Condensed tannins from steamed Acacia mearnsii bark

Abstract

The optimum steaming conditions for extraction of condensed tannins from Acacia mearnsii bark were explored, after which characterization of proanthocyanidins from bark steamed under optimum conditions was carried out. The optimum conditions were as follows: steaming time, 30 min; steaming temperature, 140°C; and water volume, 75 ml. The total phenolics content obtained under these conditions amounted to 25.31%, which was much higher than the 21.70% obtained by conventional hot water extraction. Six proanthocyanidin dimers were isolated from the steamed bark. Analysis revealed them to be fisetinidol-(4β-8)-catechin, fisetinidol-(4α-8)-catechin, robinetinidol-(4β-8)-catechin, robinetinidol-(4α-8)-catechin, robinetinidol-(4β-8)-gallocatechin, and robinetinidol-(4α-8)-gallocatechin. Proanthocyanidin polymers were found to consist mainly of prorobinetinidin extender units, similar to those obtained from the same bark by conventional extraction with 70% acetone aqueous solution. However, nuclear magnetic resonance and gel permeation chromatography analyses suggested that during steaming the polymers undergo condensation reactions, as well as inversion of the configuration of interflavanoid bonds.

Pine Bark and Green Tea Concentrated Extracts: Antioxidant Activity and Comprehensive Characterization of Bioactive Compounds by HPLC–ESI-QTOF-MS

“…These compounds have been identified as (epi)fisetinidol–(epi)catechin for the first time in pine bark. According to several authors, they have been detected in different kinds of bark extracts, such as Acacia mearnsii , Cotinus coggygria wood and Mimosa [ 33 , 34 , 35 , 36 ] and as gambiriin B in Uncaria gambir extract [ 37 , 38 ].…”

Biological Activity of Tannins from Acacia mangium Bark Extracted by Diff erent Solvents

“…According to Li & Maplesden (1998), only water extraction with or without addition of chemicals (sulphite or sodium hydroxide) is relatively economically feasible. However, this water extraction should be carried out at high temperature and pressure (Duan et al, 2005).…”

“…Several commercial tannins, however, were extracted mainly from the bark. Those barks were Acacia mearsnii (Duan et al, 2005), quebracho, Pinus radiata (Li & Maplesden, 1998), Eucalyptus camadulensis (Ofi nade, 1997), Western hemlock (Herrick, 1980), chestnut (Castanea vesca) (Krisper et al, 1992) Tannins are utilized for several purposes. A er mimosa and quebracho tannin, tannin from chestnut is the third most important vegetable tannin used for leather production in Northern side of Mediterranean Sea (Krisper et al, 1992).…”

“…There are several methods to extract tannin from bark have been reported (Herrick, 1980;Susana et al, 1994;Ofi nade, 1997;Li & Maplesden, 1998;Duan et al, 2005;Yano, personal communication). Tannins were extracted by water or aqueous solvent and have been used mostly for industrial purposes and very limited for animal feed.…”

Structure and antioxidant activity of diarylheptanoids extracted from bark of grey alder (Alnus incana) and potential of biorefinery-based bark processing of European trees

“…Phenolic compounds and grandidentatin were isolated from the bark of Suwon poplar by Kim et al (2006), and Kim and Bae (2009), respectively. Condensed tannins were isolated from the bark of Acacia mearnsii (Duan et al 2005). Coumarins and secoiridoid glucosides were found in the bark of Fraxinus rhynchophylla by Si et al (2008).…”