methylenewhite
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https://cancerres.aacrjournals.org/content/canres/48/24_Part_1/7038.full.pdf
Citral is a GRAS2 status food and drug ingredient in widespread
use as an additive to cosmetics and toiletries, and as a lemon
flavor in foods. Citral is a simple, partially saturated, analogue of retinal, which may explain its ability to inhibit both steps in
retinoic acid synthesis from retinol, since as an aldehyde it can
act as a substrate for both the alcohol- and aldehyde-dehydro-
genases involved.
The ability of citral to inhibit retinol oxidation provides an
experimental tool for testing the paradigm that retinoic acid is
an obligatory intermediate in at least some aspects of vitamin
A activity in the epithelia in vivo. Citral was proposed as a
vitamin A antagonist in 1956 (7). Aydelotte (8, 9) studied the
interaction of citral and retinol in whole organ cultures of chick
epithelial tissues and concluded that citral had a competitive
effect on vitamin A activity. Crocker and Sanders (10) observed
that citral increased the degree of squamous metaplasia induced
by benzo(a)pyrene in hamster trachea grown as expiants, pos
sibly through an effect on vitamin A. Preliminary evidence thus
suggests that citral can antagonize vitamin A activity in epithe
lial tissues.
Citral is a GRAS2 status food and drug ingredient in widespread
use as an additive to cosmetics and toiletries, and as a lemon
flavor in foods. Citral is a simple, partially saturated, analogue of retinal, which may explain its ability to inhibit both steps in
retinoic acid synthesis from retinol, since as an aldehyde it can
act as a substrate for both the alcohol- and aldehyde-dehydro-
genases involved.
The ability of citral to inhibit retinol oxidation provides an
experimental tool for testing the paradigm that retinoic acid is
an obligatory intermediate in at least some aspects of vitamin
A activity in the epithelia in vivo. Citral was proposed as a
vitamin A antagonist in 1956 (7). Aydelotte (8, 9) studied the
interaction of citral and retinol in whole organ cultures of chick
epithelial tissues and concluded that citral had a competitive
effect on vitamin A activity. Crocker and Sanders (10) observed
that citral increased the degree of squamous metaplasia induced
by benzo(a)pyrene in hamster trachea grown as expiants, pos
sibly through an effect on vitamin A. Preliminary evidence thus
suggests that citral can antagonize vitamin A activity in epithe
lial tissues.