Effect of synthetic acyclic polyisoprenoids on the cold-restraint stress induced gastric ulcer in rats.

The antiulcer effect of a series of synthetic acyclic polyisoprenoids on cold-restraint stress induced ulcer in female rats was determined, and the relationship between their antiulcer effect and chemical structure was also investigated. As a result, the following findings were obtained: The antiulcer effect of acyclic polyisoprenoids closely correlated with the number of intramolecular isoprene units, and geranylgeranyl derivatives showed a particularly marked antiulcer effect. The terminal polar groups such as 2-oxopropyl and 2-hydroxypropyl groups in geranylgeranylacetone seemed to play an important role in the antiulcer activity of acyclic polyisoprenoids. Terminal bulky groups decreased their antiulcer activity, however. The antiulcer activity of geranylgeranylacetone correlated with the number of intramolecular double bonds. There was no significant difference in antiulcer activity between all-trans-geranylgeranylacetone, 5-cis-geranylgeranylacetone and the mixture of these isomers (1:1 and 3:2). The results of this experiment suggested that the antiulcer activity of acyclic polyisoprenoids might be governed by such factors as the number of isoprene units, terminal polar groups, and number of intramolecular double bonds.