Mentha L., the genus belonging to family Lamiaceae, subfamily Nepetoidae, has high commercial importance in the pharmacy as well as in food industry. Mints are available in all five continents and are important sources of each traditional medicine in the prevention and therapy of plenty of diseases. The most active compounds are essential oil and polyphenols. In the past the secondary metabolites in aerial parts were examined, but there is no evidence about the determination of secondary metabolites in underground parts of mints. Therefore the object of this work was to determine the content of phenolic compounds (total hydroxycinnamic derivatives (THD) and flavonoids) of methanol extracts of rhizomes of different Mentha L. and their comparison with leaves extracts. The contents of secondary metabolites were determined using spectrophotometric methods of Slovak Pharmacopoeia. We have detected similar quantities of THD in leaves (0.79 - 2.48 %) and rhizomes (0.96 - 2.18 %), but underground parts were poor in content of flavonoids (< 0.1 %). The free radical scavenging activity using DPPH free radical was investigated as well. A bit stronger antioxidant activity was shown in leaves extracts considering flavonoids content.
