Bioprospecção de cianobactérias dulcícolas isoladas do semiárido brasileiro

Abstract

The purpouse of work was test different species of freshwater cyanobacteria as to their ability to produce secondary metabolites of biotechnological interest in the pharmaceutical industry. The cultures were carried out with strains from the Microalgae Culture Bank of LARBIM/UFPB, which through morphological and molecular analyzes were identified as Arthrospira platensis (D39Z), Stanieria cyanosphaera (D112Z) and Brasilonema sp. (D298WC). The strains did not present microcystin. The water-soluble protein contents (%)were 23.3 ± 1.20 (D39Z), 36.7 ± 0.50 (D112Z), 36.0 ± 1.57 (D298WC); for total carbohydrates (%) were 8.27 ± 0.68 (D39Z), 13.3 ± 1.55 (D112Z), 17.4 ± 2.35 (D298WC); and for total lipids (%) were 6.00 ± 3.31 (D39Z), 6.00 ± 0.00 (D112Z), 14.00 ± 1.09 (D298WC). Analysis of the fatty acid methyl esters profile for the three strains allowed the identification and quantification of eighteen different fatty acids (saturated, unsaturated and polyunsaturated). In order to extract and isolate secondary metabolites, crude extracts of the three strains were obtained. A little bit fraction of the crude extract was directed to tests of antioxidant and antimicrobial activity. The excess portion of the D298WC extract was defatted and subjected to Medium Pressure Liquid Chromatography (MPLC) analyzes for fractionation. The fractions were analyzed by 1H NMR, the chemical profile evaluated and later purified on preparative and semi-preparative High Performance Liquid Chromatography (HPLC). The fractions was analyzed by NMR (1H, 13C, HMBC and HSQC) for structural elucidation of the obtained substances, being these, confirmed by the technique of mass spectrometry and directed to evaluate the cytotoxic activity. The highest total extractable phenolic contents were presented by D112Z (33.35 ± 0.05) and D298WC (34.19 ± 0.95). Regarding the determination of the antioxidant capacity, the result of the DPPH assay, the activity was higher for D39Z (79.33 ± 013); for the ABTS assay, the best total antioxidant capacity was for D39Z (18.16 ± 0.26) and D112Z (10.27 ± 0.69); and for the FRAP assay the highest capacity was for D39Z (16.14 ± 0.18). The antimicrobial activity, the D39Z methanolic extract, at concentrations of 512 to 1024 μg / mL, inhibited the growth of six of the eight strains (75%) of the microorganisms, including bacteria and fungi, while D112Z and D298WC showed inhibitory activity on three of the six strains of the microorganisms used in antimicrobial activity assays. The phytochemical study of the cyanobacteria Brasilonema sp. allowed the isolation and identification of three substances. A substance derived from chlorophyll, the chlorin-e6-trimethyl ester and two mixtures, one of them being a mixture of the aporphonic alkaloids methyl12-methoxy-6,7,7a,8-tetrahydro-5H-benzo[1,10]phenanthro[3,4-d][1,3]dioxole-7-carboxylate (Sassicine A) and ethyl12-methoxy-7a,8-dihydro-5H-[1,3]dioxolo[4',5':4,5]benzo[1,2,3-de]benzo[g]quinolone 7(6H)-carboxylate (Sassicine B). And other a mixture of nucleosides (deoxycytidine and cytidine) and amino acids (tyrosine, isoleucine and leucine). The substance and mixtures when evaluated for cytotoxic activity showed moderate activity, except for the alkaloids that the activity was low for colorectal carcinoma cells (HCT-116) and zero for mammary adenocarcinoma cells (MCF-7).