Detection of plant-based adulterants in turmeric powder using DNA barcoding

Abstract

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.

Assessment of Genetic and Chemical Variability in Curcumae Longae Rhizoma (<i>Curcuma longa</i>) Based on DNA Barcoding Markers and HPLC Fingerprints

“…2,9,12,16,33,34) However, little is known about the relationship of genetic and chemical differences by using integrated approach. In this study, we found a low correlation (r=0.1721, p=0.047) between genetic distance and HPLC distance using the Mantel test.…”

“…A previous study 2) showed that the primer pair 390F/1326R did not work for matK gene amplification in turmeric. In contrast, we found that this primer pair produced PCR products if additional PCR cycles (45) were completed ( Table 1).…”

Towards a Universal Approach Based on Omics Technologies for the Quality Control of Food

“…As an example, DNA barcoding was used to characterize the bean germplasm ( Phaseolus vulgaris L.) and was found able to distinguish among different haplotypes of bean accessions from the Mesoamerican and Andean areas [ 57 ]. Similarly, the DNA barcoding approach was adopted to assess the origin and quality of spices [ 44 , 58 ], herbal products [ 59 , 60 ], and naturally processed plant products such as multiflower honey [ 61 ]. Other studies investigated the ability of DNA barcoding in discerning toxic plants from edible species: cultivated species of the genera Solanum and Prunus were successfully distinguished from their toxic congenerics [ 62 ] and from some frequent plant species misidentifications that cause poisoning in human [ 63 ].…”

Rapid Authentication of Turmeric Powder Adulterated With Curcuma Zedoaria and Curcuma Xanthorrhiza Using Ftir-Atr Spectroscopy and Chemometrics

“…Therefore, the presence of other Curcuma species, such as C. zedoaria and C. xanthorhhiza, has been detected in turmeric powder sold in India [9]. Some analytical methods have been developed for authenticating medicinal plants, including fingerprint analysis using High-Performance Liquid Chromatography-Diode Array Detector (HPLC-DAD) combined with chemometrics [7], metabolomics technique using Proton Nuclear Magnetic Resonance (H-NMR) combined with multivariate analysis [10], and DNA based approach using DNA Barcoding [9], Random Amplified Polymorphic DNA (RAPD) [11], and Sequence Characterized Amplified Region (SCAR) [12]. The main disadvantage of these methods is that several steps are needed for sample preparation, making the process slow and costly.…”