Antileishmanial activity of semisynthetic lupane triterpenoids betulin and betulinic acid derivatives: synergistic effects with miltefosine

Pentacyclic Triterpenoid Phytochemicals with Anticancer Activity: Updated Studies on Mechanisms and Targeted Delivery

Pentacyclic triterpenoids (TTs) represent a unique family of phytochemicals with interesting properties and pharmacological effects, with some representatives, such as betulinic acid (BA) and betulin (B), being mainly investigated as potential anticancer molecules. Considering the recent scientific and preclinical investigations, a review of their anticancer mechanisms, structure-related activity, and efficiency improved by their insertion in nanolipid vehicles for targeted delivery is presented. A systematic literature study about their effects on tumor cells in vitro and in vivo, as free molecules or encapsulated in liposomes or nanolipids, is discussed. A special approach is given to liposome-TTs and nanolipid-TTs complexes to be linked to microbubbles, known as contrast agents in ultrasonography. The production of such supramolecular conjugates to deliver the drugs to target cells via sonoporation represents a new scientific and applicative direction to improve TT efficiency, considering that they have limited availability as lipophilic molecules. Relevant and recent examples of in vitro and in vivo studies, as well as the challenges for the next steps towards the application of these complex delivery systems to tumor cells, are discussed, as are the challenges for the next steps towards the application of targeted delivery to tumor cells, opening new directions for innovative nanotechnological solutions.

Semisynthetic Derivatives of Pentacyclic Triterpenes Bearing Heterocyclic Moieties with Therapeutic Potential

Medicinal plants have been used by humans since ancient times for the treatment of various diseases and currently represent the main source of a variety of phytocompounds, such as triterpenes. Pentacyclic triterpenes have been subjected to numerous studies that have revealed various biological activities, such as anticancer, antidiabetic, anti-inflammatory, antimicrobial, and hepatoprotective effects, which can be employed in therapy. However, due to their high lipophilicity, which is considered to exert a significant influence on their bioavailability, their current use is limited. A frequent approach employed to overcome this obstacle is the chemical derivatization of the core structure with different types of moieties including heterocycles, which are considered key elements in medicinal chemistry. The present review aims to summarize the literature published in the last 10 years regarding the derivatives of pentacyclic triterpenes bearing heterocyclic moieties and focuses on the biologically active derivatives as well as their structure-activity relationships. Predominantly, the targeted positions for the derivatization of the triterpene skeleton are C-3 (hydroxyl/oxo group), C-28 (hydroxyl/carboxyl group), and C-30 (allylic group) or the extension of the main scaffold by fusing various heterocycles with the A-ring of the phytocompound. In addition, numerous derivatives also contain linker moieties that connect the triterpenic scaffold with heterocycles; one such linker, the triazole moiety, stands out as a key pharmacophore for its biological effect. All these studies support the hypothesis that triterpenoid conjugates with heterocyclic moieties may represent promising candidates for future clinical trials.

Plant Bioactive Ingredients in Delivery Systems and Nanocarriers for the Treatment of Leishmaniasis: An Evidence-Based Review

Background

This study was designed considering the challenges of leishmaniasis treatment and the benefits of carriers of drug delivery systems to review plant bioactive ingredients in delivery systems and nanocarriers for the treatment of leishmaniasis.

Methods

The methodology of this review investigation followed the 06-PRISMA recommendations. The searches were carried out up to January 30, 2022, in the central English databases SCOPUS, WEB OF SCIENCE, EMBASE, PUBMED, and GOOGLE SCHOLAR using the search terms "ç", "leishmaniasis", "herbal medicines", "drug delivery", "nanocarriers", "herbal compounds", and "secondary metabolites".

Results

Out of 5731 articles, 19 publications, including 12 in vivo (63.15%), 3 in vitro (15.8%), and 4 in vitro/in vivo (21.1%) up to 2022, fulfilled the criteria presence for argument in the current systematic study. Plant bioactive ingredients were curcumin, betulinic acid, artemisinin, 4-nitrobenzaldehyde thiosemicarbazone, andrographolide, pentalinonsterol, ursolic acid, amarogentin, carvacrol, 14-deoxy-11-oxo-andrographolide, quercetin, beta-lapachone, cedrol, 2',6'-dihydroxy-4'-methoxychalcone, and oleanolic acid.

Conclusion

The high potential of plant bioactive ingredients in delivery systems due to the load on the nanocarrier for the treatment of leishmaniasis through some main mechanisms of action, e.g. changes in the fluidity and the structure of the cell wall, creation of reactive oxygen species (ROS) and mitochondrial dysfunction, inhibition of DNA topoisomerase I enzyme, minimal cytotoxicity, stimulation of cell cycle disruption, stimulation of apoptosis, enhancement of the immune system. However, further investigations, especially in the clinical setting, are required to confirm these findings.

Triterpenoid pyrazines and pyridines - Synthesis, cytotoxicity, mechanism of action, preparation of prodrugs

A set of fifteen triterpenoid pyrazines and pyridines was prepared from parent triterpenoid 3-oxoderivatives (betulonic acid, dihydrobetulonic acid, oleanonic acid, moronic acid, ursonic acid, heterobetulonic acid, and allobetulone). Cytotoxicity of all compounds was tested in eight cancer and two non-cancer cell lines. Evaluation of the structure-activity relationships revealed that the triterpenoid core determined whether the final molecule is active or not, while the heterocycle is able to increase the activity and modulate the specificity. Five compounds (1b, 1c, 2b, 2c, and 8) were found to be preferentially and highly cytotoxic (IC₅₀ ≈ 1 μM) against leukemic cancer cell lines (CCRF-CEM, K562, CEM-DNR, or K562-TAX). Surprisingly, compounds 1c, 2b, and 2c are 10-fold more active in multidrug-resistant leukemia cells (CEM-DNR and K562-TAX) than in their non-resistant analogs (CCRF-CEM and K562). Pharmacological parameters were measured for the most promising candidates and two types of prodrugs were synthesized: 1) Sugar-containing conjugates, most of which had improved cell penetration and retained high cytotoxicity in the CCRF-CEM cell line, unfortunately, they lost the selectivity against resistant cells. 2) Medoxomil derivatives, among which compounds 26-28 gained activities of IC₅₀ 0.026-0.043 μM against K562 cells. Compounds 1b, 8, 21, 22, 23, and 24 were selected for the evaluation of the mechanism of action based on their highest cytotoxicity against CCRF-CEM cell line. Several experiments showed that the majority of them cause apoptosis via the mitochondrial pathway. Compounds 1b, 8, and 21 inhibit growth and disintegrate spheroid cultures of HCT116 and HeLa cells, which would be important for the treatment of solid tumors. In summary, compounds 1b, 1c, 2b, 2c, 24, and 26-28 are highly and selectively cytotoxic against cancer cell lines and were selected for future in vivo tests and further development of anticancer drugs.

Therapeutic Options for the SARS-CoV-2 Virus: Is There a Key in Herbal Medicine?

SARS-CoV-2 has been responsible for over 500 million cumulative cases all over the world since December 2019 and has marked the third introduction of a highly pathogenic virus after SARS-CoV and MERS-CoV. This virus is in a winning situation because scientists are still racing to explore effective therapeutics, vaccines, and event treatment regimens. In view of progress in current disease management, until now none of the preventive/treatment measures can be considered entirely effective to treat SARS-CoV-2 infection. Therefore, it is required to look up substitute ways for the management of this disease. In this context, herbal medicines could be a good choice. This article emphasizes the antiviral potential of some herbal constituents which further can be a drug of choice in SARS-CoV-2 treatment. This article may be a ready reference for discovering natural lead compounds and targets in SARS-CoV-2 associated works.

A Betulinic Acid Derivative, BA5, Induces G0/G1 Cell Arrest, Apoptosis Like-Death, and Morphological Alterations in Leishmania sp

Leishmaniasis are endemic diseases caused by different species of intracellular parasites of the genus Leishmania. Due to the high toxicity and drug resistance of current antileishmanial drugs, it is necessary to identify new and more effective drugs. Previously, we investigated the immunomodulatory and anti-Trypanosoma cruzi action of BA5, a derivative of betulinic acid. In the present study, we investigated the in vitro activity of BA5 against different species of Leishmania and their action mechanism. BA5 exhibited low cytotoxicity against macrophages and inhibited the proliferation of promastigote forms of Leishmania amazonensis (IC₅₀ = 4.5 ± 1.1 μM), Leishmania major (IC₅₀ = 3.0 ± 0.8 μM), Leishmania braziliensis (IC₅₀ = 0.9 ± 1.1 μM) and Leishmania infantum (IC₅₀ = 0.15 ± 0.05 μM). Incubation with BA5 reduced the percentage of Leishmania amazonensis-infected macrophages and the number of intracellular parasites (IC₅₀ = 4.1 ± 0.7 μM). To understand the mechanism of action underlying BA5 antileishmanial activity (incubation at IC₅₀/2_, IC₅₀ or 2xIC₅₀ values of the drug), we investigated ultrastructural changes by scanning electron microscopy and evaluated cell cycle, membrane mitochondrial potential, and cell death against promastigote forms of Leishmania amazonensis by flow cytometry. Promastigotes incubated with BA5 presented membrane blebbing, flagella damage, increased size, and body deformation. Flow cytometry analysis showed that parasite death is mainly caused by apoptosis-like death, arrested cell cycle in G0/G1 phase and did not alter the membrane mitochondrial potential of Leishmania amazonensis. Surprisingly, the combination of BA5 and amphotericin B, an assay used to determine the degree of drug interaction, revealed synergistic effects (CI = 0.15 ± 0.09) on promastigotes forms of Leishmania amazonensis. In conclusion, BA5 compound is an effective and selective antileishmanial agent.

Potential of Triterpenic Natural Compound Betulinic Acid for Neglected Tropical Diseases New Treatments

Neglected tropical diseases are one of the most important public health problems in many countries around the world. Among them are leishmaniasis, Chagas disease, and malaria, which contribute to more than 250 million infections worldwide. There is no validated vaccine to prevent these infections and the treatments available are obsolete, highly toxic, and non-effective due to parasitic drug resistance. Additionally, there is a high incidence of these diseases, and they may require hospitalization, which is expensive to the public health systems. Therefore, there is an urgent need to develop new treatments to improve the management of infected people, control the spread of resistant strains, and reduce health costs. Betulinic acid (BA) is a triterpene natural product which has shown antiparasitic activity against Leishmania, Trypanosoma cruzi, and Plasmodium. Here, we review the main results regarding the in vitro and in vivo pharmacological activity of BA and its derivatives against these parasites. Some chemical modifications of BA have been shown to improve its activities against the parasites. Further improvement on studies of drug-derived, as well as structure–activity relationship, are necessary for the development of new betulinic acid-based treatments.

Bio-guided isolation of anti-leishmanial natural products from Diospyros gracilescens L. (Ebenaceae)

BACKGROUND

Plants represent an intricate and innovative source for the discovery of novel therapeutic remedies for the management of infectious diseases. The current study aimed at discovering new inhibitors of Leishmania spp., using anti-leishmanial activity-guided investigation approach of extracts from Diospyros gracilescens Gürke (1911) (Ebenaceae), targeting the extracellular (promastigotes) and intracellular (amastigotes) forms of Leishmania donovani.

METHODS

The plant extracts were prepared by maceration using H20: EtOH (30:70, v/v) and further fractionated using a bio-guided approach. Different concentrations of D. gracilescens extracts, fractions and isolated compounds were tested in triplicate against L. donovani promastigotes and amastigotes in vitro. The antileishmanial potency and cytotoxicity on RAW 264.7 cells were determined using the resazurin colorimetric assay. The time kill kinetic profile of the most active sample was also investigated. The structures of all compounds were elucidated on the basis of extensive spectroscopic analyses, including 1D and 2D NMR, and HR-ESI-MS and by comparison of their data with those reported in the literature.

RESULTS

The hydroethanolic crude extract of D. gracilescens trunk showed the most potent antileishmanial activity (IC50 = 5.84 μg/mL). Further fractionation of this extract led to four (4) fractions of which, the hexane fraction showed the most potent activity (IC50 = 0.79 μg/mL), and seven (07) compounds that exhibited moderate potency (IC50 = 13.69-241.71 μM) against L. donovani. Compound 1-deoxyinositol (7) inhibited the promastigote and amastigote forms of L. donovani with IC50 values of 241.71 μM and 120 μM respectively and also showed the highest selectivity against L. donovani promastigotes (SI > 5.04). To the best of our knowledge, the antileishmanial activity of this compound is being reported here for the first time. The promising hexane fraction showed significant inhibition of parasites growth at different concentrations, but with no evidence of cidal effect over an exposure period of 120 h.

CONCLUSIONS

The results obtained indicated that the hydroethanolic extract from the D. gracilescens trunk and the derived hexane fraction have very potent inhibitory effect on cultivated promastigotes and amastigotes of L. donovani parasite. The isolated compounds showed a lesser extent of potency and selectivity. However, further structure-activity-relationship studies of 1-deoxyinositol could lead to more potent and selective hit derivatives of interest for detailed drug discovery program against visceral leishmaniasis.

Chemical Strategies towards the Synthesis of Betulinic Acid and Its More Potent Antiprotozoal Analogues

Betulinic acid (BA, 3β-hydroxy-lup-20(29)-en-28-oic acid) is a pentacyclic triterpene acid present predominantly in Betula ssp. (Betulaceae) and is also widely spread in many species belonging to different plant families. BA presents a wide spectrum of remarkable pharmacological properties, such as cytotoxic, anti-HIV, anti-inflammatory, antidiabetic and antimicrobial activities, including antiprotozoal effects. The present review first describes the sources of BA and discusses the chemical strategies to produce this molecule starting from betulin, its natural precursor. Next, the antiprotozoal properties of BA are briefly discussed and the chemical strategies for the synthesis of analogues displaying antiplasmodial, antileishmanial and antitrypanosomal activities are systematically presented. The antiplasmodial activity described for BA was moderate, nevertheless, some C-3 position acylated analogues showed an improvement of this activity and the hybrid models—with artesunic acid—showed the most interesting properties. Some analogues also presented more intense antileishmanial activities compared with BA, and, in addition to these, heterocycles fused to C-2/C-3 positions and amide derivatives were the most promising analogues. Regarding the antitrypanosomal activity, some interesting antitrypanosomal derivatives were prepared by amide formation at the C-28 carboxylic group of the lupane skeleton. Considering that BA can be produced either by isolation of different plant extracts or by chemical transformation of betulin, easily obtained from Betula ssp., it could be said that BA is a molecule of great interest as a starting material for the synthesis of novel antiprotozoal agents.

Leishmanicidal Activity of Betulin Derivatives in Leishmania amazonensis; Effect on Plasma and Mitochondrial Membrane Potential, and Macrophage Nitric Oxide and Superoxide Production

Herein, we evaluated in vitro the anti-leishmanial activity of betulin derivatives in Venezuelan isolates of Leishmania amazonensis, isolated from patients with therapeutic failure.

METHODS

We analyzed promastigote in vitro susceptibility as well as the cytotoxicity and selectivity of the evaluated compounds. Additionally, the activity of selected compounds was determined in intracellular amastigotes. Finally, to gain hints on their potential mechanism of action, the effect of the most promising compounds on plasma and mitochondrial membrane potential, and nitric oxide and superoxide production by infected macrophages was determined.

RESULTS

From the tested 28 compounds, those numbered 18 and 22 were chosen for additional studies. Both 18 and 22 were active (GI50 ≤ 2 µM, cytotoxic CC50 > 45 µM, SI > 20) for the reference strain LTB0016 and for patient isolates. The results suggest that 18 significantly depolarized the plasma membrane potential (p < 0.05) and the mitochondrial membrane potential (p < 0.05) when compared to untreated cells. Although neither 18 nor 22 induced nitric oxide production in infected macrophages, 18 induced superoxide production in infected macrophages.

CONCLUSION

Our results suggest that due to their efficacy and selectivity against intracellular parasites and the potential mechanisms underlying their leishmanicidal effect, the compounds 18 and 22 could be used as tools for designing new chemotherapies against leishmaniasis.

Promastigotes of Leishmania donovani exhibited sensitivity towards the high altitudinal plant Cicer microphyllum

In this study, we explored Cicer microphyllum (CM), a Trans-Himalayan plant for its chemical components by GC-MS, phytochemical quantitation, and anti-leishmanial efficacy against sensitive strain (SS) and resistant strain (RS) promastigotes of L. donovani in vitro. The hydroethanolic extract of aerial parts of CM was screened for the presence of chemical compounds and phytochemical estimation. The antileishmanial activity of CM was assessed against the promastigotes of L. donovani. The cell volume and cell viability were analyzed by flow cytometry. The generation of reactive oxygen species (ROS) and lipid bodies was determined after treatment with reference and test drug. The extract of CM is complemented with major plant secondary metabolites and the quantitative assessment for phytoconstituents showed the highest concentration of phenols followed by flavonoids and terpenoids. Different biologically active chemical compounds were identified by the GC-MS analysis. The 50% inhibitory concentrations against L. donovani sensitive strain were 14.40 μg/ml and 23.03 μg/ml whereas for resistant promastigotes these were 49.84 μg/ml and 26.77 μg/ml after SAG (sodium stibogluconate) and CM exposure, respectively. CM treatment reduced cell viability induced by loss in plasma membrane integrity. Drug treatment resulted in higher ROS generation and production of lipid bodies. GC-MS screening of the extract revealed the richness of active chemical components in CM. The presence of diverse phytochemicals, no cytotoxicity to human macrophages, and the antileishmanial action of CM depicted its potential as an alternative future drug.

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First report of in vitro leishmanial activity of Cicer microphyllum (CM) against SAG-resistant and SAG-sensitive strain.

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Chemical characterization of CM by GC-MS revealed biologically active components.

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CM augmented ROS production and lipid bodiesʼ formation in Leishmania parasites.

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Parasitic cells exhibited loss of membrane integrity upon drug treatment.

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No significant toxicity on THP-1 cell line was observed.

Bioprospecting of Nitrogenous Heterocyclic Scaffolds with Potential Action for Neglected Parasitosis: A Review

Neglected parasitic diseases are a group of infections currently considered as a worldwide concern. This fact can be attributed to the migration of these diseases to developed and developing countries, associated with therapeutic insufficiency resulted from the low investment in the research and development of new drugs. In order to overcome this situation, bioprospecting supports medicinal chemistry in the identification of new scaffolds with therapeutically appropriate physicochemical and pharmacokinetic properties. Among them, we highlight the nitrogenous heterocyclic compounds, as they are secondary metabolites of many natural products with potential biological activity. The objective of this work was to review studies within a 10-year timeframe (2009- 2019), focusing on the pharmacological application of nitrogen bioprospectives (pyrrole, pyridine, indole, quinoline, acridine, and their respective derivatives) against neglected parasitic infections (malaria, leishmania, trypanosomiases, and schistosomiasis), and their application as a template for semi-synthesis or total synthesis of potential antiparasitic agents. In our studies, it was observed that among the selected articles, there was a higher focus on the attempt to identify and obtain novel antimalarial compounds, in a way that an extensive amount of studies involving all heterocyclic nitrogen nuclei were found. On the other hand, the parasites with the lowest number of publications up until the present date have been trypanosomiasis, especially those caused by Trypanosoma cruzi, and schistosomiasis, where some heterocyclics have not even been cited in recent years. Thus, we conclude that despite the great biodiversity on the planet, little attention has been given to certain neglected tropical diseases, especially those that reach countries with a high poverty rate.

Leishmanicidal Potential of Hardwickiic Acid Isolated From Croton sylvaticus

Leishmania is a parasitic protozoon responsible for the neglected tropical disease Leishmaniasis. Approximately, 350 million people are susceptible and close to 70,000 death cases globally are reported annually. The lack of effective leishmanicides, the emergence of drug resistance and toxicity concerns necessitate the pursuit for effective antileishmanial drugs. Natural compounds serve as reservoirs for discovering new drugs due to their chemical diversity. Hardwickiic acid (HA) isolated from the stembark of Croton sylvaticus was evaluated for its leishmanicidal potential against Leishmania donovani and L. major promastigotes. The susceptibility of the promastigotes to HA was determined using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide/phenazine methosulfate colorimetric assay with Amphotericin B serving as positive control. HA showed a significant antileishmanial activity on L. donovani promastigotes with an IC₅₀ value of 31.57± 0.06 µM with respect to the control drug, amphotericin B with IC₅₀ of 3.35 ± 0.14 µM). The cytotoxic activity was observed to be CC₅₀ = 247.83 ± 6.32 µM against 29.99 ± 2.82 µM for curcumin, the control, resulting in a selectivity index of SI = 7.85. Molecular modeling, docking and dynamics simulations of selected drug targets corroborated the observed antileishmanial activity of HA. Novel insights into the mechanisms of binding were obtained for trypanothione reductase (TR), pteridine reductase 1 (PTR1), and glutamate cysteine ligase (GCL). The binding affinity of HA to the drug targets LmGCL, LmPTR1, LdTR, LmTR, LdGCL, and LdPTR1 were obtained as -8.0, -7.8, -7.6, -7.5, -7.4 and -7.1 kcal/mol, respectively. The role of Lys16, Ser111, and Arg17 as critical residues required for binding to LdPTR1 was reinforced. HA was predicted as a Caspase-3 stimulant and Caspase-8 stimulant, implying a possible role in apoptosis, which was shown experimentally that HA induced parasite death by loss of membrane integrity. HA was also predicted as antileishmanial molecule corroborating the experimental activity. Therefore, HA is a promising antileishmanial molecule worthy of further development as a biotherapeutic agent.

Giardia lamblia Decreases NF-κB p65RelA Protein Levels and Modulates LPS-Induced Pro-Inflammatory Response in Macrophages

The protozoan Giardia lamblia is the most common cause of parasitic gastrointestinal infection worldwide. The parasite developed sophisticated, yet not completely disclosed, mechanisms to escape immune system and growth in the intestine. To further understand the interaction of G. lamblia with host immune cells, we investigated the ability of parasites to modulate the canonical activation of mouse macrophages (Raw 264.7 cell line) and human monocyte-derived macrophages triggered by the TLR4 agonist, lipopolysaccharide (LPS). We observed that G. lamblia impairs LPS-evoked pro-inflammatory status in these macrophage-like cells through inhibition of cyclooxygenase-2 and inducible nitric oxide synthase expression and subsequent NO production. This effect was in part due to the activity of three G. lamblia proteases, a 135 kDa metalloprotease and two cysteine proteases with 75 and 63 kDa, that cleave the p65^RelA subunit of the nuclear factor-kappa B (NF-κB). Moreover, Tnf and Ccl4 transcription was increased in the presence of the parasite. Overall, our data indicates that G. lamblia modulates macrophages inflammatory response through impairment of the NF-κB, thus silencing a crucial signaling pathway of the host innate immune response.

Current Advances in the Synthesis and Biological Evaluation of Pharmacologically Relevant 1,2,4,5-Tetrasubstituted-1H-Imidazole Derivatives

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In recent years, the synthesis and evaluation of the biological properties of 1,2,4,5-tetrasubstituted-1H-imidazole derivatives have been the subject of a large number of studies by academia and industry. In these studies it has been shown that this large and highly differentiated class of heteroarene derivatives includes high valuable compounds having important biological and pharmacological properties such as antibacterial, antifungal, anthelmintic, anti-inflammatory, anticancer, antiviral, antihypertensive, cholesterol-lowering, antifibrotic, antiuricemic, antidiabetic, antileishmanial and antiulcer activities.

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The present review with 411 references, in which we focused on the literature data published mainly from 2011 to 2017, aims to update the readers on the recent developments on the synthesis and biological evaluation of pharmacologically relevant 1,2,4,5-tetrasubstituted-1H-imidazole derivatives with an emphasis on their different molecular targets and their potential use as drugs to treat various types of diseases. Reference was also made to substantial literature data acquired before 2011 in this burgeoning research area.

2-Deoxyglycoside Conjugates of Lupane Triterpenoids with High Cytotoxic Activity-Synthesis, Activity, and Pharmacokinetic Profile

A set of 41 glycosidic conjugates of pentacyclic triterpenes was synthesized in order to improve the solubility of highly cytotoxic parent compounds. Their in vitro cytotoxic activity was evaluated in 25 cancer cell lines and 2 noncancer fibroblasts. Fifteen compounds had high cytotoxicity on the T-lymphoblastic leukemia cell line CCRF-CEM and 6 of them were active in multiple cell lines of various histogenic origin and not toxic in fibroblasts. Compound 11a had IC₅₀ of 0.64 μM in CCRF-CEM cells, 0.60 μM in K-562 cells, and 0.37 μM in PC-3 cells; compound 12a had IC₅₀ of 0.64 μM in CCRF-CEM cells and 0.71 μM in SW620 cells; compound 17b had IC₅₀ of 0.86 μM in HCT116 cells and 0.92 μM in PC-3 cells. Compounds 11b and 12b were slightly less active than the previously mentioned derivatives; however, their solubility was significantly better, and therefore they were selected for the in vivo evaluation of the pharmacokinetic profile in mice. In both compounds, the maximum concentration in plasma was achieved very rapidly-the highest level in plasma was found 1 h after administration (22.2, respectively, 6.4 μM). For compound 12b, the resorption was followed with fast elimination, and 12 h after administration, the compound was not detected in plasma. In contrast, compound 11b was eliminated more slowly; it was still present in plasma after 12 h, but its concentration dropped below the detection limit after 24 h. The elimination half-time determined for compound 11b was 2.4 h and for compound 12b just about 1.4 h. These values are reasonable for further drug development.

Comparative analysis between four model nanoformulations of amphotericin B-chitosan, amphotericin B-dendrimer, betulinic acid-chitosan and betulinic acid-dendrimer for treatment of Leishmania major: real-time PCR assay plus

Background

Amphotericin B (Amp) and Betulinic acid (BA) as antileishmanial agents have negligible water solubility and high toxicity. To solve these problems, for the first time, chitosan nanoparticles and Anionic Linear Globular Dendrimer (D) were synthesized for the treatment of Leishmania major (L. major).

Method

Chitosan and dendrimer nanoparticles were synthesized, and Amp and BA were loaded into the nanoparticles. The particles were then characterized using various methods and their efficacy was evaluated in vitro and in vivo environments (parasite burden was confirmed using pathological studies and real-time PCR methods).

Result

The results of docking showed that Amp and BA can be loaded into chitosan and dendrimer nanoparticles. The results of physically drug loading efficiency for AK (Amphotericin B-chitosan), BK (Betulinic acid-chitosan), AD (Amphotericin B-Dendrimer) and BD (Betulinic acid- Dendrimer) were 90, 93, 84 and 96 percent, respectively. The characterization results indicated that the drugs were loaded into nanoparticles physically. Moreover, the increased solubility rate for AD=478, BD=790, AK=80 and BK=300 folds. Furthermore, the results of the drug delivery system showed the slow controlled drug release pattern with cellular uptake of more than 90%. The treatment results showed a 100 percent decrease of toxicity for the all nanodrugs was observed in vivo and in vitro environments. Moreover, AK10 and BK20 mg/kg reduced parasite burden by 83 percent (P<0.001), while AD50 and BD40 mg/kg reduced it to a lesser extent compared to glucantime.

Conclusion

All the synthesized nanodrugs were completely succeeded by 100% to recovery the L. major induced pathological effects in the infected footpad. Also, the results of present study were confirmed with real-time PCR and the results showed that AK and BK were succeeded in a large extent to the treatment of L. major infection (P<0.001), therefore AK and BK could be considered as proper alternatives of choices drugs.

Design and synthesis of pentacyclic triterpene conjugates and their use in medicinal research

Triterpenoids are natural products from plants and many other organisms that have various biological activities, such as antitumor, antiviral, antimicrobial, and protective activities. This review covers the synthesis and biological evaluation of pentacyclic triterpene (PT) conjugates with other molecules that have been found to increase the IC₅₀ or improve the pharmacological profile of the parent PT. Some of these molecules are designed to target specific proteins or cellular organelles, which has resulted in highly selective lead structures for drug development. Other PT conjugates are useful for investigating their mechanism of action. This concept has been very successful: 1) Many compounds, especially mitochondria-targeting PT conjugates, have reached a selective cytotoxicity at low nanomolar concentrations in cancer cells. 2) A number of PT conjugates have had high activity against HIV or the influenza virus. 3) Fluorescent PT conjugates have been able to visualize the PT in living cells, which has allowed quantification of the uptake and distribution of the PT within the cell. 4) Biotinylated PT conjugates have been used to identify target proteins, which may help to show their mechanism of action. 5) A large number of PT conjugates with polyethylene glycol (PEG), polyamines, etc. form nanometer-sized micelles that have a much better pharmacological profile than the PT alone. In summary, the connection of a PT to an appropriate modifying molecule has resulted in extremely useful semisynthetic compounds with a high potential to treat cancer or viral infections or compounds that are useful for the study of the mechanism of action of PTs at the molecular level.

Indirubin derivatives are potent and selective anti-Trypanosoma cruzi agents

Current treatment for combatting Chagas disease, a life-threatening illness caused by the kinetoplastid protozoan parasite Trypanosoma cruzi is inadequate, and thus the discovery of new antiparasitic compounds is of prime importance. Previous studies identified the indirubins, a class of ATP kinase inhibitors, as potent growth inhibitors of the related kinetoplastid Leishmania. Herein, we evaluated the inhibitory activity of a series of 69 indirubin analogues screened against T. cruzi trypomastigotes and intracellular amastigotes. Seven indirubins were identified as potent T. cruzi inhibitors (low μΜ, nM range). Cell death analysis of specific compounds [3'oxime-6-bromoindirubin(6-BIO) analogues 10, 11 and 17, bearing a bulky extension on the oxime moiety and one 7 substituted analogue 32], as evaluated by electron microscopy and flow cytometry, showed a different mode of action between compound 32 compared to the three 6-BIO oxime- substituted indirubins, suggesting that indirubins may kill the parasite by different mechanisms dependent on their substitution. Moreover, the efficacy of four compounds that show the most potent anti-parasitic effect in both trypomastigotes and intracellular amastigotes (10, 11, 17, 32), was evaluated in a mouse model of T. cruzi infection. Compound 11 (3ʹpiperazine-6-BIO) displayed the best in vivo efficacy (1/6 mortality, 94.5% blood parasitaemia reduction, 12 dpi) at a dose five times reduced over the reference drug benznidazole (20 mg/kg vs100 mg/kg). We propose 3ʹpiperazine-6-BIO as a potential lead for the development of new treatments of Chagas disease.

Neuroprotective Effects of Betulin in Pharmacological and Transgenic Caenorhabditis elegans Models of Parkinson's Disease

Parkinson’s disease (PD) is the second most common degenerative disorder of the central nervous system in the elderly. It is characterized by progressive loss of dopaminergic neurons in the substantia nigra pars compacta, as well as by motor dysfunction. Although the causes of PD are not well understood, aggregation of α-synuclein (α-syn) in neurons contributes to this disease. Current therapeutics for PD provides satisfactory symptom relief but not a cure. Treatment strategies include attempts to identify new drugs that will prevent or arrest the progressive course of PD by correcting disease-specific pathogenic process. Betulin is derived from the bark of birch trees and possesses anticancer, antimicrobial, and anti-inflammatory properties. The aim of the present study was to evaluate the potential for betulin to ameliorate PD features in Caenorhabditis elegans (C. elegans) models. We demonstrated that betulin diminished α-syn accumulation in the transgenic C. elegans model. Betulin also reduced 6-hydroxydopamine-induced dopaminergic neuron degeneration, reduced food-sensing behavioral abnormalities, and reversed life-span decreases in a pharmacological C. elegans model. Moreover, we found that the enhancement of proteasomes activity by promoting rpn1 expression and downregulation of the apoptosis pathway gene, egl-1, may be the molecular mechanism for betulin-mediated protection against PD pathology. Together, these findings support betulin as a possible treatment for PD and encourage further investigations of betulin as an antineurodegenerative agent.

Predictive classification models and targets identification for betulin derivatives as Leishmania donovani inhibitors

Betulin derivatives have been proven effective in vitro against Leishmania donovani amastigotes, which cause visceral leishmaniasis. Identifying the molecular targets and molecular mechanisms underlying their action is a currently an unmet challenge. In the present study, we tackle this problem using computational methods to establish properties essential for activity as well as to screen betulin derivatives against potential targets. Recursive partitioning classification methods were explored to develop predictive models for 58 diverse betulin derivatives inhibitors of L. donovani amastigotes. The established models were validated on a testing set, showing excellent performance. Molecular fingerprints FCFP_6 and ALogP were extracted as the physicochemical properties most extensively involved in separating inhibitors from non-inhibitors. The potential targets of betulin derivatives inhibitors were predicted by in silico target fishing using structure-based pharmacophore searching and compound-pharmacophore-target-pathway network analysis, first on PDB and then among L. donovani homologs using a PSI-BLAST search. The essential identified proteins are all related to protein kinase family. Previous research already suggested members of the cyclin-dependent kinase family and MAP kinases as Leishmania potential drug targets. The PSI-BLAST search suggests two L. donovani proteins to be especially attractive as putative betulin target, heat shock protein 83 and membrane transporter D1.

Novel Nanosized Chitosan-Betulinic Acid Against Resistant Leishmania Major and First Clinical Observation of such parasite in Kidney

Regarding the antiparasitic effects of Betulinic acid (B) against Leishmaniasis, it was loaded into nanochitosan (K) for the first time in order to improve its therapeutic effects and decrease its side effects for the treatment of Leishmania major-infected Balb/c mice. Improvement the therapeutic efficacy of Bas an anti-leishmania agent through increasing the effective dose was achieved by using a novel solvent and phase separation method for K synthesis. The synthesized K with the size of 102 nm and Betulinic acid-nanochitosan (BK) with the size of 124 nm and drug loading efficiency of 93%, cellular uptake of 97.5% with the slow drug release pattern was prepared. To increase the therapeutic dose, a modified 10% acetic acid solvent was used. The in vitro and in vivo results showed that the nanodrug of BK was non toxic by 100% and BK20 mg/kg could completely performed the wound healing and inhibit the parasite in a large extent (P ˂ 0.001) compared to other groups. Therefore, BK could be considered as an alternative regimen for treatment of L. major.

Triterpenic azines, a new class of compounds with selective cytotoxicity to leukemia cells CCRF-CEM

Aim: From betulinic acid (1a), we synthesized 30-oxobetulinic acid (2a) that is highly cytotoxic against many cancer cell lines; however, its generic toxicity is the main obstacle in further development as cytostatic. Methodology & results: From 2a, we prepared a new class of compounds – nonsymmetrical azines and tested their in vitro cytotoxicity. All new azines with a free 28-COOH group (4a–4e) were highly and selectively cytotoxic against the T-lymphoblastic leukemia cell line CCRF-CEM and exhibited dose-dependent inhibition of RNA and DNA synthesis and other cell-cycle alterations, including the M-phase block. Conclusion: The potential use of azines (4a–4e) in drug development focused on hematological cancers is significantly higher than that of previously studied acids 1a and 2a.

Betulinic acid induces cell death by necrosis in Trypanosoma cruzi

Chagas' disease is a neglected disease caused by the protozoan parasite Trypanosoma cruzi and constitutes a serious health problem worldwide. The treatment is limited, with variable efficacy of benznidazole and nifurtimox. Betulinic Acid (BA), a triterpene, can be found in medicinal herbs and has a wide variety of biological and pharmacological activities. The objective was to evaluate betulinic acid effects on the cell death mechanism in Trypanosoma cruzi strain Y. BA inhibited the growth of epimastigotes in periods of 24h (IC₅₀=73.43μM), 48h (IC₅₀=119.8μM) and 72h (IC₅₀=212.2μM) of incubation; of trypomastigotes (IC₅₀=51.88μM) in periods of 24h and intracellular amastigotes (IC₅₀=25.94μM) in periods of 24 and 48h of incubation, no toxicity on LLC-MK₂ cells at the concentrations used. Analysis of the possible mechanism of parasite cell death showed alterations in mitochondrial membrane potential, alterations in cell membrane integrity, an increase in the formation of reactive oxygen species and increase swelling of the reservosomes. In conclusion, betulinic acid was be able to inhibition all developmental forms of Trypanosoma cruzi Y strain with necrotic mechanism and involvement of mitochondrial membrane potential alteration and increase in reactive oxygen species.

Leishmanicidal and cytotoxic activity of hederagenin-bistriazolyl derivatives

Aiming to obtain new potent leishmanicidal and cytotoxic compounds from natural sources, the triterpene hederagenin was converted into several new 1,2,3-triazolyl derivatives tethered at C-23 and C-28. For this work hederagenin was isolated from fruits of Sapindus saponaria and reacted with propargyl bromide to afford as a major product bis-propargylic derivative 1 in 74%. Submitting this compound to Huisgen 1,3-dipolar cycloaddition reactions with several azides afforded the derivatives 2-19 with yields in the range of 40-87%. All compounds have been screened for in vitro cytotoxic activity in a panel of five human cancer cell lines by a SRB assay. The bioassays showed that compound 19 was the most cytotoxic against all human cancer cell lines with EC₅₀ = 7.4-12.1 μM. Moreover, leishmanicidal activity was evaluated through the in vitro effect in the growth of Leishmania infantum, and derivatives 1, 2, 5 and 17 were highly effective preventing proliferation of intracellular amastigote forms of L. infantum (IC₅₀ = 28.8, 25.9, 5.6 and 7.4 μM, respectively). All these compounds showed a higher selectivity index and low toxicity against two strains of kidney BGM and liver HepG2 cells. Compound 5 has higher selectivity (1780 times) in comparison with the commercial antimony drug and is around 8 times more selective than the most active compound previously reported hederagenin derivative. Such high activity associated with low toxicities make the new bis-traiazolyl derivatives promising candidates for the treatment of leishmaniasis. In addition, hederagenin and some derivatives (2, 5 and 17) showed interaction in the binding site of the enzyme CYP51_Li.

Anti-inflammatory, antimycobacterial and genotoxic evaluation of Doliocarpus dentatus

ETHNOPHARMACOLOGICAL RELEVANCE

Doliocarpus dentatus is a medicinal plant widely used in Mato Grosso do Sul State for removing the swelling pain caused by the inflammation process and for treating urine retention.

AIM OF THE STUDY

The genotoxic aspects and the anti-inflammatory and antimycobacterial activity of the ethanolic extract obtained from the leaves of D. dentatus (EEDd) were investigated.

MATERIALS AND METHODS

The EEDd was evaluated against Mycobacterium tuberculosis, and the compound composition was evaluated and identified by nuclear magnetic resonance (NMR). The mice received oral administration of EEDd (30-300mg/kg) in carrageenan models of inflammation, and EEDd (10-1000mg/kg) was assayed by the comet, micronucleus, and phagocytosis tests and by the peripheral leukocyte count.

RESULTS

Phenols (204.04mg/g), flavonoids (89.17mg/g), and tannins (12.05mg/g) as well as sitosterol-3-O-β-D-glucopyranoside, kaempferol 3-O-α-L-rhamnopyranoside, betulinic acid and betulin were present in the EEDd. The value of minimal inhibitory concentration (MIC) of EEDd was 62.5µg/mL. The EEDd induced a significant decrease in the edema, mechanical hypersensitivity and leukocyte migration induced by carrageenan. The comet and micronucleus tests indicated that the EEDd was not genotoxic. The EEDd also did not change the phagocytic activity or the leukocyte perLipheral count.

CONCLUSIONS

The EEDd does not display genotoxicity, phagocytosis and could act as an antimycobacterial and anti-inflammatory agent. This study should contribute to ensuring the safe use of EEDd.

Highly potent anti-leishmanial derivatives of hederagenin, a triperpenoid from Sapindus saponaria L

Leishmaniasis is a neglected tropical disease (NTDs), endemic in 88 countries that affect more than 12 million people. Current drugs are limited due to their toxicity, development of biological resistance, length of treatment and high cost. Thus, the search for new effective and less toxic treatments is an urgent need. In this study, we report the synthesis of 3 new amide derivatives of hederagenin (22-24) with yields between 70% and 90%, along with 57 other derivatives of hederagenin (1-21, 25-60) carrying different groups at C-28 previously reported by our group, and the results of their in vitro ability to inhibit the growth of Leishmania infantum. Some derivatives (3, 4, 44, 49 and 52), showed activity at micromolar level and low toxicity against BGM and HepG2 cells. Moreover, the ability of hederagenin derivatives 3 (IC₅₀ = 9.7 μM), 4 (12 μM), 44 (11 μM) and 49 (2 μM), to prevent proliferation of intracellular amastigote forms of L. infantum and their higher selectivity index and low toxicity compared to commercial positive drug control of choice (potassium antimonyl tartrate trihydrate) (IC₅₀ = 80 μM, SI = 0.1), make these compounds promising candidates for the treatment of leishmaniasis.

Antiparasitic evaluation of betulinic acid derivatives reveals effective and selective anti-Trypanosoma cruzi inhibitors

Betulinic acid is a pentacyclic triterpenoid with several biological properties already described, including antiparasitic activity. Here, the anti-Trypanosoma cruzi activity of betulinic acid and its semi-synthetic amide derivatives (BA1-BA8) was investigated. The anti-Trypanosoma cruzi activity and selectivity were enhanced in semi-synthetic derivatives, specially on derivatives BA5, BA6 and BA8. To understand the mechanism of action underlying betulinic acid anti-T. cruzi activity, we investigated ultrastructural changes by electron microscopy. Ultrastructural studies showed that trypomastigotes incubated with BA5 had membrane blebling, flagella retraction, atypical cytoplasmic vacuoles and Golgi cisternae dilatation. Flow cytometry analysis showed that parasite death is mainly caused by necrosis. Treatment with derivatives BA5, BA6 or BA8 reduced the invasion process, as well as intracellular parasite development in host cells, with a potency and selectivity similar to that observed in benznidazole-treated cells. More importantly, the combination of BA5 and benznidazole revealed synergistic effects on trypomastigote and amastigote forms of T. cruzi. In conclusion, we demonstrated that BA5 compound is an effective and selective anti-T. cruzi agent.

Synergistic Interactions of Eugenol-tosylate and Its Congeners with Fluconazole against Candida albicans

We previously reported the antifungal properties of a monoterpene phenol “Eugenol” against different Candida strains and have observed that the addition of methyl group to eugenol drastically increased its antimicrobial potency. Based on the results and the importance of medicinal synthetic chemistry, we synthesized eugenol-tosylate and its congeners (E1-E6) and tested their antifungal activity against different clinical fluconazole (FLC)- susceptible and FLC- resistant C. albicans isolates alone and in combination with FLC by determining fractional inhibitory concentration indices (FICIs) and isobolograms calculated from microdilution assays. Minimum inhibitory concentration (MIC) results confirmed that all the tested C. albicans strains were variably susceptible to the semi-synthetic derivatives E1-E6, with MIC values ranging from 1–62 μg/ml. The test compounds in combination with FLC exhibited either synergy (36%), additive (41%) or indifferent (23%) interactions, however, no antagonistic interactions were observed. The MICs of FLC decreased 2–9 fold when used in combination with the test compounds. Like their precursor eugenol, all the derivatives showed significant impairment of ergosterol biosynthesis in all C. albicans strains coupled with down regulation of the important ergosterol biosynthesis pathway gene-ERG11. The results were further validated by docking studies, which revealed that the inhibitors snugly fitting the active site of the target enzyme, mimicking fluconazole, may well explain their excellent inhibitory activity. Our results suggest that these compounds have a great potential as antifungals, which can be used as chemosensitizing agents with the known antifungal drugs.

Leishmanicidal Activity of Piper nigrum Bioactive Fractions is Interceded via Apoptosis In Vitro and Substantiated by Th1 Immunostimulatory Potential In Vivo

Visceral leishmaniasis (VL) is a life-threatening protozoal infection chiefly impinging the rural and poor population in the tropical and sub-tropical countries. The deadly affliction is rapidly expanding after its association with AIDS, swiftly defying its status of a neglected disease. Despite successful formulation of vaccine against canine leishmaniasis, no licensed vaccine is yet available for human VL, chemotherapy is in appalling state, and the development of new candidate drugs has been painfully slow. In face of lack of proper incentives, immunostimulatory plant preparations owing antileishmanial efficacy bear potential to rejuvenate awful antileishmanial chemotherapy. We have earlier reported profound leishmanicidal activity of Piper nigrum hexane (PNH) seeds and P. nigrum ethanolic (PNE) fractions derived from P. nigrum seeds against Leishmania donovani promastigotes and amastigotes. In the present study, we illustrate that the remarkable anti-promastigote activity exhibited by PNH and PNE is mediated via apoptosis as evidenced by phosphatidylserine externalization, DNA fragmentation, arrest in sub G₀/G₁ phase, loss of mitochondrial membrane potential and generation of reactive oxygen species. Further, P. nigrum bioactive fractions rendered significant protection to L. donovani infected BALB/c mice in comparison to piperine, a known compound present in Piper species. The substantial therapeutic potential of PNH and PNE was accompanied by elicitation of cell-mediated immune response. The bioactive fractions elevated the secretion of Th1 (INF-γ, TNF-α, and IL-2) cytokines and declined IL-4 and IL-10. PNH and PNE enhanced the production of IgG2a, upregulated the expression of co-stimulatory molecules CD80 and CD86, augmented splenic CD4⁺ and CD8⁺ T cell population, induced strong lymphoproliferative and DTH responses and partially stimulated NO production. PNH and PNE were devoid of any hepatic or renal toxicity. These encouraging findings merit further exploration of P. nigrum bioactive fractions as a source of potent and non-toxic antileishmanials.

Plant-derived compounds in treatment of leishmaniasis

Leishmaniasis is a neglected public health problem caused by the protozoan species belonging to the genus Leishmania affecting mostly the poor populations of developing countries. The causative organism is transmitted by female sandflies. Cutaneous, mucocutaneous, and visceral clinical manifestations are the most frequent forms of leishmaniasis. Chemotherapy still relies on the use of pentavalent antimonials, amphotericin B, paromomycin, miltefosin and liposomal amphotericin B. However, the application of these drugs is limited due to low efficacy, life-threatening side effects, high toxicity, induction of parasite resistance, length of treatment and high cost. Given the fact that antileishmanial vaccines may not become available in the near future, the search for better drugs should be continued. Natural products may offer an unlimited source of chemical diversity to identify new drug modules. New medicines should be less toxic or non-toxic, safe, more efficient, less expensive and readily available antileishmanial agents, especially for low-income populations. In the present review, special focus is on medicinal plants used against leishmanaiasis. The bioactive phytocompounds present in the plant derivatives including the crude extracts, essential oils, and other useful compounds can be a good source for discovering and producing new antileishmanial medicines.

Metabolic and functional diversity of saponins, biosynthetic intermediates and semi-synthetic derivatives

Saponins are widely distributed plant natural products with vast structural and functional diversity. They are typically composed of a hydrophobic aglycone, which is extensively decorated with functional groups prior to the addition of hydrophilic sugar moieties, to result in surface-active amphipathic compounds. The saponins are broadly classified as triterpenoids, steroids or steroidal glycoalkaloids, based on the aglycone structure from which they are derived. The saponins and their biosynthetic intermediates display a variety of biological activities of interest to the pharmaceutical, cosmetic and food sectors. Although their relevance in industrial applications has long been recognized, their role in plants is underexplored. Recent research on modulating native pathway flux in saponin biosynthesis has demonstrated the roles of saponins and their biosynthetic intermediates in plant growth and development. Here, we review the literature on the effects of these molecules on plant physiology, which collectively implicate them in plant primary processes. The industrial uses and potential of saponins are discussed with respect to structure and activity, highlighting the undoubted value of these molecules as therapeutics.

Synthesis and activity of new triphenylphosphonium derivatives of betulin and betulinic acid against Schistosoma mansoni in vitro and in vivo

We studied the antischistosomal activity of betulin, betulinic acid and its 9 triphenylphosphonium derivatives characterized by a covalently linkage of the hydrophobic fragment of triterpenoid at C(2)- or C(30)-position with the triphenylphosphonium moiety via a hydrocarbon bridge. The triphenylphosphonium salts showed in vitro antischistosomal activity against newly transformed schistosomula (NTS) and adult worms of Schistosoma mansoni at low micromolar concentrations. In contrast betulin and betulinic acid were inactive against NTS and adult S. mansoni. Of the 9 triphenylphosphonium derivatives tested, the allyl salts 10 (IC50 of 0.76 μg/mL) and 11 (IC50 of 0.64 μg/mL) demonstrated the highest antischistosomal activity against adult S. mansoni. Low worm burden reductions of 22% were observed in vivo for these two compounds. In conclusion, triphenylphosphonium derivatives were obtained from available natural betulin by simple transformations, rendering it practical and useful for large scale application. However, further structural modifications are necessary to translate the promising antischistosomal in vitro activities into in vivo.