Antibacterial Salinaphthoquinones from a Strain of the Bacterium Salinispora arenicola Recovered from the Marine Sediments of St. Peter and St. Paul Archipelago, Brazil.

Salinaphthoquinones A-E (1-5) were isolated from a marine Salininispora arenicola strain, recovered from sediments of the St. Peter and St. Paul Archipelago, Brazil. The structures of the compounds were elucidated using a combination of spectroscopic (NMR, IR, HRESIMS) data, including single-crystal X-ray diffraction analysis. A plausible biosynthetic pathway for 1-5 is proposed. Compounds 1 to 4 displayed moderate activity against Staphylococcus aureus and Enterococcus faecalis with MIC values of 125 to 16 µg/mL.

Silver nanoparticle stabilized by hydrolyzed collagen and natural polymers: Synthesis, characterization and antibacterial-antifungal evaluation.

In synthesis of silver nanoparticles (AgNPs), the composition of the stabilizer used can be closely related to the effectiveness of the synthesis and to the shape of the final nanoparticles. Recently, the use of collagen as an effective nanoparticle stabilization agent was reported. In this work, synthesis of silver nanoparticles using mixed capping agents is reported. The capping agents used were cashew gum-hydrolyzed collagen; kappa carrageenan-hydrolyzed collagen, and agar-hydrolyzed collagen. We evaluated antibacterial action against Gram-positive and Gram-negative bacteria, as well as antifungal activity and cytotoxicity. Homogenized mixtures of collagen and aqueous cashew gum, carrageenan or agar respectively were used to produce the nanoparticles AgNPcolCashew, AgNPcolCarr and AgNPcolAgar. AgNP characterization was performed using Uv-vis, XRD, TEM and DLS and the biological activities were assayed using MIC and MBC analyses for both antibacterial and antifungal application. Results showed that the AgNPcollcar sample showed the strongest bacterial inhibition with MIC values of 62.5 and 31.25 µM/mL Ag against E. coli and P. aeruginosa respectively. Interestingly, AgNPcollAgar also presented the lowest cytotoxicity when compared with other AgNPs and AgNO3.