Mannich Bases of 1,2,4-Triazolones as Potent Anti-Tubercular and Antifungal Agents

Three-Dimensional Quantitative Structure-Activity Relationship-Based Molecular Design through a Side Arm Strategy to Synthesize Phenylpyrazole Oxime Derivatives and Improve Their Insecticidal Activity and Photoself-Degradation

Three-dimensional quantitative structure-activity relationship (3D-QSAR) serves as one of the most important and effective tools to guide molecular design for the development of new pesticides. According to the principle of structural splicing, only changing a small group may lead to a great increase in activity while maintaining the active center unchanged. Under the guidance of 3D-QSAR, three series of phenylpyrazole oxime fluorescent insecticides acting on the GABA receptor, namely, esters (POEs), ethers (POETs), and triazoles (POTs), were designed through a side arm strategy and synthesized by an ultrasonic bath reaction, which were fully characterized and crystal-analyzed. The preliminary bioassay results indicated that the insecticidal activities of POE12 and POT2 against Plutella xylostella were 4.2 and 2.7 times higher than that of fipronil and better than that of the isolated Mythimna separata. Through the trend of insecticidal activity, the introduction of an aryl ring and an electron-withdrawing group in the substituted functional group of the side arm can enhance the insecticidal activity. Reversed-phase HPLC also confirmed that POEs and POTs had good lipid solubility, which was beneficial to improve their fluidity in the cell membrane. Through molecular packing, molecular docking, and Hirshfeld surface, the intermolecular interaction brought by side arms of POEs, POETs, and POTs and the strong interaction with GABA receptors were preliminarily verified. Photophysical tests revealed that the introduction of the side arm expanded the conjugated system and improved its light absorption and fluorescence. Under the irradiation of simulated sunlight, it was found that they had photoself-degradation and could be retransformed into the parent fragment of phenylpyrazole, thereby improving its biological activity and reducing residues.

Emerging impact of triazoles as anti-tubercular agent

Tuberculosis, a disease of poverty is a communicable infection with a reasonably high mortality rate worldwide. 10 Million new cases of TB were reported with approx 1.4 million deaths in the year 2019. Due to the growing number of drug-sensitive and drug-resistant tuberculosis cases, there is a vital need to develop new and effective candidates useful to combat this deadly disease. Despite tremendous efforts to identify a mechanism-based novel antitubercular agent, only a few have entered into clinical trials in the last six decades. In recent years, triazoles have been well explored as the most valuable scaffolds in drug discovery and development. Triazole framework possesses favorable properties like hydrogen bonding, moderate dipole moment, enhanced water solubility, and also the ability to bind effectively with biomolecular targets of M. tuberculosis and therefore this scaffold displayed excellent potency against TB. This review is an endeavor to summarize an up-to-date innovation of triazole-appended hybrids during the last 10 years having potential in vitro and in vivo antitubercular activity with structure activity relationship analysis. This review may help medicinal chemists to explore the triazole scaffolds for the rational design of potent drug candidates having better efficacy, improved selectivity and minimal toxicity so that these hybrid NCEs can effectively be explored as potential lead to fight against M. tuberculosis.