Andinermals A-C, antiplasmodial constituents from Andira inermis

Fabaceae: a significant flavonoid source for plant and human health

The Fabaceae is recognized as the third largest and one of the most influential families among the flowering plants. Furthermore, its name is linked to “Legumes”, which represent a vast group of angiosperms in the continents utilized as crops, forages, and green manures. It is recognized for diverse constituents, covering both primary metabolites include lectins, chitinases, various proteases, and α-amylase inhibitors, as well as secondary metabolites include flavonoids, alkaloids, terpenoids, tannins, and phenolics. Fabaceae flavonoid plays an important role in the legumes’ adaptability to biological surroundings as defensive agents (phytoalexins) and as chemical signals in a symbiotic relationship with a bacterial species known as rhizobia. Considering their important role in plant defense and benefits to human healthiness, a number of studies on the Fabaceae plant have been performed, namely isolation and screening of the purified compounds and their biological activity. This study outlines specified issues on the chemical structure, biosynthesis, biological activities, and medicinal uses of Fabaceae compounds.

Structural revision of sesbagrandiflorains A and B, and synthesis and biological evaluation of 6-methoxy-2-arylbenzofuran derivatives

Sesbagrandiflorains A (1) and B (2), isolated from the stem bark of the Indonesian fabaceous plant Sesbania grandiflora, were reported to be 6-methoxy-2-(2´,3´-dihydroxy-5´-methoxyphenyl)-1-benzofuran-3-carbaldehyde and 6-hydroxy-2-(2´,3´-dihydroxy-5´-methoxyphenyl)-1-benzofuran-3-carbaldehyde, respectively. However, based on reevaluation of their 1D and 2D NMR data, the chemical structures of 1 and 2 have been revised to 4-hydroxy-2-(4´-hydroxy-2´-methoxyphenyl)-6-methoxybenzofuran-3-carbaldehyde and 4-hydroxy-2-(4´-hydroxy-2´-hydroxyphenyl)-6-methoxybenzofuran-3-carbaldehyde, respectively. In addition, seven new derivatives of 1 have been synthesized from the natural product in good yields (65 - 93%). The chemical structures of the synthetic compounds-one diester (6), four ethers (7-10), one secondary amine (11), and one oxime (12)-were confirmed by MS and NMR analysis. Compound 6 exhibited moderate antibacterial activity against the plant pathogen Rhodococcus fascians with a MIC of 0.1 mg/mL. Compounds 8 and 12 demonstrated respectable cytotoxicity against A375 melanoma cancer cells line with the relative IC₅₀ values of 22.8 and 32.7 μM, respectively.

Structure Characterization and Biological Activity of 2-Arylbenzofurans from an Indonesian Plant, Sesbania grandiflora (L.) Pers

A new 2-arylbenzofuran, sesbagrandiflorain C (1), together with four known compounds, 2-(3,4-dihydroxy-2-methoxyphenyl)-4-hydroxy-6-methoxybenzofuran-3-carbaldehyde (2), 2-(4-hydroxy-2-methoxyphenyl)-5,6-dimethoxybenzofuran-3-carboxaldehyde (3), sesbagrandiflorain A (4) and sesbagrandiflorain B (5), have been isolated from the stem bark of an Indonesian plant, Sesbania grandiflora (L.) Pers. The chemical structure of compound 1 was elucidated by UV, IR, MS, and NMR spectroscopic techniques. The proton and carbon NMR resonances of 1 were also compared with the predicted chemical shifts obtained from DFT quantum mechanical calculations with Gaussian. None of the compounds showed antibacterial activity against Bacillus subtilis, Escherichia coli, Mycobacterium smegmatis, Pseudomonas aeruginosa, and Staphylococcus aureus in an agar diffusion assay. However, sesbagrandiflorains A (4) and B (5) exhibited moderate activity against Mycobacterium tuberculosis H37Rv. In addition, compounds 1 - 5 have moderate cytotoxicity against HeLa, HepG2, and MCF-7 cancer cell lines.

Flavonoids as efficient scaffolds: Recent trends for malaria, leishmaniasis, Chagas disease, and dengue

Endemic in 149 tropical and subtropical countries, neglected tropical diseases (NTDs) affect more than 1 billion people annually with over 500,000 deaths. Among the NTDs, some of the most severe consist of leishmaniasis, Chagas disease, and dengue. The impact of the combined NTDs closely rivals that of malaria. According to the World Health Organization, 216 million cases of malaria were reported in 2016 with 445,000 deaths. Current treatment options are associated with various limitations including widespread drug resistance, severe adverse effects, lengthy treatment duration, unfavorable toxicity profiles, and complicated drug administration procedures. Flavonoids are a class of compounds that has been the subject of considerable scientific interest. New developments of flavonoids have made promising advances for the potential treatment of malaria, leishmaniasis, Chagas disease, and dengue, with less toxicity, high efficacy, and improved bioavailability. This review summarizes the current standings of the use of flavonoids to treat malaria and neglected diseases such as leishmaniasis, Chagas disease, and dengue. Natural and synthetic flavonoids are leading compounds that can be used for developing antiprotozoal and antiviral agents. However, detailed studies on toxicity, pharmacokinetics, and mechanisms of action of these compounds are required to confirm the in vitro pharmacological claims of flavonoids for pharmaceutical applications. HIGHLIGHTS: In the current review, we have tried to compile recent discoveries on natural and synthetic flavonoids as well as their implication in the treatment of malaria, leishmaniasis, Chagas disease, and dengue. A total of 373 (220 natural and 153 synthetic) flavonoids have been evaluated for antimalarial, antileishmanial, antichagasic, and antidengue activities. Most of these flavonoids showed promising results against the above diseases. Reports on molecular modeling of flavonoid compounds to the disease target indicated encouraging results. Flavonoids can be prospected as potential leads for drug development; however, more rigorously designed studies on toxicity and pharmacokinetics, as well as the quantitative structure-activity relationship studies of these compounds, need to be addressed.

Non-nitrogenous Plant-derived Constituents with Antiplasmodial Activity

The paper is a compilation of the studies reported in the literature concerning non-nitrogenous natural constituents that have shown antiplasmodial activity and aims to provide a basis for further in vivo studies as well as for clinical trials to develop new antimalarial agents. Due to the increasingly unsatisfactory outcomes for N-heterocyclic drugs, coupled with the rising incidence of the deadly falciparum malaria, the advent of non-nitrogenous lead compounds is timely, signaling a new era of antimalarial chemotherapy. Currently a few non-nitrogenous molecules are used in therapy, but many promising molecules of plant origin are under study, such as peroxide sesquiterpenes, quinoid triterpenes, quassinoids, gallic acid derivatives, lignans, flavonoids and biflavonoids, xanthones, naphthoquinones and phenylanthraquinones. Many of these constituents are isolated from plants used traditionally to treat malaria and fever. Ethnopharmacology can still be considered as a rich source of lead molecules.

The antiplasmodial and radical scavenging activities of flavonoids of Erythrina burttii

The acetone extract of the root bark of Erythrina burttii showed in vitro antiplasmodial activity against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum with IC(50) values of 0.97 ± 0.2 and 1.73 ± 0.5 μg/ml respectively. The extract also had radical scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical with an EC(50) value of 12.0 μg/ml. The isoflav-3-enes burttinol-A and burttinol-C, and the 2-arylbenzofuran derivative burttinol-D were identified as the most active antiplasmodial (IC(50)<10 μM) and free radical scavenging (EC(50)ca. 10 μM) principles. The acetone extract of E. burttii at 800 mg/kg/day, in a 4-day Plasmodium berghei ANKA suppressive test, showed in vivo antimalarial activity with 52% chemosuppression. In the same in vivo test, marginal activities were also observed for the extracts of the root and stem bark of Erythrina abyssinica and the root bark of Erythrina sacleuxii.

In vitro activity of extract and fractions of natural cocoa powder on Plasmodium falciparum

Several flavonoids isolated from certain plants have demonstrated antiplasmodial activity, after their initial indigenous use in malaria treatment. Cocoa has been found to be a rich food source of flavonoids in comparison with many common foods and beverages. The aim of this work was to investigate the in vitro activity of natural cocoa powder on the growth of Plasmodium falciparum. Prepared crude methanol extract was partitioned successively with petroleum ether, ethyl acetate, chloroform, and butanol. Total flavonoid concentration in the crude methanol extract and fractions was measured by the AlCl(3) colorimetric assay. Direct inhibitory activity of the natural cocoa powder was assessed by culturing extract and fractions with P. falciparum in vitro. Greater antiplasmodial activity was observed in nonpolar solvent fractions (chloroform, ethyl acetate, and petroleum ether) compared with polar solvents. The chloroform fraction was most active, with mean±SEM 50% and 90% inhibition concentrations of 48.3±0.9 and 417±7.8 μg/mL, respectively. The study showed a weak association between total flavonoid concentration and antiplasmodial activity. Early trophozoite (ring-stage) synchronized cultures treated with the chloroform fraction of natural cocoa powder showed a decline in growth. Further reduction in parasitemia was also observed for other erythrocytic stages. These results suggest that natural cocoa powder has measurable direct in vitro inhibitory effect on P. falciparum and support the anecdotal reports of its ability to prevent malaria as a result of regular intake as a beverage.

Antimalarial natural products drug discovery in Panama

CONTEXT

Malaria is still a major public health problem. The biodiversity of the tropics is extremely rich and represents an invaluable source of novel bioactive molecules. For screening of this diversity more sensitive and economical in vitro methods are needed, Flora of Panama has been studied based on ethnomedical uses for discovering antimalarial compounds.

OBJECTIVE

This review aims to provide an overview of in vitro screening methodologies for antimalarial drug discovery and to present results of this effort in Panama during the last quarter century.

METHODS

A literature search in SciFinder and PubMed and original publications of Panamanian scientists was performed to gather all the information on antimalarial drug discovery from the Panamanian flora and in vitro screening methods.

RESULTS AND CONCLUSIONS

A variety of colorimetric, staining, fluorometric, and mass spectrometry and radioactivity-based methods have been provided. The advantages and limitations of these methods are also discussed. Plants used in ethnomedicine for symptoms of malaria by three native Panamanian groups of Amerindians, Kuna, Ngöbe Buglé and Teribes are provided. Seven most active plants with IC(50) values < 10 μg/mL were identified Talisia nervosa Radlk. (Sapindaceae), Topobea parasitica Aubl.(Melastomataceae), Monochaetum myrtoideum Naudin (Melastomataceae), Bourreria spathulata (Miers) Hemsl.(Boraginaceae), Polygonum acuminatum Kunth (Polygonaceae), Clematis campestris A. St.-Hil. (Ranunculaceae) and Terminalia triflora (Griseb.) Lillo (Combretaceae). Thirty bioactive compounds belonging to a variety of chemical classes such as spermine and isoquinoline alkaloids, glycosylflavones, phenylethanoid glycosides, ecdysteroids, quercetin arabinofuranosides, clerodane-type diterpenoids, sipandinolid, galloylquercetin derivatives, gallates, oleamide and mangiferin derivatives.

In vitro antiplasmodial activity of crude extracts of Tetrapleura tetraptera and Copaifera religiosa

Background

Malaria remains a major public health problem, especially in tropical and subtropical regions because of the emergence and widespread of antimalarial drug resistance. Traditional medicine represents one potential source of new treatments. Here, we investigated the in vitro antiplasmodial activity of bark extracts from two Fabaceae species (Tetrapleura tertaptera and Copaifera religiosa) traditionally used to treat malaria symptoms in Haut-Ogooué province, Gabon.

Findings

The antiplasmodial activity of dichloromethane and methanolic extracts was tested on P. falciparum strains FCB (chloroquine-resistant) and 3D7 (chloroquine-sensitive) and on fresh clinical isolates, using the DELI method. Host cell toxicity was analyzed on MRC-5 human diploid embryonic lung cells using the MTT test.

The dichloromethane extracts of the two plants had interesting activity (IC₅₀ between 8.5 ± 4.7 and 13.4 ± 3.6 μg/ml). The methanolic extract of Tetrapleura tetraptera was less active (IC₅₀ around 30 μg/ml) and the methanolic extract of Copaifera religiosa was inactive. The selectivity index (toxicity/antiplasmodial activity) of the dichloromethane extract of Tetrapleura tetraptera was high (around 7), while the dichloromethane extract of Copaifera religiosa had the lowest selectivity (0.6). The mean IC₅₀ values for field isolates were less than 1.5 μg/ml for dichloromethane extracts of both plants, while methanolic extracts of Tetrapleura tetraptera showed interesting activity (IC₅₀ = 13.1 μg/ml). The methanolic extract of Copaifera religiosa was also inactive on field isolates.

Conclusions

Dichloromethane extracts of Tetrapleura tetraptera and Copaifera religiosa, two plants used to treat malaria in Gabon, had interesting antiplasmodial activity in vitro. These data provide a scientific rationale for the traditional use of these plants against malaria symptoms. Bioactivity-guided phytochemical analyses are underway to identify the active compounds.

Ebenfurans IV-VIII from Onobrychis ebenoides: evidence that C-prenylation is the key determinant of the cytotoxicity of 3-formyl-2-arylbenzofurans

Phytochemical investigation of a methanol extract of Onobrychis ebenoides yielded five new 3-formyl-2-arylbenzofurans, namely, ebenfurans IV-VIII (1-5), together with the known compounds ebenfurans I, II (6), and III (7). Only 1 and 7 exhibited growth inhibitory activity against MCF-7 and Ishikawa cells, suggesting that the prenyl moiety at position C-5 is the key determinant of the cytotoxic activity of this group of compounds.

Common dietary flavonoids inhibit the growth of the intraerythrocytic malaria parasite

BACKGROUND

Flavonoids are abundant plant phenolic compounds. More than 6000 have been identified to date, and some have been shown to possess antiparasitic activity. Here we investigate the effects of a range of common dietary flavonoids on the growth of two strains of the human malaria parasite Plasmodium falciparum.

FINDINGS

A chloroquine-sensitive (3D7) and a chloroquine-resistant (7G8) strain of P. falciparum were tested for in vitro susceptibility to a range of individual dietary flavonoids and flavonoid combinations. Parasite susceptibility was measured in 96-well plates over 96 h using a previously described [3H]hypoxanthine incorporation assay. Of the eleven flavonoids tested, eight showed antiplasmodial activity against the 3D7 strain (with IC50 values between 11 and 66 muM), and all showed activity against the 7G8 strain (with IC50 values between 12 and 76 muM). The most active compound against both strains was luteolin, with IC50 values of 11 +/- 1 muM and 12 +/- 1 muM for 3D7 and 7G8, respectively. Luteolin was found to prevent the progression of parasite growth beyond the young trophozoite stage, and did not affect parasite susceptibility to the antimalarial drugs chloroquine or artemisinin. Combining low concentrations of flavonoids was found to produce an apparent additive antiplasmodial effect.

CONCLUSION

Certain common dietary flavonoids inhibit the intraerythrocytic growth of the 3D7 and 7G8 strains of P. falciparum. Flavonoid combinations warrant further investigation as antiplasmodial agents.

Antioxidant 2-phenylbenzofurans and a coumestan from Lespedeza virgata

Two 2-phenylbenzofurans, lespedezavirgatol (1) and lespedezavirgatal (2), and a coumestan, lespedezacoumestan (3), were isolated from the aerial parts of Lespedeza virgata, together with nine known flavonoids. Their structures were determined on the basis of spectroscopic data. The three new compounds showed strong oxygen radical absorbance capacity and potent inhibition toward lipid peroxidation in both plasma and kidney homogenate of renal failure rats.

NMR spectral assignments of a new [C--O--C] isoflavone dimer from Andira surinamensis

The phytochemical investigation of extracts from the branch wood and branch barks of Andira surinamensis yielded a novel isoflavone dimer, 4'-methoxyisoflavone-(7-O-7'')-3''',4'''-methylenedioxyisoflavone (surinamensin), along with the triterpene lupeol and the known isoflavones 5,7-dihydroxy-4'-methoxyisoflavone (biochanin A), 5,4'-dihydroxy-7-methoxyisoflavone (prunetin), 7,3'-dihydroxy-4'-methoxyisoflavone (calycosin), and 5,7,3'-trihydroxy-4'-methoxyisoflavone (pratensein). The structure of the new isoflavone was elucidated by 1D and 2D homonuclear and heteronuclear NMR spectroscopy and by comparison with published data for closely related compounds.

Isoflavonoids of the leguminosae

Isoflavonoids are found predominantly in subfamily Papilionoideae of the Leguminosae. This review describes more than 420 new examples of Leguminosae isoflavonoids, giving details of their source, identification, biological activity, synthesis, and ecological or chemosystematic significance. Other topics addressed include the application of hyphenated analytical techniques to the characterisation of legume-derived isoflavonoids, and advances made in biosynthetic studies. A checklist of new compounds by species is given, and 404 references are cited.

Cytotoxic constituents from Butea superba Roxb

A carpin (3-hydroxy-9-methoxypterocarpan) (Medicarpin) (1) and four isoflavones, 7-hydroxy-4'-methoxy-isoflavone (Formononetin) (2); 7,4'-dimethoxyisoflavone (3); 5,4'-dihydroxy-7-methoxy-isoflavone (Prunetin) (4) and 7-hydroxy-6,4'-dimethoxyisoflavone (5) were isolated from the tuber roots of Butea superba Roxb. Compounds 2 and 4 showed moderate cytotoxic activity on KB cell lines with IC(50) (microM) values of 37.3+/-2.5 and 71.1+/-0.8 and on BC cell lines with IC(50) (microM) values of 32.7+/-1.5 and 47.3+/-0.3, respectively.

Characterization of phenolic compounds in the crude extract of Hedysarum multijugum by high-performance liquid chromatography with electrospray ionization tandem mass spectrometry

The fragmentation behavior of four types of phenolic compounds: coumestans, pterocarpenes, benzofurans and isoflavones, were studied using electrospray ionization multistage mass spectrometry (ESI-MS(n)) (n = 2-5) in negative ion mode. Losses of methyl (15 Da), CO (28 Da), CO(2) (44 Da), isopropyl (43 Da) and isobutenyl (55 Da) were dominating fragmentation patterns. Different positions and numbers of the substituents also led to the different fragmentation behavior. These fragmentation rules were applied for the identification of constituents in methanolic extracts of Hedysarum multijugum, in which 29 compounds were characterized, including nine new compounds. The method established in this study could be applied to the comprehensive quality control of the herb and its formulations. It could also be applied to the biological and pharmacological research of traditional Chinese medicines.

Two new arylbenzofurans from the roots of Hedysarum multijugum

Two new arylbenzofurans, hedysarimbenzofuran A (1) and hedysarimbenzofuran B (2), were isolated from the roots of Hedysarum multijugum. The structures were determined by spectroscopic methods.

Isoflavonoids and other compounds from Psorothamnus arborescens with antiprotozoal activities

Bioactivity-guided fractionation of the root extract of Psorothamnus arborescens yielded the new isoflavone 5,7,3',4'-tetrahydroxy-2'-(3,3-dimethylallyl)isoflavone (1a) and the new 2-arylbenzofuran 2-(2'-hydroxy-4',5'-methylenedioxyphenyl)-6-methoxybenzofuran-3-carbaldehyde (2), together with seven known compounds, including three isoflavones, fremontin (3a), glycyrrhisoflavone (4a), and calycosin (5), two pterocarpans, maackiain (6) and 4-hydroxymaackiain (7), one triterpene, oleanolic acid (8), and one chalcone, isoliquiritigenin (9). In addition, the structure of the isoflavone fremontin was revised using spectroscopic and chemical methods and was assigned the new structure 3a. The isoflavone 1a and the chalcone 9 displayed leishmanicidal activity with IC50 values of 13.0 and 20.7 microM, respectively, against Leishmania donovani axenic amastigotes. Calycosin (5) exhibited selective toxicity against Trypanosoma brucei brucei (IC50 12.7 microM) compared to L. donovani amastigotes and Vero cells (IC50 100 and 159 microM, respectively). These results prompted us to test a small group of structurally related isoflavones for their antitrypanosomal activities. Genistein and 7,3',4'-trihydroxyisoflavone displayed promising activity (IC50 values 4.2 and 7.1 microM, respectively) and selectivity (IC50 versus Vero cells: 32.9 and 135 microM, respectively). These studies suggest that the isoflavone skeleton deserves further investigation as a template for novel antileishmanial and trypanocidal compounds.

Antiplasmodial activity of naphthoquinones and one anthraquinone from Stereospermum kunthianum

A lipophilic extract of the root bark of Stereospermum kunthianum revealed antiplasmodial activity in vitro. Bioassay-guided fractionation led to the isolation of four novel naphthoquinones (sterekunthals A and B, pyranokunthones A and B) and one novel anthraquinone (anthrakunthone) together with the known naphthoquinone pinnatal. The structures of the novel compounds were determined by comprehensive analyses of their 1D and 2D NMR data. The antiplasmodial activities and toxicity against the endothelial cell line ECV-304 of the isolated compounds have been assessed.