Background: 8-Phenyltheophylline derivatives exhibit prophylactic effects at a specific
dose but do not produce the cardiovascular or emetic side effects associated with xanthines, thereby
exhibiting unique characteristics of potential therapeutic importance.
Methods: Novel series of 8-(proline/pyrazole)-substituted xanthine analogs have been synthesized.
The affinity and selectivity of compounds to adenosine receptors have been assessed by radioligand
binding studies. The synthesized compounds also showed good bronchospasmolytic properties
(increased onset of bronchospasm; decreased duration of jerks) with 100% survival of animals
in comparison to the standard drug. Besides, compound 8f & 9f showed good binding affinity in
comparison to other synthesized compounds in the micromolar range.
Results: The maximum binding affinity of these compounds was observed for A2B receptors,
which was ~ 7 or 10 times higher as compared to A1, A2A and A3 receptors. The newly synthesized
derivatives 8f, 9a-f, 17g-m, and 18g-m displayed significant protection against histamine
aerosol induced bronchospasm in guinea pigs.
Conclusion: Newly synthesized proline/pyrazole based xanthines compounds showed a satisfactory
binding affinity for adenosine receptor subtypes. Replacement or variation of substituted proline
ring with substituted pyrazole scaffold at the 8th-position of xanthine moiety resulted in the reduction
of adenosine binding affinity and bronchospasmolytic effects.