The growing popularity of functional foods causes increasing interest in raw materials, which can raise the pro-health value of food when supplemented. The aim of the study was to assess the effect of compounds with antioxidant properties on Lactobacillus casei, as a representative of probiotic microorganisms. In the experiments the pure antioxidants and plant extracts were used. The results showed that catechin at concentration of 100-400 μM and chlorogenic acid (400 μM) had a stimulatory effect on L. casei growth. Quercetin at concentrations of 25-50 μM showed an inhibitory effect when incubation time was ≥ 6 h. The lingonberry leaves extract caused a slight increase in the dry substance of biomass in comparison with control. Extracts of coffee, chokeberry, and dog rose should not be used as additives for probiotic food as they significantly inhibited L. casei. We conclude that: 1) antioxidants at concentrations higher than 100 μM may stimulate growth of L. casei; 2) except the antioxidants, some other compounds which are present in plants extracts e.g. tannins and alkaloids may exert an antibacterial influence; 3) the probiotic yoghurts supplementation with fruit and other plant materials should be preceded by careful studies about their influence on the bacteria.

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