Abstract
Preparations from carnivorous plants belonging to genus Drosera (Droseraceae) were shown to possess antimicrobial properties [1]. The objective of this research was to evaluate antibacterial properties of secondary metabolites obtained from Drosera aliciae Raym.-Hamet plants grown in vitro and to examine mechanism of their antimicrobial action. Bactericidal activity of chloroform and methanol extracts from D. aliciae as well as pure ramentaceone as the major naphthoquinone present in this plant were examined against resistant and susceptible to antibiotics strains from the following species of human bacterial pathogens (hospital isolates): Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. Chloroform extract proved to be more effective than methanol preparation against all of the tested strains except for P. aeruginosa isolates with the lowest minimal bactericidal concentration (MBC) values in case of S. aureus (25–50mg FW ml-1). Methanol extract from D. aliciae caused 3 and 8-fold increase (for 0.1 and 0.25 MBC respectively) in generation time of E. faecalis in relation to control, chloroform preparation elevated generation time 1.2 and 2-fold, while both tested concentrations of ramentaceone caused no statistically significant growth retardation. The influence of D. aliciae extracts and ramentaceone on the synthesis of DNA, RNA and proteins in cultures of E. faecalis was estimated by measurement of incorporation of radioactive precursors: [3H]thymidine, [3H]uridine or [3H]leucine, respectively. Methanol extract from D. aliciae except for a moderate effect on DNA synthesis had no influence on neither RNA nor protein synthesis. Chloroform preparation caused about 75% decrease in [3H]uridine incorporation into RNA in comparison to control after 60min and a significant reduction of DNA and protein synthesis (44% and 30% respectively). Ramentaceone also reduced DNA and RNA synthesis but less efficiently than chloroform extract and caused no changes in protein synthesis.
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