Available online at www.sciencedirect.com
GENOMICS
PROTEOMICS &
BIOINFORMATICS
Genomics Proteomics Bioinformatics 10 (2012) 364–367
www.elsevier.com/locate/gpb
Application Note
DNA Barcode ITS Effectively Distinguishes the Medicinal Plant
Boerhavia diffusa from Its Adulterants
Dhivya Selvaraj 1, Dhivya Shanmughanandhan 1, Rajeev Kumar Sarma 1, Jijo C. Joseph 1,
Ramachandran V. Srinivasan 2, Sathishkumar Ramalingam 1,⇑
1
Plant Genetic Engineering Laboratory, Department of Biotechnology, Bharathiar University, Coimbatore 641046, India
2
Department of Botany, Bharathiar University, Coimbatore 641046, India
Received 2 September 2011; revised 9 March 2012; accepted 21 March 2012
Available online 29 November 2012
Abstract
Boerhavia diffusa (B. diffusa), also known as Punarnava, is an indigenous plant in India and an important component in traditional
Indian medicine. The accurate identification and collection of this medicinal herb is vital to enhance the drug’s efficacy and biosafety.
In this study, a DNA barcoding technique has been applied to identify and distinguish B. diffusa from its closely-related species. The
phylogenetic analysis was carried out for the four species of Boerhavia using barcode candidates including nuclear ribosomal DNA
regions ITS, ITS1, ITS2 and the chloroplast plastid gene psbA-trnH. Sequence alignment revealed 26% polymorphic sites in ITS,
30% in ITS1, 16% in ITS2 and 6% in psbA-trnH, respectively. Additionally, a phylogenetic tree was constructed for 15 species using
ITS sequences which clearly distinguished B. diffusa from the other species. The ITS1 demonstrates a higher transition/transversion ratio,
percentage of variation and pairwise distance which differentiate B. diffusa from other species of Boerhavia. Our study revealed that ITS
and ITS1 could be used as potential candidate regions for identifying B. diffusa and for authenticating its herbal products.
Keywords: Adulterant; Boerhavia diffusa; ITS; DNA barcoding; Punarnava
Introduction
Boerhavia is one of the highly polymorphic genus in Nyctaginaceae family [1]. About 40 species are distributed in
tropical, subtropical and temperate regions. Among these,
6 species are reported in India and Boerhavia diffusa (B.
diffusa) is indigenous [2]. B. diffusa is described as Punarnava by an Indian system of medicine, Ayurveda [3]. Roots
and whole plants of B. diffusa are used in the Ayurvedic
and Unani systems of medicine in Arabian countries [4]
and many tribal communities in India still use it for the
treatment of jaundice and various other liver disorders. It
has anti-inflammatory, diuretic, fibrinolytic, anti-convulsant properties [5–8] and also used as carminatives [9–10].
The two pharmaceutically important alkaloids, Punarna⇑ Corresponding author.
E-mail: rsathish@buc.edu.in (Ramalingam S).
vine-1 and Punarnavine-2, belonging to the group of quinolizidine were separated from B. diffusa [11–12].
B. diffusa is known to be extensively adulterated with
other species like Boerhavia erecta, Boerhavia repanda,
Boerhavia coccinea and Boerhavia verticillata. B. diffusa
have taxonomical conflicts with B. coccinea, Boerhavia
repens, Boerhavia tetranda and Boerhavia albiflora, making
it difficult to distinguish from one another [13–14]. The species B. verticillata display similar morphological features
and phytochemical properties with B. diffusa, but they differ by their habits [15]. Determination of plant specimens
by DNA barcodes will be an effective, reliable and simple
pharmacognostic tool to resolve the confusion in morphological identification. Due to different rates of evolution,
nuclear ribosomal internal transcribed spacer (ITS) regions
have become the routine marker in evolutionary studies at
different taxonomic levels [16,17]. There is a report using
the chloroplast intergenic spacer psbA-trnH for identifying
1672-0229/$ - see front matter Ó 2012 Beijing Institute of Genomics, Chinese Academy of Sciences and Genetics Society of China. Published by Elsevier
Ltd and Science Press. All rights reserved.
http://dx.doi.org/10.1016/j.gpb.2012.03.002
365
Selvaraj D et al / ITS Distinguishes Boerhavia diffusa from Its Adulterants
the Dendrobium species of Chinese pharmacopoeia and
psbA-trnH is recommended as an ideal DNA barcode candidate [18]. Recently the sequence variations are used to
develop specific markers for the identification and authentication of drugs and herbal formulations [19].
The objective of the present study is to evaluate an ideal
barcode candidate for distinguishing and authenticating
the species B. diffusa from its common adulterants.
Results
Genomic DNA was isolated from the species of B. diffusa,
B. repanda, B. erecta and B. verticillata and used for PCR
amplification of the ITS and psbA-trnH. The obtained
sequences were submitted to GenBank. The size and accession number for the gene ITS and psbA-trnH is shown in
Table S1. Additionally, ITS sequences from 11 species of
Boerhavia were taken from the GenBank (Table S2) and
used for sequence alignments.
Multiple sequence alignment and pairwise alignment
analysis were performed for nuclear ITS and chloroplast
psbA-trnH (Figure S1). The ITS region consists of ITS1,
5.8S rDNA and ITS2. The ribosomal sites of 5.8S rRNA
and 28S rRNA are highly conserved. The regions ITS1
and ITS2 were compared by multiple sequence alignment,
where ITS1 showed more variation than ITS2. Phylogenetic analysis using ITS1 and ITS2 indicated B. diffusa
and B. erecta in the same clade while B. verticillata and
B. diffusa was shown in the same clade when using
psbA-trnH region for phylogenetic analysis (Figure 1).
The tree also constructed using ITS region clearly distin-
guished the morphologically similar species B. diffusa from
the 14 other species of Boerhavia as shown in the Figure 2.
We further analyzed the nucleotide variations of ITS
and psbA-trnH between different species. Percentage of variation shown in Figure 3 indicated that ITS demonstrated
higher inter-specific divergence. The Wilcoxson rank test
indicated significant variation between the species for
ITS1 when compared to ITS2 and psbA-trnH. BLAST 1
and distance method also indicated that ITS1 showed
higher identification percentage at species level (Table 1).
Discussion
Recent molecular methods like DNA barcoding have been
extensively used for species identification, diversity, forensic medicine and ecological studies [20–21]. It also plays
an important role in the identification of traditional medicinal herbs. ITS2 has been effectively used in differentiating
morphologically similar species like Swartzia grandifolia
and Swartzia longicarpa and also in solving the controversial species Caranga rosea and Caranga sinica of the family
Fabaceae [22]. Medicinal plant species like the family
Polygonaceae [23] and the genus Dendrobium [24] have
been identified using ITS2 region. In addition, ITS1 was
used to demonstrate that species of Amomum villosum
belongs to the family Zingiberaceae [25].
In our study, multiple sequence alignment of ITS1 and
ITS2 from four Boerhavia species showed that B. diffusa
had a unique basepair variation, which can distinguish it
from the other three species, despite the fact that they share
many morphological similarities. On the other hand,
although psbA-trnH distinguishes some species of Polygonaceae [18], less sequence variation in psbA-trnH was
revealed among the four species of Boerhavia. This result
is consistent with a previous report that psbA-trnH does
not show any variation for closely-related Cycad species
[26]. Hence, ITS1 may be a better barcode region for distinB. repens
B. diffusa
100
B. coccinea
B. gracillima
B. anisophylla
B. linearifolia
99
66
B. ciliata
B. dominii
94 B. intermedia
B. lateriflora
100
B. purpurascens
B. erecta
99
74 B. spicata
B. repanda
100 B. verticillata
84
88
73
53
0.01
Figure 1 Phylogenetic trees of the four Boerhavia species constructed using
ITS1, ITS2 and psbA-trnH
Phylogenetic trees were constructed by Minimum Evolution method using
ITS1, ITS2 and psbA-trnH, respectively, for the four species of Boerhavia,
including B. diffusa, B. erecta, B. repanda and B. verticillata.
Figure 2 Phylogenetic tree of the 15 Boerhavia species constructed using
ITS
Phylogenetic tree was constructed by Minimum Evolution method for the
15 species of Boerhavia using ITS region.
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Genomics Proteomics Bioinformatics 10 (2012) 364–367
Figure 3 Sequence variation of ITS and psbA-trnH between four Boerhavia
species
Percentage of nucleotide variations between different Boerhavia species,
including B. diffusa, B. erecta, B. repanda and B. verticillata, was indicated
for ITS (dark gray) and psbA-trnH (light gray), respectively.
Table 1
species
Validation of ITS1, ITS2 and psbA-trnH from four Boerhavia
Gene name
Correct identification (%)
BLAST 1
ITS1
ITS2
psbA-trnH
Distance
At genus level
At species level
At species level
98
99
94
94
92
91
93.2
91.1
76.86
psbA-trnH F 50 -GTTATGCATGAACGTAAGCTC-30 ,
psbA-trnH R 50 -CGCGCATGGTGGATTCAAATCC-30 ,
respectively. The forward primer of ITS region from [29]
was modified at the position of 6 (T ! G) and 8
(A ! G). The PCR program was as follows, an
initial denaturation at 94 °C 5 min, followed by 35 cycles
of 94 °C 1 min, 57 °C 30 s, 72 °C 1 min and final
extension at 72 °C 10 min. PCR products were resolved
by gel electrophoresis, purified and subjected to sequencing. The obtained ITS and psbA-trnH sequences
were deposited in the GenBank of NCBI database (GenBank Accessions: HQ386701, HQ386689, HQ386691,
HQ386695, HQ386696, HQ407399, HQ386690 and
JF423303) (Table S1). Sequences of ITS genes from 11
additional species of Boerhavia were obtained from
GenBank (Table S2).
Sequence alignment and phylogenetic analysis
The DNA sequences were compared and aligned using the
programs ClustalW [30] and MULTALIGN (http://
www.multalin.toulouse.inra.fr/multalin/). Further, the
DNA sequences were subjected to BLAST (http://
www.ncbi.nlm.nih.gov/blast/blast.cgi) for better identification of sequence at species level. Phylogenetic trees were
constructed with the Minimum Evolution method using
MEGA 4.0. The intra-specific variation between the species
was calculated using MEGA 4.0 [31] and StatsDirect was
used to calculate the Wilcoxon signed rank [32].
guishing the species of Boerhavia, although ITS2 has been
widely used to distinguish the plant species [27]. This study
clearly indicates that DNA barcoding using candidate like
ITS1 is a reliable method for differentiating B. diffusa from
the other three species, which can also be applied to rapid
identification of medicinal plants and their adulterants or
substitutes.
Authors’ contributions
Materials and methods
Competing interests
Sample collection
The authors have declared that no competing interests
exist.
Four species of Boerhavia (B. diffusa, B. erecta, B. repanda,
B. verticillata) were collected from the regions of Western
Ghats (one of the hotspots), Coimbatore, India. The species were collected and identified by the taxonomist.
DNA extraction, PCR amplification and DNA sequencing
Fresh leaves from each plant species were used for isolating
total genomic DNA by CTAB method [28]. The ITS and
psbA-trnH gene amplifications were performed using Taq
DNA polymerase with the primers indicated below. The
forward and reverse primers for ITS and psbA-trnH used
were ITS F 50 -GGAAGGAGAAGTCGTAACAAGG-30 ,
ITS R 50 - TCCTCCGCTTATTGATATGC-30 [28] and
SR supervised the research. RVS collected and identified
the specimens. DS, DS, RKS and JCJ carried out the
experimental study. Dhivya Selvaraj prepared the manuscript and SR revised it. All authors read and approved
the final manuscript.
Acknowledgements
Dhivya Selvaraj thanks the University Grant CommissionResearch Fellowship for Meritorious Students (UGCRFMS). Sathishkumar Ramalingam thanks the financial
support from UGC (Grant No. 34-272/2008(SR)).
Supplementary material
Supplementary data associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/
j.gpb.2012.03.002.
Selvaraj D et al / ITS Distinguishes Boerhavia diffusa from Its Adulterants
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