Structure-activity relationship of natural and synthetic coumarin derivatives against Mycobacterium tuberculosis.

Aim: Eight coumarin derivatives (1a-h) obtained from natural (-)-mammea A/BB (1) and 13 synthetic coumarins (2-14) had their cytotoxicity and biological activity evaluated against Mycobacterium tuberculosis H37Rv reference strain and multidrug-resistant clinical isolates. Materials & methods: Anti-M. tuberculosis activity was evaluated by resazurin microtiter assay plate, and the cytotoxicity of natural and synthetic products using J774A.1 macrophages by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. Results: Compounds 1g, 5, 6, 12 and 14 were more active against M. tuberculosis H37Rv and multidrug-resistant clinical isolates with MIC values ranging from 15.6 to 62.5 µg/ml. Conclusion: These results demonstrate that the coumarin derivatives were active against multidrug-resistant clinical isolates, becoming potential candidates to be used in the treatment of resistant tuberculosis.

Anti-biofilm activity against Staphylococcus aureus MRSA and MSSA of neolignans and extract of Piper regnellii

ABSTRACT Many infections worldwide are associated with bacterial biofilms. The effects of isolated neolignans (conocarpan and eupomathenoid-5) and the dichloromethane extract of Piper regnellii (Miq.) C. DC., Piperaceae, were tested against isolates of methicillin-resistant Staphylococcus aureus and methicillin-sensitive S. aureus biofilms and S. aureus planktonic cells. The dichloromethane extract presented better results than isolated neolignans against all of the biofilms tested, with a minimum inhibitory concentration <400 µg/ml for preformed biofilms and minimal biofilm inhibitory concentration of 15.6 µg/ml for biofilm formation. The minimum inhibitory concentration to planktonic cells was <12.5 µg/ml. These results indicate a good effect of the dichloromethane extract against methicillin-resistant S. aureus and methicillin-sensitive S. aureus biofilms and efficient prophylaxis.