EXTRACTION, QUANTIFICATION, AND FTIR CHARACTERIZATION OF BARK TANNINS OF FOUR FOREST SPECIES GROWN IN NORTHEAST BRAZIL

Marques, Sarah Rebeka Rodrigues; Azevêdo, Tatiane Kelly Barbosa; Castilho, Aline Rogéria Freire de; Braga, Renata Martins; Pimenta, Alexandre Santos

doi:10.1590/1806-908820210000041

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Scientific Article • Rev. Árvore 45 • 2021 • https://doi.org/10.1590/1806-908820210000041 copy

EXTRACTION, QUANTIFICATION, AND FTIR CHARACTERIZATION OF BARK TANNINS OF FOUR FOREST SPECIES GROWN IN NORTHEAST BRAZIL

EXTRAÇÃO, QUANTIFICAÇÃO E CARACTERIZAÇÃO POR FTIR DE TANINOS DA CASCA DE QUATRO ESPÉCIES FLORESTAIS CULTIVADAS NO NORDESTE DO BRASIL

Authorship SCIMAGO INSTITUTIONS RANKINGS

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.

Keywords:
Forest species bark; Proanthocyanidins; Prodelphinidins

Table 1 Results of extraction and quantification of tannins from the bark of four forest species grown in Northeast Brazil.

Species	TSC (%)	SN (%)	CTC (%)	NTC (%)
Mimosa tenuiflora	27.79a	83.39b	23.40a	4,30a
Mimosa caesalpiniifolia	9.18c	91.27a	8.38c	0,80d
Acacia mangium	14.80b	83.89b	12.41b	2,39b
Azadirachta indica	7.11c	73.18c	5.02d	2,09c

Table 2 Attributes of FTIR spectra acquired for bark tannins from Acacia mangium (Am), Mimosa caesalpiniifolia (Mc), Azadirachta indica (Ai), and Mimosa tenuiflora (Mt) trees grown in Northeast Brazil.

Peak (cm^-1)				Event
Am	Mc	Mt	Ai
3,418	3,425	3,439	3,438	OH stretching vibrations of hydrogen bonds
-	2,925	-	2,927	C-H asymmetrical stretching vibrations of aromatic methoxyl, methyl and lateral-chain methylene groups
-	2,852	-	2,799	C-H symmetrical stretching vibrations of aliphatic methylene groups
2,361	2,360	2,356	2,357	-
2,335	2,336	2,332	2,335	-
1,604	1,605	1,605	1,607	C=C stretching vibrations of aromatic bond
1,566	1,567	1,568	1,567	C=C stretching vibrations of aromatic bond
1,454	1,450	1,515	1,447	Vibrational movement of C = C bonds in the aromatic rings, aromatic C-H bending, C-O stretching and C-OH deformation
1,399	1,427	1,454	1,395	Vibrational movement of C = C bonds in the aromatic rings, aromatic C-H bending, C-O stretching and C-OH deformation
-	-	1,350	-	C=C stretching vibrations
1,337	1,410	1,332	1,280	Region of C-H bond deformation
1,194	1,275	1,240	1,203	C-O extension in the pyran ring of tannins
1,156	1,248	1,153	1,143	C-O extension in the pyran ring of tannins and C-OH stretching vibrations
793	826	793	806	Deformation of C-H from aromatic rings out-of-plane vibrations

Sociedade de Investigações Florestais Universidade Federal de Viçosa, CEP: 36570-900 - Viçosa - Minas Gerais - Brazil, Tel: (55 31) 3612-3959 - Viçosa - MG - Brazil
E-mail: rarvore@sif.org.br

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