Integrating synthesis, pharmacological evaluation, and molecular dynamics simulation of novel 8-substituted theophylline hybrids as potential PDE-4B inhibitors, bronchodilators and antibacterial.

Methylxanthines, particularly theophylline, have long served as effective bronchodilators for severe asthma. Emerging evidence links bacterial infection to asthma pathogenesis, motivating the search for multifunctional therapeutic agents. In this study, a series of 8-substituted 1,3-dimethylxanthines bearing aryl and heteroaryl groups were synthesized and structurally characterized by NMR, elemental analysis, and HR-ESI-MS. Most compounds exhibited significant bronchodilator activity in an acetylcholine-induced guinea pig model, surpassing theophylline. The compounds demonstrated potent in vitro PDE-4B inhibition relevant to asthma-related inflammation. Several derivatives also showed antibacterial activity against susceptible Gram-positive and Gram-negative strains in asthmatic patients. Molecular docking and 200 ns molecular dynamics simulations revealed strong and stable binding of the most active compounds, 14d and 17 k, within the PDE-4B active site, correlating with their in vivo efficacy. Notably, 17 k displayed superior oral pharmacokinetic properties, high lipophilicity, moderate solubility, and optimal molecular size, comparable to theophylline and roflumilast (standard PDE-4B inhibitor). These findings identify 17 k as a promising lead for the development of orally active dual-acting agents for asthma management.