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At least 883 records · Page 49Linked to original sources
PubMed1982

Antipicornavirus flavone Ro 09-0179.

Ro 09-0179 (4',5-dihydroxy-3,3',7-trimethoxyflavone), isolated from a Chinese medicinal herb, was found to have potent antiviral activity. It selectively inhibited the replication of human picornaviruses, such as rhinoviruses and coxsackieviruses in tissue culture, but not other DNA and RNA viruses. Ro 09-0298 (4',5-diacetyloxy-3,3',7-trimethoxyflavone), an orally active derivative of Ro 09-0179, prevented coxsackievirus (B1) infection in mice. The critical time for the inhibition of rhinovirus replication by Ro 09-0179 was 2 to 4 h after virus adsorption, i.e., in the early stages of virus replication. It markedly inhibited coxsackievirus and rhinovirus RNA synthesis in infected HeLa cells, but not in a cell-free system using the RNA polymerase complex isolated from the infected cells. In the infected cells, the RNA polymerase complex was not formed in the presence of Ro 09-0179. Therefore, it is suggested that Ro 09-0179 interferes with some process of viral replication which occurs between viral uncoating and the initiation of viral RNA synthesis.

Animals↗
PubMed1987

Induction of the nodA promoter of Rhizobium leguminosarum Sym plasmid pRL1JI by plant flavanones and flavones.

An expression vector containing the Rhizobium leguminosarum nodA promoter cloned in front of the Escherichia coli lacZ gene was used to characterize the properties of the R. leguminosarum nodA gene-inducing compound(s) present in sterile root exudate of the host plant Vicia sativa L. subsp. nigra (L.). The major inducing compound was flavonoid in nature, most likely a flavanone. The commercially available flavonoids naringenin (5,7,4'-trihydroxyflavanone), eriodictyol (5,7,3'4'-tetrahydroxyflavanone), apigenin (5,7,4'-trihydroxyflavone), and luteolin (5,7,3',4'-tetrahydroxyflavone) induced the nodA promoter to the same level as the root exudate. On the basis of chromatographic properties, it was concluded that none of these compounds is identical to the inducer that is present in root exudate. The induction of the nodA promoter by root exudate and by the most effective inducer naringenin was very similar, as judged from the genetic requirements and the kinetics of induction.

Escherichia coli↗
PubMed1988

Chemotaxis of Rhizobium meliloti to the plant flavone luteolin requires functional nodulation genes.

Luteolin is a phenolic compound from plants that acts as a potent and specific inducer of nodABC gene expression in Rhizobium meliloti. We have found that R. meliloti RCR2011 exhibits positive chemotaxis towards luteolin. A maximum chemotactic response was observed at 10(-8) M. Two closely related flavonoids, naringenin and apigenin, were not chemoattractants. The presence of naringenin but not apigenin abolished chemotaxis of R. meliloti towards luteolin. A large deletion in the nif-nod region of the symbiotic megaplasmid eliminated all chemotactic response to luteolin but did not affect general chemotaxis, as indicated by swarm size on semisoft agar plates and chemotaxis towards proline in capillary tubes. Transposon Tn5 mutations in nodD, nodA, or nodC selectively abolished the chemotactic response of R. meliloti to luteolin. Agrobacterium tumefaciens GMI9050, a derivative of the C58 wild type lacking a Ti plasmid, responded chemotactically to 10(-8) M luteolin. The introduction of a 290-kilobase nif-nod-containing sequence of DNA from R. meliloti into A. tumefaciens GMI9050 enabled the recipient to respond to luteolin at concentrations peaking at 10(-6) M as well as at concentrations peaking at 10(-8) M. The response of A. tumefaciens GMI9050 to luteolin was also abolished by the presence of naringenin.

Chamomile↗
PubMed2000

Baicalin, the predominant flavone glucuronide of scutellariae radix, is absorbed from the rat gastrointestinal tract as the aglycone and restored to its original form.

When baicalin was orally administered to conventional rats, it was detected in their plasma for 24 h after administration, but baicalein, the aglycone of baicalin, was not detected. However, when baicalin was given to germ-free rats, only a small amount of baicalin was detected in their plasma within 2 h after the administration, its AUC0-lim (the area under the concentration-time curve from 0 to last determination time) being 12.0% of that in conventional rats. Subsequently, a considerable amount (55.1 +/- 6.2%) of baicalin was recovered from the gastrointestinal tract even 4 h after administration. When baicalein was orally administered to conventional rats, however, baicalin appeared rapidly in their plasma at an AUC0-lim value similar to that obtained after oral administration of baicalin, despite the absence of baicalein in plasma. When intestinal absorption was evaluated by the rat jejunal loop method, baicalein was absorbed readily, but only traces of baicalin were absorbed. Moreover, in conventional rats a small amount (13.4 +/- 3.1%) of baicalin and an appreciable amount (21.9 +/- 3.4%) of baicalein were recovered from the gastrointestinal tract even 4 h after oral administration of baicalin, but only a small amount (3.93 +/- 1.43%) of baicalein was detected in the intestinal tract 1 h after administration of baicalein. Baicalin was transformed to baicalein readily by the rat gastric and caecal contents. When baicalin was administered orally to conventional rats, an appreciable amount of baicalein was recovered in their gastrointestinal tracts. Moreover, baicalein was efficiently conjugated to baicalin in rat intestinal and hepatic microsomes. These results indicate that baicalin itself is poorly absorbed from the rat gut, but is hydrolysed to baicalein by intestinal bacteria and then restored to its original form from the absorbed baicalein in the body.

Administration, Oral↗
PubMed2007

Efflux of baicalin, a flavone glucuronide of Scutellariae Radix, on Caco-2 cells through multidrug resistance-associated protein 2.

Baicalin and its aglycone, baicalein, being are strong antioxidants and have various pharmacological actions. Baicalein has shown a unique metabolic fate in rat intestine, being excreted into the intestinal lumen from mucosal (epithelial) cells following glucuronidation of baicalein absorbed after oral administration. The purpose of this study was to examine the absorption and excretion of baicalin and baicalein in a Caco-2 cell monolayer model to evaluate the disposition of baicalin and baicalein in the human intestine. When baicalein at 5 microM was loaded on the apical side of the Caco-2 cell monolayer, baicalein was not transferred to the basolateral side, but more baicalin was excreted onto the apical side than was being absorbed onto the basolateral side. The amount of baicalin recovered on both sides accounted for more than 90% of the baicalein absorbed from the apical surface. This was supported by the fact that Caco-2 cell microsomes showed UDP-glucuronate glucuronosyltransferase activity towards baicalein to form baicalin. On the other hand, when baicalein was loaded at higher concentrations, baicalin excretion became saturated, and then baicalein was transferred to the basolateral side. Furthermore, baicalin efflux was not inhibited by MDR1/P-glycoprotein substrates such as ciclosporin and vinblastine, but significantly inhibited by multidrug resistance-associated protein 2 (MRP2, ABCC2) substrates such as probenecid and genistein. MRP2 was also detected in Caco-2 cells by Western blotting using specific antibodies. In addition, baicalin, but not baicalein, enhanced dose-dependently the vanadate-sensitive ATPase activity of human MRP2. These results indicated that, in Caco-2 cells, any baicalein absorbed after loading at low concentrations of baicalein was not transferred to the basolateral side, but was first transformed into baicalin in the cells and excreted through the action of MRP2, mainly to the apical side.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed1996

[The constituents of Taxillus kaempferi and the host, Pinus thunbergii. I. Catechins and flavones of Taxillus kaempferi].

Four flavonoid compounds, avicularin (1), hyperin (2), quercitrin (3), taxillusin (4), were isolated from leaves of Taxillus kaempferi, and three catechin compounds, (+)-catechin (6), procyanidin B-1 (7), procyanidin B-3 (8), showing a reddish purple color on the reaction with Ehrlich reagent, were also isolated from the stems. Each of these seven isolated compounds were identified by comparing the spectral data with those of the references. Compound 8 was examined to substantiate the stereochemical configurations of conformer, a and b in the detailed 1H-nuclear magnetic resonance (1H-NMR) spectrum using the nuclear Overhauser effect (NOE) difference spectroscopy and spin decoupling experiment in the acetone-d6 solution.

Biflavonoids↗
PubMed2002

Luteolin, a flavone, does not suppress postprandial glucose absorption through an inhibition of alpha-glucosidase action.

In order to clarify the postprandial glucose suppression via alpha-glucosidase (AGH) inhibitory action by natural compounds, flavonoids were examined in this study. Among the flavonoids (luteolin, kaempferol, chrysin, and galangin), luteolin showed the potent maltase inhibitory activity with the IC50 of 2.3 mM, while less inhibitions were observed against sucrase. In addition, the effects of maltase inhibition by flavonoids were observed in the descending order of potency of luteolin > kaempferol > chrysin > galangin. Apparently, the AGH inhibition power greatly increased with the replacement of hydroxyl groups at 3' and 4'-position of the B-ring. However, the inhibitory power of luteolin was poorer than a therapeutic drug (acarbose: IC50; 430 nM). As a result of a single oral administration of maltose or sucrose (2 g/kg) in SD rats, no significant change in blood glucose level with the doses of 100 and 200 mg/kg of luteolin was observed. These findings strongly suggested that luteolin given at less than 200 mg/kg did not possess the ability to suppress the glucose production from carbohydrates through the inhibition of AGH action in the gut.

Animals↗