Resumo A atividade carrapaticida in vitro do extrato metanólico (EM) e da fração de alcaloides (FA) de Prosopis juliflora foi investigada, frente ao Rhipicephalus microplus, e relacionada com a inibição da enzima acetilcolinesterase (AChE). A predição in silico das interações de alcaloides dessa fração com a AChE1 de R. microplus (RmAChE1) foi realizada por acoplamento molecular. A atividade carrapaticida foi avaliada, utilizando-se os ensaios de imersão de adultos e larvas. Maior efeito sobre parâmetros reprodutivos de teleóginas foi verificado para a FA, com valor de Concentração Efetiva 50% (CE50) (31.6 mg/mL), quatro vezes menor do que o valor do EM (121 mg/mL). A FA induziu mortalidade de larvas (Concentração Letal de 50% - CL50 = 13,8 mg/mL). A inibição da atividade da AChE de larvas do carrapato foi observada para EM e FA, sendo a FA mais ativa (Concentração Inibitória 50%- CI50 de 0,041mg/mL). As análises químicas da FA permitiram a identificação dos alcaloides prosopina (1), juliprosinina (2) e juliprosopina (3). No ensaio in silico, observou-se que esses alcaloides podem interagir com o sítio ativo da RmAChE1, principalmente por ligações de hidrogênio e interações cátion-pi. Os alcaloides de P. juliflora têm atividade carrapaticida contra R. microplus, atuando através do mecanismo anticolinesterásico.

Abstract We investigated the in vitro acaricide activity of the methanolic extract (ME) and alkaloid-rich fraction (AF) of Prosopis juliflora on Rhipicephalus microplus and correlated this effect with acetylcholinesterase (AChE) inhibition. The acaricide activity was evaluated using adult and larval immersion tests. Also, we studied the possible interaction mechanism of the major alkaloids present in this fraction via molecular docking at the active site of R. microplus AChE1 (RmAChE1). Higher reproductive inhibitory activity of the AF was recorded, with effective concentration (EC50) four times lower than that of the ME (31.6 versus 121 mg/mL). The AF caused mortality of tick larvae, with lethal concentration 50% (LC50) of 13.8 mg/mL. Both ME and AF were seen to have anticholinesterase activity on AChE of R. microplus larvae, while AF was more active with half-maximal inhibitory concentration (IC50) of 0.041 mg/mL. The LC-MS/MS analyses on the AF led to identification of three alkaloids: prosopine (1), juliprosinine (2) and juliprosopine (3). The molecular docking studies revealed that these alkaloids had interactions at the active site of the RmAChE1, mainly relating to hydrogen bonds and cation-pi interactions. We concluded that the alkaloids of P. juliflora showed acaricide activity on R. microplus and acted through an anticholinesterase mechanism.

Abstract This study investigated the effects of the flavonoids 5-hydroxy-7,4′-dimethoxyflavone, casticin, and penduletin, isolated from Croton betulaster Müll Arg., Euphorbiaceae, a plant utilized in popular medicine in Brazil, on the growth and viability of the human glioblastoma cell line GL-15. We observed that 5-hydroxy-7,4′-dimethoxyflavone and casticin were not toxic to GL-15 cells after 24 h of exposure. However, casticin and penduletin inhibited the metabolic activity of glioblastoma cells significantly at a concentration of 10 µM (p ≤ 0.05). Flavonoids casticin and penduletin also induced a significant and dose-dependent growth inhibition beginning at 24 h of exposure, and the most potent flavonoid was penduletin. It was also observed that penduletin and casticin induced an enlargement of the cell body and a reduction of cellular processes, accompanied by changes in the pattern of expression of the cytoskeletal protein vimentin. Signs of apoptosis, such as the externalization of membrane phosphatidyl serine residues, nuclear condensation, and fragmentation, were also detected in cells treated with 50–100 µM flavonoids. Our results indicate that flavonoids extracted from C. betulaster present antitumoral activity to glioblastoma cells, with penduletin proving to be the most potent of the tested flavonoids. Our results also suggest that these molecules may be promising supplementary drugs for glioblastoma treatment.

O 3-metilcatecol (3MC) é um metabólito do tolueno. Para esclarecer se o 3MC seria tóxico para o sistema nervoso central, examinou-se seus efeitos sobre a peroxidação de biomoléculas em frações nucleares e a respiração mitocondrial em organelas obtidas de cérebros de ratos. Também se testou a citotoxicidade para astrócitos primários de ratos. O 3MC a 1mM oxida-se consumindo oxigênio a uma taxa de 1,98 ± 0,19 mM.min-1, formando quinonas reativas. Nessa mesma concentração o 3MC peroxidou biomoléculas nas frações nucleares. Esse composto também inibiu o estado 2 da respiração mitocondrial associada ao FADH2. Além disso, o 3MC também se oxida em meio de cultura levando à formação de quinonas. Esse metabólito do tolueno foi citotóxico para astrócitos de ratos. A concentração que matou 50% das células após 72 horas foi 107 mM. Os resultados desse estudo indicam uma relação direta entre a citotoxicidade e a oxidação do 3MC.

The aim of this work was to study the effects of 3MC on the peroxidation of biomolecules in nuclear fractions and nonsynaptic mitochondrial respiration in organelles obtained from rat brains. The cytotoxicity towards rat primary astrocytes in vitro was also tested. 3MC at 1mM oxidized consuming oxygen at a rate of 1.98 ± 0.19 µM.min-1 and formed reactive quinones. At the same concentration, 3MC induced peroxidation of biomolecules in nuclear fractions obtained from rat brain homogenates and inhibited state 2 FADH2-linked respiration in nonsynaptic mitochondria. Furthermore, 3MC oxidized in the culture medium, leading to the formation of quinones. This toluene metabolite was cytotoxic to rat primary astrocytes. The concentration that killed 50% of cells after 72 h was 107 mM. The results of the study indicated a direct relationship between cytotoxicity and 3MC oxidation.