Fig. 5
a Typical examples of an unassigned fingerprint proton nuclear magnetic resonance (1H-NMR) spectra of Masquelier’s grape seed extract (1) and another grape seed extract (2). b Three-dimensional plot of the principle component analysis (PCA) using unassigned fingerprint proton nuclear magnetic resonance (1H-NMR) spectra to compare the phytochemical content of different plant extracts e.g. from distinct manufacturers or from different batches. The small white dotted lines indicate the 95% confidence interval per cluster. The cluster of Masquelier’s grape seed extract (Anthogenol®, yellow) clearly distinguish from the cluster of French pine bark extract (M-PM, red) and other grape seed extracts (GSEs, magenta). Samples of the Endotélon extract (red) and samples of Masquelier’s extract from 1985 (VV-OPC 1985, yellow) are located within the cluster of Masquelier’s grape seed extract proofing the qualitative and quantitative equality of these extracts. The green-blue lines represent the 3 strongest principal components (PC), i.e. the variables derived from the 1H-NMR spectra which define the biggest differences between all the samples. The farther 2 samples are apart from each other in respect of one particular axis, the more different they are in this particular aspect. The data were provided by the extract’s manufacturer