DNA Barcoding for Discriminating the Economically Important Cinnamomum verum from Its Adulterants

Abstract

Traded forms of spice and spice powders are often subjected to admixing with inferior substances by design or default, affecting public health and national prestige. Cinnamomum verum (true cinnamon), a high-value spice, is often adulterated with its inferior species such as C. cassia and C. malabatrum. The presence and detection of the spurious species in traded barks (whole or powder) of true cinnamon is posing problems. DNA markers are now used to detect such adulteration. Here we report the application of a DNA barcoding method to detect these adulterants in traded market samples of true cinnamon using the barcoding loci rbcL, matK and psbA-trnH. The PCR success rate, sequencing efficiency, inter and intra specific divergence, and occurrence of single nucleotide polymorphisms (SNPs) were utilized to assess the potential of each barcode loci to authenticate C. verum from its related adulterants. The amplification and sequencing success was 100% for rbcL and psbA-trnH while matK failed to amplify in the market samples. The locus of rbcL showed higher interspecific divergence while psbA-trnH exhibited lower interspecific divergence. SNPs specific to C. cassia were detected in rbcL locus in seven out of the ten market samples studied thereby confirming the presence of C. cassia adulteration in commercial samples of true cinnamon. Out of the three loci, rbcL locus proved to be efficient in tracing out adulterants in traded cinnamon. The SNP sites in this locus can be exploited in designing C. cassia specific primers, enabling kit development for easy detection of adulterants at the band level itself thereby bypassing the cost of sequencing.