Modulation of S. aureus and P. aeruginosa biofilm: an in vitro study with new coumarin derivatives.

Coumarin is an important heterocyclic molecular framework of bioactive molecules against broad spectrum pathological manifestations. In the present study 18 new coumarin derivatives (CDs) were synthesized and characterized for antibiofilm activity against two model bacteria such as Staphylococcus aureus and Pseudomonas aeruginosa. It was observed that all the CDs executed significant effect in moderating activities against both planktonic and biofilm forms of these selected bacteria. Hence, to interpret the underlying probable reason of such antibiofilm effect, in-silico binding study of CDs with biofilm and motility associated proteins of these organisms were performed. All CDs have shown their propensity for occupying the native substrate binding pocket of each protein with moderate to strong binding affinities. One of the CDs such as CAMN1 showed highest binding affinity with these proteins. Interestingly, the findings of in-silico studies coincides the experimental results of antibiofilm and motility affect of CDs against both S. aureus and P. aeruginosa. Moreover, in-silico studies suggested that the antibiofilm activity of test CDs may be due to the interference of biofilm and motility associated proteins of the selected model organisms (PilT from P. aeruginosa and TarK, TarO from S. aureus). The detailed synthesis, characterization, methodology and results of biological screening along with computational studies have been reported. This study could be of greater interest in the context of the development of new anti-bacterial agent in the future.

Exploration of Phytoconstituents from Mussaenda roxburghii and Studies of Their Antibiofilm Effect.

In the context of ethno botanical importance with no phytochemical investigations, Mussaenda roxburghii have been investigated to explore it's phytoconstituents and studies of their antibiofilm activity. Four compounds have been isolated from the aerial parts of this plant and were characterized as 2α,3ß,19α,23-tetrahydroxyurs-12-en-28-oic acid (1), ß-sitosterol glucoside (4), lupeol palmitate (5), and myoinositol (6). All these compounds were tested for antibacterial and antibiofilm activity against Pseudomonas aeruginosa. Compound 1 exhibited three times more antibiofilm activity with minimum inhibitory concentration (MIC) at 0.74 mm compared to that of streptomycin. Molecular docking studies exhibited a very high binding affinity of 1 with P. aeruginosa quorum sensing proteins and motility associated proteins viz. LasR and PilB, PilY1, PilT, respectively. Compound 1 was also found to be non-cytotoxic against sheep RBC and murine peritoneal macrophages at selected sub-MIC doses.