Title : Classification of medicinal plants according to their antioxidant capacity using chromatographic profiles and chemometrics
High-performance liquid chromatography (HPLC) combined with chemometric methods were successfully applied to classify 42 medicinal plant extracts (commercially available) according to their antioxidant capacity determined using DPPH* radical scavenging method: high (group 1), medium (group 2), low (group 3). The chromatographic separations were run on a Zorbax SB-C18 column (250 mm x 4.6 mm, 5 µm particle size) from Agilent and conducted using six different detection wavelengths: 242, 260, 280, 320, 340 and 380 nm, respectively. The optimum method (maximum number of compounds separated and maximum resolution) consisted of a multistep isocratic and gradient elution system using solvent A, 10 mM ammonium acetate pH 5 and as solvent B acetonitrile. The evaluation of the numerical data corresponding to the six wavelengths was performed by employing appropriate multivariate methods: principal component analysis (PCA), fuzzy principal component analysis (FPCA) and linear discriminant analysis (LDA) applied to the first relevant principal components (100% cumulative proportion). A good classification of the samples into high and medium/low antioxidant activity was obtained from PCA analysis at 242 nm. The results obtained by applying LDA to the scores corresponding to the first relevant PCs indicate a highly accurate separation of the medicinal plant hydro-alcoholic extracts within the three groups, in good agreement with their antioxidant capacity estimated by the above mentioned method (96.7 % for PCA at 260 nm and 73.8, respectively for FPCA at 242 nm). In conclusion, the HPLC method combined with chemometrics can be viewed as a useful holistic tool to classify the medicinal plant extracts according to their antioxidant capacity and predict them with high accuracy and precision.