Isolation of the MAO-inhibitor naringenin from Mentha aquatica L

Aims of the study To isolate the compound(s) responsible for the MAO-inhibitory activity. Materials and Methods Six extracts of varying polarity of Mentha aquatica L. were tested in a photometric peroxidase linked MAO bioassay. The 70% ethanol extract had highest inhibitory activity. (S)-Naringenin was isolated from the extract by bioassay guided fractionation on VLC and preparative TLC. The structure of the compound was determined by 1H, 13C and 13C-DEPT NMR and optical rotation. Results The IC50 values for MAO inhibition by naringenin were 342 ± 33 μM for the rat liver mitochondrial fraction, 955 ± 129 μM for MAO-A and 288 ± 18 μM for MAO-B. Conclusions The content of naringenin in Mentha aquatica might explain its use in traditional medicine for depression-like conditions.