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Publication Abstract from PubMed

Twenty-five naturally occurring pentacyclic triterpenes, 15 of which were synthesized in this study, were biologically evaluated as inhibitors of rabbit muscle glycogen phosphorylase a (GPa). From SAR studies, the presence of a sugar moiety in triterpene saponins resulted in a markedly decreased activity ( 7, 18- 20) or no activity ( 21, 22). These saponins, however, might find their value as potential natural prodrugs which are much more water-soluble than their corresponding aglycones. To elucidate the mechanism of GP inhibition, we have determined the crystal structures of the GPb-asiatic acid and GPb-maslinic acid complexes. The X-ray analysis indicates that the inhibitors bind at the allosteric activator site, where the physiological activator AMP binds. Pentacyclic triterpenes represent a promising class of multiple-target antidiabetic agents that exert hypoglycemic effects, at least in part, through GP inhibition.

Naturally occurring pentacyclic triterpenes as inhibitors of glycogen phosphorylase: synthesis, structure-activity relationships, and X-ray crystallographic studies.,Wen X, Sun H, Liu J, Cheng K, Zhang P, Zhang L, Hao J, Zhang L, Ni P, Zographos SE, Leonidas DD, Alexacou KM, Gimisis T, Hayes JM, Oikonomakos NG J Med Chem. 2008 Jun 26;51(12):3540-54. Epub 2008 Jun 3. PMID:18517260^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.