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.