摘要：Rhei Rhizoma (Dahuang in Chinese) is widely known as a purgative and antiinflammatory agent. In the Japanese Pharmacopoeia, Rhei Rhizoma is prescribed for four Rheum species, Rheum palmatum , R. tanguticum , R. officinale , and R. coreanum , while the first three species are prescribed for Dahuang in the Chinese Pharmacopoeia. Due to the morphologic similarity of the aerial parts and frequent occurrence of intermediate forms, the taxonomy of this genus and the correct identification of Rheum species and their derivative drugs are very difficult. To resolve taxonomic problems of the genus Rheum and develop an ultimate identification method for plants and drugs, molecular analysis of the chloroplast mat K gene and nuclear 18S ribosomal RNA gene were performed on nine species. The sequence comparison of the mat K gene revealed that most species had variable sequences not only inter- but also intraspecies. However, the specimens of the same species belonged to the same subclade in the phylogenetic tree constructed based on mat K gene sequences, except for R. palmatum , in which specimens belonged to three subclades related to their production areas. The nucleotide differences at positions 587, 707, and 838 distinguished official species from others, while specific nucleotides at positions 367 and 937 became identification markers for R. palmatum , R. tanguticum , and R. officinale (or R. coreanum ). Moreover, three groups of R. palmatum , each belonging to three subclades, were characterized by the nucleotides at positions 619, 769, 883, and 1061. By detecting marker nucleotides, the botanical origins of Rhei Rhizoma were determined.
