Antibacterial effects of single or combined plant extracts

Single or combined extracts of black thyme, fennel, sage, wild tea and wild mint were used to evaluate in vitro antibacterial activity against common pathogenic bacteria and lactic acid bacteria (LAB). The antibacterial effects of combined plant extracts (I to 1 mixing ratio) were similar to single plant extracts against pathogenic bacteria. The inhibition of LAB was weaker with single plant extracts than that of the combined plant extract. Among the plant extracts, black thyme had the strongest antibacterial activity, and this was followed by the sage, wild tea and wild mint in a descending order. The combined plant extracts with black thyme had strong antibacterial activity against pathogenic bacteria and LAB. However, combined plant extracts without black thyme had slight antibacterial effect on all bacteria. Generally single and combined extracts had lower inhibitory effects against LAB than that against pathogenic bacteria. Therefore, these extracts are considered a natural food and/or feed additives to improve the gut health of humans and animals.