Application of COI barcode sequence for the identification of snake medicine (Zaocys)

Abstract

Counterfeits in the medicine market make the authentication of snakes used for Chinese medicine a challenge to Chinese drug regulatory control agencies. This paper explores existing methods that can be used to quickly and accurately distinguish Zaocys (Z. dhumnades) from its counterfeits for routine identification of snake meats in food and drug control laboratories. In this research, the Cytochrome Oxidase I (COI) fragments of 51 samples from 17 species of snakes were amplified using Polymerase Chain Reaction (PCR) and sequenced. The inter- and intra-specific variations of COI sequences were analyzed and compared based on Kimura-2-parameter (K-2P) distances; the minimal interspecific K-2P distance was 0.0934, which was bigger than the maximum intraspecific K-2P distance in Z. dhumnades (0.0523), indicating that Zaocys can be separated from its counterfeits. The Neighbor-Joining (N-J) tree of the snakes was constructed and the results show that snakes of the same species cluster with 100% bootstrap values. Since the Zaocys and its counterfeits are of different species, they can be distinguished using the N-J tree method. Another 10 samples of Zaocys from markets and drug stores were identified at the species level, among which 5 samples were proven to be the counterfeits – Ptyas korros.