Identification of individual herbal drugs in tea mixtures using restriction analysis of ITS DNA and real-time PCR.

We have studied a sedative tea made of Valerianae radix (Valeriana officinalis L.), Lupuli strobuli (Humulus lupulus L.), Melissae folium (Melissa officinalis L.) and Menthae piperitae folium (Mentha piperita L.). In order to identify the constituent drugs a method was established involving amplification of the internal transcribed spacers (ITS) region of nuclear ribosomal DNA on the basis of restriction analysis and real-time PCR. ITS regions of individual drugs were amplified and sequenced. Restriction analysis was performed with selected restriction endonucleases Nae I, PshA I and Xcm I. Real-time PCR was carried out, using primers specifically designed for each individual herbal drug. Real-time PCR proved to be a method for identifying individual herbal drugs in a tea mixture with a single DNA extraction in a single PCR run, since its limit of detection is lower than that for restriction analysis.