In vitro antileishmanial properties of new flavonoids against Leishmania donovani

Investigation of the Potential Targets behind the Promising and Highly Selective Antileishmanial Action of Synthetic Flavonoid Derivatives

Leishmaniases are among the neglected tropical diseases that still cause devastating health, social, and economic consequences to more than 350 million people worldwide. Despite efforts to combat these vector-borne diseases, their incidence does not decrease. Meanwhile, current antileishmanial drugs are old and highly toxic, and safer presentations are unaffordable to the most severely affected human populations. In a previous study by our research group, we synthesized 17 flavonoid derivatives that demonstrated impressive inhibition capacity against rCPB2.8, rCPB3, and rH84Y. These cysteine proteases are highly expressed in the amastigote stage, the target form of the parasite. However, although these compounds have been already described in the literature, until now, the amastigote effect of any of these molecules has not been proven. In this work, we aimed to deeply analyze the antileishmanial action of this set of synthetic flavonoid derivatives by correlating their ability to inhibit cysteine proteases with the action against the parasite. Among all the synthesized flavonoid derivatives, 11 of them showed high activity against amastigotes of Leishmania amazonensis, also providing safety to mammalian host cells. Furthermore, the high production of nitric oxide by infected cells treated with the most active cysteine protease B (CPB) inhibitors confirms a potential immunomodulatory response of macrophages. Besides, considering flavonoids as multitarget drugs, we also investigated other potential antileishmanial mechanisms. The most active compounds were selected to investigate another potential biological pathway behind their antileishmanial action using flow cytometry analysis. The results confirmed an oxidative stress after 48 h of treatment. These data represent an important step toward the validation of CPB as an antileishmanial target, as well as aiding in new drug discovery studies based on this protease.

High throughput biochemical profiling, and functional potential analysis for valorization of grape peduncles

Vitis vinifera L., commonly known as grape is a major fruit crop in the world. Grapes seem to confer health benefits due to their chemical components, biological and antioxidant activities. The present study is conducted to evaluate the biochemical constituents, antioxidant, and antimicrobial potential of ethanolic grape peduncles (EGP) extract. The result of phytochemical analysis revealed the presence of various phytochemicals such as flavonoid, tannin, carbohydrates, alkaloids, cardiac glycoside, phenol, steroid, terpenoids, quinones and anthraquinones. Furthermore, total phenolic content (TPC) and total flavonoid contents (TFC) were 7.35 ± 0.25 mg GAE/g (Gallic Acid Equivalent per gram) and 29.67 ± 0.13 mg QE/g (Quercetin Equivalent per gram) respectively. DPPH (2, 2-diphenyl-1-picrylhydrazyl) free radical scavenging assay revealed IC₅₀ = 159.3 μg/mL. The antibacterial and antifungal study disclosed that the extract was highly potent against Salmonella typhi with maximum zone of inhibition of 27.2 ± 1.60 mm and Epidermophyton floccosum with 74 ± 1.81% inhibition. The extract was analyzed for its cytotoxicity and antileishmanial activity and showed no activity against HeLa cell line and promastigotes of Leishmania major. Elements Fe, Mn, Ni, Pb and Cd were determined by atomic absorption spectroscopy and approximately 50 compounds were identified by Gas Chromatography-Mass Spectrometry (GC-MS). Current work suggest that grape peduncles can be a promising source of bioactive medicinal component.

Anti-Toxoplasma Activities of Some Egyptian Plant Extracts: An In Vitro Study

Purpose

Toxoplasmosis is a globally widespread parasitic disease which causes major health problems in human and animals. This research was conducted to assess the effect of some Egyptian herbal extracts against Toxoplasma gondii (T. gondii) tachyzoites in vitro.

Methods

The methanol extracts of Withania somnifera, Cyper rotundus, Acacia nilotica,Chrysanthemum cinerariae folium, Anethum graveolens, Raphanus sativus, Ceratonia siliqua, Elettaria cardamomum and Cuminum cyminum were tested against T. gondii tachyzoites.

Results

Among the tested plants, the extracts from Raphanus sativus, Cuminum cyminum, and Ceratonia siliqua exhibited high anti-Toxoplasma activities at 50 µg/ml, relative to sulfadiazine. They showed low IC50 values on T. gondii (7.92, 9.47 and 13.52 µg/ml, respectively) and high selectivity index values (100.79, 59.19, and 29.05, respectively). Scanning electron microscopy (SEM) findings indicated evident morphological changes in tachyzoites treated with these three herbal extracts.

Conclusion

Raphanus sativus, Ceratonia siliqua, and Cuminum cyminum methanol extracts could be promising sources of new medicament for toxoplasmosis.

Effect of some plant extracts from Egyptian herbal plants against Toxoplasma gondii tachyzoites in vitro

Nowadays, herbal extracts are considered to be a potential source for developing new drugs that will overcome resistance to conventional chemotherapeutic agents. This study was aimed to explore the efficacy of several Egyptian plant extracts against Toxoplasma gondii infection in vitro for future development of a new, safe, and effective compound for T. gondii. Methanol extracts from Matricaria chamomilla (German chamomile), Laurus nobilis, Citrullus colocynthis, Cinnamum camphora, Boswellia scara, and Melissa officionalis plants and oil extracts (either essential or fixed oils) of some plants such as: lemon grass (Cymbopogon citratus), marjoram (Origanum majorana), watercress (Nasturtium officionale), wheat germ (Triticum aestivum), sesame (Sesamum indicum), rosemary (Salvia rosmarinus), citronella (Cymbopogon nardus), clove (Syzygum aromaticum), jojoba (Simmondsia chinesis), and basil (Ocimum basilicum) were investigated for their anti-Toxoplasma activities. The methanol extracts from C. colocynthis and L. nobilis and the oil extracts from lemon grass and marjoram were active against T. gondii with half maximal inhibitory concentrations (IC₅₀) of 22.86 µg/ml, 31.35 µg/ml, 4.6 µg/ml, and 26.24 µg/ml, respectively. Their selectivity index (SI) values were <10. Interestingly, the methanol extract from M. chamomilla and oil from citronella had the lowest IC₅₀ values for T. gondii (3.56 µg/ml and 2.54 µg/ml, respectively) and the highest SI values (130.33 and 15.02, respectively). In conclusion, methanol extract from M. chamomilla and oil from citronella might be potential sources of novel therapies for treating toxoplasmosis.

Evolution of chromone-like compounds as potential antileishmanial agents, through the 21st century

INTRODUCTION

Leishmaniasis is one of the most neglected diseases of modern times that mainly affects people from developing countries, with approximately 350 million people considered at risk of developing leishmaniasis. Therefore, the development of novel antileishmanial treatments is becoming the focus of numerous research groups, with the support of the World Health Organization, which hopes to eradicate this disease in the near future.

AREAS COVERED

This review focuses on the interest of chromones for the development of future treatments against leishmaniasis. In addition to plant-based chromone derivatives, structure-activity relationship studies that aim to identify the optimal structural features of the chromones' antileishmanial activity are also described and discussed.

EXPERT OPINION

The numerous examples of chromones depicted in this paper, allied with the SAR studies presented herein, suggest that the chromone scaffold is a privileged core for the design and development of novel antileishmanial agents. However, some concerns have been raised concerning the considerable variability observed in the results throughout the scientific bibliography. These inconsistencies may explain the absence of pharmacodynamic and pharmacokinetic studies as well as clinical trials.

Biochemical characterization and chemical validation of Leishmania MAP Kinase-3 as a potential drug target

Protozoan parasites of the Leishmania genus have evolved unique signaling pathways that can sense various environmental changes and trigger stage differentiation for survival and host infectivity. MAP kinase (MAPK) plays a critical role in various cellular activities like cell differentiation, proliferation, stress regulation, and apoptosis. The Leishmania donovani MAPK3 (LdMAPK3) is involved in the regulation of flagella length and hence plays an important role in disease transmission. Here, we reported the gene cloning, protein expression, biochemical characterizations, inhibition studies and cell proliferation assay of LdMAPK3. The recombinant purified LdMAPK3 enzyme obeys the Michaelis-Menten equation with K_m and V_max of LdMAPK3 was found to be 20.23 nM and 38.77 ± 0.71 nmoles ATP consumed/mg LdMAPK3/min respectively. The maximum kinase activity of LdMAPK3 was recorded at 35 °C and pH 7. The in-vitro inhibition studies with two natural inhibitors genistein (GEN) and chrysin (CHY) was evaluated against LdMAPK3. The K_i value for GEN and CHY were found to be 3.76 ± 0.28 µM and K_i = 8.75 ± 0.11 µM respectively. The IC₅₀ value for the compounds, GEN and CHY against L. donovani promastigotes were calculated as 9.9 µg/mL and 13 µg/mL respectively. Our study, therefore, reports LdMAPK3 as a new target for therapeutic approach against leishmaniasis.

In-Vitro Activity of Silybin and Related Flavonolignans against Leishmania infantum and L. donovani

Flavonolignans from the seeds of the milk thistle (Silybum marianum) have been extensively used in folk medicine for centuries. Confirmation of their properties as hepatoprotective, antioxidant and anticancer has been obtained using standardized extracts and purified flavonolignans. Information on their potential effect on Leishmania is very scarce. We have investigated the effect of silymarin, silybin and related flavonolignans on the multiplication of promastigotes in vitro and ex vivo on intracellular amastigotes of L. infantum (Li) and L. donovani (Ld), causative agents of human and canine visceral leishmaniasis (VL). In addition, the potential synergistic effect of the most active molecule and well-established antileishmanial drugs against promastigotes was explored. Dehydroisosilybin A elicited the highest inhibition against Ld and Li promastigotes with an approximate IC₅₀ of 90.23 µM. This molecule showed a moderate synergism with amphotericin B (AmB) but not with Sb^III or paromomycin, although it was ineffective against amastigotes. Antileishmanial activity on intracellular amastigotes of the two diastereoisomers of dehydrosilybin (10 µM) was comparable to that elicited by 0.1 µM AmB. Antiproliferative activity and safety of flavonolignans suggest the interest of exploring their potential value in combination therapy against VL.

The Correlation between Chemical Structures and Antioxidant, Prooxidant, and Antitrypanosomatid Properties of Flavonoids

Flavonoids have demonstrated in vivo and in vitro leishmanicidal, trypanocidal, antioxidant, and prooxidant properties. The chemotherapy of trypanosomiasis and leishmaniasis lacks efficacy, presents high toxicity, and is related to the development of drug resistance. Thus, a series of 40 flavonoids were investigated with the purpose of correlating these properties via structure and activity analyses based on integrated networks and QSAR models. The classical groups for the antioxidant activity of flavonoids were combined in order to explain the influence of antioxidant and prooxidant activities on the antiparasitic properties. These analyses become useful for the development of efficient treatments for leishmaniasis and trypanosomiasis. Finally, the dual activity of flavonoids presenting both anti- and prooxidant activities revealed that the existence of a balance between these two features could be important to the development of adequate therapeutic strategies.

HPLC-DAD phenolic profile, cytotoxic and anti-kinetoplastidae activity of Melissa officinalis

Context Melissa officinalis subsp. inodora Bornm. (Lamiaceae) has been used since ancient times in folk medicine against various diseases, but it has not been investigated against protozoa. Objective To evaluate the activities of M. officinalis against Leishmania braziliensis, Leishmania infantum and Trypanosoma cruzi as well as its cytotoxicity in fibroblast cell line. Materials and methods The fresh leaves were chopped into 1 cm(2) pieces, washed and macerated with 99.9% of ethanol for 72 h at room temperature. Antiparasitic activity of M. officinalis was accessed by direct counting of cells after serial dilution, while the cytotoxicity of M. officinalis was evaluated in fibroblast cell line (NCTC929) by measuring the reduction of resazurin. The test duration was 24 h. High-performance liquid chromatography (HPLC) was used to characterise the extract. Results The extract at concentrations of 250 and 125 μg/mL inhibited 80.39 and 54.27% of promastigote (LC50  value = 105.78 μg/mL) form of L. infantum, 80.59 and 68.61% of L. brasiliensis (LC50 value  = 110.69 μg/mL) and against epimastigote (LC50 value  = 245.23 μg/mL) forms of T. cruzi with an inhibition of 54.45 and 22.26%, respectively, was observed. The maximum toxicity was noted at 500 μg/mL with 95.41% (LC50  value = 141.01 μg/mL). The HPLC analysis identified caffeic acid and rutin as the major compounds. Discussion The inhibition of the parasites is considered clinically relevant (< 500 μg/mL). Rutin and caffeic acids may be responsible for the antiprotozoal effect of the extract. Conclusion The ethanol extract of M. officinalis can be considered a potential alternative source of natural products with antileishmania and antitrypanosoma activities.

In-vitro sensitivity of Pakistani Leishmania tropica field isolate against buparvaquone in comparison to standard anti-leishmanial drugs

In this study, in vitro anti-leishmanial activity of buparvaquone was evaluated against promastigotes and intracellular amastigotes of Pakistani Leishmania tropica isolate KWH23 in relation to the current standard chemotherapy for leishmaniasis (sodium stibogluconate, sodium stibogluconate, amphotericin B and miltefosine). For buparvaquone, mean % inhibition in intracellular amastigotes at four different concentrations (1.35 µM, 0.51 µM, 0.17 µM and 0.057 µM) was 78%, 44%, 20% and 14% respectively, whereas, against promastigotes it was 89%, 77%, 45% and 35% respectively. IC50 values calculated to estimate the anti-leishmanial activity of buparvaquone against intra-cellular amastigotes and promastigotes was 0.53 µM (95% C.I. = 0.32-0.89) and 0.15 µM (95% C.I. = 0.01-1.84) respectively. Amphotericin B was the most potent in-vitro drug tested, with an IC50 of 0.075 µM (95% C.I. = 0.006-0.907) against promastigotes, and 0.065 µM (95% C.I. = 0.048-0.089) against intra-cellular amastigotes. Amphotericin B was more cytotoxic against THP1 cells, with an IC50 of 0.15 µM (95% C.I. = 0.01-0.95) and an apparent in-vitro therapeutic index of 2.0, than was buparvaquone, with an IC50 of 12.03 µM (95% C.I. = 5.36-26.96) against THP1 cells and a therapeutic index of 80.2. The study proposes that buparvaquone may be further investigated as a candidate drug for treatment of cutaneous leishmaniasis.