Context: In its powdered form, turmeric [Curcuma longa L. (Zingiberaceae)], a spice of medical importance, is often adulterated lowering its quality. Objective: The study sought to detect plant-based adulterants in traded turmeric powder using DNA barcoding. Materials and methods: Accessions of Curcuma longa L., Curcuma zedoaria Rosc. (Zingiberaceae), and cassava starch served as reference samples. Three barcoding loci, namely ITS, rbcL, and matK, were used for PCR amplification of the reference samples and commercial samples representing 10 different companies. PCR success rate, sequencing efficiency, occurrence of SNPs, and BLAST analysis were used to assess the potential of the barcoding loci in authenticating the traded samples of turmeric. Results: The PCR and sequencing success of the loci rbcL and ITS were found to be 100%, whereas matK showed no amplification. ITS proved to be the ideal locus because it showed greater variability than rbcL in discriminating the Curcuma species. The presence of C. zedoaria could be detected in one of the samples whereas cassava starch, wheat, barley, and rye in other two samples although the label claimed nothing other than turmeric powder in the samples. Discussion and conclusion: Unlabeled materials in turmeric powder are considered as adulterants or fillers, added to increase the bulk weight and starch content of the commodity for economic gains. These adulterants pose potential health hazards to consumers who are allergic to these plants, lowering the product's medicinal value and belying the claim that the product is gluten free. The study proved DNA barcoding as an efficient tool for testing the integrity and the authenticity of commercial products of turmeric.

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IntroductionSpices are widely used as medicine and food flavorants. Although there are about 109 species listed as spices in the International Standards Organization (ISO) list, their uses are specific as each of these commodities have different uses in flavoring foods or in medicine. Cinnamomum aromaticum, C. zeylanincum syn. C. verum, C. burmanii, C. loureirii, and C. tamala are included in the ISO list. While barks of the first 4 species are used as food flavorant, in beverages and in medicine, it is the leaves of C. tamala that are economically important for flavoring food items.The genus Cinnamomum belongs to the family Lauraceae and consists of about 250 species of plants that are aromatic and flavoring (Leela, 2008). Their antiinflammatory, antidiabetic, and antioxidant activities have popularized the use of Cinnamomum in folk medicine (Lee et al., 2010). C. verum, a native of Sri Lanka, is known as true cinnamon. It is cultivated in Sri Lanka and India, and the bark of this species forms the most important traded Cinnamomum. The dried bark of C. verum is used as a spice in flavoring foods like biscuits, cakes, sweets, and pickles (Abeysinghe et al., 2009). However, of late, adulteration of this commodity with the hard, thick, and less aromatic bark of C. aromaticum (C. cassia, cassia cinnamon or Chinese cinnamon) has been reported, as this species bears close resemblance with the bark of true cinnamon, making fraudulent practices easy (Thomas and Duethi, 2001). This commodity has a bitter and burning flavor. A high amount of coumarin is also present in C. aromaticum, which is known to cause liver and kidney damage in rats, mice, and probably in humans (Lungarini et al., 2008). The dried bark of C. malabatrum, another Cinnamomum species, common in many tropical countries as wild growth and, on rare occasion, in homestead gardens in India and Sri Lanka, is also passed off as true cinnamon. Identification of true cinnamon from adulterant species based on physical traits is very difficult, and the situation is all the more difficult once the commodity loses its physical form (e.g., powder). Incidentally, powdered bark is more frequently used as food flavorant and in medicine.Molecular markers are useful in discriminating adulterants from the genuine products in cases where there is high physical resemblance between the entities, or in the instances of change of the physical form. The first step in any DNA-based discrimination technique is the isolation and amplification of DNA.