Oregano has been identified as one of the herbs most susceptible to adulteration. Methods based on DNA, spectroscopic analysis and even microscopy have already been used. In this paper, a new approach for authentication of oregano, which combines metabarcoding by NGS (next generation sequencing) and metabolomics/chemometrics by NMR, has been developed. The industry standard for oregano permits only 2% extraneous matter. A previous survey on oregano has shown that the most common plant adulterants are olive, sweet marjoram and myrtle leaves, and non-leaf plant material. In this study, 92 oregano, 38 sweet marjoram, and 2 olive leaf samples from 6 different countries in total were used. Metabarcoding by NGS was used to identify the nature of oregano products and possible adulterations. Metabolomic profiles obtained by NMR correlated well with oregano species and their regional origin. Using chemometric analysis, it was possible to quantify of the percentage of an adulterant with error rates of 3–7%.
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