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At least 721 records · Page 40Linked to original sources
PubMed2000

Increased oxidative modification of albumin when illuminated in vitro in the presence of a common sunscreen ingredient: protection by nitroxide radicals.

We previously reported on the ability of dibenzoylmethane (DBM) and a relative, Parsol 1789, used as a ultraviolet A (UVA)-absorbing sunscreen, to generate free radicals upon illumination, and as a consequence, to inflict strand breaks in plasmid DNA in vitro. This study has now been extended to determine the effects of Parsol 1789 and DBM on proteins, under UVA illumination, with the sole purpose of gaining more knowledge on the photobiological effects of sunscreen chemicals. Parsol 1789 (100 microM) caused a 2-fold increase in protein carbonyl formation (an index of oxidative damage) in bovine serum albumin (BSA) when exposed to illumination, and this damage was both concentration- and time-dependent. The degree of protein damage was markedly reduced by the presence of free radical scavengers, namely piperidinic and indolinonic nitroxide radicals, in accordance with our previous study. Vitamin E had no effect under the conditions used. The results obtained corroborate the fact that Parsol 1789 generates free radicals upon illumination and that these are, most probably, responsible for the protein damage observed under the conditions used in our system. However, at present, we cannot extrapolate from these results the relevance to human use of sunscreens; therefore, further studies should be necessary to determine the efficacy at the molecular and cellular level of this UVA-absorber in order to ascertain protection against photocarcinogenic risk.

Animals↗
PubMed1998

Synthesis and anti-inflammatory activity of chalcone derivatives.

Chalcones and their derivatives were synthesized and evaluated for their anti-inflammatory activity. In vitro, chalcones 2, 4, 8, 10 and 13 inhibited degranulation and 5-lipoxygenase in human neutrophils, whereas 11 behaved as scavenger of superoxide. Only four compounds (4-7) inhibited cyclo-oxygenase-2 activity. The majority of these samples showed anti-inflammatory effects in the mouse air pouch model.

Animals↗
PubMed1994

Potential radioprotective agents--V. Melatonin analogs. Oral activity of p-aminopropiophenone and its ethylene ketal.

Seven new amides of 5-methoxytryptamine were synthesized and tested for radioprotective activity in mice. One of them, the heptafluorobutyramide 4, is moderately active (57% survivors), the rest demonstrate little or no activity. Of twelve compounds that had been found to exhibit high radioprotective activity by ip injection, only two [p-aminopropiophenone (9) and its ethylene ketal 8] retain that high activity (92-95% survivors) when administered orally. Three are moderately active: p-aminobenzonitrile (10, 55%), 5-methoxytryptamine octanoic amide (11, 50%), and p-aminobenzophenone (12, 48%).

5-Methoxytryptamine↗
PubMed1994

Potential radioprotective agents--IV. Schiff bases.

Twelve Schiff bases were prepared using salicylaldehyde, one with 5-chlorosalicylaldehyde, one with benzaldehyde, and a series of anilines substituted in the m- or p-positions. They were assayed for radioprotective activity in male, Swiss mice irradiated with a nearly lethal dose (950 cGy) of 6 mV photons produced by a linear accelerator, and were compared with the parent amines. Schiff base formation reduced toxicity of the parent amines; its effect on radioprotective activity was erratic, increasing activity in some cases, decreasing activity in others, and having no effect in still others. Radioprotective activity appears to be unrelated to a number of molecular descriptors. The highest radioprotection (100%) was observed for mixtures of p-aminopropiophenone with its Schiff base, or with the Schiff base of 1-(p-aminophenyl)-1-propanol (95%).

Amines↗
PubMed2001

Photochemical studies of 4-tert-butyl-4'-methoxydibenzoylmethane (BM-DBM).

Kinetic UV-VIS absorption data following 355 and 266 nm nanosecond laser flash photolysis of 4-tert-butyl-4'-methoxydibenzoylmethane (BM-DBM) solutions is presented. The kinetics of the decay of the non-chelated enol (NCE) produced following 355 nm excitation of BM-DBM solutions are analysed in terms of mixed 1st- and 2nd-order kinetics. The temperature dependences of the component rate constants are unusual and both 1st- and 2nd-order components display negative activation energies, which are explained by invoking pre-equilibria. In addition, it is shown for the first time that 266 nm laser photolysis of BM-DBM solutions leads to formation of the triplet state of the keto (K) form with a lifetime of approximately 500 ns. Under these conditions the triplet state of the K form is quenched by oxygen.

Benzoates↗
PubMedDate not supplied

Comparison of the uptake and O-methylation of isoprenaline by cardiac and respiratory tissues of guinea-pigs.

An attempt was made to correlate the extraneuronal uptake and O-methylation of isoprenaline in cardiac and respiratory tissues with the predominant beta-adrenoceptor subtype known to mediate the sympathetic responses of these tissues. Papillary muscles, left atria, trachealis muscles and lung parenchymal strips of guinea-pigs were incubated with [3H]isoprenaline ([3H]ISO) (0.1 microM) for 60 min. Levels of total radioactivity and of separated [3H]ISO and [3H]O-methylisoprenaline ([3H]OMI) in each tissue and of [3H]OMI in the medium were determined. U-0521 (10(-4) M) inhibited tissue O-methylation and caused an elevation of unchanged [3H]ISO in the tissues. The latter effect was attributed to the fact that the normal conversion of [3H]ISO to [3H]OMI did not occur. Metanephrine (10(-5) and 10(-4) M) did not affect tissue levels of unchanged [3H]ISO, but reduced tissue levels of [3H]OMI. Levels of [3H]OMI in tissue and medium were only slightly reduced, indicating possible extracellular sites of O-methylation. In the presence of U-0521, metanephrine (10(-4) M) reduced the accumulation of [3H]ISO, indicating that metanephrine was an inhibitor of the extraneuronal uptake of isoprenaline. It is concluded that two cellular compartments for O-methylation exist, access to one being dependent upon metanephrine-sensitive extraneuronal uptake. The extraneuronal uptake capacities of the tissues (when O-methylation was inhibited) was in the order papillary muscle less than lung = atria less than trachea. Cellular O-methylating capabilities, measured from tissue [3H]OMI, was in the order papillary muscle less than atria = trachea less than lung. These orders are discussed in relation to the beta-adrenoceptor mediating the response of each tissue and to the reported degree of sympathetic innervation.

Animals↗
PubMed2002

Studies on the metabolism and toxicological detection of the new designer drug 4'-methyl-alpha-pyrrolidinopropiophenone in urine using gas chromatography-mass spectrometry.

4'-Methyl-alpha-pyrrolidinopropiophenone (MPPP) is a new designer drug which has appeared on the illicit drug market. The aim of our study was to identify the MPPP metabolites and to develop a toxicological detection procedure in urine using solid-phase extraction, ethylation and GC-MS. In urine samples of rats treated with MPPP, MPPP was found to be completely metabolized by oxidative desamination, hydroxylation of the 4'-methyl group followed by oxidation finally to the corresponding carboxy compound and/or by hydroxylation of the pyrrolidine ring followed by dehydrogenation to the corresponding lactam. The carboxy groups were found to be partly conjugated. Based on these data, MPPP could be detected in urine via its metabolites by GC-MS using mass chromatography for screening and library search for identification.

Animals↗
PubMed2003

New designer drug 4'-methyl-alpha-pyrrolidinohexanophenone: studies on its metabolism and toxicological detection in urine using gas chromatography-mass spectrometry.

R,S-4'-Methyl-alpha-pyrrolidinohexanophenone (MPHP) is a new designer drug which has appeared on the illicit drug market. The aim of this study was to identify the MPHP metabolites using solid-phase extraction, ethylation or acetylation, as well as to develop a toxicological detection procedure in urine using solid-phase extraction, trimethylsilylation and GC-MS. Analysis of urine samples of rats treated with MPHP revealed that MPHP was completely metabolized by hydroxylation of the tolyl methyl group followed by dehydrogenation to the corresponding carboxylic acid, hydroxylation of the side chain, hydroxylation of the pyrrolidine ring with subsequent dehydrogenation to the corresponding lactam and/or reduction of the keto group. The carboxy and/or hydroxy groups were found to be only partly conjugated. Based on these data, MPHP could be detected in urine via its metabolites by GC-MS using mass chromatography for screening and library search for identification.

Animals↗
PubMed2003

Metabolism and toxicological detection of the new designer drug 4'-methoxy-alpha-pyrrolidinopropiophenone studied in rat urine using gas chromatography-mass spectrometry.

R,S-4'-Methoxy-alpha-pyrrolidinopropiophenone (MOPPP) is a new designer drug with assumed amphetamine-like effects, which has appeared on the illicit drug market. The aim of this study was to identify the MOPPP metabolites using solid-phase extraction, ethylation or acetylation as well as to develop a toxicological detection procedure in urine using solid-phase extraction, trimethylsilylation and GC-MS. Analysis of urine samples of rats treated with MOPPP revealed that MOPPP [limit of detection (S/N 3) was 100 ng/ml] was completely metabolized by demethylation of the methoxy group, hydroxylation of the pyrrolidine ring with subsequent dehydrogenation to the corresponding lactam and/or oxidative desamination to the corresponding diketo compounds. To some extent, the demethylated MOPPP metabolites were hydroxylated with partial subsequent methylation in position 3'. The hydroxy groups were found to be partly conjugated. Based on these data, MOPPP could be detected in urine via its metabolites by full-scan GC-MS using MS for screening and library search for identification by comparison of the spectra with reference spectra.

Animals↗
PubMed2003

Metabolism and toxicological detection of the new designer drug 3',4'-methylenedioxy-alpha-pyrrolidinopropiophenone studied in urine using gas chromatography-mass spectrometry.

R,S-3',4'-Methylenedioxy-alpha-pyrrolidinopropiophenone (MDPPP) is a new designer drug with assumed amphetamine-like effects, which has appeared on the illicit drug market. The aim of this study was to identify the MDPPP metabolites using solid-phase extraction, ethylation or acetylation as well as to develop a toxicological detection procedure in urine using solid-phase extraction, trimethylsilylation and GC-MS. Analysis of urine samples of rats treated with MDPPP revealed that MDPPP was completely metabolized by demethylenation of the methylenedioxy group followed by partial 3'-methylation of the resulting catechol, oxidative desamination to the corresponding diketo compounds and/or hydroxylation of the pyrrolidine ring with subsequent dehydrogenation to the corresponding lactam. The hydroxy groups were found to be partly conjugated. Based on these data, MDPPP could be detected in urine via its metabolites by full-scan GC-MS using mass chromatography for screening and library search for identification by comparison of the spectra with reference spectra.

Animals↗
PubMed2002

A protein-encapsulation technique by the sol-gel method for the preparation of monolithic columns for capillary electrochromatography.

A novel protein-encapsulation technique using sol-gels was developed for the preparation of monolithic capillary columns for capillary electrochromatography. Two chiral compounds, bovine serum albumin (BSA) and ovomucoid (OVM) from chicken egg white, were encapsulated in tetramethoxysilane-based hydrogel and their chiral selectivity was evaluated for the separation of some selected enantiomers (tryptophan, benzoin, eperisone, chlorpheniramine). The protein encapsulation was carried out within a capillary in a single step under mild conditions. The resultant monolithic columns showed adequate chromatographic performance, including mechanical strength, penetration of pressurized flow, and chiral separation. Two different proteins, BSA and OVM, were successfully encapsulated into the gel matrixes by changing the alkoxysilane compositions of the gel. Run-to-run repeatability was quite satisfactory. The consecutive analysis of the neutral compound, benzoin, by the OVM-encapsulated column showed good repeatability in the retention time (RSD = 1.23% for the first peak, N = 10). Under optimized conditions, the theoretical plate number for the first peak of benzoin reached 72,000 plates/m.

Benzoin↗
PubMed2003

Mechanism-based inactivation of thioredoxin reductase from Plasmodium falciparum by Mannich bases. Implication for cytotoxicity.

Thioredoxin reductase (TrxR) is the homodimeric flavoenzyme that catalyzes reduction of thioredoxin disulfide (Trx). For Plasmodium falciparum, a causative agent of tropical malaria, TrxR is an essential protein which has been validated as a drug target. The high-throughput screening of 350000 compounds has identified Mannich bases as a new class of TrxR mechanism-based inhibitors. During catalysis, TrxR conducts reducing equivalents from the NADPH-reduced flavin to Trx via the two redox-active cysteine pairs, Cys88-Cys93 and Cys535'-Cys540', referred to as N-terminal and C-terminal cysteine pairs. The structures of unsaturated Mannich bases suggested that they could act as bisalkylating agents leading to a macrocycle that involves both C-terminal cysteines of TrxR. To confirm this hypothesis, different Mannich bases possessing one or two electrophilic centers were synthesized and first studied in detail using glutathione as a model thiol. Michael addition of glutathione to the double bond of an unsaturated Mannich base (3a) occurs readily at physiological pH. Elimination of the amino group, promoted by base-catalyzed enolization of the ketone, is followed by addition of a second nucleophile. The intermediate formed in this reaction is an alpha,beta-unsaturated ketone that can react rapidly with a second thiol. When studying TrxR as a target of Mannich bases, we took advantage of the fact that the charge-transfer complex formed between the thiolate of Cys88 and the flavin in the reduced enzyme can be observed spectroscopically. The data show that it is the C-terminal Cys 535'-Cys540' pair rather than the N-terminal Cys88-Cys93 pair that is modified by the inhibitor. Although alkylated TrxR is unable to turn over its natural substrate Trx, it can reduce low M(r) electron acceptors such as methyl methanethiolsulfonate by using its unmodified N-terminal thiols. On the basis of results with chemically distinct Mannich bases, a detailed mechanism for the inactivation of TrxR is proposed.

Alkylating Agents↗
PubMed2003

Formation and accumulation of alpha-acids, beta-acids, desmethylxanthohumol, and xanthohumol during flowering of hops (Humulus lupulus L.).

Important secondary metabolites, present in hops (Humulus lupulus L.), include alpha-acids and beta-acids, which are essential for the brewing of beer, as well as the prenylated chalcones, desmethylxanthohumol, and xanthohumol, which exhibit interesting bioactive properties. Their formation and accumulation in five selected hop varieties, Wye Challenger, Wye Target, Golding, Admiral, and Whitbread Golding Variety, were quantitatively monitored by high-performance liquid chromatography using UV detection. All target compounds were present from the onset of flowering, not only in female hop cones but also in male inflorescences, albeit in low concentrations. During development from female inflorescences to cones, levels of alpha-acids, beta-acids, desmethylxanthohumol, and xanthohumol gradually increased, while each hop variety exhibited individual accumulation rates. Furthermore, these compounds were present in leaves of fully grown hops as well. The study demonstrated that key compounds for flavor and potential beneficial health effects associated with beer not only reside in the glandular lupulin structures but also are distributed over various parts of the hop plant.

Beer↗