Molecular Characterization of Akebia Plants and the Derived Traditional Herbal Medicine

The stems of Akebia plants, Akebiae Caulis, have long been used in traditional Chinese and Japanese medicines, and are mainly produced in western Japan. Three Akebia plants, Akebia quinata (AQ), A. trifoliata (AT), and A. pentaphylla (AP) grow wild in Japan. With the aim of carrying out molecular biological identification of Akebia plant species and discriminating Akebiae Caulis from other related crude drugs originating from non-Akebia plants, sequencing analysis of Akebia plants collected from various parts of Japan and the southern Korean Peninsula was performed. Specimens identified morphologically as AQ and AT had their respective common internal transcribed spacer one (ITS1) sequences, which could be distinguished. Cloning experiments of AP specimens showed that their ITS1 contained both common sequences of AQ and AT as well as their chimera. These chimeric sequences were not identical between AP specimens, suggesting that AP is not a species with uniform DNA sequences but a group of individuals with hybrid genomes of AQ and AT. Based on the sequences of Akebia species found here, we propose polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) methods to discriminate Akebiae Caulis from the related crude drugs and to distinguish three Akebia plants. Comparison of triterpene-rich fractions of extracts from Akebia plants by TLC showed that AP had an intermediate profile of AQ and AT.