A. Roda et al., Antioxidant properties of bile salt micelles evaluated with different chemiluminescent assays: A possible physiological role, J BIOLUM CH, 13(6), 1998, pp. 327-337
The antioxidant activity of a representative series of free, glycine- and t
aurine-conjugated bile acids was evaluated by two different chemiluminescen
t assays: (a) the enhanced chemiluminescence system based on horseradish pe
roxidase and luminol/oxidant/enhancer reagent, and (b) the hypoxanthine/xan
thine oxidase/Fe2+-EDTA/luminol system. Bile acids were studied at final co
ncentrations ranging from 1 to 28 mmol/L. All of the bile acids studied inh
ibited the steady-state chemiluminescent reaction and the extent of inhibit
ion depended upon the structure of the bile acids, whereas the duration was
related to bile acid concentration. The mechanism of the light inhibition
is probably due to trapping of oxygen free radicals generated in the chemil
uminescent reactions, within bile acid micelles. The free radicals trapped
into micelles reduced the formation of luminol radicals and consequently th
e light output; when the micelles were saturated, the oxygen free radicals
in solution again produced luminol radicals. The micelle interaction with r
eactive oxygen species could be a physiological mechanism of defence agains
t the toxicity of those species in the intestinal content. On the other han
d, alterations in bile acid organ distribution, concentration and compositi
on leads to a membrane damage caused by their detergent-like properties, wh
ich could be associated to oxygen free radical production. (C) 1998 John Wi
ley & Sons, Ltd.