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O processo de biorredução enzimática do grupo nitro é de grande importância para a ação molecular de nitrocompostos aromáticos biologicamente ativos. Os métodos eletroquímicos são considerados ferramentas úteis para a simulação de processos metabólicos in vivo. No presente trabalho, realizaram-se estudos eletroquímicos em meio aprótico (N,N-dimetilformamida (DMF) mais perclorato de tetrabutilamônio (TBAP) 0,1 mol L -1 ) utilizando-se as técnicas de voltametria cíclica (CV), de pulso diferencial (DPV) e de onda quadrada (SWV) de 12 adutos de Morita-Baylis-Hillman (MBHA) com atividade leishmanicida significativa. Para facilitar a análise, os adutos foram agrupados em quatro classes de acordo com a cadeia lateral. Os estudos de CV evidenciam duas ondas referentes à redução do grupo nitro e uma ou duas outras ondas (em potencial mais negativo) relativas à redução da função carbonila α,β-insaturada ou da olefina ativada por grupos nitrila. Adutos orto-substituídos apresentam maior facilidade de redução quando comparados aos demais isômeros (meta e para) em função, provavelmente, da ligação de hidrogênio entre o grupo nitro e a hidroxila benzílica, o que estabiliza mais o produto eletrogerado do que o composto de partida. Derivados orto também mostram uma maior atividade leishmanicida em comparação com seus isômeros em cada série. Estudos conformacionais usando HF/6-31+G(d)/PCM como nível de cálculo evidenciaram este efeito. Valores calculados de dureza molecular (N) e de cargas atômicas (Q N ) explicam corretamente os dados experimentais obtidos.Enzymatic bioreduction of nitro groups plays an important role on the activity of biologically active nitroaromatic compounds. Electrochemical methods are useful tools to simulate in vivo metabolic processes. This work presents electrochemical studies in aprotic media (N,N-dimethylformamide (DMF) plus tetrabutylammonium perchlorate (TBAP) 0.1 mol L -1 ) using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV) of twelve Morita-Baylis-Hillman adducts (MBHA) with significant leishmanicidal activity. To facilitate the analysis, the molecules were grouped in four classes according to the side chain. CV studies show three up to four reduction waves, in which the first two waves are related to nitro group reduction. The other waves (presenting more negative potential) refer to the reduction of the α,β-unsaturated carbonyl or to the nitrile activated olefin side-chain. Ortho adducts present facilitated reduction in comparison to the other isomers (meta and para) possibly due to hydrogen bond formation between the benzylic-OH and the nitro group, which stabilizes the reduction product (anion radical nitro) more efficiently than the original compound. Ortho derivatives also present higher leishmanicidal activity upon comparison to the other derivatives of each class. Conformational studies using HF/6-31+G(d)/PCM as a calculation level highlight this effect. Molecular hardness (N) and atomic charges (Q N ) values corroborate the obtained expe...

Electrochemical methods are considered useful tools for simulations of biological redox reactions. The activities of quinones depend on their bioreduction. Biologically active pterocarpanquinones LQB-149 (nitroderivative), 150 and 151 (bromo and chloroderivatives, respectively) were electrochemically investigated by cyclic voltammetry, differential pulse voltammetry, and in situ UV-Vis spectroelectrochemistry, in aprotic media (N,N-dimethylformamide (DMF) + tetra-N-butylammonium (TBAPF 6)). The data obtained regarding their reduction mechanisms, positive reactivity with oxygen and analysis of the electrogenerated intermediates were useful in explaining their biological outcomes. The appearance of bands at 397 and 480 nm, for the halogenated compounds, suggests the generation of transient quinonemethides (QM), electrophilic intermediates related to their activity. As an additional proof for the intermediacy of QM, in the redox processes, chemical reduction of LQB-150, in the presence of hexanethiol was performed and led to a thioalkylated quinone. For the nitroderivative, a broad band appeared at 432 nm, corresponding to the generation of the nitroradical anion, giving rise to a dianion diradical, after reduction at the second wave potential. Computational data correlate well with electrochemical experiments. Homogeneous electron transfer to oxygen, yielding reactive oxygen species, the generation of electrophilic species and the radical reactivity, explain partially the mechanism of biological action.

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The electrochemistry of a redox‐based bioactive pterocarpanquinone, designated as LQB‐118, and its precursor chromenquinone (CQ) was investigated in protic and aprotic media with a focus on the reduction mechanism in both media, the reactivity with oxygen, and the interaction with biological targets, such as DNA. UV/Vis spectroelectrochemistry clarified the proposed mechanism. The appearance of bands at λ=331, 400, and 600 nm suggests the generation of transient quinonemethides (QM). Electrochemical experiments revealed homogeneous electron transfer to oxygen. LQB‐118 itself interacts with calf‐thymus DNA and ssDNA in solution. It, and its electrogenerated intermediates, have been shown to decrease the diagnostic oxidation peaks of guanosine and adenosine residues. These results, together with electrochemical evidence for the formation of QMs and the reductive addition of thiols, partly explain the reported cytotoxic and parasiticidal effects of this quinone. Overall, the electrochemical methods do well to predict the molecular mechanism of the biological activity of the present class of compounds. As an additional competitive advantage, electrochemistry allows reductive cleavage in situ, the characterization of the generated intermediate, the calculation of the number of transferred electrons, and positively mimics in vitro and in vivo experiments.

The present study aims to determine the antioxidant capacity of the ethanolic extracts of husk fiber of four coconut (Cocos nucifera L.) varieties (yellow dwarf, green dwarf, giant and hybrid) and to evaluate the electrochemical behavior of these extracts on a glassy carbon electrode and on a modified glassy carbon electrode. The highest values of total phenolic content were obtained for the hybrid (531 ± 24 mg GAE g(-1) dry extract) and yellow dwarf (501 ± 29 mg GAE g(-1) dry extract) varieties and the lowest was for the green dwarf variety with 58 ± 9 mg GAE g(-1) dry extract. The ability of the extracts to scavenge DPPH˙ radicals was in the order of giant > yellow dwarf > hybrid > green dwarf and the IC50 values varied from 8.6 to 55.9 μg mL(-1). All varieties showed reducing potential by the use of FRAP and CUPRAC methods, with the lowest performance obtained for the green dwarf variety. Additionally, through the use of mimetic biomembranes, ethanolic extracts of coconut husk were shown to protect lipids against oxidative damage independent of the variety. The main antioxidants identified in the extract of yellow dwarf variety by UPLC-MS were quercetin and catechin. Cyclic voltammetric studies of the ethanolic extracts on glassy carbon electrode confirmed the presence of easily oxidized compounds, and the high antioxidant capacity of the varieties. This capacity was expressed as mg quercetin equivalents g(-1) dry extract and ranged from 25.9 up to 53.5 mg QE g(-1). A poly-xanthurenic acid (poly-Xa)/multi-walled carbon nanotube (MWCNT) / glassy carbon modified electrode (poly-Xa/MWCNT/GCE) was used for this purpose. Our findings suggest that these extracts are potentially important antioxidant supplements for the everyday human diet, pharmaceutical and cosmetic industries, thereby aggregating value to the enormous amount of waste from the coconut industry, mostly used for burning purposes.

Introduction: Depression disables and compromises quality of life, so that its high prevalence in medical students is a relevant problem. It is known that hormonal variables, such as cortisolemia, as well as socioeconomic factors can be related to the onset of depressive symptoms. This study aimed to verify the prevalence of depressive symptoms in medical students at a University Center in Maceió and analyze their correlation with serum cortisol levels, lifestyle and socioeconomic profile. Method: Quantitative, analytical and cross-sectional study of medical students from a private medical school in Maceió. A sample of 122 students participated in the study, which applied the Beck Depression Inventory, socioeconomic questionnaire and serum cortisol dosage. Results: Of the 78 women and 44 men participating in the study, 40 cases of depressive symptoms were identified (32.9%), of which 3 cases had severe depressive symptoms (2.5%), 9 cases had moderate depressive symptoms (7.4%) and 28 had mild depressive symptoms (23.0%). As for the cortisol levels, the mean value obtained was 12.72 µg/dL, with a maximum and minimum value of 29.7 µg/dL and 0.9 µg/dL, respectively. No correlation was found between depressive symptoms and morning serum cortisol levels in this study. Among the explanatory variables analyzed, only religion attained a statistically significant correlation with depressive symptoms, with a prevalence of higher scores in students who did not have a religion. Conclusion: It can be emphasized that there is a high prevalence of depression among medical students. The results obtained in this study show that the hypothalamic-pituitary-adrenal axis alteration is not the only etiology associated with the development of depression. In turn, religious practice showed to be statistically significant in relation to the lowest rate of depressive symptoms, revealing itself as a probable protective factor against the development of depression.