Browsing by Author "Laakso, Riina"

Diseases caused by foodborne pathogens are a global threat, which is why new bioactive compounds are expected in the food industry. The purpose of this work was to investigate the antimicrobial effects of three different plants, blackcurrant (Ribes nigrum), rhubarb (Rheum spp.), and Scots pine (Pinus sylvestris), against seven pathogenic bacteria. Bioactivity of these plants has been previously shown, but results have varied widely depending for example on the plant part, extraction solvent and pathogen. The plant samples were extracted with 30 % or 80 % ethanol-water solution. There was a total of 12 extracts: rhubarb petiole (dried at 45 °C or lyophilized), rhubarb root (dried at 50 °C), blackcurrant berry (dried at 45 °C or lyophilized) and lyophilized juice of Scots pine needles. Extracts were dissolved in dimethyl sulfoxide and bioactivity screening of the extracts was determined at a concentration of 1,0 mg/ml, after which the active extracts were subjected to minimum inhibitory concentration (MIC) determination (n=2-3) at eight concentrations (0,0625-4,0 mg/ml). Antimicrobial experiments were performed on a 96-well plate following Clinical and Laboratory Standards Institute guidelines. Bioactivity was determined based on absorbance measurements and visual inspection. The extract of rhubarb root showed most potential against tested bacteria. The lowest MIC values (0,25 mg/ml and 0,50 mg/ml) were obtained with rhubarb root extracts (extracted with 80% or 30 % ethanol-water solution) against Staphylococcus aureus and Bacillus cereus and 1,0 mg/ml against Listeria monocytogenes. Based on this study rhubarb root extract could be a potential natural antimicrobial against foodborne pathogens.