Polyphenolic composition and antichlamydial effect of commercial peppermint (Mentha x piperita L.) teas

The qualitative and quantitative polyphenolic content of the infusions of the commercial peppermint tea (Mentha ×piperita L.) samples (n = 27) from different countries was studied using HPLC-UV-MS/MS analysis. Overall, 22 polyphenols were identified in the peppermint infusions. The major polyphenols were eriocitrin, 12-hydroxyjasmonate sulphate, luteolin-O-rutinoside and rosmarinic acid. The total polyphenolic content varied largely among the 27 peppermint tea infusions, found in a range of 10.0 – 218.0 mg/ml. In order to determine the content of samples by finding chemosystematic markers, essential oil composition of the samples was determined by GC. Of the analysed peppermint tea samples, 24 met the standards set by Ph. Eur. 7^th Ed., whereas the analyses indicated that three samples may contain Mentha spicata, a species different from that claimed on the package.

The effects of seven peppermint tea extracts against a respiratory tract pathogen Chlamydia pneumoniae were investigated in vitro. All the teas prepared from the selected commercial peppermint products inhibited chlamydial growth, inhibitions ranging from 20.7 to 69.5% at the extract concentration of 250 µg/ml. The effect on the inclusion counts at the second passage of infection was studied, showing an inhibitory effect on the infectious progeny production ranging from 7.8 to 78.1%. In most cases, the antichlamydial activity was a characteristic of the peppermint teas having high contents of luteolin and apigenin glycosides. This study supports the consumption of peppermint tea to potentially elicit beneficial health effects on acute respiratory tract infections.