Potential anti-amoebic effects of synthetic 1,4-benzothiazine derivatives against Acanthamoeba castellanii

Alishba, Usman Ahmed, Muhammad Taha, Naveed Ahmed Khan, Uzma Salar, Khalid Mohammed Khan, Ayaz Anwar, Ruqaiyyah Siddiqui

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A rare but lethal central nervous system disease known as granulomatous amoebic encephalitis (GAE) and potentially blinding Acanthamoeba keratitis are diseases caused by free-living Acanthamoeba. Currently, no therapeutic agent can completely eradicate or prevent GAE. Synthetic compounds are a likely source of bioactive compounds for developing new drugs. This study synthesized seventeen 1,4-benzothiazine derivatives (I -XVII) by a base-catalyzed one-pot reaction of 2-amino thiophenol with substituted bromo acetophenones. Different spectroscopic techniques, such as EI-MS, 1H-, and 13C NMR (only for the new compounds), were used for the structural characterization and conformation of compounds. These compounds were assessed for the first time against Acanthamoeba castellanii. All compounds showed anti-amoebic potential in vitro against A. castellanii, reducing its ability to encyst and excyst at 100 μM. Compounds IX, X, and XVI showed the most potent activities among all derivatives and significantly reduced the viability to 5.3 × 104 (p < 0.0003), 2 × 105 (p < 0.006), and 2.4 × 105 (p < 0.002) cells/mL, respectively. The cytotoxicity profile revealed that these molecules showed lower to moderate cytotoxicity, i.e., 36 %, 2 %, and 21 %, respectively, against human keratinocytes in vitro. These results indicate that 1,4-benzothiazines showed potent in vitro activity against trophozoites and cysts of A. castellanii. Hence, these 1,4-benzothiazine derivatives should be considered to develop new potential therapeutic agents against Acanthamoeba infections.

Original languageEnglish
Article numbere23258
Issue number1
Early online date10 Dec 2023
Publication statusPublished - 15 Jan 2024


  • Acanthamoeba
  • Amoebicidal
  • Benzothiazine
  • One-pot synthesis

ASJC Scopus subject areas

  • General


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