Avaliação da atividade antimicrobiana de extratos e caracterização parcial de saponinas obtidas do resíduo de Agave sisalana Perrine (SISAL)

Abstract

The plant Agave sisalana, commonly known as sisal, has great economic importance for the northeast region of Brazil, as a provider of hard fibers. In this case, the use of the plant is approximately 5%, the remains being discarded as waste. Among the states, Bahia is highlighted by significant production (95%), corresponding to 234,000 tons of fiber, in 2008. This paper describes: 1) the antimicrobial activity comparison between the extracts of the leaf and the residue discarded, 2) the obtain, the chemical analysis and anti-Candida activity of different extracts from the residue, and 3) the partial characterization of a mixture of spirostan saponins residue. Initially a survey was conducted spirostan saponins in the genus Agave and their biological activities. Then, the evaluation of the antimicrobial activity of plant extracts and the residue of Agave sisalana against five Gram-positive bacteria, four Gram-negative bacteria and yeast revealed a significant inhibition of the extracts against Candida albicans and weak inhibition for the other microorganisms. After this finding, it was performed the obtaining of extracts containing saponins. The dried crude extract obtained from the residue was partitioned using ethyl acetate and isobutanol to provide the substrates ethyl acetate, butanol and aqueous. The analysis of NMR spectra of ¹ H demonstrated characteristic signs for steroidal saponins for all extracts. The ethyl acetate extract was fractionated using open column with silica gel and eluted with this solvent in order to increase the polarity yielding 28 fractions. Fractions 7-9 were combined and purified by Sephadex LH-20 resulted in obtaining a mixture of saponins spirostan. This mixture of saponins was analyzed by nuclear magnetic resonance of ¹H and ¹³C, including 2D NMR techniques. From these results, the extracts of the residue were evaluated against Candida albicans for the minimum inhibitory concentration. The butanol extract demonstrated higher inhibition (0.19 mg / mL) compared with the ethyl acetate extract and aqueous tested.