Synthesis of Mycobacterium tuberculosis ATP synthase inhibitors

Abstract

Tuberculosis (TB) is a lethal disease considered a direct threat to human wellbeing in all regions worldwide Mycobacterium tuberculosis (Mtb) is a species of bacteria that causes almost all cases of TB in humans. Currently, multidrug therapy is a key strategy for treating TB. However, TB can mutate to resist the common TB drugs; therefore, more potent drugs, which commonly come with greater side effects, are required to cure MDR-TB. One of the potent second-line drugs with a high success rate is Bedaquiline (BDQ). However, it carries a risk of arrhythmias, which is potentially lethal. Nonetheless, the BDQ binding site of Mtb F1F0 ATP synthase remains a promising drug target. In this work, the development of novel Mtb ATP synthase inhibitors was studied.

Recently, GaMF1 was reported to exhibit good inhibition in ATP synthesis of Mtb by binding at a unique and crucial peptide loop in the γ-subunit of Mycobacterium FoF1-ATP synthase. Nevertheless, the water solubility and in vivo stability of GaMF1 are potentially problematic. In this work, 28 GaMF1 analogs are synthesized to overcome those issues and improve both ATP synthesis and mycobacterial growth inhibition. Inverted Membrane Vesicle (IMV) and M. smeg. growth inhibition assays were done to evaluate the synthetic analogs’ properties. The pyrimidine (ring C) substituents are crucial moieties for inhibition, and the modification of this ring results in a significant decrease in potency. However, the modification of the middle p-phenylenediamine (ring B) is quite well-tolerated, and aromatic or cyclic alkanes are favored for efficiency.

Recently, EGCG was discovered to have promising enzymatic activity at the nanomolar level to inhibit Mycobacterium ATP synthesis by interfering with Mycobacterium FoF1-ATP synthase at the ε subunit. However, EGCG does not show mycobacterial growth activity. In this work, 16 EGCG analogs are synthesized to understand the structure-activity relationship in which both catechin and gallate ester moieties are required for mycobacterial ATP synthesis inhibition. However, catechin gallate and gallocatechin gallate derivatives revealed different patterns in structural activity relationships. Additionally, catechol ester can improve the effectiveness of inhibiting ATP synthesis in catechin analogs. The bacterial growth assay showed that EGCG analogs still lack the mycobacterial growth inhibition property. The lipophilic ester-protected catechin gallate could not solve the bacterial growth inhibition problem.