Formation of 1,N6-etheno-2'-deoxyadenosine adducts by trans,trans-2, 4-Decadienal

Antigiardial Activity of Foeniculum vulgare Hexane Extract and Some of Its Constituents

Foeniculum vulgare is used for the treatment of diarrhea in Mexican traditional medicine. Hexane extract showed 94 % inhibition of Giardia duodenalis trophozoites at 300 μg/mL. Therefore, 20 constituents of hexane extract were evaluated to determine their antigiardial activity. Interestingly, six compounds showed good activity toward the parasite. These compounds were (1R,4S) (+)-Camphene (61%), (R)(−)-Carvone (66%), estragole (49%), p-anisaldehyde (67%), 1,3-benzenediol (56%), and trans, trans-2,4-undecadienal (97%). The aldehyde trans, trans-2,4-undecadienal was the most active compound with an IC₅₀ value of 72.11 µg/mL against G. duodenalis trophozoites. This aldehyde was less toxic (IC₅₀ 588.8 µg/mL) than positive control metronidazole (IC₅₀ 83.5 µg/mL) against Vero cells. The above results could support the use of F. vulgare in Mexican traditional medicine.

Structural studies of malonaldehyde–glyoxal and malonaldehyde–methylglyoxal etheno adducts of adenine nucleosides based on spectroscopic methods and DFT-GIAO calculations

The substitution position in the etheno rings of M₁Gx-A and M₁MGx-dA was determined based on the comparison of data derived from NMR spectra with results obtained from computational calculations.

Interaction of 2'-deoxyadenosine with cis-2-butene-1,4-dial: computational approach to analysis of multistep chemical reactions

The computational analysis of multistep chemical interactions between 2'-deoxyadenosine and cis-2-butene-1,4-dial has been performed. The applied protocol includes generation of a multistep Gibbs free-energy reaction profile (PCM/M05-2X/6-311+G(d) level) for the transformations of the reagents to products, followed by evaluation of the rate constants, construction of the corresponding kinetic equations, and solving them. Such a procedure allows one to significantly extend the number of experimentally determined steps by addition of the ones computationally predicted. The primary products of the reaction are found to be four diastereomeric adducts characterized by virtually the same stability. The acid-catalyzed dehydration of these adducts leads to a more stable secondary product. Computational verification of UV and NMR spectra has also been performed. It has been revealed that simulated UV and NMR spectra of primary and secondary 2'-deoxyadenosine adducts of cis-2-butene-1,4-dial are in agreement with the experimental observations.

Oxidatively generated base damage to cellular DNA

Search for the formation of oxidatively base damage in cellular DNA has been a matter of debate for more than 40 years due to the lack of accurate methods for the measurement of the lesions. HPLC associated with either tandem mass spectrometry (MS/MS) or electrochemical detector (ECD) together with optimized DNA extraction conditions constitutes a relevant analytical approach. This has allowed the accurate measurement of oxidatively generated single and clustered base damage in cellular DNA following exposure to acute oxidative stress conditions mediated by ionizing radiation, UVA light and one-electron oxidants. In this review the formation of 11 single base lesions that is accounted for by reactions of singlet oxygen, hydroxyl radical or high intensity UVC laser pulses with nucleobases is discussed on the basis of the mechanisms available from model studies. In addition several clustered lesions were found to be generated in cellular DNA as the result of one initial radical hit on either a vicinal base or the 2-deoxyribose. Information on nucleobase modifications that are formed upon addition of reactive aldehydes arising from the breakdown of lipid hydroperoxides is also provided.

The influence of bioactive oxylipins from marine diatoms on invertebrate reproduction and development

Diatoms are one of the main primary producers in aquatic ecosystems and occupy a vital link in the transfer of photosynthetically-fixed carbon through aquatic food webs. Diatoms produce an array of biologically-active metabolites, many of which have been attributed as a form of chemical defence and may offer potential as candidate marine drugs. Of considerable interest are molecules belonging to the oxylipin family which are broadly disruptive to reproductive and developmental processes. The range of reproductive impacts includes; oocyte maturation; sperm motility; fertilization; embryogenesis and larval competence. Much of the observed bioactivity may be ascribed to disruption of intracellular calcium signalling, induction of cytoskeletal instability and promotion of apoptotic pathways. From an ecological perspective, the primary interest in diatom-oxylipins is in relation to the potential impact on energy flow in planktonic systems whereby the reproductive success of copepods (the main grazers of diatoms) is compromised. Much data exists providing evidence for and against diatom reproductive effects; however detailed knowledge of the physiological and molecular processes involved remains poor. This paper provides a review of the current state of knowledge of the mechanistic impacts of diatom-oxylipins on marine invertebrate reproduction and development.

A microarray to measure repair of damaged plasmids by cell lysates

DNA repair mechanisms constitute major defences against agents that cause cancer, degenerative disease and aging. Different repair systems cooperate to maintain the integrity of genetic information. Investigations of DNA repair involvement in human pathology require an efficient tool that takes into account the variety and complexity of repair systems. We have developed a highly sensitive damaged plasmid microarray to quantify cell lysate excision/synthesis (ES) capacities using small amounts of proteins. This microsystem is based on efficient immobilization and conservation on hydrogel coated glass slides of plasmid DNA damaged with a panel of genotoxic agents. Fluorescent signals are generated from incorporation of labelled dNTPs by DNA excision-repair synthesis mechanisms at plasmid sites. Highly precise DNA repair phenotypes i.e. simultaneous quantitative measures of ES capacities toward seven lesions repaired by distinct repair pathways, are obtained. Applied to the characterization of xeroderma pigmentosum (XP) cells at basal level and in response to a low dose of UVB irradiation, the assay showed the multifunctional role of different XP proteins in cell protection against all types of damage. On the other hand, measurement of the ES of peripheral blood mononuclear cells from six donors revealed significant diversity between individuals. Our results illustrate the power of such a parallelized approach with high potential for several applications including the discovery of new cancer biomarkers and the screening of chemical agents modulating DNA repair systems.

Diatom/copepod interactions in plankton: the indirect chemical defense of unicellular algae

Numerous coexisting species can be observed in the open oceans. This includes the complex community of the plankton, which comprises all free floating organisms in the sea. Traditionally, nutrient limitation, competition, predation, and abiotic factors have been assumed to shape the community structure in this environment. Only in recent years has the idea arisen that chemical signals and chemical defense can influence species interactions in the plankton as well. Key players at the base of the marine food web are diatoms (unicellular algae with silicified cell walls) and their main predators, the herbivorous copepods. It was assumed that diatoms represent a generally good food source for the grazers but recent work indicates that some species use chemical defenses. Secondary metabolites, released by these algae immediately after wounding, are targeted not against the predators themselves but rather at interfering with their reproductive success. This strategy allows diatoms to reduce the grazer population, thereby influencing the marine food web. This review addresses the chemical ecology of the defensive oxylipins formed by diatoms and the question of how these metabolites can act in such a dilute environment. Aspects of biosynthesis, bioassays, and the possible implications of such a chemical defense for the plankton community structure are also discussed.

Structural characterization of diastereoisomeric ethano adducts derived from the reaction of 2'-deoxyguanosine with trans,trans-2,4-decadienal

Background levels of exocyclic DNA adducts have been detected in rodent and human tissues. Several studies have focused on bifunctional electrophiles generated from lipid peroxidation as one of the endogenous sources of these lesions. We have previously shown that the reaction of 2'-deoxyguanosine (dGuo) with trans,trans-2,4-decadienal (DDE), a highly cytotoxic aldehyde generated as a product of lipid peroxidation in cell membranes, results in the formation of a number of different base derivatives. Three of these derivatives have been fully characterized as 1,N(2)-etheno-2'-deoxyguanosine adducts. In the present work, four additional adducts, designated A3-A6, were isolated from in vitro reactions by reversed-phase HPLC and fully characterized on the basis of spectroscopic measurements. Adducts A3-A6 are four diastereoisomeric 1,N(2)-hydroxyethano-2'-deoxyguanosine derivatives possessing a carbon side chain with a double bond and a hydroxyl group. The systematic name of these adducts is 6-hydroxy-3-(2'-deoxy-beta-D-erythro-pentafuranosyl)-7-((E)-1-hydroxy-oct-2-enyl)-3,5,6,7-tetrahydro-imidazo[1,2-a]purin-9-one. The proposed reaction mechanism yielding adducts A3-A6 involves DDE epoxidation at C2, followed by nucleophilic addition of the exocyclic amino group of dGuo to the C1 of the aldehyde and cyclization, via nucleophilic attack, on the C2 epoxy group by N-1. The formation of adducts A1-A6 has been investigated in acidic, neutral, and basic pH in the presence of H(2)O(2) or tert-butyl hydroperoxide. Neutral conditions, in the presence of H(2)O(2), have favored the formation of adducts A1 and A2, with minor amounts of A3-A6, which were prevalent under basic conditions. These data indicate that DDE can modify DNA bases through different oxidative pathways involving its two double bonds. It is important to structurally characterize DNA base derivatives induced by alpha,beta-unsaturated aldehydes so that the genotoxic risks associated with the lipid peroxidation process can be assessed.

Induction of 1,N(2)-etheno-2'-deoxyguanosine in DNA exposed to beta-carotene oxidation products

Epidemiological studies testing the effect of beta-carotene in humans have found a relative risk for lung cancer in smokers supplemented with beta-carotene. We investigated the reactions of retinal and beta-apo-8'-carotenal, two beta-carotene oxidation products, with 2'-deoxyguanosine to evaluate their DNA damaging potential. A known mutagenic adduct, 1,N(2)-etheno-2'-deoxyguanosine, was isolated and characterized on the basis of its spectroscopic features. After treatment of calf thymus DNA with beta-carotene or beta-carotene oxidation products, significantly increased levels of 1,N(2)-etheno-2'-deoxyguanosine and 8-oxo-7,8-dihydro-2'-deoxyguanosine were quantified in DNA. These lesions are believed to be important in the development of human cancers. The results reported here may contribute toward an understanding of the biological effects of beta-carotene oxidation products.

Genotoxicity of 5-aminolevulinic and 4,5-dioxovaleric acids in the salmonella/microsuspension mutagenicity assay and SOS chromotest

5-Aminolevulinic acid (ALA) is a heme precursor that accumulates in some porphyric disorders and in lead poisoning which can undergo metal-catalyzed oxidation producing reactive oxygen species and the keto-aldehyde, 4,5-dioxovaleric acid (DOVA). Evidence in vitro of ALA-induced DNA lesions suggests that ALA and DOVA have mutagenic potential that could possibly contribute to an increased frequency of hepatocellular carcinoma (HCC) in patients with acute intermittent porphyria (AIP). In this study, we evaluated the genotoxic potential of ALA and DOVA. In the absence of exogenous metabolic activation, ALA and DOVA were mutagenic in Salmonella typhimurium tester strain TA104. ALA was also mutagenic in S. typhimurium TA102, but not in TA98, TA100, or TA1535, indicating an oxidative mechanism. Removal of H(2)O(2) with catalase gave only partial protection, suggesting generation of other mutagenic species. Both ALA and DOVA damaged the DNA of Escherichia coli PQ37, inducing the SOS response detected by an increase in beta-galactosidase activity. These results verified the potential mutagenic activity of ALA and DOVA and reinforce the hypothesis that DNA damage induced by ALA may be associated with the development of HCC in individuals suffering from AIP.