Cytotoxicity of Extracts from Petiveria alliacea Leaves on Yeast.

Petiveria alliacea L. is a plant used in traditional medicine harboring pharmacological properties with anti-inflammatory, antinociceptive, hypoglycemiant and anesthetic activities. This study assessed the potential cytotoxic, genotoxic and mutagenic effects of ethanolic extract of P. alliacea on Saccharomyces cerevisiae strains. S. cerevisiae FF18733 (wild type) and CD138 (ogg1) strains were exposed to fractioned ethanolic extracts of P. alliacea in different concentrations. Three experimental assays were performed: cellular inactivation, mutagenesis (canavanine resistance system) and loss of mitochondrial function (petites colonies). The chemical analyses revealed a rich extract with phenolic compounds such as protocatechuic acid, cinnamic and catechin epicatechin. A decreased cell viability in wild-type and ogg1 strains was demonstrated. All fractions of the extract exerted a mutagenic effect on the ogg1 strain. Only ethyl acetate and n-butanol fractions increased the rate of petites colonies in the ogg1 strain, but not in the wild-type strain. The results indicate that fractions of mid-polarity of the ethanolic extract, at the studied concentrations, can induce mutagenicity mediated by oxidative lesions in the mitochondrial and genomic genomes of the ogg1-deficient S. cerevisiae strain. These findings indicate that the lesions caused by the fractions of P. alliacea ethanolic extract can be mediated by reactive oxygen species and can reach multiple molecular targets to exert their toxicity.

Nuclear and mitochondrial genome instability induced by fractions of ethanolic extract from Hovenia dulcis Thunberg in Saccharomyces cerevisiae strains.

Hovenia dulcis is a plant commonly used as a pharmaceutical supplement, having displayed important pharmacological properties such antigiardic, antineoplastic and hepatoprotective. The purpose of this work was investigate the cytotoxic, genotoxic and mutagenic potential from fractions of Hovenia dulcis ethanolic extract on Saccharomyces cerevisiae strains FF18733 (wild type) and CD138 (ogg1). Ethanolic extract from Hovenia dulcis leaves was fractioned using organic solvents according to increasing polarity: Hexane (1:1), dichlorometane (1:1), ethyl acetate (1:1) and butanol (1:1). Three experimental assays were performed, such as (i) inactivation of cultures; (ii) mutagenesis (canavanine resistance system) and (iii) loss of mitochondrial function (petites colonies). The findings shown a decrease in cell viability in FF18733 and CD138 strains; all fractions of the extract were mutagenic in CD138 strain; only ethyl acetate and butanol fractions increased the rate of petites colonies for CD138 strains. Ethyl acetate and n-butanol fractions induces mutagenicity, at the evaluated concentrations, in mitochondrial and genomic DNA in CD138 strain, mediated by oxidative lesions. In conclusion, it is possible to infer that the lesions caused by the extract fractions could be mediated by reactive oxygen species and might reach multiple molecular targets to cause cellular damage.

Endonuclease IV is the main base excision repair enzyme involved in DNA damage induced by UVA radiation and stannous chloride.

Stannous chloride (SnCl(2)) and UVA induce DNA lesions through ROS. The aim of this work was to study the toxicity induced by UVA preillumination, followed by SnCl(2) treatment. E. coli BER mutants were used to identify genes which could play a role in DNA lesion repair generated by these agents. The survival assays showed (i) The nfo mutant was the most sensitive to SnCl(2); (ii) lethal synergistic effect was observed after UVA pre-illumination, plus SnCl(2) incubation, the nfo mutant being the most sensitive; (iii) wild type and nfo mutants, transformed with pBW21 plasmid (nfo(+)) had their survival increased following treatments. The alkaline agarose gel electrophoresis assays pointed that (i) UVA induced DNA breaks and fpg mutant was the most sensitive; (ii) SnCl(2)-induced DNA strand breaks were higher than those from UVA and nfo mutant had the slowest repair kinetics; (iii) UVA + SnCl(2) promoted an increase in DNA breaks than SnCl(2) and, again, nfo mutant displayed the slowest repair kinetics. In summary, Nfo protects E. coli cells against damage induced by SnCl(2) and UVA + SnCl(2).

Cytotoxic and genotoxic effects induced by stannous chloride associated to nuclear medicine kits.

At present, more than 75% of routine nuclear medicine diagnostic procedures use technetium-99m (99mTc). The binding between 99mTc and the drug to obtain the radiopharmaceutical needs a reducing agent, with stannous chloride (SnCl2) being one of the most used. There are controversies about the cytotoxic, genotoxic and mutagenic effects of SnCl2 in the literature. Thus, the approaches below were used to better understand the biological effects of this salt and its association in nuclear medicine kits [methylenediphosphonate (MDP) bone scintigraphy and diethylenetriaminepentaacetic acid (DTPA) kidney and brain scintigraphy]: (i) bacterial inactivation experiments; (ii) agarose gel electrophoresis of supercoiled and linear plasmid DNA and (iii) bacterial transformation assay. The Escherichia coli strains used here were AB1157 (wild type) and BW9091 (xthA mutant). Data obtained showed that both MDP and SnCl2 presented a high toxicity, but this was not observed when they were assayed together in the kit, thereby displaying a mutual protect effect. DTPA salt showed a moderate toxicity, and once more, the DTPA kit provided protection, compared to the SnCl2 effect alone. The results suggest a possible complex formation, either MDP-SnCl2 or DTPA-SnCl2, originating an atoxic compound. On the other hand, SnCl2-induced cell inactivation and the decrease in bacterial transformation generated by DTPA found in XthA mutant strain suggest that the lack of this enzyme could be responsible for the effects observed, being necessary to induce DNA damage repair.

Interaction of stannous chloride leads to alteration in DNA, triphosphate nucleotides and isolated bases.

Stannous chloride (SnCl2) is a reducing chemical agent used in several man-made products. SnCl2 can generate reactive oxygen species (ROS); therefore, studies have been carried out in order to better understand its damaging action in biological systems. In this work, calf thymus DNA, triphosphate nucleotides and isolated bases were incubated with SnCl2 and the results were analyzed through UV spectrophotometry. The presence of stannous ions altered the absorption spectra of all three isolates. The amount of stannous ions associated to DNA was measured by atomic absorption spectrophotometry. Data showed that more than 40% of the initial SnCl2 concentration was present in the samples. Our results are in accordance with the damaging potential of this salt and present evidence that stannous ions can complex with DNA, inducing ROS in its vicinity, which may be responsible for the observed lesions.

Assessment of Aloe vera (L.) genotoxic potential on Escherichia coli and plasmid DNA.

Aloe vera is a tropical plant, known in Brazil as babosa and several reputable suppliers produce a stabilized aloe gel for topic use. Since people use Aloe vera topically, they could be exposed to solar ultraviolet light in addition and it might cause a cross damage effect between these agents. The aim of this work was to investigate the biological effects of Aloe vera pulp extract, associated or not to UVA radiation, on Escherichia coli-deficient repair mutants and plasmid DNA, in order to test its genotoxic potential. Data obtained from analysis of survival fractions, bacterial transformation and agarose gel electrophoresis suggest that Aloe vera has genotoxic properties, but it seems not to be able to damage the cell membrane.

Biological effects of rutin on the survival of Escherichia coli AB1157 and on the electrophoretic mobility of plasmid PUC 9.1 DNA.

The use of natural products as medicines is growing in the world. The rutin, a compound isolated from Ruta graveolens, is a flavonoid, which has been suggested to have antioxidant properties and to reduce the triacylglycerol levels. In this study, plasmid desoxyribonucleic acid (DNA) was exposed to rutin (0.33, 10, 20, 30 microg/ml) in presence of stannous chloride (SnCl2), a reducing agent widely used to obtain radiopharmaceuticals labeled with technetium-99m. Samples of the plasmid DNA were analyzed through agarose gel electrophoresis. E. coli AB1157 culture was also incubated with rutin (3, 30, 50, 100 microg/ml) and the survival fractions were calculated. The results show that the rutin, in these concentrations, is not capable of: i/ damaging the DNA, ii/ protecting the DNA from the SnCl2 redox action, and iii/ inactivating the E. coli AB1157 culture. The analysis of our data indicates that rutin do not present toxic activity in the evaluated systems.

Stannous chloride participates in the generation of reactive oxygen species

A genotoxic potentiality to stannous salts has been reported. The relevance of these data is due to the wide application of this metal in our society. The biological effect of these salts might depend on the physicochemical conditions and the route of their administration. There are situations in which stannous salts can be directly administered to human beings endovenously and there is not doubt about their absorption into the body. The disparate and largely unexplained differences suggest that stannous salts as a simple poisoning and/or a remarkable genotoxic agent might be a fertile field for additional investigation. Reactive oxygen species scavengers and metal ion chelators can abolish, at least in part, the effect of stannous salts. This suggests that the generation of free radicals by the reducing agent is involved in the biological effect induced by this metal.