Inhibition of Toxoplasma gondii by Indirubin and Tryptanthrin Analogs

Abstract

New drugs are needed for treatment of Toxoplasma gondii infections. We tested derivatives of principles found in Isatis indigotica for in vitro efficacy against T. gondii infection. Indirubin-3-oxime analogs showed modest micromolar activity, while tryptanthrin derivatives displayed 50% inhibitory doses in the low nanomolar range. Tryptanthrins have potential as anti-Toxoplasma infection therapeutics.Toxoplasma gondii is an apicomplexan parasite with worldwide distribution. T. gondii infections in humans range from overwhelming infection in neonates and immunocompromised individuals to inapparent infections in immunocompetent hosts. Current medications for the prevention and treatment of Toxoplasma infection are hampered by toxicity and limited efficacy.Our approach to address this drug deficit was to examine natural and synthetic derivatives of principles found in the Chinese medicinal herb Isatis indigotica for the ability to disrupt the in vitro growth of T. gondii. Our primary focus centered around analogs of the components indirubin 1a (Table 1) and tryptanthrin 2a (Table 2) (7). Derivatives of these compounds have been shown to possess activity against several protozoan pathogens. Specifically, both classes of compounds have been shown to inhibit some strains of Leishmania spp. (3, 4; E. Xingi, V. Myrianthopoulos, D. Smirlis, S. Bisti, P. Magiatis, E. Mikros, L. Skaltsounis, and K. Soteriadou, presented at the 3rd COST B22 Annual Congress, Drug Discovery and Development for Parasitic Diseases, Athens, Greece, 2006). In addition, tryptanthrin derivatives have been reported to inhibit Trypanosoma brucei (11) and another apicomplexan parasite, Plasmodium falciparum (2). To our knowledge, there are no reports of the activities of these compounds as inhibitors of T. gondii. Therefore, we examined the ability of derivatives of indirubin and tryptanthrin to inhibit the growth of T. gondii in cell culture.Indirubin-5-sulfonic acid 1c was obtained from Alexis Biochemicals, San Diego, CA. Indirubin-3Ј-oxime-5-sulfonic acid 4c and indirubin derivative E804 6 (9) were purchased from Calbiochem, Darmstadt, Germany. Trimethoprim and indirubin-3Ј-oxime 4a were obtained from Sigma Chemical Co. (St. Louis, MO). All other indirubin and tryptanthrin derivatives were synthesized by standard methods (1, 12). The analogs of indirubin 1a were prepared by condensation of 3-acetoxy indole with the appropriate isatin derivatives in the presence of sodium carbonate. Treatment of 1a with hydroxylamine hydrochloride in pyridine gave the 3Ј-oxime analogs 4 (4a to 4k). The 1-N-acetyl derivative 3 and 3Ј-acetoxy-oxime compounds 5 (5a and 5k) were prepared by treatment of compound 1a or 4a with acetic anhydride. The analogs of tryptanthrin 2a were synthesized from isatoic anhydride and the corresponding isatin derivatives in refluxing toluene with triethylamine as cosolvent.Compounds were tested for in vitro efficacy against T. gondii tachyzoites, using methods which have been described in detail in previous publications (5). Briefly, tes...

7,9-Dichloro-6H,12H-indolo[2,1-b]quinazoline-6,12-dione

“…For the synthesis, chemistry, and biological activity of the title compound see: Krivogorsky et al (2008). For chemistry and biological activity of the natural product tryptanthrin (indolo[2,1-b]quinazoline-6,12-dione) and its derivatives and for related structures, see: Honda et al…”

“…For the synthesis, chemistry, and biological activity of the title compound see: Krivogorsky et al (2008). For chemistry and biological activity of the natural product tryptanthrin (indolo[2,1-b]quinazoline-6,12-dione) and its derivatives and for related structures, see: Honda et al (1979); Mitscher & Baker (1998); Kataoka et al (2001); Bandekar et al (2010); Sharma et al (2002); Motoki et al (2005); Yu et al (2009); Bhattacharjee et al (2002); Scovill et al (2002); Bhattacharjee et al (2004); Pitzer et al (2000).…”

A cascade synthetic route to new bioactive spiroindolinepyrido[1,2-a]indolediones from indirubin

“…The signal in the 13 C NMR spectra at 48.0 ppm was assigned to the spiro C3, and the C2 amide carbonyl was assigned to the peak at 175.6 ppm whereas the peak at 199.1 ppm was attributed to the C10' carbonyl. † Note: C-allyl substituent is not crotyl but has rearranged -see Figure 4 for details of structure.…”

“…Indirubin also inhibits intersegmental vessel growth and induces cellular apoptosis in an in vivo zebrafish model 9 while other indirubin derivatives or analogues, 10 including N-glycosides, show antiproliferative activity against a number of human cancer cell lines. 11,12 Other effects of indirubin or derivatives include anti-protozoal activity 13 as well as inhibition of lipoxygenase.…”

Modulatory Effects and Action Mechanisms of Tryptanthrin on Murine Myeloid Leukemia Cells

“…It was first isolated from Strobilanthes cusia as an anti-fungal agent against dermatophytes (7). Tryptanthrin is a weakly basic alkaloid and has been reported to have various biological and pharmacological activities, such as inhibitory activities against a variety of microorganisms and parasites (7)(8)(9)(10), immunomodulatory (11)(12)(13) and anti-inflammatory activities (13)(14)(15), and anti-tumor activity towards human leukemia and breast cancer cell lines in vitro (16)(17)(18). Moreover, the crude ethyl acetate extract and tryptanthrin extracted from the indigo plant Polygonum tinctorium have cancer chemopreventive activity by prevention of azoxymethane-induced intestinal tumor formation in F344 rats (19).…”