Assessment of adulteration in raw herbal trade of important medicinal plants of India using DNA barcoding

A number of studies have shown that there could be widespread substitution and/or adulteration (hereafter referred to as substitution) in raw herbal trade of medicinal plants. Substitution could potentially endanger the health and safety of the consumers. In this study, the extent of adulteration in raw herbal trade of 30 important medicinal plants in South India was analyzed. Biological reference material (BRM) consisting of taxonomically authenticated samples of each of the 30 species along with 14 other co-occurring and congeneric allied species that are likely to be used in adulteration was established. DNA barcode signatures of 124 BRM using two candidate regions, nr-ITS and psbA-trnH were identified. A total of 203 herbal trade samples representing the 30 medicinal plant species were collected from 34 locations in South India. Using the DNA barcode sequences of the BRM as reference, the analysis indicated that the substitution ranged from 20 to 100%. Overall, approximately 12% of the market samples were adulterated. Considering the potential health hazard that such adulteration can cause, the need for a national regulatory framework that can authenticate and regulate raw herbal trade in the country is discussed.