Identification of constituent herbs in ginseng decoctions by DNA markers

BACKGROUND DNA in herbal decoctions is usually fragmented by extensive boiling and is usually regarded as unsuitable for molecular authentication. This study aims to evaluate the feasibility for molecular authentication methods by multiplex polymerase chain reaction (PCR) and DNA sequencing for decoctions. METHODS The DNA extraction procedure, sample pulverization and boiling time were examined in (1) single herb decoction with Panax ginseng ("ginseng") or P. quinquefolius ("American ginseng"), (2) decoctions of two classical ginseng prescriptions of five herbal materials (Aconitum carmichaeli, Atractylodes macrocephala, P. ginseng, Glycyrrhiza uralensis and Zingiber officinale) and (3) a commercial ready-to-serve ginseng soup. Primers were designed from 26S-18S, ITS2 and trnH-psbA region, with DNA sequences obtained from GenBank. Multiplex PCR was also employed in ginseng or American ginseng decoctions to differentiate between these two herbs. RESULTS All six herbal species tested in this study could be identified in decoctions. We had four main observations: (1) sample pulverization before boiling improved PCR detection; (2) prolonged boiling increased the DNA concentration but decreased the intactness of DNA fragments; (3) ginseng could be differentiated from American ginseng by multiplex PCR; (4) identification of individual herbs in multi-herb decoctions with prolonged boiling time of 180 min could be achieved. CONCLUSIONS DNA could be amplified from extensively boiled ginseng decoctions, multi-herb decoctions and commercial soup although DNA degradation was critical to successful PCR.