Investigation of pesticide residues and heavy metals content in various peppermint samples

Abstract

Taking into consideration, that peppermint tea is frequently used in phytotherapy due to its wide range of therapeutic effects, ten samples of peppermint leaves were analysed in order to assess the level of pesticide residues and heavy metals. Pesticide residues were under the detection limit for six samples. However, in four peppermint samples we have determined λcyhalothrin (42-45 µg/kg), chlorpyrifos-ethyl (20-43 µg/kg), and cyfluthrin (78 ± 21 µg/kg), in concentrations below the maximum residues limits. In order to evaluate the negative impact of pesticides on patients health, a sample was spiked with the most common pesticide residues used in agricultural practice, by accumulation in the herbal product (diphenylamine 195.8 ± 16 µg/kg, chlorpropham 108.6 ± 12.4 µg/kg, hexachlorobenzene 76.7 ± 6 µg/kg, tolclofos-methyl 111.4 ± 39 µg/kg, cyfluthrin 472.7 ± 39.7 µg/kg). Moreover, we have observed that pesticide residues had a high transfer rate in infusion (diphenylamine 71.5%, chlorpropham 158.4%, chlordane-gamma 63%, tolclofos-methyl 61.5%). From the point of view of the heavy metals content, the sample shown concentrations over allowed limits (cadmium 98 µg/kg, copper 7140 µg/kg, lead 1500 µg/kg, mercury 170 µg/kg), some being transferable in infusion (nickel 123.3 %, copper 28%).