Application of a modified tetra-primer ARMS-PCR assay for rapid Panax species identity authentication in ginseng products.

Panax ginseng products can be adulterated with materials from other Panax species. The purpose of this study is to provide a rapid P. ginseng authentication method for simultaneous identification of P. ginseng and detection of adulteration in ginseng products at different processing stages. First, a tetra-primer ARMS-PCR assay was designed based on a single-nucleotide polymorphism (SNP) within the trnL-trnF region and was tested at 28 PCR cycles with DNA extracted from Botanical Reference Materials (BRMs). Next, 5' end random nucleotide and 3' terminus phosphorothioates linkage modifications were incorporated into the inner primers to improve sensitivity and specificity at 40 PCR cycles. Finally, the modified assay was validated using characterized market ginseng materials and the detection limit was determined. The modified tetra-primer ARMS-PCR assay can achieve the desired sensitivity and specificity using one set of reaction conditions in ginseng materials at different stages. In validation, it was able to correctly identify target species P. ginseng and differentiate it from closely related species. This study suggests that the modified tetra-primer ARMS-PCR assay can be used for the rapid, species identity authentication of P. ginseng material in ginseng products. This assay can be used to complement chemical analytical methods in quality control, so both species identity and processing attributes of ginseng products can be efficiently addressed.

Authentication of Hedyotis products by adaptor ligation-mediated PCR and metabarcoding.

DNA barcoding is a widely used tool for species identification and authentication. However, it may not be applicable to highly processed herbal products due to severe DNA fragmentation. The emergence of DNA metabarcoding provides an alternative way to solve the problem. In this study, we are the first to combine the use of adaptor ligation-mediated PCR method and metabarcoding to reveal species identities in herbal products. As an illustration, we applied the method on three Hedyotis herbal products collected from China and Thailand. Results showed that H. diffusa and H. corymbosa were present in the products which were consistent with their label claims. Our study indicated that the adaptor ligation-mediated PCR with metabarcoding approach is useful for authentication of highly processed herbal products.

Application of next-generation sequencing for the identification of herbal products.

Conventional Sanger Sequencing for authentication of herbal products is difficult since they are mixture of herbs with fragmented DNA. Next-generation sequencing (NGS) techniques give massive parallelization of sequencing reaction to generate multiple reads with various read length, thus different components in herbal products with fragmented DNA can be identified. NGS is especially suitable for animal derived products with the lack of effective markers for chemical analysis. Currently, second generation sequencing such as Illumina Sequencing and Ion Torrent Sequencing, and third generation sequencing such as PacBio Sequencing and Nanopore Sequencing are representative NGS platforms. The constructed library is first sequenced to obtain a pool of genomic data, followed by bioinformatics analysis and comparison with DNA database. NGS also facilitates the determination of contaminant which is essential for quality control regulation in Good Manufacturing Practice (GMP) factory. In this article, we provide an overview on NGS, summarize the cases on the use of NGS to identify herbal products, discuss the key technological challenges and provide perspectives on future directions for authentication and quality control of herbal products.

Effective authentication of Placenta Hominis.

BACKGROUND: Human placenta is used to make the medicinal product Placenta Hominis in Asian countries. With its therapeutic benefits and limited supply, intentional or inadvertent adulteration is found in the market. In order to enforce the implementation of product description laws and protect customer rights, we established a hierarchical protocol involving morphological, chemical, biochemical and molecular diagnosis to authenticate this medicinal product. METHODS: Ten samples claimed as Placenta Hominis were collected from herbal shops in China, Hong Kong and Taiwan. Species-specific diagnostic primers for human, cow, deer and sheep were designed for PCR amplification and subsequent DNA sequencing for species identification. Commercially available pregnancy test strip was used to detect human chorionic gonadotropin (hCG), and progesterone competitive ELISA kit was used to detect the presence of progesterone in samples. The presence of starch in samples was tested by adding small amount of iodine solution onto the samples. RESULTS: Among the ten samples studied, results showed that no cow, deer and sheep DNA sequence was found in all samples. Five samples were genuine with the presence of human DNA, hCG and progesterone accompanied with the absence of starch fillers. On the other hand, four samples were adulterants which may be made from starch products. In addition, a sample was found as a mixture of Placenta Hominis and starch fillers, and it did not conform to the product requirement of Placenta Hominis. CONCLUSIONS: The comprehensive protocol developed involving morphological, chemical, biochemical and molecular diagnosis provides an accurate method to regulatory bodies and testing laboratories for the quality control of Placenta Hominis.

DNA barcoding in concentrated Chinese medicine granules using adaptor ligation-mediated polymerase chain reaction.

The use of DNA barcodes for species identification is a common laboratory practice. However, PCR amplification of full-length DNA barcode in processed material is difficult because of severe DNA fragmentation. In this study, an adaptor ligation-mediated PCR protocol was derived to amplify sets of target DNA fragments isolated from two CCMG products. The specially designed adaptor with asymmetric strands and terminal modification avoids amplification of non-target DNA sequences. DNA extracted from Angelica sinensis and Panax notoginseng CCMG were ligated with the adaptors and amplified by an adaptor primer and a single universal barcode primer to obtain partial ITS2 sequence. Results showed that various length of DNA fragments within the ITS2 region were amplified and could be used to identify the concerned species. The adaptor ligation-mediated PCR is therefore a promising universal method for species identification in highly processed herbal products.

DNA-based techniques for authentication of processed food and food supplements.

Authentication of food or food supplements with medicinal values is important to avoid adverse toxic effects, provide consumer rights, as well as for certification purpose. Compared to morphological and spectrometric techniques, molecular authentication is found to be accurate, sensitive and reliable. However, DNA degradation and inclusion of inhibitors may lead to failure in PCR amplification. This paper reviews on the existing DNA extraction and PCR protocols, and the use of small size DNA markers with sufficient discriminative power for molecular authentication. Various emerging new molecular techniques such as isothermal amplification for on-site diagnosis, next-generation sequencing for high-throughput species identification, high resolution melting analysis for quick species differentiation, DNA array techniques for rapid detection and quantitative determination in food products are also discussed.

Quantification of concentrated Chinese medicine granules by quantitative polymerase chain reaction.

Determination of the amount of constituent in a multi-herb product is important for quality control. In concentrated Chinese medicine granules (CCMG), no dregs are left after dissolution of the CCMG. This study is the first to examine the feasibility of using quantitative polymerase chain reaction (qPCR) to find the amount of CCMG in solution form. DNA was extracted from Hirudo and Zaocys CCMG mixed at different ratios and amplified in qPCR using species-specific primers. The threshold cycle (CT) obtained was compared with the respective standard curves. Results showed that reproducible quantification results could be obtained (1) for 5-50mg CCMG using a modified DNA extraction protocol, (2) amongst DNA extracted from the same batch of CCMG and (3) amongst different batches of CCMG from the same company. This study demonstrated the constitute amount of CCMG in a mixture could be determined using qPCR. This work has extended the application of DNA techniques for the quantification of herbal products and this approach may be developed for quality assurance in the CCMG industry.

DNA authentication of animal-derived concentrated Chinese medicine granules.

Concentrated Chinese medicine granules (CCMG) offer patients a convenient option for traditional therapy. However with morphological and microscopic characteristics lost, it is difficult to authenticate and control the quality of these medicinal products. This study is the first to examine the feasibility of using DNA techniques to authenticate animal-derived CCMG, which has so far lacking of effective means for authentication. Primers targeting amplicons of different sizes were designed to determine the presence of PCR-amplifiable DNA fragments in two types of CCMG, namely Zaocys and Scorpio. Species-specific primers were designed to differentiate the genuine drugs from their adulterants. The specificity of the designed primers was evaluated in crude drugs (including genuine and adulterant) and CCMG. Results showed that by using species-specific primers, DNA fragments of less than 200bp could be isolated from the CCMG and the concerned source materials. This study demonstrated the presence of small size DNA in animal-derived CCMG and the DNA is effective in species identification. The work has extended the application of DNA techniques in herbal medicine and this approach may be further developed for quality control and regulatory compliance in the CCMG industry.

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.