots and roots, as well as chlorophyll concentration in the leaves.The results obtained partly confirmed the earlier findings that quercetin inhibits nodulation since increasing quercetin concentration decreased the number of nodules. However, at very low concentrations, quercetin stimulated the number of nodules. Quercetin also exerted a stimulating influence on other characteristics of the plant and nodules which did not correlate with nodule number and quantity of N fixed. These are: nodule weight, leghemoglobin concentration, total soluble protein content in shoots and roots as well as shoot and root weight.     

Temperature-allelochemical interactive effects on performance ofManduca sexta caterpillars from its host and certain nonhosts

A series of experiments was conducted to ascertain the effects of temperature and allelochemicals on the performance of an insect herbivore, with the goal of methodically expanding the cumulative data set on interactive effects of temperature and allelochemicals. The allelochemicals examined were caffeine, chlorogenic acid, quercetin, tannic acid and tomatine with the thermal regimes 20:15 °C versus 30:15 °C. Growth, molting time and food utilization efficiencies of third instar tobacco hornworms (Manduca sexta (L.)) were measured. Our results indicated that reductions in developmental rate by the phenolics were primarily due to effects occurring around and during molt initiation, that different phenolics may affect molt processes differently, and that some of the effects of the phenolics were a function of temperature, with greater negative effects at cool temperature. Negative effects of caffeine were most pronounced earlier in the stadium rather than during molt processes and, for some variables, the effect of caffeine was also a function of temperature.     

Functional properties of anti-inflammatory substances from quercetin-treated Bifidobacterium adolescentis

Abstract

The genus Bifidobacterium is well known to have beneficial health effects. We discovered that quercetin and related polyphenols enhanced the secretion of anti-inflammatory substances by Bifidobacterium adolescentis. This study investigated characteristics of the anti-inflammatory substances secreted by B. adolescentis. The culture supernatant of B. adolescentis with quercetin reduced the levels of inflammatory mediators in activated macrophages. Spontaneous quercetin degradant failed to increase anti-inflammatory activity, while the enhancement of anti-inflammatory activity by quercetin was sustained after washout of quercetin. Physicochemical treatment of the culture supernatant indicated that its bioactive substances may be heat-stable, non-phenolic, and acidic biomolecules with molecular weights less than 3 kDa. Acetate and lactate have little or no effect on nitric oxide production. Taken together, the anti-inflammatory substances secreted by B. adolescentis may be small molecules but not short chain fatty acids. In agreement with these findings, stearic acid was tentatively identified as a bioactive candidate compound.     

Neuroprotection by quercetin via mitochondrial function adaptation in traumatic brain injury: PGC‐1α pathway as a potential mechanism

The aim of this study was to investigate the neuroprotective effects of quercetin in mouse models of traumatic brain injury (TBI) and the potential role of the PGC‐1α pathway in putative neuroprotection. Wild‐type mice were randomly assigned to four groups: the sham group, the TBI group, the TBI+vehicle group and the TBI+quercetin group. Quercetin, a dietary flavonoid used as a food supplement, significantly reduced TBI‐induced neuronal apoptosis and ameliorated mitochondrial lesions. It significantly accelerated the translocation of PGC‐1α protein from the cytoplasm to the nucleus. In addition, quercetin restored the level of cytochrome c, malondialdehyde and superoxide dismutase in mitochondria. Therefore, quercetin administration can potentially attenuate brain injury in a TBI model by increasing the activities of mitochondrial biogenesis via the mediation of the PGC‐1α pathway.     

Quercetin augments apoptosis of canine osteosarcoma cells by disrupting mitochondria membrane potential and regulating PKB and MAPK signal transduction

Osteosarcoma is a mesenchymal malignant bone tumor accompanied by a high rate of lung metastasis and short survival in dogs. Although various therapies have been reported, the etiological mechanism of osteosarcoma remains undetermined and the development of novel therapeutic agents is warranted. In this study, we have reported the diverse functions of quercetin, one of the well-known flavonoid, in D-17 and DSN (canine osteosarcoma) cell lines. Current results indicate that quercetin decreases proliferative properties and increases programmed cell death, in addition to altering the cell cycle, mitochondrial depolarization, level of reactive oxygen species, and concentration of cytoplasmic calcium in both cells. Furthermore, it was observed that quercetin suppresses phosphorylation of AKT, P70S6K, and S6 proteins and upregulates phosphorylation of ERK1 or 2, P38, c-Jun N-terminal kinase, and P90RSK proteins in both cell lines. Collectively, we suggest that quercetin can be used as a pharmacological agent for suppressing the proliferation and inducing the apoptosis of canine osteosarcoma cells.     

Inhibition of heat shock proteins (HSP) expression by quercetin and differential doxorubicin sensitization in neuroblastoma and Ewing's sarcoma cell lines

Neuroblastoma (NB) and Ewing's sarcoma (ES) represent the most common extracranial solid tumors of childhood. Heat shock proteins (HSP) are elevated in cancer cells and their over-expression was correlated to drug-resistance. In this work we identified the HSP by a sensitive proteomic analysis of NB and ES cell lines, then, we studied the HSP response to doxorubicin. Some identified HSP were constitutively more expressed in NB than in ES cells. Doxorubicin-stimulated HSP response only in NB cells. Quercetin was found to inhibit HSP expression depleting heat shock factor 1 (HSF1) cellular stores. Quercetin caused a higher anti-proliferative effect in NB (IC₅₀: 6.9 ± 5.8 μmol/L) than in ES cells (IC₅₀: 85.5 ± 53.1 μmol/L). Moreover, quercetin caused a very pronounced doxorubicin sensitizing effect in NB cells (241 fold IC₅₀ decrease) and a moderate effect in ES cells. HSP involvement in NB cells sensitization was confirmed by the silencing of HSF1. Quercetin treatment and HSF1 silencing increased the pro-apoptotic effect of doxorubicin. In conclusion, the higher HSP levels, observed in NB cells, did not confer increased resistance to doxorubicin; on the contrary, HSP inhibition by quercetin or gene silencing caused higher sensitization to doxorubicin. These results may have a potential application in the treatment of NB.     

Chemistry of toxic range plants. Highly oxygenated flavonol methyl ethers from Gutierrezia microcephala

The perennial American desert shrub, Gutierrezia microcephala, contains 20 flavonol methyl ethers displaying nine different oxygenation patterns. These include 11 new flavonols: 5,7-dihydroxy-3,6,8,3′,4′,5′-hexamethoxyflavone, 5,7,4′-trihydroxy-3,6,8,3′,5′-pentamethoxyflavone, 5,7,3′-trihydroxy-3,6,8,4′,5′-pentamethoxyflavone, 5,7,2′,4′-tetrahydroxy-3,6,8,5′-tetramethoxyflavone, 5,7,3′,4′-tetrahydroxy-3,6,8-trimethoxyflavone, 5,7,8,3′,4′-pentahydroxy-3,6-dimethoxyflavone, 3,5,7,3′,4′-pentahydroxy-6,8-dimethoxyflavone, 5,7,4′-trihydroxy-3,6,8-trimethoxyflavone, 5,7,8,4′-tetrahydroxy-3,3′-dimethoxyflavone, 5,7,8,3′,4′-pentahydroxy-3-methoxyflavone and 5,7,8,4′-tetrahydroxy-3-methoxyflavone. In addition, the following known flavonols were isolated: 5,7-dihydroxy-3,8,3′,4′,5′-pentamethoxyflavone, 5,7,4′-trihydroxy-3,8-dimethoxyflavone, 5,7,4′-trihydroxy-3,8,3′-trimethoxyflavone, 5,7,3′,4′-tetrahydroxy-3,8-dimethoxyflavone, 5,7,4′-trihydroxy-3,6,3′-trimethoxyflavone, 5,7,3′,4′-tetrahydroxy-3-methoxyflavone, 5,4′-dihydroxy-3,6,7,8,3′-pentamethoxyflavone, 5,7,4′-trihydroxy-3,6,8,3′-tetramethoxyflavone and 3,5,7,4′-tetrahydroxy-6,8,3′-trimethoxyflavone.     

Flavonol 3-glycosides from the leaves of Flemingia stricta

A new glycoside, tamarixetin 3-rhamnoside together with kaempferol 3-rhamnoside, mearnsetin 3-rhamnoside, quercetin 3-rhamnoside, myricetin 3-rhamnoside and sitosterol glucoside, was identified from the leaves of Flemingia stricta