Dual inhibition of monoamine oxidase B and antagonism of the adenosine A2A receptor by (E,E)-8-(4-phenylbutadien-1-yl)caffeine analogues

The adenosine A2A receptor has emerged as an attractive target for the treatment of Parkinson’s disease (PD). Evidence suggests that antagonists of the A2A receptor (A2A antagonists) may be neuroprotective and may help to alleviate the symptoms of PD. We have reported recently that several members of the (E)-8-styrylcaffeine class of A2A antagonists also are potent inhibitors of monoamine oxidase B (MAO-B). Since MAO-B inhibitors are known to possess anti-parkinsonian properties, dual-target-directed drugs that block both MAO-B and A2A receptors may have enhanced value in the management of PD. In an attempt to explore this concept further we have prepared three additional classes of C-8 substituted caffeinyl analogues. The 8-phenyl- and 8-benzylcaffeinyl analogues exhibited relatively weak MAO-B inhibition potencies while selected (E,E)-8-(4-phenylbutadien-1-yl)caffeinyl analogues were found to be exceptionally potent reversible MAO-B inhibitors with enzyme–inhibitor dissociation constants (Ki values) ranging from 17 to 149 nM. Furthermore, these (E,E)-8-(4-phenylbutadien-1-yl)caffeines acted as potent A2A antagonists with Ki values ranging from 59 to 153 nM. We conclude that the (E,E)-8-(4-phenylbutadien-1-yl)caffeines are a promising candidate class of dual-acting compounds.

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