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At least 487 records · Page 27Linked to original sources
PubMed1987

Inhibition of epoxide hydrolases and glutathione S-transferases by 2-, 3-, and 4-substituted derivatives of 4'-phenylchalcone and its oxide.

4'-Phenylchalcones, chalcone oxides, and related compounds were synthesized and tested as inhibitors of cytosolic epoxide hydrolase, microsomal epoxide hydrolase, and glutathione S-transferases from mouse and rat liver. Several compounds were more potent inhibitors of the cytosolic epoxide hydrolase than the parent 4'-phenylchalcone oxide while large substituents in the 4- and especially the 2-position caused a reduction in inhibition. The chalcone oxides showed selectivity as inhibitors of the cytosolic epoxide hydrolase acting on trans-stilbene oxide, while chalcones were inhibitors of cytosolic glutathione S-transferase acting on cis-stilbene oxide. Data are consistent with the hypothesis that much of the inhibition of the glutathione S-transferase is caused by the glutathione conjugate of the chalcone.

Animals↗
PubMed1989

Phytoalexin synthesis in soybean cells: elicitor induction of reductase involved in biosynthesis of 6'-deoxychalcone.

Chromatofocusing on Mono P proved to be an efficient purification procedure for the NADPH-dependent reductase from soybean (Glycine max L.) cell cultures which acts together with chalcone synthase in the biosynthesis of 2',4',4-trihydroxychalcone (6'-deoxychalcone). By isoelectric focusing the pI of reductase was determined to be 6.3. Addition of pure soybean reductase to cell-free extracts from stimulated cell cultures of parsley and bean (Phaseolus vulgaris) and from young flowers of Dahlia variabilis caused in each case synthesis of 6'-deoxychalcone. When 4-coumaroyl-CoA was replaced by caffeoyl-CoA in the reductase assay, formation of 2',4',3,4-tetrahydrochalcone (butein) was observed. A polyclonal antireductase antiserum was raised in rabbits and proved to be specific in Ouchterlony diffusion experiments, Western blots and immunotitration. The reductase antiserum showed no cross-reactivity with soybean chalcone synthase (CHS). A biotin/[125I]streptavidin system provided a quantitative Western blot for the reductase. Changes in the activities, amounts of protein, and mRNA activities of reductase and CHS were determined after challenge of soybean cell cultures by elicitor (from Phytophthora megasperma f.sp. glycinea or yeast). For both enzymes a pronounced and parallel increase in activity and amounts of protein was observed after elicitor addition with a maximum at about 16 h after challenge. Parallel increases in mRNA activities occurred earlier. The results indicate a parallel induction of de novo synthesis of reductase and CHS which coact in synthesis of 6'-deoxychalcone.

Acyltransferases↗
PubMed1983

Anti-mutagenic chalcones: antagonizing the mutagenicity of benzo(a)pyrene on Salmonella typhimurium.

Several chalcone derivatives; e.g. Ro 09-0204, Ro 09-0323 and Ro 09-0501 were found to reduce markedly the revertant increase of Salmonella typhimurium TA100 by benzo(a)pyrene during the incubation with S-9 Mix. The antimutagenic activity was 100 - 700 times stronger than that of L-ascorbic acid. Effect on other mutagens, the structure activity relationship and the possible mechanism of action are briefly discussed.

Benzo(a)pyrene↗
PubMed1984

N-acetyl-5-methoxy kynurenamine, a brain metabolite of melatonin, is a potent inhibitor of prostaglandin biosynthesis.

Although the hypothesis that melatonin may act by inhibiting prostaglandin synthesis arose in part from the similar structures of melatonin and indomethacin, melatonin does not share the in vitro efficacy of indomethacin in inhibiting prostaglandin synthesis. One possibility is that a metabolite of melatonin formed within the target cell might inhibit prostaglandin synthesis and in this study we have tested this by examining the action of the two oxidised metabolites, N-formyl-N-acetyl-5-methoxy kynurenamine formed by the action of indole 2,3-dioxygenase and N-acetyl-5-methoxy kynurenamine , formed in the brain by the action of formamidase . This latter compound which has a structure resembling the fenamate inhibitors of PG biosynthesis had a marked and time dependant inhibiting effect in synthesis using bovine and ovine seminal vesicle microsome preparations and measuring the products by using (1-14C) arachidonic acid and by using a specific antiserum for PGE methyl oxime.

Animals↗
PubMed1989

Inhibition of mouse liver sialidase by plant flavonoids.

Flavonoids (103 species) were tested for inhibitory activity against mouse liver sialidase using sodium p-nitrophenyl-N-acetyl-alpha-D-neuraminate (PNP-NeuAc) as substrate. Isoscutellarein-8-O-glucuronide from the leaf of Scutellaria baicalensis showed most potent activity (IC50, 40 microM), and this flavone appeared to be a non-competitive inhibitor of the enzyme. This flavone inhibited the lysosomal solubilized sialidase against PNP-NeuAc and sialyllactose effectively, but not microsomal enzyme against gangliosides and colominic acid, whereas, negligible or weak inhibitory activities were observed for influenza virus sialidase, beta-galactosidase, alpha-mannosidase, and alpha-glucosidase tested. These results indicate that this flavone may be useful to elucidate the function of the lysosomal solubilized sialidase.

Animals↗