Benzothiazoles: A New Profile of Biological Activities

Benzothiazoles are bicyclic ring system with multiple developed and examined, in vitro, their antitumor activity in applications. In the 1950s, a number of 2-aminobenzothiazoles ovarian, breast, lung, renal and colon carnicoma human cell were intensively studied as central muscle relaxants. Since lines. Pyrimido benzothiazole and benzothiazolo then medicinal chemists have not taken active interest in quinoline derivatives, imidazo benzothiazoles as well this chemical family. Biologist’s attention was drawn to this as, polymerized benzothiazoles showed antitumor activity. series when the pharmacological profile of Riluzole was discovered. Riluzole (6-trifluoromethoxy-2-benzothiazolamine, 2-(4-Aminophenyl) benzothiazoles (1) comprise a novel PK-26124, RP-25279, Rilutek) was found to interfere with mechanistic class of antitumor agents. Their unusual glutamate neurotransmission in biochemical, electrophysiological activity was first recognized from the distinctive biphasic­ and behavioral experiments. After that benzothiazole dose response relationship shown in in vitro assays derivatives have been studied extensively and found to against sensitive breast tumor cell lines, e.g., MCF-7 and have diverse chemical reactivity and broad spectrum of MDA-468. Potency against these breast lines and others biological activity. was independent of the estrogen or growth factor receptor status of the cells. Introduction of methyl or Although they have been known from long ago to be halogen substituent into the 3’-position of the 2-phenyl biologically active, their varied biological features are still group enhances potency and extends the spectrum of of great scientific interest. Benzothiazoles show antitumor action to certain colon, lung, melanoma, renal and ovarian activity, especially the phenyl-substituted benzothiazoles, cell lines. while condensed pyrimido benzothiazoles and benzothiazolo quinazolines exert antiviral activity. 6-Amidino-substituted-2-aminobenzothiazoles (2), N-methylRecently, Racane et al. have described the synthesis of 2-(4-cyanostyryl) benzothiazolium, cyano-substituted-2­ bis-substituted amidino benzothiazoles as potential anti HIV styryl benzothiazoles (3) and amidino and bis-amidino­ agents. Substituted 6-nitro-and 6-aminobenzothiazoles substituted 2-styryl benzothiazoles (4) were prepared by show antimicrobial activity. Given below is a brief account Caleta et al. All new compounds were tested on of various alterations conducted on benzothiazole ring and cytostatic activities against malignant cell lines. The their associated biological activities. compounds exerted a different inhibitory effect, depended on concentration and type of the cells. The Antitumor activity: best inhibitory effect was achieved with compounds (3) A series of potent and selective antitumor agents mostly and (4) with slight differences among them. All of them from substituted 2-(4-aminophenyl) benzothiazoles were inhibited the growth of examined tumor cell lines and also normal fibroblasts. Other examined compounds