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Updated: May 11, 2026
Determination of Chemical Inhibitor Efficiency against Intracellular Toxoplasma Gondii Growth Using a Luciferase-Based Growth Assay
Published on: April 29, 2020
In vitro evaluation of β-carboline alkaloids as potential anti-Toxoplasma agents
Maria L Alomar1, Federico A O Rasse-Suriani, Agustina Ganuza
1Laboratorio de Parasitología Molecular, IIB-INTECH, CONICET/UNSAM, Av, Intendente Marino Km, 8,2, C,C 164, (B7130IIWA) Chascomús, Prov, Buenos Aires, Argentina.
Background:
Toxoplasmosis is a worldwide infection caused by the protozoan parasite Toxoplasma gondii, which causes chorioretinitis and neurological defects in congenitally infected newborns or immunodeficient patients. The efficacy of the current treatment is limited, primarily by serious host toxicity. In recent years, research has focused on the development of new drugs against T. gondii. β-Carbolines (βCs), such as harmane, norharmane and harmine, are a group of naturally occurring alkaloids that show microbicidal activity. In this work, harmane, norharmane and harmine were tested against T. gondii.
Findings:
The treatment of extracellular tachyzoites with harmane, norharmane and harmine showed a 2.5 to 3.5-fold decrease in the invasion rates at doses of 40 μM (harmane and harmine) and 2.5 μM (norharmane) compared with the untreated parasites. Furthermore, an effect on the replication rate could also be observed with a decrease of 1 (harmane) and 2 (norharmane and harmine) division rounds at doses of 5 to 12.5 μM. In addition, the treated parasites presented either delayed or no monolayer lysis compared with the untreated parasites.
Conclusions:
The three βC alkaloids studied (norharmane, harmane and harmine) exhibit anti-T. gondii effects as evidenced by the partial inhibition of parasite invasion and replication. A dose-response effect was observed at a relatively low drug concentration (< 40 μM), at which no cytotoxic effect was observed on the host cell line (Vero).
Insights
Three beta-carboline alkaloids (norharmane, harmane, and harmine) show potential against Toxoplasma gondii, inhibiting parasite invasion and replication at low concentrations without host cell toxicity.
Area of Science:
- Parasitology
- Pharmacology
- Infectious Diseases
Background:
- Toxoplasmosis, caused by *Toxoplasma gondii*, leads to severe health issues in newborns and immunocompromised individuals.
- Current treatments for toxoplasmosis are limited by significant host toxicity.
- Research is exploring novel therapeutic agents, including naturally occurring alkaloids like beta-carbolines (βCs).
Purpose of the Study:
- To evaluate the anti-*Toxoplasma gondii* activity of three βC alkaloids: norharmane, harmane, and harmine.
- To determine the effects of these compounds on parasite invasion, replication, and host cell lysis.
- To assess the safety profile of these βCs on host cells.
Main Methods:
- Treatment of extracellular *T. gondii* tachyzoites with varying concentrations of norharmane, harmane, and harmine.
- Quantification of parasite invasion rates into host cells (Vero cell line).
- Assessment of parasite replication rates and host cell lysis following treatment.
Main Results:
- Norharmane, harmane, and harmine significantly reduced parasite invasion rates (2.5 to 3.5-fold decrease) at low micromolar concentrations.
- These βCs also inhibited parasite replication, reducing division rounds by 1-2.
- Treated parasites exhibited delayed or no monolayer lysis, indicating reduced pathogenicity.
Conclusions:
- Norharmane, harmane, and harmine demonstrate significant anti-*T. gondii* properties, partially inhibiting parasite invasion and replication.
- A dose-dependent effect was observed at concentrations below 40 μM.
- Importantly, no cytotoxic effects were noted on the host Vero cell line at effective concentrations, suggesting a favorable safety profile.