Molecular Authentication of Acanthopanacis Cortex by Multiplex-PCR Analysis Tools

Abstract

Acanthopanacis Cortex has been used for oriental medicinal purposes in Asian countries especially in Korea and China. In the Korean Pharmacopeia, the cortexes of the dried roots, stems and branches of all species in Eleutherococcus and Eleutherococcus sessiliflorus are known as 'Ogapi'. Mostly the cortexes of E. gracilistylus roots and E.senticosus roots were used as 'Ogapi' in China and Japan, respectively. Therefore, the purpose of this study was to determine and compare the molecular authentication of Korean 'Ogapi' by using the ribosomal internal transcribed spacer (ITS) region. The ITS region has the highest possibility of effective and successful identification for the widest variety of molecular authentication. The ITS region was targeted for molecular analysis with Single nucleotide polymorphisms (SNPs) specific for morphologically similar to E. gracilistylus, E. senticosus, E. sessiliflorus from their adulterant, moreover, E. sieboldianus were detected within sequence data. Thus, based on these SNP sites, specific primers were designed and multiplex PCR analysis were conducted for molecular authentication of four plants (E. gracilistylus, E. senticosus, E. sessiliflorus, and E. sieboldianus). The findings of results indicated that ITS region might be established multiplex-PCR analysis systems and hence were proved to be an effective tools for molecular evaluation and comparison of 'Ogapi' with other plants.

Introduction

Acanthopanacis Cortex (Ogapi in Korean) is important Oriental medicinal herbs in Korea and China. The trees Ogapi the Eleutherococcus sessiliflorum Seman or same plants (Ohgagwa Araliaceae) of the bark of roots, stems and branches is defined the Eleutherococcus as Natural Currently Pharmacopoeia of various origins and mountains, and medicinal parts are mixed distribution. In contrast, China E. gracilistylus (Ogapi) the dried root bark of E. senticosus (Oga) defined as the root, stem, and bark, and is defined to be different. It is cortexes of dried roots, stems and branches with clinical properties that belong to the Araliaceae family, the cortical root and stem tissues of Eleutherococcus genus are used as tonic and sedative as well as to treat rheumatism and diabetic disorders (Umeyama et al.,1992; Davydov and Krikorian 2000). The treatment of various diseases such as psychophysical stress, fatigue, allergic conditions and cancer (Fujikawa et al., 1996; Deyama et al., 2001; Yi et al., 2002; Jung et al., 2003). In China, Acanthopanacis Cortex is Radix Cortex of E. gracilistryus (Chinese Pharmacopoeia Commission, 2010). In Korea, the Republic of Korea Food and Drug Administration has defined Acanthopanacis Cortex in the Pharmacopoeia as E. sessillorum and belonging to the Araliaceae (Korea Food and Drug Administration, 2008).

Traditionally, medicinal plants have been authenticated by historical and morphological features, but growth stages and environmental conditions can affect this authentication (Zhu et al., 2004). Most of medicinal plant products in markets are packaged as powders of slices that no longer bear the original morphological features of the plants (Park et al., 2006; Jigden et al., 2010; Jin et al., 2013). In this study, E. gracilistylus, E. senticosus, E. sessiliflorus are morphologically similar and their adulterant, E. sieboldianus are often sold dried or in slices, which makes it even more difficult to distinguish between the plants.

We describe general ways to differentiate medicinally important plants in a more reproducible and robust approach by analyzing single-nucleotide polymorphism (SNP). For the SNP analysis, there are several genes to be tested. Therefore, more robust and advanced DNA technology such as multiplex PCR should be applied when identifying these plants (In et al., 2010; Sun et al., 2010). The established multiplex-PCR systems were proved to be effective for molecular identification of Acanthopanacis Cortex. The medicinal materials collected in markets were identified by multiplex-PCR tests.

These markers nucleotide would be useful to identify the medicinal herbs by providing of definitive information that can identify the standard medicinal plant species and distinguish from unauthentic adulterant Eleutherococcus species. In this study, a simple and reliable DNA method was developed for simultaneous detection of Acanthopanacis Cortex (Ogapi in Korean), Cortex Acanthopanacis (Ogapi in China), Acanthopanacis Senticosi (Oga in China and Japan) form their adulterant, Plant, E. Sieboldianus by SNP analysis in nuclear ribosomal ITS region.

 

Materials and Methods

Plant materials

The samples of E. gracilistylus, E. senticosus, E. sessiliflorus and E. sieboldianus were collected from Plant DNA bank, Korea Cosmeceutical Material Bank. The E. gracilistylus samples were purchased from Korea local market. All the plant materials were collected from different localities and identified by the Table 1.

Table 1.Plant samples used in this study

DNA extraction and PCR amplification of the ITS region

Sample branches were frozen in liquid nitrogen and ground to a fine powder. Genomic DNA was isolated and purified using a G-spin TM genomic DNA extraction kit (iNtRON, Biotechnology, Seoul, Korea), and each dried sample was isolated using a modified cetyltrimethylammonium bromide (CTAB) method (Murray et al., 1980). The primer pairs used for amplification of the ribosomal ITS region was amplified using primer pair ITSPF (5’-TAC CGA TTG AAT GGT CCG-3’) and ITSPR (5’-ATA TGC TTA AAC TCA GCG GGT-3’) (Wang et al., 2012). PCR amplification was performed in a total volume of 20 μl, and the reaction mixture consisted of each of the primers at a concentration of 0.5 μm, 20 ng of template DNA, and 10 μl of 2 × PCR premix (Genotech, South Korea). The amplification profile consisted of one pre-denaturation cycle of 4 min at 94℃, followed by 35 cycles of 30 s at 94℃, 30 s at 58℃, 1 min at 72℃, and a final extension at 72℃ for 7 min. The PCR products were visualized via 1.0% agarose gel electrophoresis with Ethidium bromide staining under UV light.

Sequencing and DNA sequence analysis

The PCR products were purified using a PCR product purification kit (GENEALL PCR SV, General Bio Systems) per the manufacturer’s instructions and then sequenced by Genotech, Inc. The DNA sequences of the ITS region obtained in sequencing experiments were compiled using SeqMan software, and sequences were edited with the BioEdit program (Hall, 1999). Multiple sequence alignments were performed using the online ClustalW2 program (http://www.ebi.ac.uk/ Tools/clustalw2/).

Design of specific primers

Specific primers were designed for E. sessiliflorus, E. senticosus, E. sieboldianus and E. gracilidtylus based on the detected DNA polymorphisms (Fig. 1). E0F, ESF, ESiF and EGF were designed for authentication of E. sessiliflorus, E. senticosus, E. sieboldianus and E. gracilidtylus respectively, based on specific polymorphism sites. Primer E0F was designed for specific identification of E. sessiliflorus based on its specific 1-bp polymorphism. Primer ESF was designed for specific identification of E. senticosus, based on its specific 1-bp polymorphism. Primer ESiF was designed for specific identification of E. sieboldianus, based on its specific 1-bp polymorphism. Another sense primer of EGF was designed for specific identification of E. gracilidtylus, based on its specific 1-bp polymorphism. The primer was designed to serve as a positive control for Ogapi. The sequences and orientations of specific primers and common primers are shown in Table 1 and Fig. 2.

Fig. 1.Comparison of the ITS regions of E. gracilistylus, E. sessiliflorus, E. sieboldianus and E. senticosus.

Fig. 2.Schematic diagrams of the primers used in multiplex PCR.

Multiplex PCR

Molecular authentication of E. sessiliflorus, E. senticosus, E. sieboldianus and E. gracilidtylus was performed using multiplex PCR. Five primers (E0F, ESF, ESiF, EGF and ITSPR) were used simultaneously in multiplex PCR amplification. The reaction mixture was identical to the one described above except the concentrations of E0F, ESF, ESiF, EGF and ITSPR were 0.5 μm, 0.5 μm, 0.38 μm, and 0.5 μm, respectively. PCR amplification was performed in a total volume of 20 μl. The amplification profile consisted of one pre-denaturation cycle of 4 min at 95℃, followed by 32 cycles of 30 s at 95℃, 30 s at 62.5℃, 1 min at 72℃, and a final extension at 72℃ for 7 min. The PCR products were visualized on a 1.0% agarose gel.

 

Results and Discussion

Ribosomal DNA ITS regions have proven useful for species-level identification (Olmstead et al., 1994). The coding sequence of nrDNA is distantly related among different species and populations, whereas the non-coding internal transcribed spacers (ITS) are vary widely (Baldwin 1992). These regions can be used for authentication of E. sessiliflorus, E. senticosus, E. sieboldianus and E. gracilidtylus.

As an effort to minimize negative side effects from misuses of relatively common medicinal materials, Acanthopanacis Cortex, which might be misidentified from the standards, this study was carried out to analyzed the phylogenies and develop the molecular markers of three medicinal herbs to identify correctly and efficiently. The herbal criteria of medicinal herbs are documented in the Korean Pharmacopoeia (KHP) as follows: Acanthopanacis Cortex is the cortexes of roots, stems and branches of the Eleutherococcus sessiliflorum or of plants the same Eleutherococcus genus in Araliaceae.

The DNA information of three medicinal plants for analyses of phylogenetic relationship were obtained from National Center for Biotechnology Information (NCBI). In this study, analyzed nucleotide sequences of the Internal transcribed spacer (ITS) region in nrDNA showed close genetic relationships among E. sessiliflorus, E. senticosus, E. sieboldianus and E. gracilidtylus in Eleutherococcus genus.

Seventeen plants samples of Eleutherococcus genus ITS regions DNA sequences were collected from NCBI, and aligned in Bioedit program with ClustalX program and a phylogenetic tree was built using the Mega4 program. Eleutherococcus genus E. senticosus, E. seoulensis and E. trifoliatus is classified cousin relationship with E. sessiliflorus, while E. gracilistylus and E. koreanus is classified distant relationship (Fig. 3).

Fig. 3.The neighbor-joining tree of species in genus Eleutherococcus by ITS sequences.

Thus it renders them as a suitable target for the investigation of phylogenetic relationships within the same species. These regions can be used for authentication of E. sessiliflorus, E. senticosus, E. sieboldianus and E. gracilidtylus. The sequences of introns and intergenic regions are highly variable due to the lack of sequence conservation (Quandt et al., 2004). ITS reference to a piece of non-functional situated between structural (rRNA), which were excised during rRNA maturation. Because, this region is not only easy to amplify even from small amount of DNA but also has a high degree of variation even between closely related species (Wang and Hong, 2014). In this study, the ITS regions non-coding region was targeted for molecular analysis and differentiation among E. sessiliflorus, E. senticosus, E. gracilidtylus and their adulterant, E. sieboldianus.

The ribosomal ITS region of four species were PCRamplified using the universal primer sets of ITS non-coding region, ‘ITSPF’ and ‘ITSPR. The ITS regions non-coding region of E. sieboldianus, E. senticosus, E. gracilistylus and E. sessiliflorus was determined to be 259 bp, 339 bp, 479 bp and 618 bp. Their sequences were deposited in GeneBank (KJ170230-KJ 170233).

Multiplex alignments of the ITS regions non-coding region of E. sessiliflorus, E. senticosus, E. gracilidtylus and their adulterant, E. sieboldianus were performed with the CLUSTAL X program. DNA polymorphisms, including SNP sites, insertions and deletions were detected among these three species. The E. sessiliflorus- specific primer E0F was designed according to the insertions located at the 543th - 565th nucleotide positions. The E. senticosus-specific primer ESF was designed according to the deletions located at the 461th - 481th nucleotide positions. The E. sieboldianus-specific primer ESiF was designed according to DNA polymorphisms located at the 321th - 340th nucleotide positions. The E. gracilidtylus-specific primer EGF was designed according to DNA polymorphisms located at the 183th - 205th nucleotide positions (Fig. 1).

Molecular discrimination of E. sessiliflorus, E. senticosus, E. sieboldianus and E. gracilidtylus was conducted using multiplex PCR with the five primers described. The combination of five specific primers, as shown in Fig. 4, yielded expected amplicons for different species. E. sessiliflorus yielded specific amplicons of 618 bp and E. senticosus, E. sieboldianus and E. gracilidtylus yielded specific amplicons of 479 bp, 339 bp and 259 bp, generated by their specific primer sets, E0F, ESF, ESiF, EGF and ITSPR, respectively. Therefore, E. sessiliflorus, E. senticosus, E. sieboldianus, E. gracilidtylus can be clearly differentiated from each other by the multiplex PCR system developed in this study.

Fig. 4.Gel image of multiplex-PCR products. Lane M: 1000 bp DNA ladder; lane 1,2,3: E. gracilistylus; lane 4,5,6: E. sessiliflorus: lane 7,8,9: E. sieboldianus: lane 10,11,12 E. senticosus.

In the present study, we identified four plant species, E. sessiliflorus, E. senticosus, E. gracilidtylus and their adulterant plants E. sieboldianus, by simultaneously amplifying their specific primer using multiplex PCR. The results indicate that it is possible to identify “Ogapi” and “Oga” from their adulterant using the ribosomal ITS regions non-coding region. Compared to other molecular markers, this method is reliable, efficient, and can be used for numerous repeated tests of many medicinal plants. In this result have great impact to prevent adulteration and the authentication of precise E. sessiliflorus, E. senticosus, E. sieboldianus form their adulterant plant E. gracilidtylus using the ITS region. Compared to other molecular markers, this method is reliable, efficient and can be used for numerous repeated tests of many medicinal plants. We hope the described method should serve as a powerful tool in the multiplex PCR for the identification of medicinal plants, and the methodology presented in this study can be adapted for authentication of other medicinal materials.