Novos compostos com propriedades antibióticas de Salinispora arenicola, uma bactéria associada ao sedimento marinho do Arquipélago de São Pedro e São Paulo

Abstract

This work describes the chemical investigation of the ethyl acetate extract (EtOAc) obtained from a bacterial strain identified as Salinispora arenicola, which was isolated from marine sediments collected in the Saint Peter and Saint Paul Archipelago-Brazil (ASPSP), aiming at the isolation of new bioactive compounds. The chemical investigation resulted in the isolation of thirteen new compounds: five aminonaphthoquinones designated as salinaphthoquinones A-E (SA-1 to SA-5), two N-methyl-2-oxindole derivatives 3-hydroxy-6-methoxy-3-(2-oxo-propyl)-N-methyl-2-oxindole (SA-6) and 5-chloro-3-hydroxy-6-methoxy-3-(2-oxo-propyl)-N-methyl-2-oxindole (SA-7), a tetraketide named 3-hydroxy-5-(1-hydroxy-1-phenylpropan-2-yl)-2- methyl-pyran-2-one (SA-8), besides five rifamycin derivatives designated as salinirifamycins A-E (SA-9 to SA-13). All isolated compounds were subjected to antibacterial assays against Staphylococcus aureus, including a methicillin-resistant strain, Enterococcus faecalis, also including a vancomycin-resistant strain and Escherichia coli. Salinirifamycins SA-9, SA-10, SA-11, and SA-13 showed potent activity against S. aureus and E. faecalis with MIC values ranging from 0.02 through 3.1 µg/mL. Salinirifamycin A (SA-9), the first example of rifamycin bearing a natural tetracyclic 5/6/6/6 pyridine-fused system isolated from Salinispora, revealed an activity (MIC of 0.02 µg/mL) similar to rifampicin (MIC 0.03 µg/mL), used as positive control. Regarding the other compounds, only Salinaphthoquinone B (SA-2) exhibited satisfactory activity (MIC 15.6-125.0 µg / mL) against both S. aureus and E. faecalis.