Efficacy of the bisbenzylisoquinoline alkaloids in acute and chronic Trypanosoma cruzi murine model

Pharmacological Activity of Cepharanthine

Cepharanthine, a natural bisbenzylisoquinoline (BBIQ) alkaloid isolated from the plant Stephania Cephalantha Hayata, is the only bisbenzylisoquinoline alkaloid approved for human use and has been used in the clinic for more than 70 years. Cepharanthine has a variety of medicinal properties, including signaling pathway inhibitory activities, immunomodulatory activities, and antiviral activities. Recently, cepharanthine has been confirmed to greatly inhibit SARS-CoV-2 infection. Therefore, we aimed to describe the pharmacological properties and mechanisms of cepharanthine, mainly including antitumor, anti-inflammatory, anti-pathogen activities, inhibition of bone resorption, treatment of alopecia, treatment of snake bite, and other activities. At the same time, we analyzed and summarized the potential antiviral mechanism of cepharanthine and concluded that one of the most important anti-viral mechanisms of cepharanthine may be the stability of plasma membrane fluidity. Additionally, we explained its safety and bioavailability, which provides evidence for cepharanthine as a potential drug for the treatment of a variety of diseases. Finally, we further discuss the potential new clinical applications of cepharanthine and provide direction for its future development.

Traditional herbal compounds as candidates to inhibit the SARS-CoV-2 main protease: an in silico study

COVID-19, a disease caused by the SARS-CoV-2 virus, is responsible for a pandemic since March 2020 and it has no cure. Therefore, herein, different theoretical methods were used to obtain potential candidates from herbal compounds to inhibit the SARS-CoV-2 main protease (M^pro). Initially, the 16 best-scored compounds were selected from a library containing 4066 ligands using virtual screening by molecular docking. Among them, six molecules (physalin B 5,6-epoxide (PHY), methyl amentoflavone (MAM), withaphysalin C (WPC), daphnoline or trilobamine (TRI), cepharanoline (CEP) and tetrandrine (TET)) were selected based on Lipinski's rule and ADMET analysis as criteria. These compounds complexed with the M^pro were submitted to triplicate 100 ns molecular dynamics simulations. RMSD, RMSF, and radius of gyration results show that the overall protein structure is preserved along the simulation time. The average ΔG_binding values, calculated by the MM/PBSA method, were -41.7, -55.8, -45.2, -38.7, -49.3, and -57.9 kcal/mol for the PHY-M^pro, MAM-M^pro, WPC-M^pro, CEP-M^pro, TRI-M^pro, and TET-M^pro complexes, respectively. Pairwise decomposition analyses revealed that the binding pocket is formed by His41-Val42, Met165-Glu166-Leu167, Asp187, and Gln189. The PLS regression model generated by QSPR analysis indicated that non-polar and polar groups with the presence of hydrogen bond acceptors play an important role in the herbal compounds-M^pro interactions. Overall, we found six potential candidates to inhibit the SARS-CoV-2 M^pro and highlighted key residues from the binding pocket that can be used for future drug design. Communicated by Ramaswamy H. Sarma.

Alkaloids in genus stephania (Menispermaceae): A comprehensive review of its ethnopharmacology, phytochemistry, pharmacology and toxicology

ETHNOPHARMACOLOGICAL RELEVANCE

Approximately 60 species of the genus Stephania (Menispermaceae) are distributed worldwide. Among these, 39 species are located in South and Southwest China; in particular, these plants are rich in alkaloids and were used in traditional Chinese medicine (TCM) against numerous ailments.

AIM OF THIS REVIEW

The purpose of this study was to provide organized information on the ethnopharmacological uses as well as the phytochemical, pharmacological, and toxicological evaluation of the alkaloids derived from plant species included in the genus Stephania. In addition, we aimed to provide comprehensive basic knowledge on the medicinal properties of these plants and establish meaningful guidelines for further research.

MATERIALS AND METHODS

Information related to the Stephania genus was collected from scientific databases, such as Web of Science, PubMed, Baidu Scholar, and China Academic Journals (CNKI), within the last 20 years on phytochemistry, pharmacology, and toxicology of the plants in genus Stephania. Furthermore, information was obtained from the Pharmacopoeia of the People's Republic of China. Chinese Pharmacopoeia and Flora of China.

RESULTS

Plant species belonging to the genus Stephania have been mentioned as traditional remedies and various alkaloidal compounds have been identified and isolated, including aporphine, proaporphine, morphinane, hasubanane, protoberberine, benzylisoquinoline, and bisbenzylisoquinoline and among others. The isolated alkaloidal compounds reportedly exhibited promising pharmacological properties, such as antimicrobial, antiviral, antitumor, antioxidant, antihyperglycemic, anti-inflammatory, antinociceptive, anti-multidrug resistance, neuroprotective, and cardioprotective activities.

CONCLUSIONS

The genus Stephania is widely used in TCM. The ethnopharmacological uses, phytochemistry, and pharmacology of the Stephania sp. Described in this review demonstrated that these plants contain numerous alkaloids and active constituents and display myriad pharmacological activities. Typically, research on the plants' pharmacological activity focuses on parts of the plants and the associated compounds. However, many Stephania species have rarely been studied, and the ethnomedicinal potential of those discovered has not been scientifically evaluated and needs to be further elucidated. Furthermore, quality control and toxicology studies are warranted in the future.

Venom alkaloids against Chagas disease parasite: search for effective therapies

Chagas disease is an important disease affecting millions of patients in the New World and is caused by a protozoan transmitted by haematophagous kissing bugs. It can be treated with drugs during the early acute phase; however, effective therapy against the chronic form of Chagas disease has yet to be discovered and developed. We herein tested the activity of solenopsin alkaloids extracted from two species of fire ants against the protozoan parasite Trypanosoma cruzi, the aetiologic agent of Chagas disease. Although IC₅₀ determinations showed that solenopsins are more toxic to the parasite than benznidazole, the drug of choice for Chagas disease treatment, the ant alkaloids presented a lower selectivity index. As a result of exposure to the alkaloids, the parasites became swollen and rounded in shape, with hypertrophied contractile vacuoles and intense cytoplasmic vacuolization, possibly resulting in osmotic stress; no accumulation of multiple kinetoplasts and/or nuclei was detected. Overexpressing phosphatidylinositol 3-kinase-an enzyme essential for osmoregulation that is a known target of solenopsins in mammalian cells-did not prevent swelling and vacuolization, nor did it counteract the toxic effects of alkaloids on the parasites. Additional experimental results suggested that solenopsins induced a type of autophagic and programmed cell death in T. cruzi. Solenopsins also reduced the intracellular proliferation of T. cruzi amastigotes in infected macrophages in a concentration-dependent manner and demonstrated activity against Trypanosoma brucei rhodesiense bloodstream forms, which is another important aetiological kinetoplastid parasite. The results suggest the potential of solenopsins as novel natural drugs against neglected parasitic diseases caused by kinetoplastids.

The effect of benznidazole dose among the efficacy outcome in the murine animal model. A quantitative integration of the literature

Despite more than 100 years since it was firstly described Chagas disease, only two drugs are available to treat Chagas disease: Nifurtimox launched by Bayer in 1965 and benznidazole launched by Roche in 1971. Drug discovery initiatives have been looking for new compounds as an alternative to these old drugs. Although new platforms have been used with the latest technologies, a critical step on that process still relies on the in vivo model. Unfortunately, to date, available animal models have limited predictive value and there is no standardization. With the aim to better understand the role of benznidazole, the current standard of care of Chagas disease, we performed this review. We intend to analyze the influence of the experimental design of the most used animal model, the murine model, in the assessment of the efficacy endpoint.

Cepharanthine: An update of its mode of action, pharmacological properties and medical applications

BACKGROUND

Cepharanthine (CEP) is a drug used in Japan since the 1950s to treat a number of acute and chronic diseases, including treatment of leukopenia, snake bites, xerostomia and alopecia. It is the only approved drug for Human use in the large class of bisbenzylisoquinoline alkaloids. This natural product, mainly isolated from the plant Stephania cephalantha Hayata, exhibits multiple pharmacological properties including anti-oxidative, anti-inflammatory, immuno-regulatory, anti-cancer, anti-viral and anti-parasitic properties.

PURPOSE

The mechanism of action of CEP is multifactorial. The drug exerts membrane effects (modulation of efflux pumps, membrane rigidification) as well as different intracellular and nuclear effects. CEP interferes with several metabolic axes, primarily with the AMP-activated protein kinase (AMPK) and NFκB signaling pathways. In particular, the anti-inflammatory effects of CEP rely on AMPK activation and NFκB inhibition.

CONCLUSION

In this review, the historical discovery and development of CEP are retraced, and the key mediators involved in its mode of action are presented. The past, present, and future of CEP are recapitulated. This review also suggests new opportunities to extend the clinical applications of this well-tolerated old Japanese drug.

Relevance of Trypanothione Reductase Inhibitors on Trypanosoma cruzi Infection: A Systematic Review, Meta-Analysis, and In Silico Integrated Approach

Due to the rudimentary antioxidant defenses in Trypanosoma cruzi, disruptors of redox balance are promising candidates for new antitrypanosomal drugs. We developed an integrated model based on systematic review, meta-analyses, and molecular modeling to evaluate the effect of trypanothione reductase (TR) inhibitors in T. cruzi infections. Our findings indicated that the TR inhibitors analyzed were effective in reducing parasitemia and mortality due to Trypanosoma cruzi infection in animal models. The most investigated drugs (clomipramine and thioridazine) showed no beneficial effects on the occurrence of infection-related electrocardiographic abnormalities or the affinity and density of cardiac β-adrenergic receptors. The affinity between the tested ligands and the active site of TR was confirmed by molecular docking. However, the molecular affinity score was unable to explain TR inhibition and T. cruzi death in vitro or the antiparasitic potential of these drugs when tested in preclinical models of T. cruzi infection. The divergence of in silico, in vitro, and in vivo findings indicated that the anti-T. cruzi effects of the analyzed drugs were not restricted to TR inhibition. As in vivo studies on TR inhibitors are still scarce and exhibit methodological limitations, mechanistic and highly controlled studies are required to improve the quality of evidence.

Antileishmanial activity of warifteine: a bisbenzylisoquinoline alkaloid isolated from Cissampelos sympodialis Eichl. (Menispermaceae)

Leishmania (L.) chagasi is the etiological agent of visceral leishmaniasis, an important endemic zoonosis in the American continent, as well as in many other countries in Asia, Africa, and Mediterranean Europe. The treatment is difficult due to the high toxicity of the available drugs, high costs, and emergence of resistance in the parasites. Therefore, there is an urgent need for new leishmanicidal agents. The bisbenzylisoquinoline alkaloids have been related to antibacterial, antiprotozoal, and antifungal activities. The aim of this study was to evaluate the growth inhibitory activity of warifteine (bisbenzylisoquinoline alkaloid) against L. chagasi promastigotes in axenic cultures and the occurrence of drug-induced ultrastructural changes in the parasite. This bisbenzylisoquinoline alkaloid was isolated from the leaves and roots of Cissampelos sympodialis Eichl. (Menispermaceae), a plant commonly used for the treatment of various diseases in Brazilian folk medicine. Using the purified warifteine, the 50% inhibitory concentration (IC₅₀) was determined at 0.08 mg/mL after 72 h in culture, inducing significant changes in the parasite morphology, like aberrant multisepted forms and blebs in the plasma membrane. In conclusion, warifteine represents an attractive candidate for future pharmacological studies aiming new leishmanicidal drugs.

In vitro antiprotozoal and cytotoxic activity of 33 ethonopharmacologically selected medicinal plants from Democratic Republic of Congo

ETHNOPHARMACOLOGICAL RELEVANCE

The antiprotozoal and cytotoxic activity of the aqueous extracts from 33 medicinal plants, used by traditional healers for the treatment of various parasitic diseases and collected after an ethnopharmacological inventory conducted in the Bolongo area, Bandundu province in DR Congo, was evaluated.

MATERIALS AND METHODS

Decoctions were prepared, lyophilized and evaluated for in vitro antiprotozoal activity against Trypanosoma b. brucei, Trypanosoma cruzi, Leishmania infantum, and the chloroquine- and pyrimethamine-resistant K1 strain of Plasmodium falciparum. Cytotoxicity against MRC-5 cells was included to assess selectivity of activity.

RESULTS

Most of the tested extracts exhibited pronounced (IC(50)≤5μg/ml) or good (5<IC(50)≤10μg/ml) antiprotozoal activity against one or more of the selected protozoa. A total of 19 plant extracts inhibited Trypanosoma b. brucei, especially the extract from Isolona hexaloba stem bark (IC(50)=1.95μg/ml, SI=16.5); 8 plant extracts were active against Trypanosoma cruzi, the extracts from Enanatia chlorantha stem bark and Quassia africana root bark being the most active with IC(50) values of 1.87 and 1.88μg/ml, respectively (SI=3.0 and 3.3, respectively); 8 plant extracts showed activity against Leishmania infantum, with extracts from Napoleona vogelii stem bark and Quassia africana root bark as the most active with IC(50) values of 5.66 and 5.04μg/ml (SI=11.3 and 1.2). Finally, 9 plant extracts inhibited Plasmodium falciparum K1 with the extracts from Quassia africana (root bark and stem bark) being the most active ones with IC(50) values of 0.46 and 1.27μg/ml (SI=13.7 and 13.6). Extracts from Enantia chlorantha stem bark, Piptadeniastrum africanum stem bark and Quassia africana root bark were cytotoxic for MRC-5 cells (CC(50)<10μg/ml).

CONCLUSIONS

These results can partly support and justify the traditional use of some of these plant species for the treatment of parasitic diseases.

Leishmanicidal activity and cytotoxicity of compounds from two Annonacea species cultivated in Northeastern Brazil

INTRODUCTION

Visceral leishmaniasis is endemic in 88 countries, with a total of 12 million people infected and 350 million at risk. In the search for new leishmanicidal agents, alkaloids and acetogenins isolated from leaves of Annona squamosa and seeds of Annona muricata were tested against promastigote and amastigote forms of Leishmania chagasi.

METHODS

Methanol-water (80:20) extracts of A. squamosa leaves and A. muricata seeds were extracted with 10% phosphoric acid and organic solvents to obtain the alkaloid and acetogenin-rich extracts. These extracts were chromatographed on a silica gel column and eluted with a mixture of several solvents in crescent order of polarity. The compounds were identified by spectroscopic analysis. The isolated compounds were tested against Leishmania chagasi, which is responsible for American visceral leishmaniasis, using the MTT test assay. The cytotoxicity assay was evaluated for all isolated compounds, and for this assay, RAW 264.7 cells were used.

RESULTS

O-methylarmepavine, a benzylisoquinolinic alkaloid, and a C37 trihydroxy adjacent bistetrahydrofuran acetogenin were isolated from A. squamosa, while two acetogenins, annonacinone and corossolone, were isolated from A. muricata. Against promastigotes, the alkaloid showed an IC50 of 23.3 µg/mL, and the acetogenins showed an IC50 ranging from 25.9 to 37.6 µg/mL; in the amastigote assay, the IC50 values ranged from 13.5 to 28.7 µg/mL. The cytotoxicity assay showed results ranging from 43.5 to 79.9 µg/mL.

CONCLUSIONS

These results characterize A. squamosa and A. muricata as potential sources of leishmanicidal agents. Plants from Annonaceae are rich sources of natural compounds and an important tool in the search for new leishmanicidal therapies.

Trypanocidal drugs: mechanisms, resistance and new targets

The protozoan parasitesTrypanosoma bruceiandTrypanosoma cruziare the causative agents of African trypanosomiasis and Chagas disease, respectively. These are debilitating infections that exert a considerable health burden on some of the poorest people on the planet. Treatment of trypanosome infections is dependent on a small number of drugs that have limited efficacy and can cause severe side effects. Here, we review the properties of these drugs and describe new findings on their modes of action and the mechanisms by which resistance can arise. We further outline how a greater understanding of parasite biology is being exploited in the search for novel chemotherapeutic agents. This effort is being facilitated by new research networks that involve academic and biotechnology/pharmaceutical organisations, supported by public–private partnerships, and are bringing a new dynamism and purpose to the search for trypanocidal agents.

Antiprotozoal activity of Brazilian plant extracts from isoquinoline alkaloid-producing families

Leishmaniasis and Chagas disease afflict the poorest countries in the world. The Brazilian flora represents a rich source for the screening of potential antiparasitic compounds. In this work, we tested the total alkaloid and ethanol extracts of nine different plants from Brazilian families which produce isoquinoline alkaloids, to determine their in vitro antiparasitic effect against L. chagasi and T. cruzi parasites. Promastigotes of L. chagasi were shown to be susceptible only to the total alkaloid extracts of A. crassiflora (EC50 value = 24.89 microg/ml), A. coriacea (EC50 value = 41.60 microg/ml), C. ovalifolia (EC50 value = 63.88 microg/ml) and G. australis (EC50 value = 37.88 microg/ml). Except for the G. australis total alkaloids, all the three extracts presented a considerable activity when tested against intracellular amastigotes. The most effective alkaloid extracts were those from A. crassiflora and C. ovalifolia, which reduced the number of infected macrophages at 25 microg/ml by 86.1% and 89.8%, respectively. Among the 18 tested extracts, 16 showed anti-Trypanosoma activity. Eight extracts (A. crassiflora, A. coriacea, C. ovalifolia, D. furfuracea, D. lanceolata, S. guianensis, X. emarginata and G. australis) were the most effective against the trypomastigotes, killing approximately 100% of the parasites at the maximal concentration of 100 microg/ml. Cytotoxicity against mammalian cells was evaluated for all extracts, but potential ones showed little or no cytotoxicity and a considerable antiparasitic effect, including D. furfuracea, D. lanceolata, G. australis, S. guianensis and X. emarginata. Plants are a rich source of natural compounds, and a powerful tool for the development of new arsenals for the therapy of protozoan diseases.

8-Methoxy-naphtho[2,3-b]thiophen-4,9-quinone, a non-competitive inhibitor of trypanothione reductase

The enzyme trypanothione reductase is a recognised drug target in trypanosomatids and has been used in the search of new compounds with potential activity against diseases such as leishmaniasis, Chagas disease and African trypanosomiasis. 8-Methoxy-naphtho [2,3-b] thiophen-4,9-quinone was selected in a screening of natural and synthetic compounds using an in vitro assay with the recombinant enzyme from Trypanosoma cruzi. Its mode of inhibition fits a non-competitive model with respect to the substrate (trypanothione) and to the co-factor (NADPH), with Ki-values of 5 and 3.6 M, respectively. When tested against human glutathione reductase, this compound did not display any significant inhibition at 100 M, indicating a good selectivity against the parasite enzyme.

In vitro activity of Triclisia patens and some bisbenzylisoquinoline alkaloids against Leishmania donovani and Trypanosoma brucei brucei

In the search for antiprotozoal compounds from natural sources, Triclisia patens displayed activity against L. donovani promastigotes (IC(50) = 1.5 microg/mL) and T. b. brucei blood stream trypomastigote forms (IC(50) = 31.25 microg/mL). In addition, a total of 20 bisbenzylisoquinoline alkaloids were screened for antileishmanial and antitrypanosomal activity in vitro. Fangchinoline (IC(50) = 0.39 microM) was found to be as active as the standard pentamidine against Leishmania donovani promastigotes. Phaeanthine was three-fold more active (IC(50) = 2.41 microM; 1.5 microg/mL) than the standard drug Pentostam against L. donovani amastigotes, but at this concentration was toxic to murine macrophages. In contrast, cocsoline (IC(50) = 12.3 microM; 6.76 microg/mL) was as active as Pentostam, and was not toxic to macrophages at this concentration. Thalisopidine showed the strongest activity (IC(50) = 1.14 microM) against Trypanosoma brucei brucei blood stream form trypomastigotes, but was less active than pentamidine.

A critical review on Chagas disease chemotherapy

In this "Critical Review" we made a historical introduction of drugs assayed against Chagas disease beginning in 1912 with the works of Mayer and Rocha Lima up to the experimental use of nitrofurazone. In the beginning of the 70s, nifurtimox and benznidazole were introduced for clinical treatment, but results showed a great variability and there is still a controversy about their use for chronic cases. After the introduction of these nitroheterocycles only a few compounds were assayed in chagasic patients. The great advances in vector control in the South Cone countries, and the demonstration of parasite in chronic patients indicated the urgency to discuss the etiologic treatment during this phase, reinforcing the need to find drugs with more efficacy and less toxicity. We also review potential targets in the parasite and present a survey about new classes of synthetic and natural compounds studied after 1992/1993, with which we intend to give to the reader a general view about experimental studies in the area of the chemotherapy of Chagas disease, complementing the previous papers of Brener (1979) and De Castro (1993).