Delving into the Mechanisms of Sponge-Associated Enterobacter against Staphylococcal Biofilms.

Staphylococci are one of the most common causes of biofilm-related infections. Such infections are hard to treat with conventional antimicrobials, which often lead to bacterial resistance, thus being associated with higher mortality rates while imposing a heavy economic burden on the healthcare system. Investigating antibiofilm strategies is an area of interest in the fight against biofilm-associated infections. Previously, a cell-free supernatant from marine-sponge-associated Enterobacter sp. inhibited staphylococcal biofilm formation and dissociated the mature biofilm. This study aimed to identify the chemical components responsible for the antibiofilm activity of Enterobacter sp. Scanning electron microscopy confirmed that the aqueous extract at the concentration of 32 µg/mL could dissociate the mature biofilm. Liquid chromatography coupled with high-resolution mass spectrometry revealed seven potential compounds in the aqueous extract, including alkaloids, macrolides, steroids, and triterpenes. This study also suggests a possible mode of action on staphylococcal biofilms and supports the potential of sponge-derived Enterobacter as a source of antibiofilm compounds.

Umbelliferone esters with antibacterial activity produced by lipase-mediated biocatalytic pathway.

OBJECTIVE: The present report describes the enzymatic acylation of umbelliferone with different vinyl esters as acyl donors biocatalyzed by the commercial lipase Novozym® 435, and the investigation for their antibacterial activity against ATCC and clinical strains isolated from hospital infection sites. RESULTS: The umbelliferone esters (1-5) were synthesized through the acylation reaction of 7-hydroxy-2H-chromen-2-one with different long chain vinyl esters catalyzed by the lipase Novozym 435. The reaction conditions were: 10% Novozym 435; tetrahydrofuran:acetone (3:1) for the reactions with acetate, propionate and butyrate vinyl esters 50-90% conversion, and (9:1) for decanoate and laurate vinyl esters 10-15% conversion; acyl donor/umbelliferone molar ratio of 10:1 and 60 °C. All the umbelliferone esters were characterized NMR and (HRMS). The antibacterial activity of the products were tested using the broth microdilution method in order to determine the minimum inhibitory concentration (MIC). The results displayed by 7-laurate and 7-decanoate-umbelliferone esters showed the highest antibacterial potential, with 1 mM inhibitory activity for ATCC 33591, a methicillin and oxacillin resistant Staphylococcus aureus strain. They were also able to inhibit gram-negative bacterial strains, such as Pseudomonas aeruginosa (MIC 0.5 mM) and Klebsiella pneumoniae (MIC 1 mM). In addition, 7-laurate- and 7-decanoate-umbelliferone esters were able to inhibit all clinical strains (MIC 1 mM; except 7-laurate-umbelliferone in which MIC 0.5 mM against 55a). CONCLUSIONS: This is the first study performing the biocatalysis of umbelliferone followed by the purification of the products and the antibacterial evaluation.

Phenolic compounds from Tocoyena bullata mart (Rubiaceae) with inhibitory activity in mast cells degranulation.

Glycosylated flavonoids, caffeoylquinic acid and 3,5-dicaffeoylquinic acid have been identified in the ethyl acetate partition from the crude ethanol extract of Tocoyena bullata (Rubiaceae) leaves. The fraction containing the mixture of flavonol rutin and a tetraglycosylated flavonoid showed 89.2% inhibition and the mixture of isoquercitrin and 3,5-dicaffeoylquinic acid showed 88.5% inhibition of mast cell degranulation. These results demonstrated that the tetraglycosylated flavonoid, rutin, isoquercitrin and 3,5-dicaffeioylquinic acid were the most promising phenolics for inhibition of mast cell degranulation. For the first time the identification of phenolic constituents and their correlation with inhibitory effect on mast cell degranulation were reported in this work.