X-Message-Number: 12973
Date: Mon, 20 Dec 1999 21:57:12 -0800 (PST)
From: Doug Skrecky <>
Subject: could some flavonoids impliment reversible chemical fixation?

Authors
  Murakami S.  Muramatsu M.  Tomisawa K.
Institution
  Medicinal Research Laboratories, Taisho Pharmaceutical Co. Ltd., Ohmiya,
  Japan. 
Title
  Inhibition of gastric H+, K(+)-ATPase by flavonoids: a structure-activity
  study.
Source
  Journal of Enzyme Inhibition.  14(2):151-66, 1999.
Abstract
  Gastric H+, K(+)-ATPase plays a pivotal role in the final step of gastric
  acid secretion. Over 80 flavonoids, including flavones, flavanones,
  isoflavones and anthocyanidins were examined for their in
  vitro effect on gastric H+, K(+)-ATPase and some were found to be inhibitors
  of this enzyme. Kinetic studies showed that the inhibition of H+, K(+)-ATPase
  by flavonoids was competitive with respect to ATP, and non-competitive with
  respect to K+. Structure-activity analysis revealed the following: (1) The
  inhibitory potency of flavonoids depends on the number of hydroxyl groups up
  to four per molecule and that above this, no marked enhancement is seen; (2)
  The hydroxylation pattern is an important determinant of inhibitory potency.
  Two adjacent hydroxyl groups (catechol-type), three adjacent hydroxyl groups
  (pyrogallol-type) or hydroxyl groups at C-3, C-5 and C-7 are a minimum
  requirement for high potency inhibition; (3) Protection of the hydroxyl
  group(s) by glycosylation or methylation decreases potency; (4) Saturation of
  the C-2-C-3 double bond results in a decrease in potency; and (5) A ketone at
  C-4 is not essential for inhibition.

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