Identification of Asari Radix et Rhizoma derived from three close Asarum species using the complete chloroplast...

Asari Radix et Rhizoma is a traditional Chinese herbal medicine derived from Asarum sieboldii, Asarum heterotropoides var. mandshuricum and Asarum sieboldii var. seoulense. However, the three Asarum species are both hard to identify morphologically and subject to taxonomic controversies. Moreover, their molecular identification based on molecular techniques remains challenging. The misidentification may ultimately affect therapeutic efficacy and safety.

We hypothesize that the failure to identify the three Asarum species using chloroplast genomes in previous studies might be due to the limited size of sampling and inconsistent assembly. Therefore, we try to reveal their genetic relationships and address identification issues using chloroplast genomes based on expanded sampling size and manual check.

This study collected 13 samples of the three Asarum species from the wild in China and obtained their chloroplast genomes through Illumina sequencing. The chloroplast genome characteristics of these samples were first compared, followed by phylogenetic analysis to elucidate the interspecific relationships among the three Asarum species.

This study observed that the chloroplast genomes of the three Asarum species are approximately 190 kb and uniformly exhibited a tripartite structure, but not a quadripartite structure. Phylogenetic analysis revealed that A. heterotropoides var. mandshuricum and A. sieboldii var. seoulense are more closely related, formed a nested branch, while A. sieboldii branched independently. Based on these findings, a potential marker region was identified to distinguish A. sieboldii from both A. heterotropoides var. mandshuricum and A. sieboldii var. seoulense.

The phylogenetic analysis corroborated the geographic distribution patterns of the three species and aligned with their customary names as documented in the Chinese Pharmacopoeia. Nevertheless, it deviates from conventional taxonomic categorizations. This investigation provides innovative perspectives on the taxonomy of the three Asarum species, thereby establishing a foundational framework for their future identification research.