Determination of water-soluble polyphenolic compounds in commercial herbal teas from Lamiaceae: peppermint, melissa, and sage

Chromatographic techniques (HPLC and HPTLC) were used for qualitative and quantitative determination of eriocitrin, luteolin 7-O-rutinoside, luteolin 7-O-beta-glucuronide, lithospermic acid, rosmarinic acid, and methyl rosmarinate together with other known compounds in commercial herbal teas from the Lamiaceae family: peppermint leaf (Menthae piperitae folium), melissa leaf (Melissae folium), and sage leaf (Salviae officinalis folium). Contents of analyzed compounds in infusions, the most popular forms, were established using a C18 column with acetonitrile-water-formic acid as a mobile phase. The HPLC method was validated for linearity, precision, and accuracy. Luteolin 7-O-beta-glucuronide and lithospermic acid were identified as new Mentha x piperita compounds. The investigated herbal teas delivered polyphenols in high amounts, up to 182.2 mg for the infusion of one peppermint tea bag.