Among the major cardenolides from the milkweed Asclepias asperula, 6'-O-(E-4-hydroxycinnamoyl) desglucouzarin has not been characterized biochemically. In this study, its binding affinity for a physiological receptor, porcine kidney Na+,K+-ATPase, was found to be lower than the other cardenolides in this plant. The order of affinities from highest to lowest was: uzarigenin (K(d) = 1.05 μM) = desglucouzarin (K(d) = 0.98 μM) > uzarin (K(d) = 4.0 μM) > 6'-O-(E-4-hydroxycinnamoyl) desglucouzarin (K(d) = 16 μM). The chemical attachment of the 4-hydroxycinnamoyl group to the 6'-carbon of desglucouzarin significantly inhibits binding. This agrees with predictions that a 5'-methyl group on cardenolides fits the receptor site optimally for the porcine kidney enzyme. The 4-hydroxycinnamic ester was also found to be fluorescent.

enzyme inhibitor, cardiac glycoside, cardenolide, Asclepias, Asclepias asperula, desglucouzarin, kidney enzyme, urarin, uzarigenin

• Compound ID: 29579
  

  pCoum-(9-6)-b-D-Glcp-(1-3)-Subst Subst = uzarigenin = SMILES O{3}[C@H]1CC[C@@]2(C)[C@](CC[C@]3([H])[C@]2([H])CC[C@@]4(C){14}[C@]3(O)CC[C@@H]4C(CO5)=CC5=O)([H])C1

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  Structure type: monomer
  Trivial name: 6'-O-(E-4-hydroxycinnamoyl) desglucouzarin
  Compound class: triterpenoid glycoside
  
   
  
  Asclepias asperula
  CSDB ID 62172 (all data & tools)