Tetrahydroisoquinolines affect the whole-cell phenotype of Mycobacterium tuberculosis by inhibiting the ATP-dependent MurE ligase

Objectives: (S)-Leucoxine, isolated from the Colombian Lauraceae tree Rhodostemonodaphne crenaticupula Madrinan, was found to inhibit the growth of Mycobacterium tuberculosis H(37)Rv. A biomimetic approach for the chemical synthesis of a wide array of 1-substituted tetrahydroisoquinolines was undertaken with the aim of elucidating a common pharmacophore for these compounds with novel mode(s) of anti-TB action. Methods: Biomimetic Pictet-Spengler or Bischler-Napieralski synthetic routes were employed followed by an evaluation of the biological activity of the synthesized compounds. Results: In this work, the synthesized tetrahydroisoquinolines were found to inhibit the growth of M. tuberculosis H(37)Rv and affect its whole-cell phenotype as well as the activity of the ATP-dependent MurE ligase, a key enzyme involved in the early stage of cell wall peptidoglycan biosynthesis. Conclusions: As the correlation between the MIC and the half-inhibitory enzymatic concentration was not particularly strong, there is a credible possibility that these compounds have pleiotropic mechanism(s) of action in M. tuberculosis.