Use of Chromatographic (SPE-HPLC) and Spectrophotometric Methods for Differentiation of Salix Species Through Correlation Analysis and FreeViz Projection.

The major concern of the present article is research into the combination of analytical assessment and multi-correlative data interpretation. For this purpose, a high performance liquid chromatography (HPLC) procedure was developed for the simultaneous quantification of salicin, salicylalcohol derivatives, phenolic acids, flavonoids, and monomeric catechins after solid phase extraction (SPE). On the basis of an established and validated HPLC method, 49 different Salix samples were extracted, purified, and analysed. Furthermore, the quantity of total polyphenols (Folin-Ciocalteau colorimetric reaction) and the antioxidant activity (DPPH radical scavenging activity test) were determined and correlated. This yielded correlation coefficients at P-values less than 0.05 of 0.775, 0.967, 0.932, and 0.989 for Salix fragilis, Salix rubens, Salix purpurea (2006), and Salix purpurea (2007), respectively. Correlation with mean values of each species between total polyphenols content and % DPPH inhibition values occurred at a correlation coefficient (r) of 0.851. Linear correlations of quantified HPLC data with DPPH data and with total polyphenols content could also be found for salicin, gentisic acid, naringin, and salicylic acid. Finally, by combining HPLC data with total polyphenols content and antioxidant capacity through 3-D scatter plots and FreeViz data projection, it was shown that primarily the amount of epicatechin and saligenin beside DPPH values and total polyphenols content enable the classification into plant species and further by year of harvest.