DNA extraction from plant food supplements: Influence of different pharmaceutical excipients

The consumption of plant food supplements (PFS) has been growing globally, with an increase of misleading labeling and fraudulent practices also being reported. Recently, the use of molecular biology techniques has been proposed to detect botanical adulterations, one of the possible frauds in PFS. However, difficulties in recovering DNA from some PFS samples have been described. Aiming at using DNA-based methods for the unequivocal identification of plant species in PFS, adequate DNA isolation is required. However, PFS often contain pharmaceutical excipients known to have adsorbent properties that might interfere with DNA extraction. Thus, the aim of this work was to assess the effect of different excipients (talc, silica, iron oxide and titanium dioxide) on the recovery/amplification of DNA. For that purpose, known amounts of template maize DNA were spiked either to PFS or to model mixtures of excipients and quantified by real-time PCR. The tested excipients evidenced clear adsorption phenomena that justify the hampering effect on DNA extraction from PFS. The use of either 10% talc or 0.5% dyes completely adsorbed DNA, resulting in negative PCR amplifications. For the first time, pharmaceutical excipients were shown to affect DNA extraction explaining the inability of recovering DNA from some PFS samples in previous studies.