Droplet digital PCR for the identification of plant-derived adulterants in highly processed products

The high sensitivity of droplet digital PCR (ddPCR) contributes to its excellent performance in animal and microorganism identification, but the utilization of ddPCR is limited in plant adulterant identification of highly processed products for which effective methods are lacking. This study investigated the feasibility of ddPCR in the identification of plant adulterants in Chinese patent medicine (CPM) as groundwork to develop ddPCR assays for other highly processed goods. The original plant, processed and highly processed products of Mutong (Akebiae Caulis) and its two adulterants were used to analyze the specificity, sensitivity, and practical performance of the developed singleplex and triplex ddPCR assays. The results revealed that the limit of detection (LOD) and limit of quantification (LOQ) for the selective ddPCR assays developed to identify Mutong and its adulterants were 0.00002 ng/μl and 0.00016 ng/μl, respectively, and that the regression equations representing the relationships between DNA concentration and target copy number all exhibited good linearity. Furthermore, the common adulterant of Mutong in three samples of Longdan Xiegan pills was successfully identified through ddPCR assays and confirmed by Sanger sequencing. This work comprehensively revealed the great ability of ddPCR technology in detecting plant adulterants in traditional Chinese medicine (TCM), providing a method for the quality control of highly processed plant products with complex components for commonly used goods.