Antioxidant properties and antibacterial activity of selected herbal teas

Herbal teas are a valuable source of bioactive compounds, which affect their pro-health properties. Especially polyphenols may play an important role against oxidative stress and could also bring tangible benefits in the treatment of bacterial and viral infections. Nowadays, the consumption of various herbal infusions is becoming more popular. Therefore, the aim of this study has been to evaluate antioxidant and antimicrobial properties of selected herbal teas. The research material was composed of eight herbal infusions: Cistus incanus L., Camellia sinensis L., Achillea millefolium L., Centaurium erythraea Rafn, Leonurus cardiaca L., Salvia officinalis L., Melissa officinalis L., Mentha piperita L. Antioxidant capacity (DPPH, ABTS), total polyphenol (TP, FBBB) and total flavonoid (TF) content were determined. Furthermore, the antimicrobial activity and the minimal inhibitory concentration (MIC) were evaluated. The results showed the highest antioxidant properties for herbal teas from Melissa officinalis L., Cistus incanus and Camellia sinensis. The lowest values were determined for Achillea millefolium and Centaurium erythraea teas. All tested herbal infusions presented varied antibacterial activity, although all of them were more efficacious against Gram-positive than Gram-negative bacteria. The highest antimicrobial properties were identified for teas from Cistus incanus and Camellia sinensis. Only Melissa officinalis tea showed activity against some Gram-positive test strains, mainly S. aureus and E. faecalis. Herbal infusions presented a high polyphenol content but had quite a low total flavonoid content, which suggests that other compounds determine their antioxidant properties, probably numerous phenolic acids, tannins and others. Further studies including the structure of polyphenols should be conducted.