Medicinal leeches have long held their place in Traditional Chinese Medicine (TCM) as treatments aimed at promoting blood circulation and eliminating blood stasis.
Nonetheless, the market has seen a surge of counterfeit leech products, casting doubt on the quality and efficacy of TCM practices reliant on these creatures. To combat this issue, researchers have developed a groundbreaking mitochondrial mini-barcode aimed at enhancing the identification accuracy of several leech species.
This novel 219 base-pair (bp) mini-barcode emerges from extensive analysis of the mitochondrial genome, particularly focusing on the variability of the 16S rRNA gene across five distinct leech species. Traditional DNA barcoding, primarily using the mitochondrial cytochrome oxidase I (COI) barcode, has exhibited limitations, particularly when it encounters degraded DNA often found within processed medicinal materials.
According to the study, the mini-barcode proved to be significantly more effective than the COI barcode. It identified 142 out of 147 leech samples from both fresh and processed materials, marking success for approximately 97% of the samples tested. By comparison, the COI barcode was only able to recognize 79 out of the same 147 samples. Impressively, the mini-barcode also distinguished six out of seven batches of leech decoction pieces—far surpassing the COI’s performance, which only managed to recognize one.
The study articulates the importance of accurately identifying leech species due to their diverse chemical compositions and effects, impacted significantly by their origin. "The traditional methods for the identification of medicinal leech materials include morphological analysis and chemical identification, but these methods depend on experience, have strong subjectivity, and are hard to distinguish between processed products," the researchers noted.
Historically, the medicinal leech has been featured prominently within TCM texts since Shen Nong Ben Cao Jing, yet the rise of imitations has posed challenges for practitioners. Given the pronounced efficiency drawbacks of standard barcoding methods, the mini-barcode approach utilizes shorter, more variable DNA segments, improving recovery rates from samples subjected to harsh processing conditions.
A key advantage of the mini-barcode is its ability to efficiently amplify degraded DNA. This batch of leech species, including Whitmania pigra, Hirudo nipponia, and others, typically undergoes extensive processing, which can negatively affect DNA quality. High-throughput sequencing techniques paired with this mini-barcode technology represent not only innovative but necessary approaches for credible identification.
Analysis confirmed the mini-barcode’s utility through the successful application of metabarcoding technology, facilitating the identification of mixed-species samples. This can significantly advance the quality control protocols within TCM, ensuring both purity and authenticity.
Reflecting on the blend of historical practice and modern technological advancement, the research team concludes, "Our results will provide a basis for accurately distinguishing medicinal leeches, ensuring the quality of medicinal materials, and offering guidance for the quality control of other animal-based medicines." This integration of genomic analysis marks yet another step forward in upholding the integrity of traditional practices within the rigor of contemporary scientific standards.
Overall, the introduction of this mitochondrial mini-barcode not only holds promise for TCM but could also be extrapolated to address similar challenges faced by various herbal medicines globally.