Atividade antibacteriana de taninos extraídos de folhas de Psidium Guineense sw. (Myrtaceae)

Abstract

Methanolic extracts from dried and fresh leaves of Psidium guineense, collected in Glaucilandia (MG) city, were submitted to purification by successives extractions with rising polarity solvents: eter oil, dichloromethane, ethylacetate and butanol. The residues from fractions were submitted to antibacterial test against cepas of Staphylococcus aureus ATCC 25923 and Pseudomonas aeruginosa ATCC 27853, by two variants of the agar diffusion method (disc and well). All fractions showed antibacterial activity. According to these results, it was prepared an extract with 70% acetone of dried and fresh leaves of P. guineense, in order to isolate tannins from the plant and evaluate if the content of these compounds in the samples had relation with antibacterial activity observed in the initial test. Thus, the extract was applied to a column of sephadex LH-20 and two methodologies were used for the isolation. The tannins present in the isolated samples were quantified and the samples were submitted to antibacterial test. The samples gotten by two methods of isolation showed a high content of tannins and inhibited the bacterial increasing. The compounds responsible for the antibacterial activity of the samples rich in tannins were extracted with major efficiency from dried leaves and the well variant of the diffusion method was more sensitive to the diffusion from these compounds.