Abstract
ABSTRACT Condensed tannins are chemical compounds derived from the secondary metabolism of plants. They are of particular interest due to their broad range of technological uses and applications. The objective of this study was to extract, quantify, and characterize by Fourier-transform infrared spectroscopy (FTIR) the bark tannins of four forest species grown in Northeast Brazil: Acacia mangium, Azadirachta indica, Mimosa tenuiflora, and Mimosa caesalpiniifolia. Bark samples were collected from 5 trees of each species grown in a five-year-old forest stand. Samples were collected, grounded, and submitted to extraction with hot water, then measured to determine total solids content (TSC), Stiasny number (SN), and condensed tannins content (CTC). FTIR spectra were acquired from tannin samples fixed in potassium bromide pellets. Among the four species, M. tenuiflora presented the highest CTC, equal to 23.4%, and the purest crude hot-water extract with SN of 91.27%. Based on FTIR characterization, tannins from M. caesalpiniifolia, A. indica, and A. mangium barks were classified as proanthocyanidins and those from M. tenuiflora bark as prodelphinidins.
Highlights
The condensed tannins or procyanidins – proanthocyanidins and prodelphinidins– are complex compounds containing in their chemical structure flavan-3-ol, galloflavan-3-ol and flavan 3 ol gallate as basic units (Pizzi, 1993; Calegari et al, 2016)
The objective of this study was to extract, quantify, and characterize by Fourier-transform infrared spectroscopy (FTIR) the bark tannins of four forest species grown in Northeast Brazil: Acacia mangium, Azadirachta indica, Mimosa tenuiflora, and Mimosa caesalpiniifolia
Based on FTIR characterization, tannins from M. caesalpiniifolia, A. indica, and A. mangium barks were classified as proanthocyanidins and those from M. tenuiflora bark as prodelphinidins
Summary
The condensed tannins or procyanidins – proanthocyanidins and prodelphinidins– are complex compounds containing in their chemical structure flavan-3-ol, galloflavan-3-ol and flavan 3 ol gallate as basic units (Pizzi, 1993; Calegari et al, 2016). Tannins can be extracted from tree bark through several methods, and the effectiveness of each technique depends directly on the selectivity of water and solvents
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