Abstract
The dietary supplement industry is rapidly growing yet, a recent study revealed that up to 60% of supplements may have substituted ingredients, some of which can be harmful contaminants or additives. When ingredients cannot be verified morphologically or biochemically, DNA barcoding complemented with a molecular phylogenetic analysis can be a powerful method for species authentication. We employed a molecular phylogenetic analysis for species authentication of the commonly used fungal supplement, reishi (Ganoderma lingzhi), by amplifying and sequencing the nuclear ribosomal internal transcribed spacer regions (ITS) with genus-specific primers. PCR of six powdered samples and one dried sample all sold as G. lucidum representing independent suppliers produced single, strong amplification products in the expected size-range for Ganoderma. Both best-hit BLAST and molecular phylogenetic analyses clearly identified the presence of G. lingzhi DNA in all seven herbal supplements. We detected variation in the ITS sequences among our samples, but all herbal supplement samples fall within a large clade of G. lingzhi ITS sequences. ITS-based phylogenetic analysis is a successful and cost-effective method for DNA-based species authentication that could be used in the herbal supplement industry for this and other fungal and plant species that are otherwise difficult to identify.
Highlights
Molecular barcoding is an efficient tool for identifying macroscopic, microscopic and biochemically enigmatic samples [1]
The average purity of the DNA measured as the 260/280 ratio was 1.34
To assess successful amplification of the internal transcribed spacer regions (ITS) region from newly extracted fungal DNA, PCR with three different primer pairs was performed and samples were visualized with gel electrophoresis
Summary
Molecular barcoding is an efficient tool for identifying macroscopic, microscopic and biochemically enigmatic samples [1]. Leveraging the DNA content of processed living organisms that is not otherwise identifiable holds great prospects for quality control—especially helpful for authenticating the ingredients and avoiding contaminants and additives that may cause allergic reactions for consumers [8], DNA of a species can be present long after losing the biological activity of its compounds (i.e. after an aggressive processing). This is relevant in the herbal supplement industry, where safety and effectiveness are loosely regulated. All other relevant data are within the manuscript and its Supporting Information files
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