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 Abstract: 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. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=12059