Fungo endofítico isolado de Achyrocline satureioides: identificação molecular, caracterização química e investigação do efeito antitumoral de metabólitos bioativos

Abstract

Cancer is the leading cause of premature death in most countries. The urgency for therapeutic alternatives has encouraged the search for new anticancer agents from natural products. Evidence suggests that medicinal plants are colonized by endophytic fungi, which are an important source of unique chemical structures generated by coevolutionary relationships with the host plant. Known as 'marcela', Achyrocline satureioides is a medicinal plant whose antitumor effects of the plant extract have been attributed to the presence of polyphenols. We recently described the isolation and antiglioma effect of an endophytic fungus of A. satureioides. Thus, the main objective of this study was to elucidate the taxonomy of the isolated fungus, to characterize the metabolites present in the purified fraction (FDCM) and to evaluate its antimelanoma and antiglioma effect. Given the antitumor properties of polyphenols associated with A. satureioides, this study also investigated the antiglioma impact of commercial gallic acid (GA) through in vitro and in vivo tests. Through molecular analysis of the ITS region, the endophytic fungus was identified as Biscogniauxia sp. (Xylariaceae). The chemical characterization of FDCM by ultra-performance liquid chromatography coupled to a mass spectrometer demonstrated for the first time the ability of this fungus to produce compounds of the isocoumarins, terpenoids, and other polyketide derivatives. This is the first study to report the biosynthesis of lactone Sch-642305 by the Xylariaceae family. According to cytotoxic analyses, FDCM (1 to 20 µg/mL) reduced the proliferation of human melanoma (A375) and mouse glioma (C6) cells, inducing death and cell cycle changes after 72 h of treatment. To understand the antiglioma activity in the tumor microenvironment, neonatal rat cortical astrocytes and C6 cells were cocultured and exposed to FDCM for 72 h. As with C6, under coculture conditions FDCM also reduced metabolic activity, regulated the catabolism of extracellular adenine nucleotides and reduced oxidative stress. In addition, FDCM reduced the inflammatory response in glioma models, in addition to modulating the expression of genes involved in tumor progression such as ERK, COX-2, Casp-1 and IL-1β. No changes were observed in healthy astrocytes. AG (50 to 400 µM) reduced C6 cell growth after 48 h, modulating the purinergic and oxidative response. Finally, the intragastric administration of AG (50 and 100 mg/kg/day) for 15 days reduced the tumor volume, regulated purinergic signaling and prevented oxidative damage in brain, serum, platelets and/or lymphocytes of rats submitted to injection of C6 intracerebroventricular. Our data highlight the high potential of natural products in modulating pathways related to neoplastic progression, highlighting the importance of endophytic fungi as excellent producers of compounds of pharmacological interest.