Predator-prey coevolution: Australian native bees avoid their spider predators.
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Australian crab spiders Thomisus spectabilis manipulate visual flower signals to lure introduced Apis mellifera. We gave Australian native bees, Austroplebia australis, the choice between two white daisies, Chrysanthemum frutescens, one of them occupied by a crab spider. The colour contrast between flowers and spiders affected the behaviour of native bees. Native bees approached spider-occupied flowers more frequently. However, native bees avoided flowers occupied by spiders and landed on vacant flowers more frequently. In contrast to honeybees that did not coevolve with T. spectabilis, Australian native bees show an anti-predatory response to avoid flowers occupied by this predator. (+info)
Xanthine oxidase inhibitory activity of Vietnamese medicinal plants.
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Among 288 extracts, prepared from 96 medicinal plants used in Vietnamese traditional medicine to treat gout and related symptoms, 188 demonstrated xanthine oxidase (XO) inhibitory activity at 100 microg/ml, with 46 having greater than 50% inhibition. At 50 microg/ml, 168 of the extracts were active, with 21 possessing more than 50% inhibition. At 25 microg/ml, 146 extracts exhibited inhibitory activity, with 8 showing over 50% inhibition, while 126 extracts presented activity at 10 microg/ml, with 2 having greater than 50% inhibition. The MeOH extracts of Artemisia vulgaris, Caesalpinia sappan (collected at the Seven-Mountain area), Blumea balsamifera (collected in Lam Dong province), Chrysanthemum sinense and MeOH-H(2)O extract of Tetracera scandens (Khanh Hoa province) exhibited strong XO inhibitory activity with IC(50) values less than 20 microg/ml. The most active extract was the MeOH extract of the flower of C. sinense with an IC(50) value of 5.1 microg/ml. Activity-guided fractionation of the MeOH extract led to the isolation of caffeic acid (1), luteolin (2), eriodictyol (3), and 1,5-di-O-caffeoylquinic acid (4). All these compounds showed significant XO inhibitory activity in a concentration-dependent manner, and the activity of 2 was more potent (IC(50) 1.3 microM) than the clinically used drug, allopurinol (IC(50) 2.5 microM). (+info)
Acacetin inhibits cell growth and cell cycle progression, and induces apoptosis in human prostate cancer cells: structure-activity relationship with linarin and linarin acetate.
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This study was carried out to assess the anticancer efficacy of linarin (LN), linarin acetate (LA) and acacetin (AC), the flavonoid compounds with the same flavone ring structure but different substitution, against human prostate cancer (PCA), LNCaP and DU145 cells. LN was isolated and purified from Chrysanthemum zawadskii; LA was chemically synthesized from LN, and AC obtained commercially. In each case, the cells were treated with these agents at 25-100 microM doses for 24-72 h. LN and LA showed moderate cell growth inhibition with different time kinetics as compared to AC. LN caused up to a 5-fold increase in cell death and LA enhanced cell death by up to 4-fold with the increase in treatment time in both cell lines. AC showed a time- as well as dose-dependent stronger cell growth inhibition (20-70%) accompanied by cell death as compared to LN and LA in both the cell lines. LN or LA did not show any profound effect on cell cycle arrest except for a moderate G1 arrest, whereas, AC showed a stronger G1 and/or G2-M arrest depending on the doses and treatment times. G1 arrest was associated with an increase in Cip1/p21 and a decrease in CDK2, CDK4 and CDK6 protein levels. G2-M arrest was associated with a decrease in Cdc25C, Cdc2/p34 and cyclin B1, which were more prominent in LNCaP compared to DU145 cells. LN, LA and AC induced cell death was associated with significant increase in apoptosis induction (up to 5-6-fold) accompanied by poly-(ADP-ribose) polymerase cleavage. Overall, AC showed more potent anticancer efficacy among these three flavonoids, which was diminished when its flavone ring was modified by disaccharide rhamnose substitution at C7 (LN) or acetylation of this substituted group (LA). These findings, for the first time, revealed the structural determinants in anticancer efficacy and mechanisms of these three flavonoids against human PCA cells. (+info)
Effects of cor15a-IPT gene expression on leaf senescence in transgenic Petunia x hybrida and Dendranthema x grandiflorum.
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To prevent leaf senescence of young transplants or excised shoots during storage under dark and cold conditions, the cytokinin biosynthetic gene isopentenyl transferase (ipt) was placed under the control of a cold-inducible promoter cor15a from Arabidopsis thaliana and introduced into Petunia x hybrida 'Marco Polo Odyssey' and Dendranthema x grandiflorum (chrysanthemum) 'Iridon'. Transgenic cor15a-ipt petunia and chrysanthemum plants and excised leaves remained green and healthy during prolonged dark storage (4 weeks at 25 degrees C) after an initial exposure to a brief cold-induction period (4 degrees C for 72 h). However, cor15a-ipt chrysanthemum plants and excised leaves that were not exposed to a cold-induction period, senesced under the same dark storage conditions. Regardless of cold-induction treatment, leaves and plants of non-transformed plants senesced under prolonged dark storage. Analysis of ipt expression indicated a marked increase in gene expression in intact transgenic plants as well as in isolated transgenic leaves exposed to a short cold-induction treatment prior to dark storage. These changes correlated with elevated concentrations of cytokinins in transgenic leaves after cold treatment. Cor15a-ipt transgenic plants showed a normal phenotype when grown at 25 degrees C. (+info)
Antidiabetic effect of Nitobegiku, the herb Tithonia diversifolia, in KK-Ay diabetic mice.
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Nitobegiku (the herb of Tithonia diversifolia (HEMSL) A. GRAY) has been used as a medicinal plant for diabetes. The antidiabetic effect of an 80% ethanol extract of Nitobegiku (Td) was investigated in KK-Ay-mice, an animal model of type 2 diabetes. Td (500 mg/kg body weight) reduced the blood glucose of KK-Ay mice 7 h after a single oral dose. No change in blood glucose in Td-treated normal mice (ddY) was seen. Td (500 mg/kg) reduced blood glucose in KK-Ay mice 3 weeks after a single oral dose and also significantly lowered plasma insulin in KK-Ay mice under similar conditions. Td-treated KK-Ay mouse blood glucose was significantly decreased in an insulin tolerance test. These results support the hypothesis that Td improves glucose metabolism by reducing insulin resistance. Therefore, Nitobegiku may be useful for the treatment of type 2 diabetes. (+info)
Hypouricemic effects of acacetin and 4,5-o-dicaffeoylquinic acid methyl ester on serum uric acid levels in potassium oxonate-pretreated rats.
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The effects of acacetin (1) and 4,5-O-dicaffeoylquinic acid methyl ester (2), compounds contained in the flowers of Chrysanthemum sinense SABINE, on the serum uric acid level were investigated using the rats pretreated with the uricase inhibitor potassium oxonate as an animal model for hyperuricemia. When administered per orally at doses of 20 and 50 mg/kg, 1 reduced the serum uric acid level by 49.9 and 63.9%, respectively and 2 reduced the level by 31.2 and 44.4%, respectively. On the other hand, when the same doses were given intraperitoneally, both of compounds also exhibited a dose-dependent and more marked reduction of the serum uric acid level (% reduction at 20 and 50 mg/kg were 63.0 and 95.1% in 1, respectively and 66.9 and 86.5% in 2, respectively). Furthermore, the compounds 1 and 2 inhibited the rat liver xanthine oxidase activity with IC(50) values of 2.22 muM and 5.27 muM, respectively. These results demonstrated the hypouricemic action of 1 and 2, which may be attributable to their xanthine oxidase inhibitory activity. (+info)
Ion-mediated flow changes suppressed by minimal calcium presence in xylem sap in Chrysanthemum and Prunus laurocerasus.
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After the discovery of ion-mediated changes in xylem hydraulic resistance a few years ago, a number of research papers were published that related ion-mediated flow changes in the xylem to various aspects of whole plant functioning and evolutionary diversification of vascular cells. Ion-mediated changes in xylem hydraulic resistance are commonly quantified as the percentile change in hydraulic resistance, relative to the hydraulic resistance measured using a reference fluid, usually (ultra) pure deionized water. In this research the impact was investigated of the complete absence of all ions in deionized water compared with reference fluids containing a minimal amount of free calcium on the quantification of ion-mediated flow changes in stem segments of Chrysanthemum (Dendranthemaxgrandiflorum Tzvelev) and Prunus L. (Prunus laurocerasus L.). The addition of 10 mM KCl to deionized water significantly increased flow rate in Chrysanthemum (17-24%) and Prunus L. (16%). The addition of 1 mM CaCl(2) to the reference fluid reduced this KCl-mediated increase in flow rate to 1-2% in both species. 1 mM Ca(2+) is within the lower range of Ca(2+)-concentrations normally measured in xylem sap of many plant species, and three times lower than the original Ca(2+)-concentration measured in the xylem sap of Chrysanthemum plants used for the present measurements. The present results indicate that the complete removal of cations from the xylem fluid with deionized water causes the major part of the ion-mediated flow change previously reported in the xylem of plants. It is concluded that the use of deionized water as a reference fluid should be avoided. Earlier proposed relationships between ion-mediated changes and water flow in xylem of plants should be re-evaluated if they were based on deionized water as the reference fluid. (+info)
Carotenoid cleavage dioxygenase (CmCCD4a) contributes to white color formation in chrysanthemum petals.
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The white petals of chrysanthemum (Chrysanthemum morifolium Ramat.) are believed to contain a factor that inhibits the accumulation of carotenoids. To find this factor, we performed polymerase chain reaction-Select subtraction screening and obtained a clone expressed differentially in white and yellow petals. The deduced amino acid sequence of the protein (designated CmCCD4a) encoded by the clone was highly homologous to the sequence of carotenoid cleavage dioxygenase. All the white-flowered chrysanthemum cultivars tested showed high levels of CmCCD4a transcript in their petals, whereas most of the yellow-flowered cultivars showed extremely low levels. Expression of CmCCD4a was strictly limited to flower petals and was not detected in other organs, such as the root, stem, or leaf. White petals turned yellow after the RNAi construct of CmCCD4a was introduced. These results indicate that in white petals of chrysanthemums, carotenoids are synthesized but are subsequently degraded into colorless compounds, which results in the white color. (+info)