Synthesis of Marine-Derived 3-Alkylpyridinium Alkaloids with Potent Antiprotozoal Activity

相似文献   

In vitro antileishmanial activity of three saponins isolated from ivy, alpha-hederin, beta-hederin and hederacolchiside A(1), in association with pentamidine and amphotericin B.

The in vitro antileishmanial activity of three saponins isolated from ivy, alpha-hederin, beta-hederin and hederacolchiside A(1), was investigated on parasites of the species Leishmania mexicana, in their promastigote and amastigote forms compared with their toxicity versus human monocytes. The results showed that saponins exhibited a strong antiproliferative activity on all stages of development of the parasite but demonstrated a strong toxicity versus human cells. Association of subtoxic concentrations of saponins with antileishmanial drugs such as pentamidine and amphotericin B demonstrated that saponins could enhance the efficiency of conventional drugs on both the promastigote and the amastigote stages of development of the parasite. The results demonstrated moreover that the action of saponins on promastigote membrane was cumulative with those of amphotericin B.     

Kigelia africana Fruit: Constituents, Bioactivity, and Reflection on Composition Disparities

Objective: Kigelia africana, a tropical tree, which has long been used in African traditional medicine. The objective of the current study has been identifying the constituents of K. africana and verifying its utilities in traditional medicine. Materials and Methods: The methanol extract of K. africana fruits was subjected to chromatographic fractionation utilizing different techniques. The methanol extract together with the isolated compounds were tested for their bioactivities in a series of cell?based assays. Results: The current work led to isolation and characterization of nine constituents including iridoid glycosides, phenylpropanoid derivatives, and a eucommiol derivative. The hexanes extract caused inhibition of the opportunistic yeast; Cryptococcus neoformans Pinh. The chloroform extract exhibited substantial antileishmanial activity of Leishmania donovani. Verminoside (1) showed weak inhibition of the CB1, CB2, and Kappa opioid receptors. Compound 4 exhibited weak inhibition of the Kappa and Mu opioid receptors. The hexanes and the chloroform extracts of K. africana exhibited inhibitory activity against the pathogenic parasite Trypanosoma brucei. The ethyl acetate extract showed the same activity. Conclusions: This is the first report on the isolation of coniferyl 4?O?β?D?glucopyranoside (7), a eucommiol derivative (crescentin IV) (6), and 6?feruloylcatalpol (4) from the genus Kigelia. It is also the first report on the separation of ajugol (2), catalpol (3), and specioside (5) from the fruits of K. africana. Revision of the 1H and 13C?NMR spectra of 6?feruloylcatalop (4) and 6?p?hydroxycinnamoylcatalpol (5, specioside) is described. Further, the results of the in vitro assays corroborate the traditional utility of this plant in medicine.     

Amphotericin B-Gum Arabic Conjugates: Synthesis, Toxicity, Bioavailability, and Activities Against Leishmania and Fungi

Purpose Gum arabic, a branched polysaccharide consisting of more than 90% arabinogalactan having a molecular weight around 250,000 Da is the oldest and best known of all natural gums. The objective of the present investigation was to examine whether amphotericin B (AmB), the polyene antibiotic when conjugated to periodate oxidized gum arabic still retained its anti-fungal and anti-leishmanial activity and to evaluate its toxicity and bioavailability. Methods AmB conjugated to the oxidized polysaccharide through Schiff’s linkages in the unreduced (imine) and reduced (amine) forms were characterized for the drug content, hemolytic potential, molecular mass, in vitro release and were examined for anti-fungal activity against Candida albicans and Cryptococcus neoformans and for anti-leishmanial activity against promastigotes of Leishmania donovani in culture. Toxicity and bioavailability were evaluated by intravenous (i.v) injections of the conjugates in mice and rabbits respectively. Results The conjugates were found to be non-hemolytic and mice withstood a dosage of 20 mg (AmB)/kg body weight of both conjugates. Histological examination of the internal organs of mice showed no lesions in kidney, brain, heart or liver. Estimation of the residual drug in the internal organs 7 days post injection showed that the spleen still retained 8.4 ± 0.53 μg/g of tissue. AmB was found to be released from both conjugates in vitro although the release from the imine conjugate was much faster than from the amine conjugate. The concentrations inhibiting parasite growth by 50% (IC₅₀) values for the imine conjugate against promastigotes of L. donovani LV9 and DD8 strains were 0.37 ± 0.04 and 1.44 ± 0.18 μM respectively. The IC₅₀ values for the amine conjugates were much higher. The minimum inhibitory concentration (MIC) against C. albicans and C. neoformans was in the range of 0.5–0.9 μg/mL for both imino and amino conjugates. The bioavailability of the conjugate in rabbits showed that the imine conjugate maintained a plasma concentration in the range of 20 to 5 μg/mL while for the amine conjugate it was in the range of 17 to 3 μg/mL over 24 h. Conclusions The drug conjugates were stable, non-hemolytic and non-toxic to the internal organs of the animal and showed good anti-fungal and anti-leishmanial activity in vitro. In spite of the large molecular weight of the polysaccharide, AmB from the conjugates showed bioavailability after i.v injection. Since the highest concentration of AmB was found in the spleen after a single injection, these conjugates may have potential in anti-leishmanial therapy. A. J dedicates this paper to Prof. M. S. Valiathan for his 72nd birthday.     

Isolation of antileishmanial sterol from the fruits of Cassia fistula using bioguided fractionation

Natural products represent a rich source of new chemical entities for the development of drugs for neglected diseases. Leishmaniasis still afflicts the poorest populations in the world, with 12 million cases worldwide. This work analysed crude extracts and fractions from the fruits of Cassia fistula against the most dramatic and fatal disease form of leishmaniasis, the visceral form (VL). Hexane extract from the fruits showed significant antileishmanial activity against the promastigote form of Leishmania L. chagasi. The bioguided fractionation resulted in the isolation of a sterol, clerosterol, which was further analysed in different models. Promastigotes presented an inhibitory concentration 50% (IC50) of 10.03 microg/mL and intracellular amastigotes demonstrated high susceptibility, with an IC50 of 18.10 microg/mL. Mammalian cytotoxicity was evaluated and it was demonstrated that clerosterol was 3.6-fold less toxic than the standard drug pentamidine. No antifungal activity of the isolated clerosterol was found. Future studies of the extracted compounds of Cassia fistula could be a useful tool for the development of new therapeutic agents for VL.     

Antileishmanial, antiplasmodial and cytotoxic activities of 12,16-dideoxy aegyptinone B from Zhumeria majdae Rech.f. & Wendelbo

The ethanol extract of Zhumeria majdae showed potent antileishmanial and antiplasmodial activity in vitro. Bioactivity guided fractionation of the extract led to the isolation of 12,16-dideoxy aegyptinone B. This compound exhibited potent in vitro antileishmanial activity with an IC(50) of 0.75 microg/mL and a strong antiplasmodial activity with IC(50) values of 1.3 and 1.4 microg/mL against chloroquine sensitive and resistant strains, respectively. This compound was further found to have mild cytotoxicity towards cancer cell lines.     

The potential antileishmanial activity of some Sudanese medicinal plants

A preliminary examination of the crude methanol extracts of eight plant species collected from Sudan, revealed that only three plant species had a considerable in vitro antileishmanial activity on Leishmania major promastigotes at a concentration < 0.5 µg/mL. The plants Azadirchta indica, Maytenus senegalensis and Eucalyptus globulus gave IC₅₀ values of 11.5, 55 and 78 µg/mL, respectively. Extracts of Pseudocedrela kotscifye and Balanites aegyptiaca had a moderate biological activity, whereas extracts of Sonchous cornatus, Khaya senegalensis and Tamarindus indica failed to exhibit any significant antileishmanial activity against L. major at concentrations <100 µg/mL. Liquid–liquid partitioning of the methanol extracts indicated that fractions of M. senegalensis in dichloromethane and ethyl acetate had the highest antileishmanial activity at 5 µg/mL; IC₅₀ values were 5.01 and 29.7 µg/mL, respectively. Preliminary phytochemical analysis of the dichloromethane fraction revealed terpenoids and traces of phenolic principles but no alkaloid, tannins or flavonoids were detected. As lymphocyte proliferation was inhibited by P. kotscifye and A. indica at higher concentrations (<50 µg/mL) in the presence of phytohaemagglutinin (PHA), M. senegalensis had no significant toxic effect whereas S. cornatus, T. indica and K. senegalensis had a stimulatory impact on lymphocyte cells. Copyright © 1998 John Wiley & Sons, Ltd.     

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

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

Plants as Antileishmanial Agents: Current Scenario

Leishmaniasis is a clinical manifestation caused by the parasites of the genus Leishmania. Plants are reservoirs of bioactive compounds, which are known to be chemically balanced, effective and least injurious as compared with synthetic medicines. The current resistance and the toxic effects of the available drugs have brought the trend to assess the antileishmanial effect of various plant extracts and their purified compound/s, which are summarized in this review. Moreover, it also highlights various traditional remedies used by local healers against leishmaniasis. A systematic cross‐sectional study for antileishmanial activity of natural products was carried out using multiple literature databases. The records retrieved since 2000 till year 2016 were analysed and summarized in the form of comprehensive tables and graphs. Natural products are potential source of new and selective agents that can significantly contribute to primary healthcare and probably are promising substitutes of chemicals for the treatment of protozoan diseases like leishmaniasis. Where the researchers prefer to use alcoholic solvents for the extraction of antileishmanial agents from plants, most of the studies are limited to in vitro conditions majorly on using promastigote forms of Leishmania. Thus, there is a need to carry out such activities in vivo and in host macrophages. Further, there is a need of mechanistic studies that can help taking few of the promising pure compounds to clinical level. Copyright © 2016 John Wiley & Sons, Ltd.     

Effectiveness of Novel 5‐(5‐amino‐1‐aryl‐1H‐pyrazol‐4‐yl)‐1H‐tetrazole Derivatives Against Promastigotes and Amastigotes of Leishmania amazonensis

In this research, a series of substituted 5‐(5‐amino‐1‐aryl‐1H‐pyrazol‐4‐yl)‐1H‐tetrazoles were synthesized and evaluated for in vitro antileishmanial activity. Among the derivatives, examined compounds 3b and 3l exhibited promising activity against promastigotes and amastigotes forms of Leishmania amazonensis. The cytotoxicity of these compounds was evaluated on murine cells, giving access to the corresponding selectivity index (SI).