Toxicological Sciences, Vol 52, 118-126, Copyright © 1999 by Society of Toxicology
T Phillips
Aflatoxins are harmful by-products of mold growth and, though invisible to
the naked eye, are potentially fatal. The aflatoxin problem is
long-standing and inextricable. Concerns about the aflatoxins originate
from the strong implications of their involvement in disease and death in
humans and animals, yet scientists and clinicians are still seeking ways to
effectively deal with these dangerous and elusive chemicals. Safe,
practical, and effective strategies for the detoxification of
aflatoxin-contaminated food and feed are highly desirable. A simple and
effective approach to the chemoprevention of aflatoxicosis has been to
diminish or block exposure to aflatoxins via the inclusion of HSCAS clay in
the diet. HSCAS clay acts as an aflatoxin enterosorbent that tightly and
selectively binds these poisons in the gastrointestinal tract of animals,
decreasing their bioavailability and associated toxicities. Further studies
to delineate the molecular mechanisms of action have shown that the
dicarbonyl system of aflatoxin is essential for tight binding by HSCAS. In
these studies, adsorption data was fitted to multiple isotherm equations
including the Langmuir, multi-Langmuir, general Freundlich,
Langmuir-Freundlich, Toth and various transforms. Information derived
included: the Gibbs standard free energy change of adsorption, enthalpy of
adsorption, capacity, affinity, and heterogeneity coefficient. Computer
modelling was also utilized to provide additional structural information
and insight into the mechanism. Evidence suggests that aflatoxins may react
at multiple sites on HSCAS particles, especially the interlayer region, but
also at edges and basal surfaces. Since clay and zeolitic minerals comprise
a broad family of functionally diverse chemicals, there may be significant
hidden risks associated with their indiscriminate inclusion in the diet.
All aflatoxin binding agents should be rigorously tested, paying particular
attention to their effectiveness and safety in aflatoxin-sensitive animals
and their potential for interactions with critical
nutrients.Keywords: clay; HSCAS clay; chemoprevention;
chemoprotection; chemoprophylaxis; enterosorbent; aflatoxin; aflatoxicosis;
primary hepatic cancer; sorption; aflatoxin binder; detoxification
ARTICLES
Dietary clay in the chemoprevention of aflatoxin-induced disease
Faculty of Toxicology, Department of Veterinary Anatomy and Public Health, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4458, USA; Fax: (409) 862 4929; E-mail: tphillips@cvm.tamu.edu
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