Abstract
The rising tide of antibacterial drug resistance has given rise to the virtual elimination of numerous erstwhile antibiotics, intensifying the urgent demand for novel agents. A number of drugs have been found to possess potent antimicrobial action during the past several years and have the potential to supplement or even replace the antibiotics. Many of these ‘non-antibiotics’, as they are referred to, belong to the widely used class of neuroleptics, the phenothiazines. Another chemically and pharmacologically related class is the thioxanthenes, differing in that the aromatic N of the central phenothiazine ring has been replaced by a C atom. Such “carbon-analogues” were primarily synthesized with the hope that these would be devoid of some of the toxic effects of phenothiazines. Intensive studies on syntheses, as well as chemical and pharmacological properties of thioxanthenes, were initiated in the late 1950s. Although a rather close parallelism with respect to structure activity relationships could be observed between phenothiazines and thioxanthenes; several thioxanthenes were synthesized in pharmaceutical industries and applied for human use as neuroleptics. Antibacterial activities of thioxanthenes came to be recognized in the early 1980s in Europe. During the following years, many of these drugs were found not only to be antibacterial agents but also to possess anti-mycobacterial, antiviral (including anti-HIV and anti-SARS-CoV-2) and anti-parasitic properties. Thus, this group of drugs, which has an inhibitory effect on the growth of a wide variety of microorganisms, needs to be explored for syntheses of novel antimicrobial agents. The purpose of this review is to summarize the neuroleptic and antimicrobial properties of this exciting group of bioactive molecules with a goal of identifying potential structures worthy of future exploration.
Highlights
For the sake of clarity, we will first present the neuroleptic properties of the thioxanthenes, followed by their antimicrobial effects.The first goal of antipsychotic medication is to minimize or eliminate the symptoms within a short period of time
In 1991, Kristiansen and her colleagues [75] observed that stereo-isomeric derivatives of thioxanthenes exhibit antiviral effects on Herpes simplex virus (HSV) and toxic effects on eukaryotic cells
Since these compounds produced an effect on the MICs of antibiotics in S. aureus and on the efflux system of different substrates, there may be an interaction with the pump itself combined with reduction in transmembrane potential
Summary
Dastidar 2,†, Debalina Sinha Roy 2, Shauroseni Palchoudhuri 2, Jette Elisabeth H. Academic Editors: Bruno Botta, Cinzia Ingallina, Andrea Calcaterra and Deborah Quaglio. Received: 11 September 2021 Accepted: 8 November 2021 Published: 29 December 2021
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