RESUMO
Increasing chronic bacterial infections create an urgent need for new antimicrobial agents or strategies for their control. Targeting virulence is one of the alternative approaches to find new medicines to treat persistent infections due to bacteria with biofilm-phenotype which are more resistant to antibiotics than their planktonic counterparts having an extreme capacity for evading the host defences. A bioguided study of sixteen extracts from flowers and leaves of four subtropical Convolvulaceae species provided evidence of the occurrence of antipathogenic natural products active against Gram positive and negative bacteria. Particularly, volatile metabolites from Merremia dissecta creeper, a food and medicinal plant, were able to interfere with the Pseudomonas aeruginosa quorum sensing system by a strong decrease of N-acyl homoserine lactone (AHL) biosynthesis (63-75%), which attenuated the virulence factor expression like biofilm (55%) and elastase activity (up to 27%), key factors that enable the colonization and dissemination of the infection in the host. Control of the P. aeruginosa biofilm and the QS process by phytochemicals, such as (+) spathulenol, isolated from a bioactive extract of M. dissecta leaves would be a good strategy for the development of new and effective antipathogenic drugs.
RESUMO
The drimane-type sesquiterpenoids (-)-polygodial (1), (-)-isopolygodial (4), drimenin (5), and isodrimenin (6) were isolated from a pungent Argentine collection of the fern Thelypteris hispidula, along with other terpenoids. As the mentioned drimanes have been previously found in liverworts, the present results strongly support the theory that Pteridophytes and Bryophytes share the same line of evolution. Our present investigations indicate that two chemotypes of T. hispidula are widespread in the northwest of Argentina. Plants belonging to the pungent chemotype contain drimanes, while nonpungent plants lack drimanes.