Background: Natural products display numerous therapeutic properties (e.g., antibacterial activity), providing the population with countless benefits. Therefore, the search for novel biologically active, naturally occurring compounds is extremely important. The present paper describes the antibacterial action of the Copaifera langsdorffii oleoresin and ten compounds isolated from this oleoresin against multiresistant bacteria; it also reports the antiproliferative activity of the Copaifera langsdorffii oleoresin and (-)-copalic acid.
Methods: MICs and MBCs were used to determine the antibacterial activity. Time-kill curve assays provided the time that was necessary for the bacteria to die. The Minimum Inhbitory Concentration of Biofilm (CIMB50) of the compounds that displayed the best results was calculated. Cytotoxicity was measured by using the XTT assay.
Results: The diterpene (-)-copalic acid was the most active antibacterial and afforded promising Minimum Inhibitory Concentration (MIC) values for most of the tested strains. Determination of the bactericidal kinetics against some bacteria revealed that the bactericidal effect emerged within six hours of incubation for Streptococcus pneumoniae. Concerning the antibiofilm action of this diterpene, its MICB50 was twofold larger than its CBM against S. capitis and S. pneumoniae. The XTT assay helped to evaluate the cytotoxic effect; results are expressed as IC50. The most pronounced antiproliferative effect arose in tumor cell lines treated with (-)-copalic acid; the lowest IC50 value was found for the human glioblastoma cell line.
Conclusions: The diterpene (-)-copalic acid is a potential lead for the development of new selective antimicrobial agents to treat infections caused by Gram-positive multiresistant microorganisms, in both the sessile and planktonic mode. This diterpene is also a good candidate to develop anticancer drugs.