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Characterization and Antioxidant Properties of the Condensed Tannins from Alaska Cedar Inner Bark

Martha Rosales-Castro, Rubén F. González-Laredo, Young-Soo Bae, Jin Kgu Kim, Jeff Morre, and Joseph J. Karchesy

Biotechnology Group, CIIDIR Durango, Instituto Politécnico Nacional, Sigma 119 Fracc. 20 de Noviembre, 34220 Durango, Dgo., México

Departamento de Ingenierías Química y Bioquímica, Instituto Tecnológico de Durango, Durango, Dgo., México,

Department of Wood Science and Engineering, Kangwon National University,

Chuncheon, Korea,

Department of Chemistry, Oregon State University, Corvallis OR, USA

Department of Wood Science and Engineering, Oregon State University, Corvallis OR, USA

Abstract: The structure and antioxidant activity of condensed tannins isolated from Alaska Cedar inner bark have been investigated. Oligomers of flavan-3-ol were purified by column chromatography (Sephadex LH-20) and analyzed by 13CNMR and MALDI-TOF MS spectrometries. Their antioxidant activities were measured using 1,1’-diphenyl-2-picrylhydrazyl (DPPH), 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) free radicals scavenging, ferric reducing/antioxidant power (FRAP), and β-carotene-linoleic acid model system (β-CLAMS) assays. Results showed that the condensed tannins consents of both homogeneous and heterogeneous oligomers of procyanidins (catechin/epicatechin) and prodelphinidins (gallocatechin/ epigallocatechin) flavan-3-ol units; and oligomers from trimmers to heptamers with dominant interflavan linkages B-type as it is most common in proanthocyanidins. Condensed tannins showed significant ntioxidant activity as the median inhibition capacity IC 50 is comparable to the catechin control response. Alaska Cedar inner bark oligomers show high antioxidant capacity, evaluated by both methods based on electron transfer mechanisms and hydrogen atom transfer reactions. This bark may be considered as a new source of natural antioxidants for nutraceutical ingredients.

Keywords: Chamaecyparis nootkatensis; MALDI-TOF; Proanthocyanidins; ABTS; DPPH; FRAP.
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