Identification of Panax japonicus and its related species or adulterants using ITS2 sequence / 中草药

ABSTRACT

Objective: To provide a scientific basis for the modern identification of Panax japonicus and ensure the clinical efficacy and medication accuracy, the molecular identification of P. japonicus and its related species or adulterants was carried out. Methods: ITS2 sequences of P. japonicus were amplified and sequenced directionally. ITS2 sequences of related species and adulterants were downloaded from GenBank. Cutting with ITS2 database, the final dataset consisted of 102 sequences from 24 species. DAMBE program was also implemented to detect substitution saturation of ITS2 sequences. MEGA 6.06 software was utilized for sequence alignment, calculating GC content, analyzing variation sites, estimating intra-specific and inter-specific genetic distances, and finally building NJ tree. Moreover, the secondary structure of ITS2 was predicted by using the ITS2 database. Results: The length of ITS2 sequences from P. japonicas was 230 bp and GC content was 63.7%. The average genetic distance analysis, NJ tree, and secondary structure characteristics of the ITS2 sequences showed that there were great differences between P japonicus and its non-identical adulterants or partial related species (P. stipuleanatus, P. pseudoginseng, P. trifolius, P. vietnamensis var. fuscidiscus, and P. vietnamensis). Howerer, the application of such method for the identification of P. japonicus and partial closely related species (P. quinquefolius, P. ginseng, P. notoginseng, P. japonicus var. major, P. japonicus var. bipinnatifidus, P. assamicus, P. variabilis, and P. japonicus var. angustifolius) had certain limitation. Conclusion: The ITS2 sequence can be used as one of the DNA barcodings for the identification of P. japonicus and its non-identical adulterants at high identification rate, however, its versatility of identification between P japonicus and related species needs to be further verified. Our study provides the basis for the identification of inter-specific genetic and affinity relationship of P. japonicas and its related species, the distinguishment between P. japonicas and non-identical adulterants, and the clinical safety of P japonicas.