Caracterização química e avaliação da atividade biológica da própolis vermelha em células tumorais e não tumorais

Abstract

Brazilian red propolis has attracted scientific and economic interests because of its varied biological activities. This natural product has different chemical compositions according to the region in which it is found, requiring a robust chemical characterization to elucidate the compounds responsible for the activities in each type of propolis investigated. So far antioxidant and antitumor properties are amongst the most studied biological activities. This study aimed to characterize chemically the hydroalcoholic extract of Brazilian propolis from the state of Sergipe, evaluate the antitumor and antioxidant activities, and to investigate the pattern o f proteins in tumor cells o f the larynx treated o r not with extracts of propolis through comparative proteomic analysis. The chemical characterization by mass spectrometry with electrospray ionization showed that propolis presents complex molecules, especially isoflavones, which has important biological and antioxidant capacity. The hydroalcoholic extracts obtained from propolis revealed a significant content of polyphenols associated with the ability to scavenge DPPH. radicais. The extracts also showed significant activities for superoxide dismutase-like and catalase-like, indicating an important role in maintaining physiological redox equilibrium, decreasing oxidative stress. Cytotoxic activity was assessed for tumor cell !ines Hep-2, HeLa and non-tumor cell line Hek-293, showing IC50 values greater for Hek-293 compared to Hep-2 and HeLa cells, which suggests a selectivity of propolis for the tumor !ines. The proteomic analysis using two-dimensional electrophoresis associated with high performance liquid chromatography coupled with mass spectrometer allowed the comparison of the protein maps of Hep-2 cell line in the absence or presence of propolis extracts in concentrations of 6 f.lg/mL (not cytotoxic) and 120 f.lg/mL (IC50). 325 spots were manually excised from the gels 2D SDS-PAGE and 177 proteins were identified. These proteins have been linked to various structural and metabolic processes, such as production and energy conversion, transport and carbohydrate metabolism, post-translational modification, protein tumover and chaperones, cytoskeletal proteins, repair proteins, among others. From the identified proteins that showed differential expression five were downregulated in the presence of propolis extract in the highest concentration (120 J.lg/mL). Only . two proteins identified in this study showed increased expression in the no cytotoxic concentration (6 J.tg/mL) ofthe red propolis extract. The results of comparative proteomic showed that the propolis interacts with a series of intracellular events and hence becomes a promising candidate to inhibit cellular growth and contribute to the different steps related to the process of carcinogenesis. Although the molecular mechanisms by which propolis interacts with the metabolism of the cells remain unknown, additional studies will better elucidate the antitumor and antioxidant activities here observed.