Evaluation of chemical composition and antibacterial activity of water extracts from selected spices

Celem pracy było otrzymanie ekstraktów wodnych z szałwii, rozmarynu i oregano, określenie ich składu chemicznego oraz aktywności przeciwdrobnoustrojowej w stosunku do wybranych szczepów bakterii. Ekstrakty otrzymywano metodą ekstrakcji ciągłej w automatycznym aparacie Soxhleta. Zawartość suchej substancji szałwii, oregano i rozmarynu w ekstraktach wodnych określono metodą suszarkowo-wagową. W pracy wyznaczano minimalne stężenie hamujące (MIC) i minimalne stężenie bakteriobójcze (MBC) ekstraktów oraz strefy zahamowania wzrostu bakterii metodą krążkowo-dyfuzyjną. Ekstrakt z szałwii charakteryzował się największym udziałem kwasu rozmarynowego (1,860 mg·cm–3) i chlorogenowego (0,104 mg·cm⁻³). W ekstrakcie z rozmarynu dominował kwas rozmarynowy (6,384 mg·cm⁻³) oraz ferulowy (0,268 mg·cm⁻³). Również w ekstrakcie z oregano oznaczono znaczące ilości kwasu rozmarynowego (1,820 mg·cm⁻³), p-kumarynowego (1,062 mg·cm⁻³), chlorogenowego (0,260 mg·cm⁻³), karnozolu (0,242 mg·cm⁻³) i mirycetyny (0,172 mg·cm⁻³). Ekstrakt wodny z szałwii był bardziej skuteczny w hamowaniu wzrostu drobnoustrojów w porównaniu z ekstraktem z rozmarynu i oregano, co uwidoczniło się w niższych wartościach MIC oraz MBC wyznaczonych dla tego ekstraktu.These days, consumers expect food products to be of high quality, as natural as possible and with a long shelf life. Raw materials of plant origin have been valued for years for their flavor attributes. They have also gained recognition owing to their stabilizing properties that are exploited in many production processes. Such properties are exhibited by plants belonging to the family Lamiaceae, i.e. e.g. oregano, sage and rosemary. The aim of this study was to obtain water extracts of sage, rosemary and oregano, to determine their chemical composition and antimicrobial activity against selected saprophytic and pathogenic strains of bacteria: Bacillus subtilis ATCC 6633, Proteus mirabilis, Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Salmonella enteritidis ATCC 13076, Microccocus sp., Tetracoccus sp., Enterococcus faecalis ATCC 29212, Proteus vulgaris 458, and Klebsiella pneumoniae 196. The antibacterial activity of plant extracts was evaluated by determining the minimum inhibitory concentration (MIC) [mg·cm⁻³] and the minimum bactericidal concentration (MBC) [mg·cm⁻³], and by determining bacteria growth inhibition zones. All of water extracts (sage, rosemary and oregano) contain the same compounds but in different amounts. The extract of sage characterized by the highest content of rosemary acid (1.860 mg·cm⁻³) and chlorogenic (0.104 mg·cm⁻³). The extract of rosemary held rosemary acid (6.384 mg·cm⁻³) and ferrulic acid (0.268 mg·cm⁻³). Also, in an extract of oregano determined significant amounts of rosemary acid (1.820 mg·cm⁻³) and p-coumaric (1.062 mg·cm⁻³), chlorogenic (0.260 mg·cm⁻³), carnosol (0.242 mg·cm⁻³) and myricetin (0.172 mg·cm⁻³). The analyzed water extracts from sage, rosemary and oregano, were exhibiting the antibacterial activity against most of the tested strains. The water extract of sage was more effective in inhibiting the growth of microorganisms as compared with the extract of rosemary and oregano, as evidenced by the lower values of MIC and MBC determined for the extract. The size of inhibition zones with an extract of sage was the largest of the tested extract and contained in the range from 2.7 mm (Tetracoccus sp. and Enterococcus faecalis ATCC 29212) to 11.1 mm (Proteus mirabilis 180). In the case of rosemary extract zones of inhibition were slightly smaller and ranged from 1.9 mm (Salmonella enteritidis ATCC 13076) to 8.1 mm (Klebsiella pneumoniae 196). The lowest zone of inhibition of bacterial growth was determined for the water extract of oregano, and they are included in the range from 1.0 mm (Salmonella enteritidis ATCC 13076) to 7.3 mm (Staphylococcus aureus ATCC 25923). It can be concluded that the water extract of sage is a source of active substances which inhibits the growth and development of selected strains of bacteria