Abstract
Among the series of metabolic analogs of the eccentric cleavage pathway of β-carotene with different side chain lengths, retinoic acid was shown to have exceedingly higher molecular flexibility to undergo photoisomerization into the geometrical isomers under white fluorescent light. When irradiated with white fluorescent lamps (1, 200lx), the velocity of photoisomerization of all-trans-retinoic acid (8.4×10-7mol/L⋅min) was exceedingly higher than those of the other analogs: ionylideneacetic acid (4×10-8 mol/L⋅min), ionylidenecrotonic acid (3.0×10-7 mol/L⋅min), all-trans-β-apo-14'-carotenoic acid (1.7×10-7 mol/L⋅min), all-trans-β-apo-12'-carotenoic acid (1.3×10-7 mol/L⋅min), and all-traps-l-apo-8'-carotenoic acid (0.1×10-7 mol/L⋅min). β-Carotene did not un-dergo photoisomerization under the experimental conditions. The mo-lecular flexibility of retinoic acid is assumed to be an important basis of the mechanism of action of retinoic acid.
