Adulteration of Botanical Raw Materials in India, Part 2: identity Determination of 112 Commercial Herbal Raw Materials Using DNA Barcoding

 

Reviewed: Stalin N, Vassou SL, Sundar P, Raju B, Madasamy P. Identification of species adulteration in traded medicinal plant raw drugs using DNA barcoding. Genome. 2016;60(2):139-146.

 

Keywords: Medicinal plant, India, adulteration, DNA barcoding

 

This investigation into the authenticity of crude raw materials sold in India also used a DNA barcoding approach. The authors created their own DNA sequence library using 521 taxonomically authenticated medicinal plant species. The choice of the two genetic regions used for sequencing, matK and rbcL, was based on recommendations by the Consortium for the Barcode of Life Plant Working Group (CBoL). Commercial samples (n = 112) were collected from eight markets in the Indian province of Tamil Nadu using Tamil vernacular names.

 

DNA sequences for the rbcL locus were obtained for all 112 samples; however, the success rate was only 64% using the matK gene region. The yield of full-length sequences was 94% and 47% for rbcL and matK, respectively. Species identification of the raw drugs was performed by the best match method using Taxon DNA software, which assigns the sequence of interest to its closest match based on the genetic divergence.

 

The results indicate that 22 commercial raw materials were completely substituted by a species from a different genus or family. Andrographis paniculata (Acanthaceae) or Senna species (Fabaceae) were each identified as adulterants in three commercial products. Reasons for the adulteration may include accidental or intentional mislabeling, similar morphology, occurrence in the same habitat, confusion in vernacular names, or substitution as result of non-availability or high cost of the authentic species. The problems in using the common names were exemplified by four cases (Table 1).

 

Table 1. Examples of species adulteration in India due to confusing vernacular names

 

Labeled species	Vernacular name	Adulterant species	Vernacular name
Bergenia ciliata (Saxifragaceae)	Sirupilai	Aerva lanata (Amaranthaceae)	Sirupilai
Swertia chirata (Gentianaceae)	Nilavembu	Andrographis paniculata (Acanthaceae)	Nilavembu
Adenanthera pavonina (Fabaceae)	Anai Kundumani	Abrus precatorius (Fabaceae)	Kundumani
Toona ciliata (Meliaceae)	Santhana Vembu	Azadirachta indica (Meliaceae)	Vembu

 

 

Comment: The determination of the identity of raw materials used in herbal medicine systems in India continues to be a focus of academic institutions on the Indian subcontinent. The use of genetic methods to authenticate crude raw materials is becoming more prominent, and plant geneticists, such as the authors of this paper, suggest that the approach should be included as part of the toolbox of regulatory agencies. However, exactly which method is best suited for general use, and how to determine the validity of the method, are a matter of debate, as evidenced in discussions during a recent roundtable discussion organized by the United States Pharmacopeia.¹ One major hurdle is the establishment of a database containing sequence data obtained from taxonomically verified voucher specimen, which will require collaboration of a number of organizations on a global scale. As an example, the barcode library created by the authors of this paper, which contains rbcL and matK sequences of 521 plant species, contains less than 10% of the estimated 7500 medicinal plant species used in India.²

 

References

1.     USP Roundtable Summary - DNA Methods for the Identification of Botanical Articles. Rockville, MD: United States Pharmacopeial Convention. August 2016. Available at: http://www.usp.org/sites/default/files/usp_pdf/EN/dietarySupp/newsletter/201608-dna-summary.pdf. Accessed March 1, 2017.

2.     Uniyal RC, Uniyal MR, Jain P. Cultivation of Medicinal Plants in India: A Reference Book. New Delhi, India: TRAFFIC India. 2000.