Prospecção fitoquímica, avaliação das atividades tóxica, citotóxica e antibacteriana de Tibouchina papyrus (Pohl) Toledo (Melastomataceae)

Abstract

The increasing search for new bioactive compounds has broadened the investigations on plants from the Brazilian Cerrado. The species Tibouchina papyrus belongs to the Melastomataceae family, which presents some species with biological activity. With the intention of increasing the knowledge of this family, the objective of this study was to investigate the bioactive potential of the species T. papyrus. The extracts were obtained from successive serial cold maceration of dried twigs and leaves pulverized with hexane, ethyl acetate and methanol solvents. Toxicity tests were performed against Artemia salina; antibacterial activity, by the broth microdilution method, against Gram-positive bacteria: Staphylococcus epidermidis (25923), Staphylococcus aureus (12228) e Gram negativas: Escherichia coli (25312) e Pseudomonas aeruginosa (27853); in vitro cytotoxic activity using colorimetric method against the cell lines of promyelocytic leukemia (HL60), human colon carcinoma (HCT-116), breast carcinoma (MCF-7), prostate carcinoma (PC3), astrocytoma (SNB-19) and non-tumor cells (L929). Phytochemical prospection was also performed to detect the main classes of secondary metabolites present in the extracts. The phytochemical screening indicated the presence of the metabolite groups: flavonoids, triterpenes, steroids and tannins. The purification process resulted in the identification of the triterpenes, α-and β-amyrin (still in mixture) and the ethyl pheophorbide A. All extracts were found to be non-toxic against A. salina. The branch and leaf methanolic extracts showed moderate antibacterial activity against S. aureus (500 μg.mL -1 , both parts), S. epidermidis (250 and 500 μg.mL -1 , respectively) and P. aeruginosa (250 μg.mL -1 , leaves only). The crude hexanic (twigs) and ethyl acetate (twigs and leaves) extracts showed high cytotoxic activity against HL60 cell line with cell inhibition values respectively equal to 93.31% (±1.85), 80.43% (±3.64) and 83.42% (±2.07).