X-Message-Number: 12059
Date: Sun, 4 Jul 1999 08:14:41 -0700 (PDT)
From: Doug Skrecky <>
Subject: could catechins protect membranes from cryoprotectant toxicity?

"Effects of Green Tea Catechins on Membrane Fluidity"
Pharmacology 59(1): 34-44 Jul 1999


  Catechins originating from green tea have been used in plaque inhibition for
caries prevention and treatment for liver damage because of their antibacteria
activity against cariogenic bacteria and protective activity on hepatic cells.
The effects of catechins on membrane fluidity were studied by a fluorescence
polarization method using liposomes prepared with dipalmitoylphosphatidycholine
and dioleoylphosphatidylcholine to assess their pharmacological mecchanism at
mumol/l levels found in human body fluids after clinical application. All eight
catechins tested, ranging from 1 to 1,000 mumol/l, significantly reduced

membrane fluidity in both hydrophilic and hydrophobic regions of lipid bilayers.
Catechin gallate esters were superior in fluidity reduction to the correspnding
nonesters. The fluidity-reducing degree was different between the cis and trans
forms, suggesting the stereospecific activity of catechins. A reference
antiplaque agent, chlorhexidine, similarly reduced membrane fluidity at the

antibacterial concentration. (+)-Catechin (250 mumol/l) and (-)-epigallocatechin
gallate (2.5 mumol/l) significantly prevented the membrane fluidization induced

by hepatotoxic chloroform. These results indicate that the reduction in membrane

fluidity is responsible for the antiplaque and hepatoprotective effects of green
tea catechins.

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