Staurosporine from Streptomyces sanyensis activates Programmed Cell Death in Acanthamoeba via the mitochondrial pathway and presents low in vitro cytotoxicity levels in a macrophage cell line

Amoebicidal effect of synthetic indoles against Acanthamoeba spp.: a study of cell death

Organic and synthetic chemistry plays a crucial role in drug discovery fields. Moreover, chemical modifications of available molecules to enhance their efficacy, selectivity and safety have been considered as an attractive approach for the development of new bioactive agents. Indoles, a versatile group of natural heterocyclic compounds, have been widely used in pharmaceutical industry due to their broad spectrum of activities including antimicrobial, antitumoral and anti-inflammatory among others. Herein, we report the amoebicidal activity of different indole analogs on Acanthamoeba castellanii Neff. Among the 40 tested derivatives, eight molecules were able to inhibit this protistan parasite. The structure-activity relationship (SAR) analysis of their anti-Acanthamoeba activity would suggest that a carboxylation of C-3 position and the incorporation of halogen as chlorine/fluorine would enhance their biological profile, presumably by increasing their lipophilicity and therefore their ability to cross the cell membrane. Fluorescence image base system was used to investigate the effect of indole 6o c-6 on the cytoskeleton network and various programmed cell death features. We were able to highlight that the methyl 6-chloro-1H-indole-3-carboxylate could induce program cell death by the mitochondrial dysfunction.

(‒)-Epicatechin reveals amoebicidal activity against Acanthamoeba castellanii by activating the programmed cell death pathway

BACKGROUND

Acanthamoeba is an opportunistic pathogen that can cause human infections such as granulomatous amebic encephalitis and acanthamoeba keratitis. However, no specific drug to treat the diseases has been developed. Therefore, the discovery or development of novel drugs for treating Acanthamoeba infections is urgently needed. The anti-protozoan activity of (‒)-epicatechin (EC) has been reported, suggesting it is an attractive anti-protozoal drug candidate. In this study, the amoebicidal activity of EC against A. castellanii was assessed and its mechanism of action was unveiled.

METHODS

The amoebicidal activity of EC against A. castellanii trophozoites and the cytotoxicity of EC in HCE-2 and C6 cells were determined with cell viability assay. The underlying amoebicidal mechanism of EC against A. castellanii was analyzed by the apoptosis/necrosis assay, TUNEL assay, mitochondrial dysfunction assay, caspase-3 assay, and quantitative reverse transcription polymerase chain reaction. The cysticidal activity of EC was also investigated.

RESULTS

EC revealed amoebicidal activity against A. castellanii trophozoites with an IC50 of 37.01 ± 3.96 µM, but was not cytotoxic to HCE-2 or C6 cells. EC induced apoptotic events such as increases in DNA fragmentation and intracellular reactive oxygen species production in A. castellanii. EC also caused mitochondrial dysfunction in the amoebae, as evidenced by the loss of mitochondrial membrane potential and reductions in ATP production. Caspase-3 activity, autophagosome formation, and the expression levels of autophagy-related genes were also increased in EC-treated amoebae. EC led to the partial death of cysts and the inhibition of excystation.

CONCLUSION

EC revealed promising amoebicidal activity against A. castellanii trophozoites via programmed cell death events. EC could be a candidate drug or supplemental compound for treating Acanthamoeba infections.

High-Throughput Screen of Microbial Metabolites Identifies F1FO ATP Synthase Inhibitors as New Leads for Naegleria fowleri Infection

Primary amebic meningoencephalitis (PAM), a brain infection caused by a free-living ameba Naegleria fowleri, leads to an extensive inflammation of the brain and death within 1-18 (median 5) days after symptoms begin. Although natural products have played a significant role in the development of drugs for over a century, research focusing on identifying new natural product-based anti-N. fowleri agents is limited. We undertook a large-scale ATP bioluminescence-based screen of about 10,000 unique marine microbial metabolite mixtures against the trophozoites of N. fowleri. Our screen identified about 100 test materials with >90% inhibition at 50 μg/mL and a dose-response study found 20 of these active test materials exhibiting an EC50 ranging from 0.2 to 2 μg/mL. Examination of four of these potent metabolite mixtures, derived from our actinomycete strains CNT671, CNT756, and CNH301, resulted in the isolation of a pure metabolite identified as oligomycin D. Oligomycin D exhibited nanomolar potency on multiple genotypes of N. fowleri, and it was five- or 850-times more potent than the recommended drugs amphotericin B or miltefosine. Oligomycin D is fast-acting and reached its EC50 in 10 h, and it was also able to inhibit the invasiveness of N. fowleri significantly when tested on a matrigel invasion assay. Since oligomycin is known to manifest inhibitory activity against F1FO ATP synthase, we tested different F1FO ATP synthase inhibitors and identified a natural peptide leucinostatin as a fast-acting amebicidal compound with nanomolar potency on multiple strains.

L-tryptophan-titanium oxide nanoparticles showed selective anti-Toxoplasma gondii activity and improved host biocompatibility

Toxoplasma gondii, the etiological agent of toxoplasmosis, currently affects nearly one-third of the human population. Treatment options for toxoplasmosis are limited, which underscores the need for new drugs. In the present study, we screened nanoparticles (NPs) of titanium dioxide (TiO₂) and molybdenum (Mo) for their potential to inhibit the growth of T. gondii in vitro. NPs of TiO₂ and Mo showed non-dose-dependent anti-T. gondii activity with EC₅₀ values of 157.6 and 253 µg/mL, respectively. Previously, we showed that amino acid modification of NPs enhances their selective anti-parasite toxicity. Therefore, to enhance the selective anti-parasitic action of TiO₂, we modified the NP surface using alanine, aspartate, arginine, cysteine, glutamate, tryptophan, tyrosine, and bovine serum albumin. The bio-modified TiO₂ showed anti-parasite activity with EC₅₀ values ranging from 45.7 to 286.4 µg/mL. At effective anti-parasite concentrations, modified-TiO₂ showed no appreciable host cytotoxicity. Of the eight bio-modified TiO₂, tryptophan-TiO₂ showed the most promising anti-T. gondii specificity and improved host biocompatibility with a selectivity index (SI) of 49.1 versus 7.5 for TiO₂ (note, pyrimethamine, a standard drug for toxoplasmosis, has an SI of 2.3). Furthermore, our data indicate that redox modulation may be part of the anti-parasite action of these NPs. Indeed, augmentation with trolox and l-tryptophan reversed the growth restriction caused by the tryptophan-TiO₂ NPs. Collectively, these findings suggest that the parasite toxicity was selective and not a result of general cytotoxic action. Furthermore, surface modification with amino acids such as l-tryptophan not only enhanced the anti-parasitic action of TiO₂ but also improved the host biocompatibility. Overall, our findings indicate that the nutritional requirements of T. gondii represent a viable target for the development of new and effective anti-T. gondii agents.

The In Vitro Anti-Parasitic Activities of Emodin toward Toxoplasma gondii

Currently, toxoplasmosis affects nearly one-third of the world’s population, but the available treatments have several limitations. This factor underscores the search for better therapy for toxoplasmosis. Therefore, in the current investigation, we investigated the potential of emodin as a new anti-Toxoplasma gondii while exploring its anti-parasitic mechanism of action. We explored the mechanisms of action of emodin in the presence and absence of an in vitro model of experimental toxoplasmosis. Emodin showed strong anti-T. gondii action with an EC50 value of 0.03 µg/mL; at this same effective anti-parasite concentration, emodin showed no appreciable host cytotoxicity. Likewise, emodin showed a promising anti-T. gondii specificity with a selectivity index (SI) of 276. Pyrimethamine, a standard drug for toxoplasmosis, had an SI of 2.3. The results collectively imply that parasite damage was selective rather than as a result of a broad cytotoxic effect. Furthermore, our data confirm that emodin-induced parasite growth suppression stems from parasite targets and not host targets, and indicate that the anti-parasite action of emodin precludes oxidative stress and ROS production. Emodin likely mediates parasite growth suppression through means other than oxidative stress, ROS production, or mitochondrial toxicity. Collectively, our findings support the potential of emodin as a promising and novel anti-parasitic agent that warrants further investigation.

Promising Antiparasitic Natural and Synthetic Products from Marine Invertebrates and Microorganisms

Parasitic diseases still threaten human health. At present, a number of parasites have developed drug resistance, and it is urgent to find new and effective antiparasitic drugs. As a rich source of biological compounds, marine natural products have been increasingly screened as candidates for developing new antiparasitic drugs. The literature related to the study of the antigenic animal activity of marine natural compounds from invertebrates and microorganisms was selected to summarize the research progress of marine compounds and the structure-activity relationship of these compounds in the past five years and to explore the possible sources of potential antiparasitic drugs for parasite treatment.

Phragmites australis (Cav.) Trin. ex Steud. Extract Induces Apoptosis-like Programmed Cell Death in Acanthamoeba castellanii Trophozoites

Acanthamoeba keratitis (AK) is an infectious ocular disease which is difficult to diagnose correctly and cure. Development of an effective and safe therapeutic drug for AK is needed. Our preliminary screening of more than 200 extracts from wild plants collected in Korea suggested the potential amoebicidal activity of Phragmites australis (Cav.) Trin. ex Steud. extract (PAE) against Acanthamoeba species. Here, we aimed to analyze the amoebicidal activity of PAE on Acanthamoeba and its underlying amoebicidal mechanism. PAE induced amoebicidal activity against both A. castellanii and A. polyphaga trophozoites, while it showed low cytotoxicity in human corneal epithelial cells (HCE-2) and human retinal pigment epithelial cells (ARPE-19). Transmission electron microscopy analysis showed subcellular morphological changes, such as increased granules, abnormal mitochondria, and atypical cyst wall formation, in the PAE-treated A. castellanii. Fluorometric apoptosis assay and TUNEL assay revealed apoptosis-like programmed cell death (PCD) in the PAE-treated A. castellanii. The PAE treatment increased reactive oxygen species production and reduced mitochondrial membrane potential in the amoeba. The enhanced expression of autophagy-associated genes was also detected. These results suggested that PAE exerted a promising amoebicidal effect on A. castellanii trophozoites via the PCD pathway. PAE could be a potential candidate for developing a therapeutic drug for AK.

Pitavastatin loaded nanoparticles: a suitable ophthalmic treatment for Acanthamoeba Keratitis inducing cell death and autophagy in Acanthamoeba polyphaga

Statins are effective sterol lowering agents with high amoebicidal activity. Nevertheless, due to their poor aqueous solubility, they remain underused especially in eye drop formulation. The aim of the present study is to develop Pitavastatin loaded nanoparticles suitable for ophthalmic administration and designed for the management of Acanthamoeba Keratitis. These nanocarriers are aimed to solve both the ophthalmic route-associated problems and the limited aqueous drug solubility issues of Pitavastatin. Nanoparticles were obtained by a nanoprecipitation-solvent displacement method and their amoebicidal activity was evaluated against four strains of Acanthamoeba: A. castellanii Neff, A. polyphaga, A. griffini and A. quina. In Acanthamoeba polyphaga, the effect of the present nanoparticles was investigated with respect to the microtubule distribution and several programmed cell death features. Nanoparticles were able to eliminate all the tested strains and Acanthamoeba polyphaga was determined to be the most resistance strain. Nanoparticles induced chromatin condensation, autophagic vacuoles and mitochondria dysfunction.

Indispensable role of microbes in anticancer drugs and discovery trends

Recent years have seen an increased focus on the advancement of naturally derived products for the treatment of cancer. Since the beginning of recorded history, nature has provided a variety of medicinal agents, and an overwhelming number of drugs that we have today are derived from natural sources. Such natural agents are prominently used to treat several diseases such as diabetes, malaria, Alzheimer's, pulmonary disorders, etc. with cancer being the highlight of this review. Due to the rapid development of resistance to chemotherapeutic drugs, the hunt for effective novel drugs is still a paramount concern in cancer treatment. Moreover, many chemotherapy drugs typically have high toxicity and adverse side effects, which necessitates the need to develop anti-tumor drugs that can be employed to treat deadly tumors with fewer negative effects on health and better efficacy. Isolation of several chemotherapeutic drugs has been conducted from a wide range of natural sources which include plants, microbes, fungi, and marine microorganisms. Considering the trends of previous decades, microbial diversity has grown to play a significant role in the formulation of pharmaceuticals and drugs, especially antibiotics and anti-cancer medications. Microbe-derived antitumor antibiotics such as anthracycline, epothilones, bleomycin, actinomycin, and staurosporine are amongst the widely used cancer chemotherapeutic agents. This review deals majorly with microbe-derived anticancer drugs taking into account their derivatives, mechanism of action, isolation procedures, limitations, and tumors targeted by them. This article also reports the phase of clinical study these drugs are undergoing. Moreover, it intends to portray the indispensable part that these microbes have been playing since time immemorial in the odyssey of chemotherapeutic agents. KEY POINTS: • Microbial diversity contributes heavily towards the formulation of anticancer drugs. • Polypeptides, carbohydrates, and alkaloids are prevalent microbe-based drug classes. • Microbe-derived anticancer agents target various sarcomas, carcinomas, and lymphomas.

Cyclolauranes as plausible chemical scaffold against Naegleria fowleri

Primary amoebic meningoencephalitis (PAM) is a central nervous system (CNS) disease caused by Naegleria fowleri that mainly affects children and young adults with fatal consequences in most of the cases. Treatment protocols are based on the combination of different antimicrobial agents, nonetheless there is the need to develop new anti-Naegleria compounds with low toxicity and full effects compared to the currently used drug combination. The marine environment is a well-established source of bioactive natural products. In this work, we have focused on the structure of Laurencia cyclolaurane-type sesquiterpenes as potential chemical model against Naegleria species. The effects of debromolaurinterol (1) to induce PCD/apoptosis-like events in Naegleria fowleri have been evaluated, revealing that this compound induced reduction of ATP production showing a decrease of 99.98% in treated parasite cells. A SAR analysis have been supported with molecular modeling and analysis of the in silico ADME/Tox properties of the Laurencia sesquiterpenes debromolaurinterol (1), laurinterol (2) and allolaurinterol (3), which reinforce cyclolaurane metabolites as plausible molecular models to develop PAM treatments.

Energetic metabolic reprogramming in Jurkat DFF40-deficient cancer cells

DNA fragmentation factor 40 (DFF40), or the caspase-activated DNase (CAD), is an endonuclease specific for double-stranded DNA. Alterations in its function and expression have been linked to apoptosis resistance, a mechanism likely used by cancer cells. However, how the DFF40-related apoptosis resistance pathway occurs remains unclear. Here, we sought to determine if DFF40 expression could be linked to cell metabolism through the regulation of mitochondrial integrity and function. We demonstrated that DFF40-deficient cells are more resistant to staurosporine and tributyltin (TBT)-induced apoptosis, and express higher levels of Mcl-1 at basal state. Treatment with TBT induces higher Bcl-2 and caspase-9 mRNA transcripts in DFF40 KO Jurkat cells, as well as enhanced Bcl-2 phosphorylation. A loss of DFF40 expression induces a higher mitochondrial mass, mtDNA copy number, mitochondrial membrane potential, and glycolysis rates in resting T cells. DFF40-deficient cells exhibit the Warburg effect phenotype, where they rely significantly more on glycolysis than oxidative phosphorylation and have a higher proliferative state, demonstrated by a higher Ki-67 transcription factor expression and AKT phosphorylation. Finally, we demonstrated with cell fractioning that DFF40 can translocate to the mitochondria following apoptosis induction. Our study reveals that DFF40 may act as a regulator of mitochondria during cell death and its loss could compromise mitochondrial integrity and cause an energetic reprogramming in pathologies such as cancer.

Opportunistic free-living amoebal pathogens

Pathogenic free-living amoebae affecting the central nervous system are known to cause granulomatous amoebic encephalitis (GAE) or primary amoebic meningoencephalitis (PAM). Although hosts with impaired immunity are generally at a higher risk of severe disease, amoebae such as Naegleria fowleri and Balamuthia mandrillaris can instigate disease in otherwise immunocompetent individuals, whereas Acanthamoeba species mostly infect immunocompromised people. Acanthamoeba also cause a sight-threatening eye infection, mostly in contact lens wearers. Although infections due to pathogenic amoebae are considered rare, recently, these deadly amoebae were detected in water supplies in the USA. This is of particular concern, especially with global warming further exacerbating the problem. Herein, we describe the epidemiology, presentation, diagnosis, and management of free-living amoeba infections.

Gene Cluster Analysis of Marine Bacteria Seeking for Natural Anticancer Products

Background: In the past decade, metabolites of marine microorganisms have been increasingly used for their various biological activities. An intense effort has been dedicated to assessing the therapeutic efficacy of the marine natural products and metabolites obtained from marine bacteria in cancer therapy. Fast and reliable analytical bacterial genome sequencing provides specialized bioinformatic tools to identify potential gene clusters in bacteria for obtaining secondary metabolites. Objectives: This study aimed to analyze the genome sequences of marine bacteria to recognize bioactive compounds with anti-cancer properties. Methods: Marine bacteria with the genomic sequences registered in the National Center for Biotechnology Information (NCBI) genome database were used in this study. The genome was analyzed for proteins, tRNAs, and rRNAs from GenBank entries by Feature Extract 1.2L Server. The Anti-SMASH webserver was used for the analysis of unique marine bacterial metabolites of the marine bacterial genome, available from the NCBI database. Results: A number of marine bacterial species, including Salinispora arenicola, Salinispora tropica, Crocosphaera watsonii, and Blastopirellula marina encoded metabolites belonging to the polyketide and nonribosomal peptide (NRP) families, showing anti-cancer properties. Among the marine species described, S. tropica and S. arenicola are richer in the genes encoding polyketide and NRP with potential antitumor activities. Conclusions: Marine bacteria are an excellent and exceptional source of anti-cancer compounds. In silico genome analysis of marine bacteria provided an opportunity to evaluate gene clusters for known natural products. Like this chemical engineering approaches for pharmaceutical application are useful in clinical evaluation of cancer treatment.

Electroselective and Controlled Reduction of Cyclic Imides to Hydroxylactams and Lactams

An efficient and practical electrochemical method for selective reduction of cyclic imides has been developed using a simple undivided cell with carbon electrodes at room temperature. The reaction provides a useful strategy for the rapid synthesis of hydroxylactams and lactams in a controllable manner, which is tuned by electric current and reaction time, and exhibits broad substrate scope and high functional group tolerance even to reduction-sensitive moieties. Initial mechanistic studies suggest that the approach heavily relies on the utilization of amines (e.g., i-Pr₂NH), which are able to generate α-aminoalkyl radicals. This protocol provides an efficient route for the cleavage of C-O bonds under mild conditions with high chemoselectivity.

In vitro validation of the amoebicidal activity of commercial eye drops as second activity

The validation of anti-Acanthamoeba activity of commercial eye drops has gained a great interest recently and a growing number of commercials eye drop were evaluated for their aptitude to inhibit Acanthamoeba as a second pharmacological effect. In the present study, three different eye drops, commercializing in Spain, including TobraDex, Cusimolol and Colircusi antiedema have been tested in vitro against trophozoites and cysts stage of the facultative pathogen Acanthamoeba. The alamarBlue™ method was used to evaluate both trophocidal and cysticidal properties. The most active eye drops were tested for their impact on some programmed cell death features. We found out that the cells inhibition was strain and eye drop dependent, and 5% eye drop was able to eliminate both trophozoite and cyst stage of Acanthamoeba spp. A treatment of 24 h with 5% of TobraDex or Cusimolol was able to show DNA condensation, collapse in the mitochondrial membrane potential and reduction of the ATP level production in Acanthamoeba. We could assume that the present eye drops could induce programed cell death like process in Acanthamoeba via mitochondrial pathway.

In vitro evaluation of commercial foam Belcils® on Acanthamoeba spp

Interest in periocular (eyelid and eyelashes margins) hygiene has attracted attention recently and a growing number of commercials eye cleanser and shampoos have been marketed. In the present study, a particular eye cleanser foam, Belcils® has been tested against trophozoites and cysts on the facultative pathogen Acanthamoeba. Viability was tested by the alamarBlue™ method and the foam was tested for the induction of programmed cell death in order to explore its mode of action. We found that a 1% solution of the foam eliminated both trophozoite and cyst stage of Acanthamoeba spp. After 90 min of incubation, Belcils® induced, DNA condensation, collapse in the mitochondrial membrane potential and reduction of the ATP level production in Acanthamoeba. We conclude that the foam destroys the cells by the induction of an apoptosis-like process. The current eye cleanser could be used as part of AK therapy protocol and as prevention from AK infections for contact lens users and post-ocular trauma patients.

Protein kinases as targets for developing anticancer agents from marine organisms

Protein kinases play a fundamental role in the intracellular transduction because of their ability to phosphorylate plethora of proteins. Over the past three decades, numerous protein kinase inhibitors have been identified and are being used clinically successfully. The biodiversity of marine organisms provides a rich source for the discovery and development of novel anticancer agents in the treatment of human malignancies and a lot of bioactive ingredients from marine organisms display anticancer effects by affecting the protein kinases-mediated pathways. In the present mini-review, anticancer compounds from marine source were reviewed and discussed in context of their targeted pathways associated with protein kinases and the progress of these compounds as anticancer agents in recent five years were emphasized. The molecular entities and their modes of actions were presented. We focused on protein kinases-mediated signaling pathways including PI3K/Akt/mTOR, p38 MAPK, and EGFR. The marine compounds targeting special pathways of protein kinases were highlighted. We have also discussed the existing challenges and prospects related to design and development of novel protein kinase inhibitors from marine sources.

Evaluation of Indolocarbazoles from Streptomyces sanyensis as a Novel Source of Therapeutic Agents against the Brain-Eating Amoeba Naegleria fowleri

Naegleria fowleri is an opportunistic pathogenic free-living amoeba which is able to rapidly colonize the central nervous system (CNS) and causes a lethal infection known as primary amoebic meningoencephalitis (PAM). Furthermore, more than 98% of the known cases of PAM are fatal and affect mainly children under 12 and young adults. Until now, no fully effective therapeutic agents against N. fowleri are available and hence the urgent need to find novel agents to treat PAM. At present, PAM therapy is based on the combination of amphotericin B, miltefosine, among others, with unwanted toxic effects. Recently, our team isolated various indolocarbazoles (ICZs) from the culture of a mangrove strain of Streptomyces sanyensis which showed activity against kinetoplastids and the Acanthamoeba genus. Hence, in this study, the activity of the previously isolated ICZs, staurosporine (STS), 7-oxostaurosporine (7OSTS), 4′-demethylamino-4′-oxostaurosporine, and streptocarbazole B, was evaluated against two type strains of N. fowleri. Furthermore, the performed activity assays revealed that STS was the most active ICZ presenting an inhibitory concentration 50 (IC₅₀) of 0.08 ± 0.02 µM (SI 109.3). Moreover, STS induced programmed cell death (PCD) in the treated amoebae by triggering DNA condensation, mitochondrial disfunction, cell membrane disruption, and reactive oxygen species (ROS) generation. Therefore, STS could be a promising therapeutic agent against PAM.

Antikinetoplastid Activity of Indolocarbazoles from Streptomyces sanyensis

Chagas disease and leishmaniasis are neglected tropical diseases caused by kinetoplastid parasites of Trypanosoma and Leishmania genera that affect poor and remote populations in developing countries. These parasites share similar complex life cycles and modes of infection. It has been demonstrated that the particular group of phosphorylating enzymes, protein kinases (PKs), are essential for the infective mechanisms and for parasite survival. The natural indolocarbazole staurosporine (STS, 1) has been extensively used as a PKC inhibitor and its antiparasitic effects described. In this research, we analyze the antikinetoplastid activities of three indolocarbazole (ICZs) alkaloids of the family of staurosporine STS, 2-4, and the commercial ICZs rebeccamycin (5), K252a (6), K252b (7), K252c (8), and arcyriaflavin A (9) in order to establish a plausive approach to the mode of action and to provide a preliminary qualitative structure-activity analysis. The most active compound was 7-oxostaurosporine (7OSTS, 2) that showed IC₅₀ values of 3.58 ± 1.10; 0.56 ± 0.06 and 1.58 ± 0.52 µM against L. amazonensis; L. donovani and T. cruzi, and a Selectivity Index (CC₅₀/IC₅₀) of 52 against amastigotes of L. amazonensis compared to the J774A.1 cell line of mouse macrophages.

Antiamoebic Activities of Indolocarbazole Metabolites Isolated from Streptomyces sanyensis Cultures

Indolocarbazoles are a family of natural alkaloids characterized by their potent protein kinase and topoisomerase I inhibitory activity. Among them, staurosporine (1) has exhibited promising inhibitory activity against parasites. Based on new insights on the activity and mechanism of action of STS in Acanthamoeba parasites, this work reports the isolation, identification, and the anti-Acanthamoeba activity of the minor metabolites 7-oxostaurosporine (2), 4′-demethylamino-4′-oxostaurosporine (3), and streptocarbazole B (4), isolated from cultures of the mangrove strain Streptomyces sanyensis. A clear correlation between the antiparasitic activities and the structural elements and conformations of the indolocarbazoles 1–4 was observed. Also, the study reveals that 7-oxostaurosporine (2) affects membrane permeability and causes mitochondrial damages on trophozoites of A. castellanii Neff.