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Inhibition
by apple polyphenols of ADP-ribosyltransferase activity of cholera toxin and
toxin-induced fluid accumulation in mice.
Saito T, Miyake M, Toba M, Okamatsu H, Shimizu S, Noda M.
Department of Molecular Infectiology, Graduate
School of
Medicine, Chiba University, Japan.
The effects of crude polyphenol extracted from immature
apples on the
enzymatic and biological activities of a cholera toxin (CT) were
investigated. When the apple polyphenol extract (APE) was examined for
properties to inhibit CT-catalyzed ADP-ribosylation of agmatine, it was
found that APE inhibited it in a dose-dependent manner. The concentration of
APE to inhibit 50% of the enzymatic activity of CT (15 microg/ml) was
approximately 8.7 microg/ml. The APE also diminished CT-induced fluid
accumulation in two diarrhea models for in vivo mice. In the ligated ileum
loops, 25 microg of APE significantly inhibited fluid accumulation induced
by 500 ng of CT. In a sealed mouse model, even when APE was administered
orally 10 min after a toxin injection, fluid accumulation was
significantly inhibited at a comparable dosage. Lineweaver-Burk
analysis demonstrated that APE had negative allosteric effects on
CT-catalyzed NAD: agmatine ADP-ribosyltransferase. We fractionated the APE
into four fractions using LH-20 Sephadex resin. One of the fractions, FAP
(fraction from apple polyphenol) 1, which contains non-catechin polyphenols,
did not significantly inhibit the CT-catalyzed ADP-ribosylation of agmatine.
FAP2, which contains compounds with monomeric, dimeric, and trimeric
catechins, inhibited the ADP-ribosylation only partially, but significantly.
FAP3 and FAP4, which consist of highly polymerized catechin compounds,
strongly inhibited the ADP-ribosylation,
indicating that the polymerized structure of catechin is responsible for the
inhibitory effect that resides in APE.
The results suggest that polymerized
catechin compounds in APE inhibit the biological and enzymatic activities of
CT and can be used in a precautionary and therapeutic manner in the
treatment of cholera patients.
PMID: 12061627 [PubMed - indexed for MEDLINE]
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