Sesqui- and triterpenoids from the liverwort Lepidozia chordulifera inhibitors of bacterial biofilm and elastase activity of human pathogenic bacteria

Abstract

Five dammarane type triterpenoids,five pentacyclictriterpenoids(three of them carrying a carboxylicacid group),and two aromadendrane-type sesquiterpenoids were isolated from an Argentinian collection of th e liverwort Lepidozia chordulifera. Compounds were characterized by comparison of their spectral data with those previously reported and tested in their ability to control bacterial growth, biofilm formation, bacterial Quorum Sensing process(QS),and elastase activity of Pseudomonas aeruginosa,as well as bacterial growth and biofilm formation of Staphylococcus aureus.The key role played by biofilm and elastase activity in bacterial virulence make them a potential target for the development of antibacterial agents.Thearomadendrane-type sesquiterpenoid viridiflorol was the most potent biofilm formation inhibitor, producing 60% inhibition in P. aeruginosa and 40% in S. aureus at 50μg/ml. Ursolic and betulinicacids(two of the pentacyclic triterpenoids isolated) were able to reduce 96 and 92% the elastase activity of P. aeruginosa at 50μg/ml,respectively.Among the analyzed triterpenoids,those that carry a dammaraneskeleton were the most potent inhibitors of the P. aeruginosa biofilm formation and were active against both P. aeruginosa and S.aureus. Subsequently,a computer- assisted study of the triterpenoid compounds was carried out for a better understanding of the structure-activity relationships.