X-Message-Number: 33288
Date: Sat, 29 Jan 2011 09:07:11 -0800 (PST)
From: 
Subject: bicarbonate not useful as a buffer

I made a mistake in my earlier suggestion of using bicarbonate as a buffer
in a glycerol/wine solution. Turns out bicarbonate destabilizes some of
the polyphenols in wine.

Biosci Biotechnol Biochem. 2010;74(1):63-8. Epub 2010 Jan 7.

Evaluation of resveratrol oxidation in vitro and the crucial role of bicarbonate
ions.

Yang NC, Lee CH, Song TY. Department of Nutrition and Health Science, Chungchou 
Institute of Technology, Changhua, Taiwan.
Abstract

  Polyphenols can oxidize in culture medium and produce artifacts in cell 
  culture studies. However, the extent and mechanism of the oxidation of 
  resveratrol, a polyphenol abundant in red wine, is unclear. We investigated 
  the oxidation of resveratrol in vitro and the effects of various components of
  the culture medium on the degradation of resveratrol and the production of 
  H(2)O(2). We found that 96% of resveratrol at a concentration of 200 microM 
  was degraded in Base Modified Eagle Medium after 24 h of incubation at 37 
  degrees C, producing about 90 microM of H(2)O(2). Including sodium bicarbonate
  in the medium markedly stimulated resveratrol degradation and H(2)O(2) 
  production. In sum, we found that bicarbonate ions played a crucial role in 
  the oxidative degradation of resveratrol in vitro, and that the degradation of
  resveratrol can be avoided by withdrawing sodium bicarbonate from the medium.
  A mechanism for the oxidation of resveratrol is proposed.
PMID: 20057154
Free text>
http://www.jstage.jst.go.jp/article/bbb/74/1/63/_pdf

J Agric Food Chem. 2004 May 19;52(10):2866-74.

Phenolic antioxidants and the protection of low density lipoprotein from 
peroxynitrite-mediated oxidations at physiologic CO2.

Ferroni F, Maccaglia A, Pietraforte D, Turco L, Minetti M. Laboratorio di 
Biologia Cellulare, Istituto Superiore di Sanita, 00161 Roma, Italy.
Abstract

  Dietary phenolic antioxidants have been shown to prevent LDL modifications 
  mediated by several physiologic oxidants including peroxynitrite. However, 
  more recent data demonstrated that CO(2) affected the fate of peroxynitrite in
  biological fluids and significantly reduced peroxynitrite scavenging by 
  polyphenols, raising doubts concerning their antioxidant activity. We found 
  that the oxidation of LDL lipids mediated by peroxynitrite decreased in the 
  presence of bicarbonate, while Trp oxidation and 3-nitroTyr formation 
  increased, suggesting a redirection of peroxynitrite reactivity toward the 
  protein moiety. We therefore evaluated the protective activity of some 
  phenolic antioxidants (quercetin, oleuropein, resveratrol, (+)-catechin, 
  (-)-epicatechin, tyrosol, alpha- and gamma-tocopherol, ascorbate) on 
  peroxynitrite-mediated oxidation of LDL aromatic residues. Some of these 
  phenols protected LDL Trp from oxidation better than ascorbate or 
  alpha-tocopherol, although protection at 100 microM did not exceed 30-40%. 
  However, the same phenolic antioxidants were more active in inhibiting 
  3-nitroTyr formation and those with a catechin structure provided significant 
  protection (IC(50%) 40-50 microM). Red wine, a polyphenol-rich beverage, 
  showed a protective effect comparable to that of the most active phenolic 
  antioxidants. Direct EPR studies showed that bicarbonate significantly 
  increased the peroxynitrite-dependent formation of O-semiquinone radicals in 
  red wine, supporting the hypothesis that polyphenols are efficient scavengers 
  of radicals formed by peroxynitrite/CO(2). Ascorbate was a poor inhibitor of 
  peroxynitrite/CO(2)-induced LDL tyrosine nitration, but the simultaneous 
  addition to the most active polyphenols halved their IC(50%). In conclusion, 
  although cooperation with other antioxidants can further decrease the IC(50%) 
  of polyphenolics, as demonstrated for ascorbate, their antioxidant activity 
  appears to occur at concentrations at least 1 order of magnitude higher than 
  their bioavailability.
PMID: 15137827

Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=33288