Table 3.

Main findings pertinent to antiparasitic activity studies of clioquinol

Antiparasitic clioquinol
References	Species	Methodology	Findings
Tavares et al. (2020)	Leishmania infantum	a) BALB/c female mice (n = 60; 12 per group), infected with promastigotes of L. infantum by subcutaneous injection, were divided into five groups: group 1 (control)—received saline solution subcutaneously; group 2—received empty Pluronic F127 mycelia; group 3—received miltefosine; group 4—received clioquinol; finally, group 5—received clioquinol incorporated into the Pluronic F127 mycelial system b) Half of the animals were euthanized 15 days after treatment to evaluate parasitological and immunological parameters c) Parasitism was investigated in the spleen, liver, and bone marrow of the animals belonging to the five groups by the dilution method d) The parasite load in the spleen of the animals was evaluated by RT-PCR e) The cytokine profile exhibited by CD4 + and CD8 + T cells of the animals belonging to the different groups was determined by flow cytometry f) The IgG1 and IgG2a anti-L. infantum produced by the animals was quantified by ELISA to determine the animals' humoral response	a) Clioquinol exhibited more significant antileishmanial activity, evidenced by the greater amounts of IL-12 and IFN-γ produced by the treated animals relative to control animals and those treated with empty mycelia alone b) Incorporated into the Pluronic F127 micellar system, clioquinol had the highest antileishmanial activity superior to all other treatments administered c) The amounts of nitrite produced by the animals were also higher in the groups treated with clioquinol and with the compound incorporated into the micellar system relative to the other treatments administered in the experiment
Nunes et al. (2019)	Plasmodium falciparum	a) Molecular targets were selected, whose three-dimensional structures were obtained from the PDB database, using the keyword “Plasmodium falciparum” b) Using the TDR Targets platform, the researchers have determined the ability of small compounds to bind with high affinity to the molecular targets of P. falciparum previously selected c) Data from the BraMMT database was evaluated against antimalarial compounds approved by the World Health Organization (WHO). With the help of the OCTOPUS engine software, the prediction of the correct molecular targets for the compounds was performed	a) Presented clioquinol as a highly active and selective compound against P. falciparum in vitro, with an IC50 (Inhibitory Concentration for 50% of Cells) of 0.56 µM and a high Selectivity Index (SI) of 178.6 b) A value of -19.41 kcal/mol suggests that clioquinol is also a potential protease inhibitor in P. falciparum
Souza et al. (2019)	Leishmania amazonensis Leishmania infantum	a) The Effective Concentration for 50% of the Maximum Effect (EC50) for clioquinol and amphotericin B against promastigotes and axenic amastigotes of L. amazonensis and L. infantum was determined via the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] method b) The cytotoxicity of clioquinol and amphotericin B was measured against murine macrophages and human erythrocytes, determining the Cytotoxic Concentration 50% (CC50), as well as the Inhibitory Concentration on 50% of Red Blood Cells (RBC50), for each one of the substances c) The efficacy of the studied compounds was evaluated against macrophages infected with L. amazonensis and L. infantum, counting the number of amastigotes per infected cell by optical microscopy d) The efficacy of clioquinol and amphotericin B was studied in mice subcutaneously infected with promastigote forms of L. amazonensis e) The immune response of both the test substance-treated animals and the positive control group (subcutaneous saline injection) was investigated by determining the amount of anti-leishmania IgG1 and IgG2a in spleen cells of both groups of animals f) The organic toxicity of the test substances was evaluated by monitoring the renal and hepatic functions of the treated animals and the positive control group	a) Clioquinol exhibited excellent in vitro antileishmanial activities (EC50) against promastigote forms of L. amazonensis (7.90 ± 0.65 μM) and L. infantum (4.45 ± 0.98 μM), as well as against axenic amastigote forms of the parasites (2.27 ± 0.44 μM, for L. amazonensis; 3.65 ± 0.25 μM, for L. infantum) b) Clioquinol also exhibited low toxicity against murine macrophages (CC50 613.27 ± 20.53 μM) and human erythrocytes (RBC50 1409.85 ± 64.35 μM) c) Clioquinol also showed high selectivity index for both promastigote (77.63) and axenic amastigote (270.16) forms of L. amazonensis, as well as for the promastigote (137.81) and axenic amastigote (168.0) forms of L. infantum
Schierenberg et al. (2019)	Blastocystis hominis Cryptosporidium spp. Dientamoeba fragilis Entamoeba histolytica/dispar Giardia spp.	a) The study comprised a retrospective analysis of patient data seen by general practitioners in various primary health care settings via the Julius General Practitioner Network (JGPN), an electronic medical record system adopted in the Netherlands b) The researchers searched medical records of patients diagnosed with gastroenteritis from 2013 to 2014 c) Information was collected for each patient, such as age, gender, number of medical visits per episode, comorbidities, immunosuppressive disorders, or occurrence of immunosuppressive therapy d) Finally, the type of therapy administered to each patient diagnosed with gastroenteritis was ascertained in cases which a drug was used	a) Therapeutic interventions employed in clinical practice and their rate of effectiveness b) In 5% of cases of gastroenteritis treated with the use of antimicrobials, clioquinol was used
Tavares et al. (2018)	Leishmania amazonensis Leishmania infantum	a) Representative strains of Leishmania amazonensis and Leishmania infantum were grown in Schneider's medium and subsequently identified by light microscopy via Giemsa staining b) In vitro growth inhibition of both parasite species was assessed in the presence of clioquinol (0–20.0 µg/mL) for both promastigotes and axenic amastigotes via the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] method c) The cytotoxicity of clioquinol and amphotericin B was measured against murine macrophages and human erythrocytes, determining the Cytotoxic Concentration on 50% (CC50), as well as the RBC50 (Inhibitory Concentration on 50% of Red Blood Cells), for each one of the substances d) The inhibition of infection in murine macrophages was evaluated using promastigotes of L. amazonensis pre-incubated with clioquinol and amphotericin B e) The effect of the substances tested was observed on morphology and cell volume and in the mitochondrial function of promastigote cells of L. amasonensis f) The in vivo toxicity of clioquinol was studied in BALB/c rats, monitoring the cardiac, hepatic, and renal functions of the animals	a) Clioquinol exhibited excellent in vitro antileishmanial activities (EC50) against promastigote forms of L. amazonensis (2.55 ± 0.25 μg/mL) and L. infantum (1.44 ± 0.35 μg/mL), as well as against axenic amastigote forms of the parasites (1.88 ± 0.13 μg/mL, for L. amazonensis; 0.98 ± 0.17 μg/mL, for L. infantum) b) Clioquinol also exhibited low toxicity against murine macrophages (CC50 = 254.90 ± 22.60 μg/mL) and human erythrocytes (RBC50 = 488.90 ± 19.50 μg/mL), as well as high selectivity index for both promastigote (99.9) and axenic amastigote (135.6) forms of L. amazonensis, as well as for promastigote (177.1) and axenic amastigote (260.1) forms of L. infantum c) The percentages of infection of murine macrophages by promastigotes of L. amazonensis and L. infantum, pretreated with clioquinol, were 16.5% ± 3.5% and 19.8% ± 1.9%, respectively d) At a subcutaneous dosage of 50 mg/kg/day for 10 days, clioquinol caused no significant alteration in the cardiac, hepatic, and renal functions of the BALBc mice tested
Jong et al. (2014)	Dientamoeba fragilis	a) The work consisted of a retrospective analysis study reviewing medical records of patients admitted to two different hospitals in the Netherlands b) From April 2011 to April 2013, 132 patients with chronic abdominal pain, aged 8 to 18 years, admitted to Jeroen Bosch Hospital, were analyzed c) The control group included 77 patients aged 8–18 years admitted to the Herlaarhof Psychiatric Hospital d) In the D. fragilis positive group presenting chronic abdominal pain, the ability of metronidazole or clioquinol to eradicate the parasite infection (evaluated by PCR of the patients' fecal samples) was determined	a) Clioquinol was able to improve symptoms in 62.5% of treated patients presenting D. fragilis and chronic abdominal pain and completely eradicate D. fragilis infection (75% of patients) in these patients