Bioactive compounds from Celaenodendron mexicanum

Understanding the Artemia Salina (Brine Shrimp) Test: Pharmacological Significance and Global Impact

BACKGROUND

The microplate benchtop brine shrimp test (BST) has been widely used for screening and bio-guided isolation of many active compounds, including natural products. Although the interpretation given to the results appears dissimilar, our findings suggest a correlation between positive results with a specific mechanism of action.

OBJECTIVE

This study aimed to evaluate drugs belonging to fifteen pharmacological categories having diverse mechanisms of action and carry out a bibliometric analysis of over 700 citations related to microwell BST.

METHODS

Test compounds were evaluated in a serial dilution on the microwell BST using healthy nauplii of Artemia salina and after 24 hrs of exposition, the number of alive and dead nauplii was determined, and the LC50 was estimated. A metric study regarding the citations of the BST miniaturized method, sorted by type of documents cited, contributing country, and interpretation of results was conducted on 706 selected citations found in Google Scholar.

RESULTS

Out of 206 drugs tested belonging to fifteen pharmacological categories, twenty-six showed LC50 values <100 μM, most of them belonging to the category of antineoplastic drugs; compounds with different therapeutical uses were found to be cytotoxic as well. A bibliometric analysis showed 706 documents citing the miniaturized BST; 78% of them belonged to academic laboratories from developing countries located on all continents, 63% interpreted their results as cytotoxic activity and 35% indicated general toxicity assessment.

CONCLUSION

BST is a simple, affordable, benchtop assay, capable of detecting cytotoxic drugs with specific mechanisms of action, such as protein synthesis inhibition, antimitotic, DNA binding, topoisomerase I inhibitors, and caspases cascade interfering drugs. The microwell BST is a technique that is used worldwide for the bio-guided isolation of cytotoxic compounds from different sources.

Insights Into Amentoflavone: A Natural Multifunctional Biflavonoid

Amentoflavone is an active phenolic compound isolated from Selaginella tamariscina over 40 years. Amentoflavone has been extensively recorded as a molecule which displays multifunctional biological activities. Especially, amentoflavone involves in anti-cancer activity by mediating various signaling pathways such as extracellular signal-regulated kinase (ERK), nuclear factor kappa-B (NF-κB) and phosphoinositide 3-kinase/protein kinase B (PI3K/Akt), and emerges anti-SARS-CoV-2 effect via binding towards the main protease (Mpro/3CLpro), spike protein receptor binding domain (RBD) and RNA-dependent RNA polymerase (RdRp) of SARS-CoV-2. Therefore, amentoflavone is considered to be a promising therapeutic agent for clinical research. Considering the multifunction of amentoflavone, the current review comprehensively discuss the chemistry, the progress in its diverse biological activities, including anti-inflammatory, anti-oxidation, anti-microorganism, metabolism regulation, neuroprotection, radioprotection, musculoskeletal protection and antidepressant, specially the fascinating role against various types of cancers. In addition, the bioavailability and drug delivery of amentoflavone, the molecular mechanisms underlying the activities of amentoflavone, the molecular docking simulation of amentoflavone through in silico approach and anti-SARS-CoV-2 effect of amentoflavone are discussed.

Amentoflavone isolated from Selaginella sellowii Hieron induces mitochondrial dysfunction in Leishmania amazonensis promastigotes

Leishmaniasis chemotherapy is a bottleneck in disease treatment. Although available, chemotherapy is limited, toxic, painful, and does not lead to parasite clearance, with parasite resistance also being reported. Therefore, new therapeutic options are being investigated, such as plant-derived anti-parasitic compounds. Amentoflavone is the most common biflavonoid in the Selaginella genus, and its antileishmanial activity has already been described on Leishmania amazonensis intracellular amastigotes but its direct action on the parasite is controversial. In this work we demonstrate that amentoflavone is active on L. amazonensis promastigotes (IC₅₀ = 28.5 ± 2.0 μM) and amastigotes. Transmission electron microscopy of amentoflavone-treated promastigotes showed myelin-like figures, autophagosomes as well as enlarged mitochondria. Treated parasites also presented multiple lipid droplets and altered basal body organization. Similarly, intracellular amastigotes presented swollen mitochondria, membrane fragments in the lumen of the flagellar pocket as well as autophagic vacuoles. Flow cytometric analysis after TMRE staining showed that amentoflavone strongly decreased mitochondrial membrane potential. In silico analysis shows that amentoflavone physic-chemical, drug-likeness and bioavailability characteristics suggest it might be suitable for oral administration. We concluded that amentoflavone presents a direct effect on L. amazonensis parasites, causing mitochondrial dysfunction and parasite killing. Therefore, all results point for the potential of amentoflavone as a promising candidate for conducting advanced studies for the development of drugs against leishmaniasis.

Podocarpusflavone A inhibits cell growth of skin cutaneous melanoma by suppressing STAT3 signaling

BACKGROUND

JAK2/STAT3 pathway is involved in the development and progression of melanoma once DNA damage is caused by environment and genetic factors.

OBJECTIVE

Here, we aimed to identify novel inhibitor of JAK2/STAT3 pathway and reveal the underlying mechanisms.

METHODS

Eighty MedChemExpress compounds were screened by using STAT3-Luc reporter in A375 cells. Podocarpusflavone A (PCFA) was identified as an inhibitor of STAT3, which was further verified in four melanoma cell lines. The anti-melanoma effects and mechanism of PCFA were examined and explored in melanoma cells and mouse xenograft models by using Western blot and cell-counting kit-8 assay.

RESULTS

PCFA exhibited potent inhibitory effects on melanoma both in vitro and in vivo. PCFA inhibited the activation of STAT3 through suppressing the phosphorylation of JAK2, and then restrained cell cycle and induced apoptosis of melanoma cells.

CONCLUSION

PCFA inhibits melanoma growth via the inhibition of JAK2/STAT3 pathway, which provides a promising therapeutic strategies of melanoma treatment.

Homology Modeling of Leishmanolysin (gp63) from Leishmania panamensis and Molecular Docking of Flavonoids

Leishmaniasis is a chronic disease caused by protozoa of the distinct Leishmania genus transmitted by sandflies of the genus Phlebotomus (old world) and Lutzomyia (new world). Among the molecular factors that contribute to the virulence and pathogenesis of Leishmania are metalloproteases, e.g., glycoprotein 63 (gp63), also known as leishmanolysin or major surface protease (MSP). This protease is a zinc-dependent metalloprotease that is found on the surface of the parasite, abundant in Leishmania promastigote and amastigote. This study describes the prediction of three-dimensional (3D) structures of leishmanolysin (UniProt ID A0A088RJX7) of Leishmania panamensis employing a homology modeling approach. The 3D structure prediction was performed using the SWISS-MODEL web server. The tools PROCHECK, Molprobyty, and Verify3D were used to check the quality of the model, indicating that they are reliable. Best docking configurations were identified applying AutoDock Vina in PyRx 0.8 to obtain a potential antileishmanial activity. Biflavonoids such as lanaroflavone, podocarpusflavone A, amentoflavone, and podocarpusflavone B showed good scores among these molecules. Lanaroflavone appears to be the most suitable compound from binding affinity calculations.

Bioassay-guided fractionation and identification of wound healing active compound from Pistacia vera L. hull extract

ETHNOPHARMACOLOGICAL RELEVANCE

Pistachio hull has traditionally been used to treat peptic ulcer, hemorrhoids, oral and cutaneous wounds.

AIM OF THE STUDY

On the basis of its traditional uses and previous pharmacological reports, a bioassay guided fractionation procedures on pistachio (Pistacia vera L.) hulls was performed to define the fractions and bioactive compound that are responsible for wound healing activity of hulls.

MATERIAL AND METHODS

A bioassay-guided fractionation of the total extract (MeOH 80%) of Pistacia vera L. hulls was carried out to evaluate wound healing activity by scratch assay on NIH/3T3 murine fibroblast cells. A combination of solvent-solvent partitioning, column chromatography, preparative thin layer chromatography and crystallization were used to obtain fractions/sub-fractions and pure compound. The wound healing potential of isolated compound was examined by fibroblasts migration and proliferation using scratch assay and CFSC dilution assay, respectively. In addition, we evaluated the gene expression of some inflammatory markers which are involved in healing process using Real Time PCR. Chemical structure of active compound was elucidated by spectrometric methods.

RESULTS

Due to the higher wound healing activity of CHCl₃ fraction from P. vera hulls, it was fractionated by successive chromatographic techniques to yield the active compound. 3-Epimasticadienolic acid was isolated and crystallized as a white powder. This active compound (200 μg/ml) significantly increased the fibroblast proliferation and migration, resulting in reduction of the scratch area about 45%. It showed a strong inhibitory effect on gene expression of IL-6 and TNF-α, and a stimulation effect on NF-κB gene expression at the same dose.

CONCLUSION

The present study supported the traditional uses of P. vera hulls for wound-healing and 3-epimasticadienolic acid showed significantly potent on wound repair.

Maytenus macrocarpa (Ruiz & Pav.) Briq.: Phytochemistry and Pharmacological Activity

Maytenus macrocarpa (Celastraceae) is a tree native to Amazonia. Its roots, leaves, bark, and combinations of these are used in traditional medicine mainly to treat rheumatism and, to a lesser extent, to heal wounds and to combat bronchitis and diarrhea. To date, mainly triterpenes and dihydro-β-agarofuran sesquiterpenes were isolated from M. macrocarpa. Extracts and selected pure compounds isolated from the leaves, roots, and stem bark showed antibacterial, antiviral, antiparasitic, anti-inflammatory, and cytotoxic activities in vitro. The aim of this review is to summarize the available ethnobotanical, phytochemical, and pharmacological information about this traditional Amazonian medicinal tree, as well as to attract the attention of phytochemists and pharmacognosists to this potentially interesting source of ethnopharmaceuticals.

Chemical Constituents with Leishmanicidal Activity from a Pink-Yellow Cultivar of Lantana camara var. aculeata (L.) Collected in Central Mexico

Lantana camara (L.) is employed by several ethnical groups to treat numerous diseases. Although there are no ethnomedical reports on its use against leishmaniasis, organic extracts prepared from L. camara were shown to display leishmanicidal activity. In the present study, we carried out a bioassay-guided fractionation of the dichloromethane extract from Mexican L. camara in order to identify the compounds responsible for the leishmanicidal activity. Eighteen chromatographic fractions (FI⁻FXVIII) were evaluated in vitro against Leishmania mexicana and L. amazonensis. FII, FX, FXI, FXV, and FXVI showed significant activity against both Leishmania strains, the most potent of which was FXV. Eicosane (1), squalene (2), β-ionone (3), caryophyllene oxide (4), β-caryophyllene (5), hexanoic acid (6), tiglic acid (7), a mixture of lantanilic (8) and camaric (9) acids, and lantadene B (10) were identified and obtained from the active fractions and evaluated for their leishmanicidal activity. The mixture of lantanilic (8) and camaric (9) acids (79%/21%) was the most potent one (half maximal inhibitory concentration (IC₅₀) = 12.02 ± 0.36 μM). This study indicates that this cultivar of L. camara has high potential for the development of phytomedicines or as a source of natural products, which might represent lead compounds for the design of new drugs against leishmaniasis.

Chemistry and Biology of Selected Mexican Medicinal Plants

Herbal medicines are an integral element of alternative medical care in Mexico, and the best testimony to their efficacy and cultural value is their persistence in contemporary Mexican marketplaces where the highest percentages of medicinal and aromatic plants are sold. This chapter summarizes current trends in research on medicinal plants in Mexico, with emphasis on work carried out at the authors' laboratories. The most relevant phytochemical and pharmacological profiles of a selected group of plants used widely for treating major national health problems are described.From this contribution, it is evident that in the last five decades a significant amount of research on medicinal plants has been performed by Mexican scientists. Such efforts have led to the publication of many research papers in noted peer-reviewed journals and technical books. The isolation and structural characterization of hundreds of bioactive secondary metabolites have been accomplished, and most importantly, these studies have tended to support the ethnomedical uses of many different species. A multidisciplinary approach for investigating these plants has led to an increased emphasis on areas such as phytopharmacology, phytotoxicology, quality control, regulation, and conservation issues for these valuable resources. The medicinal plants analyzed so far have shown a very broad chemical diversity of their constituents, which have a high potential for exhibiting novel mechanistic effects biologically. The chapter shows also that there is need to conduct additional clinical studies on herbal drugs, in particular because the longstanding traditional evidence for their safety is not always sufficient to assure their rational use. There is also need to move to "omics" approaches for investigating the holistic effect and the influence of groups of phytochemicals on the whole organism. Mexican scientists may be expected to have bright prospects in this regard, which will imbue medicinal plant research with a new dynamism in the future.

Vasodilator Activity of Compounds Isolated from Plants Used in Mexican Traditional Medicine

Arterial hypertension is one of the main risk factors in the development of cardiovascular diseases. Therefore, it is important to look for new drugs to treat hypertension. In this study, we carried out the screening of 19 compounds (triterpenes, diterpenes, sesquiterpenes, lignans, and flavonoids) isolated from 10 plants used in Mexican traditional medicine to determine whether they elicited vascular smooth muscle relaxation and, therefore, could represent novel anti-hypertension drug candidates. The vasorelaxant activity of these compounds was evaluated on the isolated rat aorta assay and the results obtained from this evaluation showed that three compounds induced a significant vasodilatory effect: meso-dihydroguaiaretic acid [half maximal effective concentration (EC₅₀), 49.9 ± 11.2 µM; maximum effect (Emax), 99.8 ± 2.7%]; corosolic acid (EC₅₀, 108.9 ± 6.7 µM; Emax, 96.4 ± 4.2%); and 5,8,4′-trihydroxy-3,7-dimethoxyflavone (EC₅₀, 122.3 ± 7.6 µM; Emax, 99.5 ± 5.4%). Subsequently, involvement of the NO/cyclic guanosine monophosphate (cGMP) and H₂S/ATP-sensitive potassium channel (K_ATP) pathways on the vasodilator activity of these compounds was assessed. The results derived from this analysis showed that the activation of both pathways contributes to the vasorelaxant effect of corosolic acid. On the other hand, the vasodilator effect of meso-dihydroguaiaretic acid and 5,8,4′-trihydroxy-3,7-dimethoxyflavone, partly involves stimulation of the NO/cGMP pathway. However, these compounds also showed an important endothelium-independent vasorelaxant effect, whose mechanism of action remains to be clarified. This study indicates that meso-dihydroguaiaretic acid, corosolic acid, and 5,8,4′-trihydroxy-3,7-dimethoxyflavone could be used as lead compounds for the synthesis of new derivatives with a higher potency to be developed as drugs for the prevention and treatment of cardiovascular diseases.

Bauerenol Acetate, the Pentacyclic Triterpenoid from Tabernaemontana longipes, is an Antitrypanosomal Agent

The Latin American plant Tabernaemontana longipes was studied in this work as a potential source of antiparasitic agents. The chloroform extract of T. longipes leaves was separated into several fractions, and tested for antitrypanosomal activity. One of the fractions displayed significant growth inhibitory activity against Trypanosoma brucei. The active principle in the fraction was isolated, purified, and characterized by NMR and mass spectrometry. The antitrypanosomal agent in the CHCl₃ extract of T. longipes leaves is the pentacyclic triterpenoid bauerenol acetate. A metabolite profiling assay suggest that the triterpenoid influences cholesterol metabolism. The molecular target(s) of bauerenol and its acetate, like many other antiparasitic pentacyclic triterpenoids is/are unknown, but they present privileged structural scaffolds that can be explored for structure-based activity optimization studies using phenotypic assays.

Antibacterial activities of medicinal plants used in Mexican traditional medicine

ETHNOPHARMACOLOGICAL RELEVANCE

We provide an extensive summary of the in vitro antibacterial properties of medicinal plants popularly used in Mexico to treat infections, and we discuss the ethnomedical information that has been published for these species.

MATERIALS AND METHODS

We carried out a bibliographic investigation by analyzing local and international peer-reviewed papers selected by consulting internationally accepted scientific databases from 1995 to 2014. We provide specific information about the evaluated plant parts, the type of extracts, the tested bacterial strains, and the inhibitory concentrations for each one of the species. We recorded the ethnomedical information for the active species, as well as their popular names and local distribution. Information about the plant compounds that has been identified is included in the manuscript. This review also incorporates an extensive summary of the available toxicological reports on the recorded species, as well as the worldwide registries of plant patents used for treating bacterial infections. In addition, we provide a list with the top plant species with antibacterial activities in this review RESULTS: We documented the in vitro antibacterial activities of 343 plant species pertaining to 92 botanical families against 72 bacterial species, focusing particularly on Staphylococcus aureus, Mycobacterium tuberculosis, Escherichia coli and Pseudomonas aeruginosa. The plant families Asteraceae, Fabaceae, Lamiaceae and Euphorbiaceae included the largest number of active species. Information related to popular uses reveals that the majority of the plants, in addition to treating infections, are used to treat other conditions. The distribution of Mexican plants extended from those that were reported to grow in just one state to those that grow in all 32 Mexican states. From 75 plant species, 225 compounds were identified. Out of the total plant species, only 140 (40.57%) had at least one report about their toxic effects. From 1994 to July 2014 a total of 11,836 worldwide antibacterial patents prepared from different sources were recorded; only 36 antibacterial patents from plants were registered over the same time period. We offered some insights on the most important findings regarding the antibacterial effects, current state of the art, and research perspectives of top plant species with antibacterial activities in vitro.

CONCLUSIONS

Studies of the antibacterial in vitro activity of medicinal plants popularly used in Mexico to treat infections indicate that both the selection of plant material and the investigation methodologies vary. Standardized experimental procedures as well as in vivo pharmacokinetic studies to document the effectiveness of plant extracts and compounds are necessary. This review presents extensive information about the medicinal plants possessing antibacterial activity that has been scientifically studied and are popularly used in Mexico. We anticipate that this review will be of use for future studies because it constitutes a valuable information tool for selecting the most significant plants and their potential antibacterial properties.

Antiprotozoal Activity of Triazole Derivatives of Dehydroabietic Acid and Oleanolic Acid

Tropical parasitic diseases such as Chagas disease and leishmaniasis are considered a major public health problem affecting hundreds of millions of people worldwide. As the drugs currently used to treat these diseases have several disadvantages and side effects, there is an urgent need for new drugs with better selectivity and less toxicity. Structural modifications of naturally occurring and synthetic compounds using click chemistry have enabled access to derivatives with promising antiparasitic activity. The antiprotozoal activity of the terpenes dehydroabietic acid, dehydroabietinol, oleanolic acid, and 34 synthetic derivatives were evaluated against epimastigote forms of Trypanosoma cruzi and promastigotes of Leishmaniabraziliensis and Leishmania infantum. The cytotoxicity of the compounds was assessed on NCTC-Clone 929 cells. The activity of the compounds was moderate and the antiparasitic effect was associated with the linker length between the diterpene and the triazole in dehydroabietinol derivatives. For the oleanolic acid derivatives, a free carboxylic acid function led to better antiparasitic activity.

A Review on the Phytochemistry, Pharmacology, and Pharmacokinetics of Amentoflavone, a Naturally-Occurring Biflavonoid

Amentoflavone (C30H18O10) is a well-known biflavonoid occurring in many natural plants. This polyphenolic compound has been discovered to have some important bioactivities, including anti-inflammation, anti-oxidation, anti-diabetes, and anti-senescence effects on many important reactions in the cardiovascular and central nervous system, etc. Over 120 plants have been found to contain this bioactive component, such as Selaginellaceae, Cupressaceae, Euphorbiaceae, Podocarpaceae, and Calophyllaceae plant families. This review paper aims to profile amentoflavone on its plant sources, natural derivatives, pharmacology, and pharmacokinetics, and to highlight some existing issues and perspectives in the future.

Antitrypanosomal activity of Verbascum sinaiticum Benth. (Scrophulariaceae) against Trypanosoma congolense isolates

BACKGROUND

African Trypanosomiasis is a neglected tropical disease with a large impact on the livelihood of the rural poor in Sub-Saharan Africa. The available drugs for managing this disease are old, expensive and are facing the problem of drug resistance. Thus, the aim of this study was to evaluate in vivo antitrypanosomal efficacy of aqueous and absolute methanol leaf extracts of Verbascum sinaiticum Benth. against Trypanosoma congolense field isolate.

METHODS

Verbascum sinaiticum (Local name 'qetetina') is a biennial plant, and 60-150 cm tall. It is traditionally used to treat wound, stomachache, viral infection, cancer, sunstroke, fever, abdominal colic, diarrhea, hemorrhage, anthrax, and hepatitis. The efficacy of aqueous and absolute methanol leaf extracts of V. sinaiticum was evaluated in a randomized experiment with Swiss albino mice infected with T. congolense field isolate. The extracts were administered at doses of 100, 200 and 400 mg/kg by intraperitoneal injection for seven days at 12 Days Post-Infection (DPI) when the peak parasitaemia level was approximately 10(8) trypanosomes/ml. Parasitaemia, Packed Cell Volume (PCV), mean survival time and change in body weight were used as indices for monitoring the efficacy of the extracts. Diminazene (28 mg/kg) was used as a positive control while 2 % Tween was used as the negative control. Phytochemicals screening were conducted following standard methods.

RESULTS

The extracts showed no toxicity effect in Swiss albino mice and had LD50 above 2000 mg/kg. The phytochemicals screened in V. sinaiticum were alkaloids, flavonoids, glycoside, saponins, steroids, phenolic compounds, and tannins. The mice treated with absolute methanol leaf extract of V. sinaiticum at 400 mg/kg dose had significantly lower mean parasitaemia (7.20 ± 0.16) (p < 0.001) as compared to the negative control group (8.82 ± 0.12) on day 14 of treatment. Animals treated with the same dose had significant (p < 0.001) higher PCV value and body weight and as well as the highest mean survival time of 40.20 ± 0.31 days as compared to the negative control at the end of the observation period.

CONCLUSION

This study established that Verbascum sinaiticum had trypanocidal activity. The crude extracts have partially eliminated trypanosomes in a dose-dependent manner. The study can be a basis for future in-depth analysis of the biologically active chemicals.

A systematic review of pentacyclic triterpenes and their derivatives as chemotherapeutic agents against tropical parasitic diseases

Parasitic infections are among the leading global public health problems with very high economic and mortality burdens. Unfortunately, the available treatment drugs are beset with side effects and continuous parasite drug resistance is being reported. However, new findings reveal more promising compounds especially of plant origin. Among the promising leads are the pentacyclic triterpenes (PTs) made up of the oleanane, ursane, taraxastane, lupane and hopane types. This paper reviews the literature published from 1985 to date on the in vitro and in vivo anti-parasitic potency of this class of phytochemicals. Of the 191 natural and synthetic PT reported, 85 have shown high anti-parasitic activity against various species belonging to the genera of Plasmodium, Leishmania, Trypanosoma, as well as various genera of Nematoda. Moreover, structural modification especially at carbon 3 (C3) and C27 of the parent backbone of PT has led to improved anti-parasitic activity in some cases and loss of activity in others. The potential of this group of compounds as future alternatives in the treatment of parasitic diseases is discussed. It is hoped that the information presented herein will contribute to the full exploration of this promising group of compounds as possible drugs for parasitic diseases.

Oleanolic acid (OA) as an antileishmanial agent: Biological evaluation and in silico mechanistic insights

Although a worldwide health problem, leishmaniasis is considered a highly neglected disease, lacking efficient and low toxic treatment. The efforts for new drug development are based on alternatives such as new uses for well-known drugs, in silico and synthetic studies and naturally derived compounds. Oleanolic acid (OA) is a pentacyclic triterpenoid widely distributed throughout the Plantae kingdom that displays several pharmacological activities. OA showed potent leishmancidal effects in different Leishmania species, both against promastigotes (IC(50 L. braziliensis) 30.47 ± 6.35 μM; IC(50 L. amazonensis) 40.46 ± 14.21 μM; IC(50 L. infantum) 65.93 ± 15.12 μM) and amastigotes (IC(50 L. braziliensis) 68.75 ± 16.55 μM; IC(50 L. amazonensis) 38.45 ± 12.05 μM; IC(50 L. infantum) 64.08 ± 23.52 μM), with low cytotoxicity against mouse peritoneal macrophages (CC(50) 235.80 ± 36.95 μM). Moreover, in silico studies performed to evaluate OA molecular properties and to elucidate the possible mechanism of action over the Leishmania enzyme sterol 14α-demethylase (CYP51) suggested that OA interacts efficiently with CYP51 and could inhibit the ergosterol synthesis pathway. Collectively, these data indicate that OA is a good candidate as leading compound for the development of a new leishmaniasis treatment.

In vitro activity of the hydroethanolic extract and biflavonoids isolated from Selaginella sellowii on Leishmania (Leishmania) amazonensis

This study is the first phytochemical investigation of Selaginella sellowii and demonstrates the antileishmanial activity of the hydroethanolic extract from this plant (SSHE), as well as of the biflavonoids amentoflavone and robustaflavone, isolated from this species. The effects of these substances were evaluated on intracellular amastigotes of Leishmania (Leishmania) amazonensis, an aetiological agent of American cutaneous leishmaniasis. SSHE was highly active against intracellular amastigotes [the half maximum inhibitory concentration (IC50) = 20.2 µg/mL]. Fractionation of the extract led to the isolation of the two bioflavonoids with the highest activity: amentoflavone, which was about 200 times more active (IC50 = 0.1 μg/mL) and less cytotoxic than SSHE (IC50 = 2.2 and 3 μg/mL, respectively on NIH/3T3 and J774.A1 cells), with a high selectivity index (SI) (22 and 30), robustaflavone, which was also active against L. amazonensis (IC50 = 2.8 µg/mL), but more cytotoxic, with IC50 = 25.5 µg/mL (SI = 9.1) on NIH/3T3 cells and IC50 = 3.1 µg/mL (SI = 1.1) on J774.A1 cells. The production of nitric oxide (NO) was lower in cells treated with amentoflavone (suggesting that NO does not contribute to the leishmanicidal mechanism in this case), while NO release was higher after treatment with robustaflavone. S. sellowii may be a potential source of biflavonoids that could provide promising compounds for the treatment of cutaneous leishmaniasis.

Heterocycle-fused lupane triterpenoids inhibit Leishmania donovani amastigotes

The synthesis of heterocyclic betulin derivatives and their activity against Leishmania donovani are reported.

Natural product based leads to fight against leishmaniasis

The growing incidence of parasitic resistance against generic pentavalent antimonials, specifically for visceral disease in Indian subcontinent, is a serious issue in Leishmania control. Notwithstanding the two treatment alternatives, that is amphotericin B and miltefosine are being effectively used but their high cost and therapeutic complications limit their use in endemic areas. In the absence of a vaccine candidate, identification, and characterization of novel drugs and targets is a major requirement of leishmanial research. This review describes current drug regimens, putative drug targets, numerous natural products that have shown promising antileishmanial activity alongwith some key issues and strategies for future research to control leishmaniasis worldwide.

In vitro antileishmanial, antiplasmodial and cytotoxic activities of a new ventiloquinone and five known triterpenes from Parinari excelsa

CONTEXT

Parinari excelsa Sabine (Chrysobalanaceae) is an indigenous tree from West and Eastern Africa. This tree is used in Ivory Coast as an antimalaria remedy.

OBJECTIVE

The in vitro antiplasmodial and antileishmanial activities of the stem bark, the leaf and the major compounds from the stem bark were investigated.

MATERIALS AND METHODS

The leaves and stem bark from P. excelsa were separately collected, air-dried and powdered. Two extracts (methylene chloride and methanol) were realized for both powders. Every extract was tested for its antiplasmodial and antileishmanial activities. Only the stem bark crude extracts were fractionated by column chromatography and their major components were analyzed by NMR, HRESIMS and IR methods. The compounds were tested for their antiplasmodial and antileishmanial activities.

RESULTS

The comparison of the IC(50) values of the crude extracts were in this order: 3.41 (IC(50) of PeBMc) <4.10 (IC(50) of PeBMc) <4.42 (IC(50) of PeLMe) against P. falciparum and 5.19 (IC(50) of PeBMc) <12.32 (IC(50) of PeBMe) <19.33 (IC(50) of PeLMc) <32.37 (IC(50) of PeLMe) against L. donovani. The stem bark crude extracts were the most active against both parasites. Their fractionation leaded to a new ventiloquinone, five triterpenes and one chlorogenic acid. All these compounds were isolated for the first time from P. excelsa. High activities were observed with (3β)-3-hydroxyolean-12-en-28-oic acid (IC(50) = 8.2 µM) and 3β-hydroxyolean-5,12-dien-28-oic acid (IC(50) = 7.7 µM) against L. donovani. With the antiplasmodial activity, the best activity was observed with 16β-hydroxylupane-1,20(29)-dien-3-one (IC(50) = 28.3 µM).

DISCUSSION AND CONCLUSION

These findings demonstrated that the constituents of P. excelsa stem bark have in vitro antiplasmodial and antileishmanial activities.

Antiplasmodial activity of (I-3,II-3)-biflavonoids and other constituents from Ormocarpum kirkii

Preliminary screening of a series of medicinal plants, traditionally used in Tanzania, showed an IC(50) of 15.6-31.2 microg/ml for the crude extract of the root of Ormocarpum kirkii S. Moore (Papilionaceae) against Plasmodium falciparum. A bioguided isolation was performed in order to isolate the active constituents. Twelve constituents were obtained and identified using NMR and MS data, and optical rotation measurements. The compounds comprised seven (I-3,II-3)-biflavonoids, three (I-3,II-3)-bi-4-phenyldihydrocoumarins, an isoflavanone and a C-glucosylated flavone. Six compounds, liquiritigeninyl-(I-3,II-3)-naringenin, apigeninyl-(I-3,II-3)-naringenin, 7-O-beta-D-glucopyranosylchamaejasmin, (3R,4S,3''R,4''S)-5,5''-di-O-methyldiphysin, 7-O-beta-D-glucopyranosyldiphysin, and 4''-hydroxydiphysolone, were isolated in addition to six known components. The compounds were evaluated for antimicrobial activity in a broad screening panel, including P. falciparum. Seven of these showed antiplasmodial activity; isochamaejasmin being the most active with an IC(50) of 7.3+/-3.8 microM, but the selectivity was rather limited. Thus, these constituents may contribute, at least in part, to the antimalarial use of O. kirkii in traditional medicine.

Antileishmanial activity of indole alkaloids from Aspidosperma ramiflorum

The present study was designated to evaluate the antileishmanial activity of acid and basic fractions that were obtained after acid-basic extraction, from ethanolic 70% crude extract and pure compounds from the stem bark of Aspidosperma ramiflorum. The basic alkaloidal fraction presented a good activity against the extracellular form (promastigotes) of Leishmania (L.) amazonensis (LD(50) value<47 microg/ml). Based on these findings, the basic fraction was fractionated on silica gel column chromatography in a bioassay-guided fractionation affording individual purified ramiflorines A and B. Both ramiflorines A and B showed significant activity against Leishmania (L.) amazonensis (LD(50) values of 16.3+/-1.6 microg/ml and 4.9+/-0.9 microg/ml, respectively). Our results are promising, showing that these compounds are biologically active against Gram-positive bacteria.

Sesquiterpene coumarins from Ferula szowitsiana and in vitro antileishmanial activity of 7-prenyloxycoumarins against promastigotes

Two new sesquiterpene coumarins, named szowitsiacoumarin A (1) and szowitsiacoumarin B (2), and a phenylpropanoid derivative, 2-epihelmanticine (3), together with nine known compounds, auraptene (4), umbelliprenin (5), galbanic acid (6), methyl galbanate (7), farnesiferol B (8), farnesiferol C (9), persicasulfide A (10), beta-sitosterol and stigmasterol were isolated from the roots of Ferula szowitsiana. The structures of these compounds were elucidated by extensive spectroscopic methods including 1D-((1)H and (13)C) and 2D-NMR experiments (DQF-COSY, HSQC, HMBC, and ROESY) as well as HR-MALDI-MS analysis. Since the configuration of 2-epihelmanticine was previously only partly determined, a relative configurational analysis of its four stereocenters was carried out on the basis of the recently reported J-based method. The inhibiting activity of prenylated coumarins, auraptene (4) and umbelliprenin (5), in addition to galbanic acid (6), as major component, and of the Me(2)CO extract of Ferula szowitsiana (Apiaceae) roots has been evaluated against promastigotes of Leishmania major. Umbelliprenin and auraptene showed significant activity with IC(50) values of 4.9microg/ml (13.3microM) and 5.1microg/ml (17.1microM) after 48h incubation, respectively.

Cytotoxic activity and effect on nitric oxide production of tirucallane-type triterpenes

Hexane extract from the bark of Amphipterygium adstringens, as well as its principal constituents, masticadienonic acid and 3alpha-hydroxymasticadienolic acid, inhibited the growth of five human cancer cell lines. Derivatives of, namely 24,25 S-dihydromasticadienonic acid and masticadienolic acid, were also evaluated. The results showed that both and had greater activity than on colon cancer cell lines. The effects of on the production of nitric oxide (NO) from both resting and lipopolysaccharide-activated macrophages were determined. It was found that and caused an increase in NO release from resting macrophages; in lipopolysaccharide-activated macrophages, only and caused an increase in NO production.

Antimicrobial activity of euplotin C, the sesquiterpene taxonomic marker from the marine ciliate Euplotes crassus

Strains of the marine ciliate protist Euplotes crassus produce exclusive terpenoids called euplotins that play an ecological role. Among these derivatives, euplotin C is the main of four secondary metabolites isolated from cultures of this protozoon and represents the sesquiterpene taxonomic marker from E. crassus. Because different terpenoid metabolites of plant origin showed a certain antimicrobial activity, we assessed the compound euplotin C, purified by high-pressure liquid chromatography and solubilized in two solubility enhancers, against the protozoa Leishmania major and Leishmani infantum, the fungus Candida albicans, and nine strains of gram-positive and gram-negative microorganisms. An activity of euplotin C against Leishmania promastigotes was demonstrated (50% lethal doses were 4.6 or 8.1 microg/ml depending on the agent used to solubilize the compound), while the effect was less evident on Candida and nearly absent on bacteria. A nonsignificant cytotoxicity (50% lethal dose, >200 microg/ml) against the J774 cell line was observed. A leishmanicidal activity was also shown by the living, euplotin-producing cells of E. crassus cultured together with promastigotes; this activity increased with time from 10 min to 6 h of incubation. This study provides an initial rationale for the evaluation of euplotin C and other similar natural products as alternative or possibly synergistic compounds for current antiprotozoon chemotherapeutics.

Uncinoside A and B, two new antiviral chromone glycosides from Selaginella uncinata

Five compounds have been isolated from the dried whole plants of Selaginella uncinata, two of them were new chromone glycosides, 5-hydroxy-2,6,8-trimethylchromone 7-O-beta-D-glucopyranoside (uncinoside A) and 5-acetoxyl-2,6,8-trimethylchromone 7-O-beta-D-glucopyranoside (uncinoside B). Their structures were elucidated by spectroscopic methods including one- and two-dimensional NMR techniques. The other three compounds were identified as 8-methyl eugenitol, amentoflavone and hinokiflavone. Uncinoside A and B showed potent antiviral activities against respiratory syncytial virus (RSV) with IC(50) value of 6.9 and 1.3 microg/ml, moderate antiviral activities against parainfluenza type 3 virus (PIV 3) with IC(50) value of 13.8 and 20.8 microg/ml, respectively.

In vitro antitrypanosomal activity of ethnopharmacologically selected Beninese plants

The in vitro antitrypanosomal activity of methylene chloride, methanol and aqueous extracts of the leaves and twigs of five plant species traditionally used in Benin for the treatment of sleeping sickness were evaluated on Trypanosoma brucei brucei and their selectivity was analysed on Leishmania mexicana mexicana and J774 macrophage-like murine cells. The results showed that the four most active extracts had MIC values < or =19 microg/ml (Hymenocardia acida twig and leaf, Strychnos spinosa leaf, Trichilia emetica leaf methylene chloride extracts). All these extracts had a lower activity on L. m. mexicana and J774 cells. Determination of the IC50 values of the methylene chloride leaf extracts on two strains of trypanosomes (T. b. brucei and T. b. rhodesiense) and two mammalian cell lines (L6 and J774 cells) showed that all extracts possessed some antitrypanosomal activity with IC50's ranging from 1.5 to 39 microg/ml. All were also toxic to the mammalian cells, but usually with higher IC50's. The only exception was the S. spinosa methylene chloride leaf extract which had no toxicity on J774 cells. Although tannins have been identified in most of the species studied, they could not be detected in the most active extracts, just as alkaloids. The presence of flavonoids and quinones may at least in part explain the observed activities of some of the active extracts.

Antileishmanial activity of isolated triterpenoids from Pourouma guianensis

The inhibiting activity of triterpenoids isolated from the methanolic extract of Pourouma guianensis (Moraceae) leaves is described for promastigotes and intracellular amastigotes of Leishmania amazonensis. Whereas the fractions containing apigenin, friedelin, epi-friedelinol, arjunolic acid, hyptatic acid B, stigmasterol and sitosterol were of no or relatively low inhibitory activity, fractions containing tormentic acid, 2alpha,3beta-dihydroxyursan-12-en-28-oic acid, 2alpha,3beta-dihydroxyolean-12-en-28-oic acid, oleanolic acid and ursolic acid were very potent in inhibiting promastigote growth at 100 microg/ml. Of the eleven isolated compounds, however, only ursolic acid and oleanolic acid showed high activity against intracellular amastigotes (IC50 value = 27 microg/ml and 11 microg/ml, respectively), which was superior to the control drug Glucantime (IC50 value = 83 microg/ml). The antileishmanial activity of oleanolic acid was directed against the parasite and not due to activation of nitric oxide intermediates by macrophages, but this triterpenoid also significantly inhibited the phagocytic capacity of those cells at concentrations above 40 microg/ml, indicating a cytotoxic effect. These results indicate that Pourouma guianensis contains many triterpenoids and some, such as ursolic and oleanolic acids, may serve as lead compounds for new antileishmanial drugs, but chemical modifications may be necessary to avoid unselective cytotoxicity.

Screening of plant extracts for antiprotozoal and cytotoxic activities

Methanolic and aqueous extracts derived from 43 plant species, selected either from ethnobotanical or chemotaxonomical data, were screened for their antiprotozoal activity against Leishmania donovani and Trypanosoma brucei brucei. The cytotoxic activity against KB cells was also determined. Eight extracts had IC50 values of less than 10 microg/ml against Leishmania donovani. The most active was Triclisia patens with an IC50 value of 1.5 microg/ml against Leishmania donovani. Annona purpurea and Alstonia macrophylla had IC50 values below 10 microg/ml against Trypanosoma brucei brucei. Annona purpurea was the most cytotoxic against KB cells.

Molecular structures and antiviral activities of naturally occurring and modified cassane furanoditerpenoids and friedelane triterpenoids from Caesalpinia minax

Further investigation of the active components of the chloroform fraction of the seeds of Caesalpinia minax led to the isolation of a new cassane furanoditerpenoid, caesalmin H (1), together with two known furanoditerpenoid lactones, caesalmin B (2) and bonducellpin D (3). Reduction of the naturally abundant caesalmin D (9), E (10) and F (11) resulted in three new furanoditerpenoid derivatives 4-6. Phytochemical study of the stem of the same plant and subsequent reduction afforded two friedelane triterpenoids (7-8), which were identified by spectroscopic methods. Compounds 1-2 and 4-8 were corroborated by single crystal X-ray analysis. The factors governing the reduction of cassane furanoditerpenoids and friedelane triterpenoids were investigated by correlating the crystallographic results with density functional theory. The inhibitory activities of 2-8 on the Para3 virus were evaluated by cytopathogenic effects (CPE) reduction assay.

Antiviral amentoflavone from Selaginella sinensis

Amentoflavone and three other flavonoids were isolated from the ethanol extract of Selaginella sinensis. Amentoflavone showed potent antiviral activity against respiratory syncytial virus (RSV), with an IC50 of 5.5 microg/ml. The contents of amentoflavone in nine species of Selaginella were determined by reversed-phase HPLC. S. sinensis showed a higher content of 1.13%.