Antimicrobial activity of blackberry leaf extract and selected phenolics mixtures on pathogenic bacteria : master thesis

Sve je veća zabrinutost potrošaĉa oko sigurnosti hrane zbog povećanja broja oboljenja uzrokovanih patogenim mikroorganizmima. Brojna znanstvena istraţivanja ukazuju na mogućnost korištenja nusproizvoda za obogaćivanje drugih proizvoda ili kao zamjena za sintetska antimikrobna sredstva. Antioksidativno i antimikrobno djelovanje bobiĉastog voća je već potvrĊeno, a navedeni uĉinci se uglavnom pripisuju njihovom fenolnom sastavu, odnosno spojevima poput flavonoida i antocijana, a poznato je da listovi kupine isto imaju zanimljiv kemijski profil kao i snaţnu biološku aktivnost. U ovom radu prouĉavano je antimikrobno djelovanje ekstrakta lista kupine u kombinaciji s odabranim fenolnim spojevima (vanilinska kiselina, katehin, rutin, apigenin i oleuropein) na patogene mikroorganizme: Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Escherichia coli, Enterococcus faecalis i Salmonella enteritidis. Analiza je provedena korištenjem dviju razliĉitih metoda: metodom odreĊivanja minimalne inhibitorne koncentracije (engl. Minimum inhibitory concentracion, MIC) i metodom odreĊivanja minimalne baktericidne koncentracije (engl. Minimum bactericidal concentration, MBC). Interakcijski antimikrobni uĉinak izmeĊu ekstrakta i spoja u smjesi odreĊen je izraĉunavanjem frakcijskog inhibitornog koncentracijskog indeksa (eng. Fractional Inhibitory Concentration Index, FICI). Niske MIC vrijednosti (0,63 mg/mL) i dobro baktericidno djelovanje (MBC 1,25 mg/mL) potvrĊeno je za ekstrakt lista kupine prema S. aureus, dok su vrijednosti MIC za ostale ispitivane bakterije bile 5 mg/mL. Sve binarne smjese ekstrakta lišća kupine i odabranih fenolnih spojeva pokazale su vrlo dobru antimikrobnu aktivnost i uglavnom su ukazivale na aditivno djelovanje sastojaka smjese. Samo je smjesa ekstrakta lista kupine i oleuropeina pokazala sinergistiĉki uĉinak prema L. monocytogenes (MIC=1,25+0,31 mg/L, te FICI 0,5).Due to the increasing number of diseases caused by pathogenic microorganisms, consumers are becoming increasingly concerned about food safety. Numerous scientific studies point to the possibility of using by-products to fortify foods or their use as substitutes for synthetic antimicrobials. The antioxidant and antimicrobial effects of berries have been already confirmed and are primarily related to their phenolic content, mainly compounds such as flavonoids and anthocyanins, blackberry leaves have interesting chemical profile and strong biological activity. In this work, the antimicrobial activity of blackberry leaf extract in combination with selected phenolic compounds (vanillic acid, catechin, rutin, apigenin and oleuropein) against foodborne pathogens: Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Escherichia coli, Enterococcus faecalis and Salmonella enteitidis was studied. Analysis was performed using two different methods: minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The interaction between extract and compoundsin terms of antibacterial activity was determined by calculating the fractional inhibitory concentration index (FICI). The low MIC (0.63 mg/mL) and good bactericidal activity (MBC 1.25 mg/mL) were confirmed for the blackberry leaf extract against S. aureus, while the MIC values for the other tested bacteria were 5 mg/mL. All binary mixtures of blackberry leaf extract and selected phenolic compounds showed very good antimicrobial activity and mostly indicated additive activity. Only mixture of blackberry leaf extract and oleuropein had a synergistic effect against L. monocytogenes (MIC=1.25+0.31 mg/L, and FICI 0.5)