Chikungunya fever is a disease caused by the Chikungunya virus (CHIKV) that is transmitted by the bite of the female of Aedes sp. mosquito. The symptoms include fever, muscle aches, skin rash, and severe joint pains. The disease may develop into a chronic condition and joint pain for months or years. Currently, there is no effective antiviral treatment against CHIKV infection. Treatments based on natural compounds have been widely studied, as many drugs were produced by using natural molecules and their derivatives. Alpha-phellandrene (α-Phe) is a naturally occurring organic compound that is a ligand for ruthenium, forming the organometallic complex [Ru2Cl4(p-cymene)2] (RcP). Organometallic complexes have shown promising as candidate molecules to a new generation of compounds that presented relevant biological properties, however, there is a lack of knowledge concerning the anti-CHIKV activity of these complexes. The present work evaluated the effects of the RcP and its precursors, the hydrate ruthenium(III) chloride salt (RuCl3⋅xH2O) (Ru) and α-Phe, on CHIKV infection in vitro. To this, BHK-21 cells were infected with CHIKV-nanoluciferase (CHIKV-nanoluc), a viral construct harboring the nanoluciferase reporter gene, at the presence or absence of the compounds for 16 h. Cytotoxicity and impact on infectivity were analyzed. The results demonstrated that RcP exhibited a strong therapeutic potential judged by the selective index > 40. Antiviral effects of RcP on different stages of the CHIKV replicative cycle were investigated; the results showed that it affected early stages of virus infection reducing virus replication by 77% at non-cytotoxic concentrations. Further assays demonstrated the virucidal activity of the compound that completely blocked virus infectivity. In silico molecular docking calculations suggested different binding interactions between aromatic rings of RcP and the loop of amino acids of the E2 envelope CHIKV glycoprotein mainly through hydrophobic interactions. Additionally, infrared spectroscopy spectral analysis indicated interactions of RcP with CHIKV glycoproteins. These data suggest that RcP may act on CHIKV particles, disrupting virus entry to the host cells. Therefore, RcP may represent a strong candidate for the development of anti-CHIKV drugs.

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Ruthenium complexes have been extensively explored as potential molecules for cancer treatment. Considering our previous findings on the remarkable cytotoxic activity exhibited by the ruthenium (II) complex 3-hydroxy-4-methoxybenzoate (hmxbato)-cis-[RuII(ŋ2-O2CC7H7O2)(dppm)2]PF6 against Leishmania promastigotes and also the similar metabolic characteristics between trypanosomatids and tumor cells, the present study aimed to analyze the anticancer potential of hmxbato against lung tumor cells, as well as the partial death mechanisms involved. Hmxbato demonstrated selective cytotoxicity against A549 lung tumor cells. In addition, this complex at a concentration of 3.8 µM was able to expressively increase the generation of reactive oxygen species (ROS) in tumor cells, causing an oxidative stress that may culminate in: (1) reduction in cellular proliferation; (2) changes in cell morphology and organization patterns of the actin cytoskeleton; (3) cell arrest in the G2/M phase of the cell cycle; (4) apoptosis; (5) changes in the mitochondrial membrane potential and (6) initial DNA damage. Furthermore, we demonstrated that the induction of programmed cell death can occur by the intrinsic apoptotic pathway through the activation of caspases. It is also worth highlighting that hmxbato exhibited predominant actions on A549 tumor cells in comparison to BEAS-2B normal bronchial epithelium cells, which makes this complex an interesting candidate for the design of new drugs against lung cancer.

I n t r o d u ç ã o | 7 RESUMO O presente trabalho descreve a síntese e caracterização físico-química de quatro complexos de rutênio(II) análogos e inéditos, contendo em suas esferas de coordenação ligantes bifosfínicos (dppm = 1,1-bis(difenilfosfina)metano e ligantes das classes tio e semicarbazonas cíclicas (5-metóxi-5,6-difenil-4,5-dihidro-2H-[1,2,4]triazina-3-tiona (Btsc) e 5-metóxi-5,6-difeniltriazina-3-ona (Bsc), para os complexos 1 e 2, respectivamente, e dppe = 1,1-bis(difenilfosfina)etano e os ligantes Btsc e Bsc, para os complexos 3 e 4, respectivamente). Os complexos foram caracterizados pelas técnicas de análise elementar, espectroscopia vibracional na região do infravermelho, espectroscopia de absorção na região do ultravioleta e visível, espectroscopia de ressonância magnética nuclear de 31 P{ 1 H} e 1 H, espectrometria de massas e difração de raios X por monocristal. A estabilidade dos complexos em dimetilsulfóxido (DMSO) foi estudada por meio da obtenção dos espectros de RMN 31 P{ 1 H} em diferentes intervalos de tempo. O estudo sugeriu que as ligações envolvidas na esfera de coordenação do metal, em todos os complexos, permanecem inalteradas durante o intervalo de tempo monitorado. Ensaios antitumorais in vitro contra a linhagem de células tumorais A549 e normais BEAS-2B foram realizados para todos os complexos, ambos precursores e ligantes livres e para cisplatina. Todos os complexos testados exibiram efeito citotóxico contra as células de câncer de pulmão, com valores de IC50 inferiores à cisplatina. Os novos complexos apresentaram valores muito similares na faixa de 0,26 a 0,52 μM, sendo o complexo 4 o mais ativo e mais seletivo dentre eles. Estudos teóricos de ancoragem molecular foram realizados com o intuito de prever e compreender as possíveis interações dos complexos 1-4 com o DNA. Palavras-chave: Complexos de rutênio(II). Câncer de pulmão. Tiossemicarbazonas.