Marcela Haun

CHEMIENERGIZED SPECIES IN PEROXIDASE SYSTEMS

Abstract— Several hemeprotein‐catalyzed reactions generate products of the type expected from the cleavage of a high energy intermediate. For some systems, the formation, in high yield, of a carbonyl compound in its excited triplet state has been firmly established on the basis of (i) equivalence of the chemiluminescence and phosphorescence spectra of the expected products; (ii) energy transfer to sensitizers containing heavy atoms and (iii) occurrence of photoproducts. The excited species appears to be generated within the enzyme and shielded from quenching by oxygen. It may be quenched, however, via long‐range triplet‐singlet energy transfer.

Photochemical-like effects in DNA caused by enzynically energized triplet carbonyl cmpounds

Abstract The same circular dichroism spectrum as that of DNA conformationally altered by UV irradiation is observed when native DNA is added to an enzymic system which produces an electronically excited triplet carbonyl compound.

Model studies of the α-peroxidase system: Formation of an electronically excited product☆

Abstract Horseradish peroxidase—as an oxidase—converts propanaldehyde to acetaldehyde and formic acid. To some extent the enzyme also acts upon linear acids, thus mimicking even better the α-peroxidase activity of higher plants. In these reactions an electronically excited species—presumably the aldehyde—is generated, as revealed by sensitized emission. The species is long-lived; in accord with its triplet nature heavy substituents are required in the acceptor for efficient sensitization. Energy transfer occurs noncollisionally and does not appear to proceed by a long-range Forster-type T-S mechanism. A long-range triplet-triplet exciton transfer to an upper triplet state of the acceptor is proposed; then ISC occurs to the fluorescent state of the acceptor. Biological compounds which might originate from excited aldehydes are pointed out.

Energy transfer from enzymically generated triplet carbonyl compounds to the fluorescent state of flavins

Abstract Enzymically generated triplet carbonyl compounds transfer energy to the fluorescent state of flavins as shown by the suppression of the carbonyl chemiphosphorescence and concomitant appearance of the flavin fluorescence. A Stern-Volmer analysis including the effect of the collisional quenching by a diene indicates that the transfer occurs by a long range process. The present results open the way to “photobiology without light”.

Photochemical oxidation of chlorpromazine in the dark induced by enzymically generated triplet carbonyl compounds

Abstract Enzymically generated triplet acetone and ethanal transfer energy to chlorpromazine as indicated by (i) suppression of the acetone chemiphosphorescence (ii) concomitant formation of chlo r promazine photoproducts, that is the radical cation and the sulfoxide (iii) inhibition of photoproduct formation by a very efficient competition for triplet carbonyl energy using the sodium salt of 9,10-dibromoanthracene-2-sulfonic acid. This is the first report of a photooxidation in the dark.

Enzymically generated triplet acetone

The oxidation of isobutyraldehyde in the horseradish peroxidase–O2 system produces triplet acetone in high yield, as shown by efficiently sensitized 9,10-dibromoanthracene-2-sulphonate emission and by the occurrence of the expected photoproducts, i.e. isopropyl alcohol and tetramethylglycol.

BINDING OF RIBOFLAVIN TO LYSOZYME PROMOTED BY PEROXIDASE-GENERATED TRIPLET ACETONE

When riboflavin and lysozyme are added to the 2‐methylpropanal/peroxidase/O2 system, which generates triplet acetone, an adduct is formed to a small extent. The adduct can be separated by gel filtration and is similar to that prepared by irradiating riboflavin in the presence of lysozyme.

Synthesis and biological activities of N,N-dimethyl-2-propen-1-amine derivatives

Summary The synthesis of several 3-(4′-bromo[1,1′-biphenyl]-4-yl)-3-(4-X-phenyl)- N,N -dimethyl-2-propen-l-amine derivatives is described. These compounds are potential trypanocide agents with relative low acute toxicities. The inhibition of growth of Escherichia coli by these drugs with different para -substitution on the phenyl moiety and their trypanocidal activities against epimastigote from Trypanosoma cruzi were investigated.

Diterpenes from Xylopia langsdorffiana inhibit cell growth and induce differentiation in human leukemia cells.

Two new diterpenes were isolated from stems and leaves of Xylopia langsdorffi ana, entatisane- 7α,16α-diol (xylodiol) and ent-7α-acetoxytrachyloban-18-oic acid (trachylobane), along with the known 8(17),12E,14-labdatrien-18-oic acid (labdane). We investigated their antitumour effects on HL60, U937 and K562 human leukemia cell lines. We found that xylodiol was the most potent diterpene in inhibiting cell proliferation of HL60, U937 and K562 cells, with mean IC50 values of 90, 80 and 50 μM, respectively. Based on the nitroblue tetrazolium (NBT) reduction assay, all the diterpenes were found to induce terminal differentiation in HL60 and K562 cells, with xylodiol being the most effective. NBT reduction was increased by almost 120% after 12 h exposure of HL60 cells to xylodiol at a concentration lower than the IC50 (50 μM). Thus, xylodiol inhibited human leukemia cell growth in vitro partly by inducing cell differentiation, and merits further studies to examine its mechanism of action as a potential antitumoural agent

Xylodiol, a New Atisane Diterpenoid from Xylopia Langsdorffiana St.-Hil. & Tul. (Annonaceae)

Abstract Two diterpenes were isolated from the leaves of Xylopia langsdorffiana, the new ent-atisane- 7α,16α-diol named xylodiol (1) and the known 8 (17),12E,14-labdatrien-18-oic acid (2). The structures of these isolates were deduced by spectroscopic data interpretation. Compound 2was less toxic than xylodiol on V79 cells and hepatocytes.