This study was undertaken to measure the liberation in vitro of ellagic acid [2], a naturally occurring inhibitor of carcinogenesis, from precursor ellagitannins under conditions found in the gut tract. Enzymes, namely beta-glucosidase, esterases, and alpha-amylase, were incubated with raspberry extract. In addition, raspberry extract and casuarictin [1] were treated at different pH's and with the contents of small intestine and cecum from rats fed AIN-76A diet. The esterase activity of the enzyme samples was measured spectrophotometrically using p-nitrophenol acetate as the substrate, and the amount of ellagic acid [2] released from all samples was analyzed by hplc. The hydrolysis of the ellagitannins was not catalyzed by any of the purified enzymes tested, and components of the raspberry extract were found to inhibit the purified esterases noncompetitively. Casuarictin [1] was hydrolyzed to yield high quantities of ellagic acid [2] when placed in buffer at pH 7 and 8, or when incubated with cecal contents for two hours. The release of ellagic acid [2] from the raspberry extract was optimal at pH 8, and maximal release in cecal contents occurred with 1 h. Small intestinal contents had no significant effect on ellagic acid liberation from either casuarictin [1] or raspberry extract.

A new class of aromatic fumaronitrile core-based compounds with different donors and linkers has been synthesized and well characterized. Compounds 1 and 2 have indole and 2-phenylindole groups as electron donors, respectively. Compounds 3 and 4 have a diphenylamino group as the electron donor, and compound 5 has a 3,6-di-tert-butylcarbazole group as an electron donor. These compounds absorb in the blue-to-green region and emit in the blue-to-red region depending on the electron donor, linker, and solvents. The quantum yields of fluorescence of these compounds in solution are measured and found to be moderate, but in solid states, they are high. These compounds display strong emission solvatochromism that is reflected by a large shift in their fluorescence emission maxima on changing the solvents. This change is accompanied by a successive decrease in fluorescence intensity. The fluorescence lifetimes of these compounds are measured in different solvent and found to vary from <1 to 7 ns. Optical switching of these compounds with solvents, concentration, and excitation energy have been studied. The correlation between the functional group and optical properties has been established to some extent. The ability of these compounds to function as colorimetric and luminescence pH sensors is demonstrated with color changes and luminescence switching upon the addition of trifluoroacetic acid. The potentiality of these compounds for application in optoelectronics has been optically assessed.

A new mixed-ligand polypyridylruthenium(II) complex, [Ru(bpy) 2 L]Cl 2 , has been prepared where bpy ) 2,2′-bipyridine and L ) 3,5-dicarboxy-2,2′-bipyridine. The ligand L is a non-symmetrically-substituted 2,2′-bipyridine having two hydrophilic carboxylate groups located at the 3-and 5-positions of only one of its two pyridyl rings. In acetonitrile, the photophysical properties of the metal complex include a long-lived excited state (λ em ) 637 nm, τ) 846 ( 11 ns, φ ) 0.046 at 295 K) whose decay involves an activated crossing to higher energy ligand field states (E a ) 4170 ( 200 cm -1 ). This behavior is similar to that observed for other ruthenium tris(bipyridyl) compounds. In contrast, the title compound displays several unusual photophysical properties in aqueous solution. These include a strongly red-shifted emission (λ em ) 685 nm) having a short, pH-dependent lifetime which is quenched by an excited-state proton transfer from solvent. The completely deprotonated form of the molecule is the dominant emissive species. Surprisingly, under neutral conditions the excited-state lifetime increases with increasing temperature, from a value of τ ) 54 ( 1 ns (λ em ) 686 nm, φ em ) 0.0036) at 280 K to τ ) 75 ( 1 ns (λ em ) 675 nm, φ em ) 0.0053) at 360 K. The data are fit to the Arrhenius expression to give E a ) -270 ( 15 cm -1 in H 2 O and E a ) -178 ( 10 cm -1 in D 2 O. Thermochromic emission data and temperature-induced energy-gap law behavior indicate that the unique photophysical properties of this compound are due to specific interactions involving protic solvent.

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