Development of methodology for identification the nature of the polyphenolic extracts by FTIR associated with multivariate analysis

• A new methodology was developed by FTIR for identification of commercial tannins.
• Six types of natural polyphenolic extracts were characterised by FTIR.
• It was possible a well-defined separation between vegetable tannins by 3 PCA.
• The HCA presented a defined separation between condensed and hydrolysable tannins.
• Chestnut and valonea tannins showed the greatest similarity by chemometric analysis.

Tannins are polyphenolic compounds of complex structures formed by secondary metabolism in several plants. These polyphenolic compounds have different applications, such as drugs, anti-corrosion agents, flocculants, and tanning agents. This study analyses six different type of polyphenolic extracts by Fourier transform infrared spectroscopy (FTIR) combined with multivariate analysis. Through both principal component analysis (PCA) and hierarchical cluster analysis (HCA), we observed well-defined separation between condensed (quebracho and black wattle) and hydrolysable (valonea, chestnut, myrobalan, and tara) tannins. For hydrolysable tannins, it was also possible to observe the formation of two different subgroups between samples of chestnut and valonea and between samples of tara and myrobalan. Among all samples analysed, the chestnut and valonea showed the greatest similarity, indicating that these extracts contain equivalent chemical compositions and structure and, therefore, similar properties.

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