Discovery of novel secondary metabolites from the basidiomycete Lentinus cf. sajor-caju and their inhibitory effects on Staphylococcus aureus biofilms.

Three novel derivatives of microporenic acid, microporenic acids H-J, were identified from submerged cultures of a Lentinus species obtained from a basidiome collected during a field trip in the tropical rainforest in Western Kenya. Their structures were elucidated via HR-ESIMS spectra and 1D/2D NMR spectroscopic analyses, as well as by comparison with known derivatives. Applying biofilm assays based on crystal violet staining and confocal microscopy, two of these compounds, microporenic acids H and I, demonstrated the ability to inhibit biofilm formation of the opportunistic pathogen Staphylococcus aureus. Thereby, they were effective in a concentration range that did not affect planktonic growth. Additionally, microporenic acid I enhanced the anti-biofilm activity of the antibiotics vancomycin and gentamicin when used in combination. This opens up possibilities for the use of these compounds in combination therapy to prevent the formation of S. aureus biofilms.

Syntheses and biological effects of natural Morinda lactone and derivatives.

2-Caffeoyl-3-ketohexulofuranosonic acid γ-lactone (morinda lactone; 1a), a natural constituent of Morinda citrifolia L. (Rubiaceae), and eight derivatives with variance in the aryl residue were synthesised by Tsuji-Trost allylation of vitamin C acetonide with the respective aryl allyl alcohol. They were screened for antibiotic activities and for effects on the growth and persistence of microbial biofilms. Some derivatives were active against biofilms of S. aureus or C. albicans at concentrations not toxic to these microorganisms or mammalian cells.