Amelioration of hepatotoxicity by biocleavable aminothiol chimeras of isoniazid: Design, synthesis, kinetics and pharmacological evaluation

Isoniazid-historical development, metabolism associated toxicity and a perspective on its pharmacological improvement

Despite the extraordinary anti-tubercular activity of isoniazid (INH), the drug-induced hepatotoxicity and peripheral neuropathy pose a significant challenge to its wider clinical use. The primary cause of INH-induced hepatotoxicity is in vivo metabolism involving biotransformation on its terminal -NH2 group owing to its high nucleophilic nature. The human N-acetyltransferase-2 enzyme (NAT-2) exploits the reactivity of INH's terminal -NH2 functional group and inactivates it by transferring the acetyl group, which subsequently converts to toxic metabolites. This -NH2 group also tends to react with vital endogenous molecules such as pyridoxine, leading to their deficiency, a major cause of peripheral neuropathy. The elevation of liver functional markers is observed in 10%-20% of subjects on INH treatment. INH-induced risk of fatal hepatitis is about 0.05%-1%. The incidence of peripheral neuropathy is 2%-6.5%. In this review, we discuss the genesis and historical development of INH, and different reported mechanisms of action of INH. This is followed by a brief review of various clinical trials in chronological order, highlighting treatment-associated adverse events and their occurrence rates, including details such as geographical location, number of subjects, dosing concentration, and regimen used in these clinical studies. Further, we elaborated on various known metabolic transformations highlighting the involvement of the terminal -NH2 group of INH and corresponding host enzymes, the structure of different metabolites/conjugates, and their association with hepatotoxicity or neuritis. Post this deliberation, we propose a hydrolysable chemical derivatives-based approach as a way forward to restrict this metabolism.

Double functionalized haemocompatible silver nanoparticles control cell inflammatory homeostasis

Infection, trauma, and autoimmunity trigger tissue inflammation, often leading to pain and loss of function. Therefore, approaches to control inflammation based on nanotechnology principles are being developed in addition to available methods. The metal-based nanoparticles are particularly attractive due to the ease of synthesis, control over physicochemical properties, and facile surface modification with different types of molecules. Here, we report curcumin conjugated silver (Cur-Ag) nanoparticles synthesis, followed by their surface functionalization with isoniazid, tyrosine, and quercetin, leading to Cur-Ag^INH, Cur-Ag^Tyr, and Cur-Ag^Qrc nanoparticles, respectively. These nanoparticles possess radical scavenging capacity, haemocompatibility, and minimal cytotoxicity to macrophages. Furthermore, the nanoparticles inhibited the secretion of pro-inflammatory cytokines such as interleukin-6, tumor necrosis factor-α, and interleukin-1β from macrophages stimulated by lipopolysaccharide (LPS). The findings reveal that the careful design of surface corona of nanoparticles could be critical to increasing their efficacy in biomedical applications.

Mannich Bases: Centrality in Cytotoxic Drug Design

Mannich bases identified by Professor Carl Mannich have been the most extensively explored scaffolds for more than 100 years now. The versatile biological roles that they play have promoted their applications in many clinical conditions. The present review highlights the application of Mannich bases as cytotoxic agents, categorizing them into synthetic, semisynthetic and prodrugs classes and gives an exhaustive account of the work reported in the last two decades. The methods of synthesis of these cytotoxic agents, their anti-cancer potential in various cell lines and promising leads for future drug development have also been discussed. Structure-activity relationships along with the targets on which these cytotoxic Mannich bases act have been included as well.

Diverse Thiophenes as Scaffolds in Anti-cancer Drug Development: A Concise Review

Thiophenes are one of the abundantly found heterocyclic ring systems in many biologically active compounds. Moreover, various substituted thiophenes exert numerous pharmacological actions on account of their isosteric resemblance with compounds of natural origin, thus rendering them with diverse actions like antibacterial, antifungal, antiviral, anti-inflammatory, analgesic, antiallergic, hypotensives, etc. In this review, we specifically explore the chemotherapeutic potential of a variety of structures consisting of thiophene scaffolds as prospective anticancer agents.

Co-drug of isoniazid and sulfur containing antioxidant for attenuation of hepatotoxicity and treatment of tuberculosis

The prolonged use of isoniazid (INH) - a highly effective drug in the treatment of tuberculosis - causes fatal liver injury. In order to overcome this adverse effect, a unique amide codrug was designed by covalently linking INH with sulfur-containing antioxidant- alpha-lipoic acid for possible hepatoprotective and antimycobacterial effect. Co-drug LI was prepared by Schotten Baumann reaction and was characterized by spectroscopic analysis. To check the bioreversibility of LI, in vitro release tests were conducted in buffers of specific pH, stomach, and intestinal homogenates of rat employing HPLC. Male Wistar rats were used for the evaluation of the hepatoprotective activity. Liver function markers, oxidative stress markers, and biochemical parameters were estimated. The antimycobacterial efficacy of LI was examined in terms of its ability to decrease the lung bacillary load in Balb/c mice infected intravenously with Mycobacterium tuberculosis. LI resisted hydrolysis in buffers of pH 1.2 (acidic), pH 7.4 (basic), and stomach homogenate of the rat while displayed significant hydrolysis (88.19%) in intestinal homogenates over a period of 6 h. The effect of LI on liver function, antioxidant and biochemical paradigms was remarkable as it reestablished the enzyme levels and restored hepatic cytoarchitecture representing its abrogating effect. The findings of antimycobacterial activity assessment evidently demonstrated that LI was as potent as INH in lowering the mycobacterial load in mice. The outcome of this exploration confirmed that the described co-drug can offer desirable safety and therapeutic benefit in the management of tuberculosis.