A preliminary analysis of the ability of standard DNA barcoding techniques to distinguish plant mixtures

摘要

The growing use of herbal medicines throughout the world has led to allegations of product adulteration, with potential deadly health risks for users. To prevent product adulteration, ingredients need to be verified, but traditional botanical identification techniques are inadequate as plant products are typically in processed forms (i.e. powder or tablet). DNA barcoding has been shown useful in verifying the components of herbal medicines; however, its accuracy in determining the ingredients of medicines with multiple plant species has not been experimentally evaluated. In theory, the use of standard DNA barcoding techniques should prove ineffective in the identification of the ingredients of mixed herbal medicines due to overlapping peaks in chromatograms which inhibit species resolution. The goal of this research is to evaluate the ability of standard DNA barcoding techniques to accurately determine the identity of species in mixed herbal medicine samples. DNA was isolated from five commonly used medicinal plant species. Fresh leaf tissue from four species was mixed at three different concentrations (25%, 50%, and 75%) with the target species (Ginkgo biloba) to create mixtures of known quantity and identity. Preliminary results show that DNA barcoding is able to determine the identity of herbal medicines containing one species but is unable to distinguish multiple species found in tested mixtures. Results may indicate that the composition of the mixed samples cannot be resolved, due in part to PCR bias caused by chloroplast copy number or secondary metabolites influencing PCR product production. As this study is one of the first to experimentally investigate standard DNA barcoding techniques for identifying species in mixed herbal medicines, more research needs to be conducted to address the issues highlighted here. In future studies, mixed samples should contain both broad and narrow phylogenetic dispersion and account for PCR bias among taxa to determine if sta