DNA Barcoding of the Market Samples of Single-Drug Herbal Powders Reveals Adulteration with Taxonomically Unrelated Plant Species

Herbal drugs are increasingly becoming a viable alternative to allopathic medicine. Since powdered herbal drugs are more prone to adulteration than intact plant parts, their authentication becomes essential to ensure the safety and efficacy of herbal drugs. This study authenticated 107 single-drug herbal powders, representing 65 species from 60 genera and 35 families, collected from the markets in Tamil Nadu, India. DNA barcoding using the rbcL marker revealed that 58 samples (54%) were authentic, and 49 (46%) were adulterant. About 41% of the adulterant samples were a mixture of more than one species, possibly due to unintentional cross-contamination during processing. In 59% of the adulterant samples, the authentic species was entirely substituted with taxonomically and medicinally unrelated species, 72% of which belonged to different orders and families, while 28% were from other genera. Despite the taxonomic diversity, 20% of adulterant spe, cies had a morphological resemblance to the authentic species. It is not known whether their use as adulterants is intentional. In a detailed study on DNA barcoding of 17 powder samples from Ocimum tenuiflorum, 88% of the samples were authentic. These results indicate that the extent of adulteration is not high in all the species. Approximately, 95% of the samples collected for this study were produced by companies with limited resources and expertise in the unorganized sector. Hence, training them on species identification and providing simple and cost-effective authentication tools will likely reduce adulteration in the market samples.