In vitro and in vivo characterization of anti-malarial acylphenoxazine derivatives prepared from basic blue 3

• Published in: Malaria Journal
• Main Authors: Takahiro Tougan, Kazunori Takahashi, Mayumi Ikegami-Kawai, Masako Horiuchi, Shiho Mori, Maiko Hosoi, Toshihiro Horii, Masataka Ihara, Masayoshi Tsubuki
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2019
• Subjects: Basic blue 3; ITT derivatives; Anti-malarial activity; Cytotoxicity; π-Delocalized lipophilic cations; DLC hypothesis; Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic
• Online Access: https://doi.org/10.1186/s12936-019-2873-0; https://doaj.org/article/e07c6fc9cddb4345b47970b509787a90

Abstract Background Basic blue 3 is a promising anti-malarial lead compound based on the π-delocalized lipophilic cation hypothesis. Its derivatives with nitrogen atoms bonded to carbon atoms at the 3- and 7-positions on the phenoxazine ring were previously shown to exert potent antiprotozoal activity against Plasmodium falciparum, Trypanosoma cruzi, Trypanosoma brucei rhodesiense, and Leishmania donovani parasites in vitro. However, compounds with nitrogen modification at the 10-position on the phenoxazine ring were not evaluated. Methods Six acylphenoxazine derivatives (ITT-001 to 006) with nitrogen modification at the 10-position on the phenoxazine ring, which were synthesized from basic blue 3, were characterized and evaluated for anti-malarial activity in vitro with an automated haematology analyzer (XN-30) and light microscopy. Intensity of self-fluorescence was measured using a fluorometer. Localization of basic blue 3 was observed by fluorescence microscopy. Cytotoxicity was evaluated using human cell lines, HEK293T and HepG2 cells. Finally, anti-malarial activity was evaluated in a rodent malaria model. Results All the six derivatives showed anti-malarial efficacy even against chloroquine-, pyrimethamine-, and artemisinin-resistant field isolates similar to the sensitive strains and isolates in vitro. The efficacy of basic blue 3 was the strongest, followed by that of ITT-001 to 004 and 006, while that of ITT-005 was the weakest. Basic blue 3 showed strong self-fluorescence, whereas ITT derivatives had five- to tenfold lower intensity than that of basic blue 3, which was shown by fluorescence microscopy to be selectively accumulated in the plasmodial cytoplasm. In contrast, ITT-003, 004, and 006 exhibited the lowest cytotoxicity in HEK293T and HepG2 cells in vitro and the highest selectivity between anti-malarial activity and cytotoxicity. The in vivo anti-malarial assay indicated that oral administration of ITT-004 was the most effective against the rodent malaria parasite, Plasmodium berghei NK65 ...