The antimicrobial effect of (+)-limonene and α-pinene on beneficial and potential pathogens isolated from food

Esencijalna biljna ulja, u čijem sastavu značajnu komponentu čine spojevi iz skupine terpena ((+)-limonen i α-pinen), intenzivno se istražuju u cilju zaštite namirnica od mikrobnog kvarenja. Također, spomenuti spojevi koriste se kao "zelena“ otapala za ekstrakciju antimikrobnih spojeva iz različitih biljaka. Budući da se antimikrobna aktivnost takvih ekstrakata ne može sa sigurnošću diferencirati, potrebno je ispitati utjecaj čistih otapala na korisne i patogene mikroorganizme što je bio i cilj ovog rada. Minimalne inhibitorne (MIK) i minimalne bakteriocidne koncentracije (MBK) određene su za oba otapala prema dvije različite biomase (103 i 106 CFU ml-1) korisnih i potencijalno patogenih bakterijskih vrsta. Dodatno, određena je stopa preživljavanja korištenih bakterija pri koncentracijama otapala nižim od MIK vrijednosti. Utvrđeno je inhibitorno i bakteriocidno djelovanje (+)-limonena i α-pinena na sve ispitivane bakterijske izolate. Antimikrobno djelovanje oba otapala detektirano je pri nižim koncentracijama otapala za nižu biomasu bakterija (103 CFU ml-1), dok je za postizanje istog učinka kod više biomase (106 CFU ml-1) bila potrebna viša koncentracija otapala. Za pojedine vrste zabilježene su visoke MIK i MBK vrijednosti (+)-limonena i α-pinena (100,0%) za testiranu biomasu od 106 CFU ml-1 bakterija. Koncentracije (+)-limonena i α-pinena niže od MIK vrijednosti, kod kojih su bakterijski izolati još uvijek rasli, utjecale su različito na redukciju bakterijske brojnosti, a ovisno o ispitivanoj bakterijskoj vrsti.Essential vegetable oils containing terpene compounds ((+)-limonene and α-pinene) are intensively investigated in order to protect food from microbial spoilage. Also, those compounds are used as "green solvents" for the extraction of antimicrobial compounds from various plants. Since the antimicrobial activity of such extracts cannot be differentiated with certainty, it is necessary to examine the effect of pure solvents on beneficial and pathogenic microorganisms, which was the aim of this work. The antimicrobial activity of the solvent was determined on the two initial biomass (103 and 106 CFU ml-1) of selected beneficial as well as potentially pathogenic bacterial species. Minimum inhibitory (MIC) and minimum bactericidal concentrations (MBC) of (+)-limonene and α-pinene were determined, as well as the influence of solvent concentrations lower than MIC on the number of tested bacterial species. At the bacterial biomass of 103 CFU ml-1, lower concentrations of (+)-limonene and α-pinene showed antimicrobial activity, while higher concentrations of solvent achieved the same antimicrobial effect on higher biomass (106 CFU ml-1 ). For particular species of biomass of 106 CFU ml-1 high MIC and MBC values of (+)-limonene and α-pinene (100,0%) were recorded. Concentrations of (+)-limonene and α-pinene lower than MIC values, at which bacterial isolates were still growing, influenced differently abundance of bacteria, depending on tested bacterial species