Design, synthesis, computational molecular docking studies of novel heterocyclics bearing 1,2,4-triazole, 1,3,4-oxadiazole conjugates as potent antibacterial and antitubercular agents

Synthesis and antimicrobial evaluation of hybrids methoxynaphthalene-N-acylhydrazones/1,3,4-oxadiazoles

AIMS

Paracoccidioidomycosis is a neglected tropical disease caused by the fungi Paracoccidoides spp. In cases of clinical manifestations involving the lung, its symptoms can be confused with tuberculosis, in addition to the possibility of patients presenting a co-infection between the two. Considering previous studies by our research group evaluating N-acylhydrazones and 1,3,4-oxadiazoles containing the 4-methoxynaphthalene ring, this work proposed the synthesis of new N-acylhydrazones and new 1,3,4-oxadiazoles containing the 2-methoxynaphthalene ring.

MATERIALS & METHODS

Starting from the precursor block 2-methoxy-1-naphthaldehyde, N-acylhydrazones and their respective 1,3,4-oxadiazoles containing the 2-methoxynaphthalene ring were synthesized. The antifungal activity was evaluated against P. brasiliensis (P.b.18) and antimycobacterial activity against M. tuberculosis (H37Rv).

RESULTS

The antimicrobial activity was tested for nine N-acylhydrazones and four 1,3,4-oxadiazoles in which structures showing anti-P.b. activity, highlighting the N-acylhyadrazone 5f and 1,3,4-oxadiazole 6f with MIC of 0.48 ug mL-1 and 1.95 ug mL-1, respectively, and substances with anti-M.tb. activity with MIC between 7.8 and 15.6 ug mL-1 (6a and 6b, respectively).

CONCLUSION

New structures containing methoxynaphalene rings and phenol or substituted phenol or pyridine groups can be added to the chemolibrary of candidates for prototypes of drugs with antimicrobial activity against P.b.18 and H37Rv.

Identification of Chemical Scaffolds Targeting Drug-Resistant and Latent Mycobacterium tuberculosis through High-Throughput Whole-Cell Screening

Identification of structurally unique chemical entities targeting unexplored bacterial targets is a prerequisite to combat increasing drug resistance against Mycobacterium tuberculosis. This study employed a whole-cell screening approach as an initial filter to scrutinize a 10,000-compound chemical library, resulting in the discovery of seven potent compounds with MIC values ranging from 1.56 to 25 μM. These compounds were categorized into four distinct chemical groups. Remarkably, they demonstrated efficacy against drug-resistant and nonreplicating tuberculosis strains, highlighting their effectiveness across different infection states. With a favorable selectivity index (>10), these compounds showed a safe therapeutic range and exhibited potency in an intracellular model of Mtb infection, mimicking the in vivo setup. Combining these identified hits with established anti-TB drugs revealed additive effects with rifampicin, isoniazid, and bedaquiline. Notably, IIIM-IDD-01 exhibited synergy with isoniazid and bedaquiline, likely due to their complementary mechanisms of targeting Mtb. Most potent hits, IIIM-IDD-01 and IIIM-IDD-02, displayed time- and concentration-dependent killing of Mtb. Mechanistic insights were sought through SEM and docking studies, although comprehensive evaluation is ongoing to unravel the hits' specific targets and modes of action. The hits demonstrated favorable pharmacokinetic properties (ADME-Tox) and showed a low risk of adverse effects, along with a predicted high level of oral bioavailability. These promising hits can serve as an initial basis for subsequent medicinal chemistry endeavors aimed at developing a new series of anti-TB agents. Moreover, the study affirms the significance of high-throughput in vitro assays for the TB drug discovery. It also emphasizes the necessity of targeting diverse TB strains to address the heterogeneity of tuberculosis bacteria.