Bioguided isolation of antiplasmodial secondary metabolites from Persea americana Mill. (Lauraceae)

The antiplasmodium assay-guided investigation of the roots, stem bark, and leaves of Persea americana Mill. led to the isolation of a new fatty alcohol, perseatriol (1), along with six known compounds (2-7). Their structures were elucidated based on the analysis of their NMR and MS data. All crude extracts and fractions exhibited good antiplasmodial activity on Plasmoduim falciparum 3D7 with IC₅₀ values ranging from 0.76 to 10.5 μg/mL; they also displayed cytotoxicity against HeLa cells with low selectivity indexes (SIs). A preliminary Plasmodium lactate dehydrogenase (pLDH) assay was also performed on the isolated compounds. 9,9'-Di-O-feruloyl-5,5'-dimethoxysecoisolariciresinol (4) turned out to be non-toxic and displayed the best activities on P. falciparum with an IC₅₀ value of 0.05 μM, comparable to the reference drug chloroquine with an IC₅₀ value of 0.03 μM. Furthermore, besides compound 4, this work reports the first isolation of lutein (2) and scopoletin (3) from P. americana. The crude extracts of roots, stem bark, and leaves of P. americana, their fractions and compounds completely suppressed the growth of P. falciparum. The observed activity supports the use of P. americana in folk medicine for the treatment of malaria.

New Metabolites From the Endophytic Fungus Cercophora samala Associated With Mitragyna inermis

Two new natural products, mitrafungidione (1) elucidated as prototrop-isomers of ( R-3-acetyl-5-ethyl-4-hydroxy-5 H-furan-2-one, and maristachone F (2a), elucidated as 5-(1-hydroxyethyl)-4-(hydroxymethyl)-3-methoxy-2-methylphenol, together with 5 known compounds have been isolated from the solid cultures of an endophytic fungus associated with Mitragyna inermis (Rubiaceae) and identified as Cercophora samala. The structures of these compounds were elucidated by detailed spectroscopic analysis and by comparison of their spectroscopic data with those reported in the literature. The absolute configuration of 1 and 2a were determined by extensive DFT calculations.

Antiparasitic Constituents of Beilschmiedia louisii and Beilschmiedia obscura and Some Semisynthetic Derivatives (Lauraceae)

The MeOH/CH₂Cl₂ (1:1) extracts of the roots and leaves of Beilschmiedia louisii and B. obscura showed potent antitrypanosomal activity during preliminary screening on Trypanosoma brucei brucei. Phytochemical investigation of these extracts led to the isolation of a mixture of two new endiandric acid derivatives beilschmiedol B (1) and beilschmiedol C (2), and one new phenylalkene obscurene A (3) together with twelve known compounds (4–15). In addition, four new derivatives (11a–11d) were synthesized from compound 11. Their structures were elucidated based on their NMR and MS data. Compounds 5, 6, and 7 were isolated for the first time from the Beilschmiedia genus. Additionally, the NMR data of compound 4 are given here for the first time. The isolates were evaluated for their antitrypanosomal and antimalarial activities against Tb brucei and the Plasmodium falciparum chloroquine-resistant strain Pf3D7 in vitro, respectively. From the tested compounds, the mixture of new compounds 1 and 2 exhibited the most potent antitrypanosomal activity in vitro with IC₅₀ value of 4.91 μM.

Brevipsidone, a New Depsidone and Other α-Glucosidase Inhibitors from Garcinia Brevipedicellata (Clusiaceae)

Brevipsidone (1), a new depsidone was isolated from the methanol extract of the stem bark of Garcinia brevipedicellata together with known damnacanthal (2), pilloin (3), scopoletin (4). The structure of the new compound was determined by analysis of spectroscopic data. Compounds 1–4 were evaluated for their α-glucosidase inhibition effect and showed significant inhibitory activity.

Compounds from Terminalia mantaly L. (Combretaceae) Stem Bark Exhibit Potent Inhibition against Some Pathogenic Yeasts and Enzymes of Metabolic Significance

Background: Pathogenic yeasts resistance to current drugs emphasizes the need for new, safe, and cost-effective drugs. Also, new inhibitors are needed to control the effects of enzymes that are implicated in metabolic dysfunctions such as cancer, obesity, and epilepsy. Methods: The anti-yeast extract from Terminalia mantaly (Combretaceae) was fractionated and the structures of the isolated compounds established by means of spectroscopic analysis and comparison with literature data. Activity was assessed against Candida albicans, C. parapsilosis and C. krusei using the microdilution method, and against four enzymes of metabolic significance: glucose-6-phosphate dehydrogenase, human erythrocyte carbonic anhydrase I and II, and glutathione S-transferase. Results: Seven compounds, 3,3'-di-O-methylellagic acid 4'-O-α-rhamnopyranoside; 3-O-methylellagic acid; arjungenin or 2,3,19,23-tetrahydroxyolean-12-en-28-oïc acid; arjunglucoside or 2,3,19,23-tetrahydroxyolean-12-en-28-oïc acid glucopyranoside; 2α,3α,24-trihydroxyolean-11,13(18)-dien-28-oïc acid; stigmasterol; and stigmasterol 3-O-β-d-glucopyranoside were isolated from the extract. Among those, 3,3'-di-O-methylellagic acid 4'-O-α-rhamnopyranoside, 3-O-methylellagic acid, and arjunglucoside showed anti-yeast activity comparable to that of reference fluconazole with minimal inhibitory concentrations (MIC) below 32 µg/mL. Besides, Arjunglucoside potently inhibited the tested enzymes with 50% inhibitory concentrations (IC50) below 4 µM and inhibitory constant (Ki) <3 µM. Conclusions: The results achieved indicate that further SAR studies will likely identify potent hit derivatives that should subsequently enter the drug development pipeline.

Purpureone, an antileishmanial ergochrome from the endophytic fungus Purpureocillium lilacinum

The ethyl acetate extracts prepared from the mycelia of three endophytic fungi Purpureocillium lilacinum, Aspergillus sp., and Fusarium sp., isolated from the roots of Rauvolfia macrophylla (Apocynaceae) were screened for their antiprotozoal activity in vitro against Plasmodium falciparum (NF54), Leishmania donovani, Trypanosoma brucei rhodesiense, and Trypanosoma cruzi. Amongst these extracts, the one from P. lilacinum showed potent antileishmanial activity against L. donovani (IC50 value of 0.174 μg mL−1) with good selectivity (SI=94.9) toward the L6 cell line, whereas the other extracts were inactive and not selective. The fractionation and purification of the active extract from P. lilacinum by column chromatography over silica gel yielded a new ergochromone derivative (1), together with six known compounds: (22E,24R)-stigmasta-5,7,22-trien-3-β-ol (2), (22E,24R)-stigmasta-4,6,8(14),22-tetraen-3-one (3), emodin (4), chrysophanol (5), aloe-emodin (6), and palmitic acid, whose structures were elucidated spectroscopically. Compound 1 was tested in vitro for its antiparasitic activities against the above listed parasites and for its antimicrobial activity against Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Escherichia coli, Providencia stuartii, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The compound displayed potent antileishmanial activity against L. donovani with an IC50 value of 0.63 μg mL−1 (0.87 μm) with good selectivity (SI=49.5) toward the L6 cell line. It also exhibited good antibacterial activity against three of the tested microbial strains B. cereus, E. coli ATCC879, and P. stuartii ATCC29916 with minimum inhibitory concentrations below 62.6 μg mL−1. Compound 1 is thus a promising active compound that could be investigated for antileishmanial and antimicrobial drug development.

Salaterpene E, a eudesmane-type sesquiterpene from Salacia longipes var. camerunensis

A mixture of two compounds with potent antiplasmodial activity in vitro against the W2 strain of Plasmodium falciparum (half maximal inhibitory concentration, 1.12 μg/mL) was obtained in a previous investigation of the CH2Cl2-MeOH extract of the seeds of Salacia longipes var. camerunensis. Separation by column chromatography led now to the isolation of salaterpene E (1) and (1R,2R,4S,5S,6R,7R,9S,10R)-2-acetoxy-1,6,9-tribenzoyloxy-4-hydroxy-dihydro-β-agarofuran (2). The structure of 1 was elucidated by spectroscopic analysis, and its absolute configuration was established unambiguously by means of single-crystal X-ray diffraction. Also the absolute configurations of the recently described salaterpenes A (2a) and D (2b) were determined by this method using the anomalous scattering of the oxygen atoms only.

In vitro antimicrobial and anti-proliferative activities of plant extracts from Spathodea campanulata, Ficus bubu, and Carica papaya

CONTEXT

African medicinal plants represent a prominent source of new active substances. In this context, three plants were selected for biological investigations based on their traditional uses.

OBJECTIVE

The antimicrobial and anti-proliferative features of three plants used for medicinal purpose were evaluated.

MATERIALS AND METHODS

The antimicrobial activities of methanol extracts of Ficus bubu Warb. (Moraceae) stem bark and leaves, of Spathodea campanulata P. Beauv. (Bignoniaceae) flowers, as well as those of Carica papaya Linn. (Caricaceae) latex, were determined using the microbroth dilution method against a set of bacteria and fungi pathogens including: Enterococcus faecalis, Staphylococcus aureus, S. saprophyticus, S. epidermididis, Escherichia coli, Klebsiella pneumonia, Salmonella typhimurium, Candida albicans, and Trichophyton rubrum. The tested concentrations of extracts ranged from 2500.0 to 2.4 μg/mL and MIC values were evaluated after 24 h incubation at 37 °C. Subsequently, MTT assay was used to estimate anti-proliferative activity of these methanol extracts and of F. bubu latex on three human cancer cell lines (U373 glioblastoma, A549 NSCLC, and SKMEL-28 melanoma).

RESULTS

The methanol extract of F. bubu stem bark exhibited the highest antimicrobial activity against C. albicans with a MIC value of 9.8 μg/mL, while the F. bubu latex and the methanol extract of F. bubu leaves induced significant anti-proliferative activity against lung (IC50 values of 10 and 14 μg/mL, respectively) and glioma (IC50 values of 13 and 16 μg/mL, respectively) cancer cells.

CONCLUSION

These results indicate that effective drugs could be derived from the three studied plants.

Naucleactonin D, an Indole Alkaloid and other Chemical Constituents from Roots and Fruits of Mitragyna inermis

Phytochemical investigation of the roots and fruits of Mitragyna inermis (Rubiaceae) resulted in the isolation of a new indole alkaloid, named naucleactonin D (1), together with fourteen known compounds: nauclefiline (2), naucleficine (3), nauclefidine (4), angustoline (5), angustine (6), barbinervic acid (7), quinovic acid 3-O-a-L-rhamnopyranoside (8), betulinic acid (9), a mixture of ursolic (10) and oleanolic acid (11), a mixture of stigmasterol and b-sitosterol, b-sitosterol 3-O- b-D-glucopyranoside, and strictosamide (12) as the major compound. The structures of the isolated compounds were elucidated by detailed spectroscopic analysis and by comparison with published data. No 13C NMR data for 2 and 3 exist in the literature and compounds 2, 3, 5, 7, and 12 are reported for the first time from the genus Mitragyna. The crude extract and isolated compounds were tested in vitro for their preliminary cytotoxicity against brine shrimps (Artemia salina).

Antibacterial Ellagic Acid Derivatives and Other Constituents from Pancovia pedicellaris

Two new ellagic acid derivatives, named panconosides A (1) andB(2) were isolated from Pancovia pedicellaris together with eleven known compounds (3 - 13). The structures of 1 and 2, as well as those of the known compounds were established by spectroscopic methods and by comparison with previously reported data. Compounds 1 and 2 were tested in vitro for their antibacterial potential against six strains of microorganisms: Micrococcus luteus, Streptococcus ferus, Streptococcus minor, Escherichia coli, Bacillus subtilis, and Pseudomonas agarici. They were found to exhibit moderate antibacterial activity against all the tested strains compared to standard drugs.

Salacetal, an Oleanane-type Triterpene from Salacia longipes var. camerunensis

Phytochemical investigation of the roots of Salacia longipes var. camerunensis led to the isolation of a new triterpenoid, salacetal (1), together with the known compounds mangiferin, 2-hydroxy- 3-oxo-D:A-friedooleanan-29-oic acid, β -sitosterol, and stigmasterol. The structure of the new compound as well as those of the known compounds were established by means of spectroscopic methods and by comparison with reported data.

Antimalarial Compounds from the Stem Bark of Vismia laurentii

A phytochemical study of the stem bark of Vismia laurentii resulted in the isolation of a tetracyclic triterpene, tirucalla-7,24-dien-3-one (1), and seven other known compounds: 3-geranyloxyemodin (2), vismiaquinone A (3), vismiaquinone B (4), bivismiaquinone (5), epifriedelinol (6), betulinic acid (7) and stigmasta-7,22-dien-3-ol (8). The structure of all these compounds was elucidated by spectroscopic means. The stem bark extract and compounds 1 and 3 showed good antimalarial activity against the W2 strain of Plasmodium falciparum.

Procerenone: a Fatty Acid Triterpenoid from the Fruit Pericarp of Omphalocarpum procerum (Sapotaceae)

Phytochemical investigation of a dichloromethane-methanol (1:1) extract of the fruit pericarp of Omphalocarpum procerum which exhibited antiplasmodial activity during preliminary screening led to the isolation of the new fatty ester triterpenoid 3β-hexadecanoyloxy-28-hydroxyolean-12-en-11-one (1), together with five known compounds 2-6. The structure of the new compound as well as those of the known compounds was established by means of spectroscopic methods and by comparison with previously reported data. Compounds 1- 4 were evaluated in-vitro for their cytotoxicity against L6 cell lines and antiprotozoal activities against Plasmodium falciparum, Leishmania donovani, Trypanosoma brucei rhodesiense and Trypanosoma cruzi (species responsible for human malaria, visceral leishmaniasis, African trypanosomiasis and Chagas disease, respectively). The tested compounds showed weak to moderate antiprotozoal activity and, no significant effect was detected regarding their cytotoxic potency.

Antiplasmodial sesquiterpenes from the seeds of Salacia longipes var. camerunensis

Phytochemical investigation of the seeds of Salacia longipes var. camerunensis led to the isolation of four sesquiterpenoid derivatives, salaterpene A (1) (1α,2β,8β-triacetoxy-6β,9β-dibenzoyloxy-4β-hydroxy-dihydro-β-agarofuran), salaterpene B (2) (1α,2β,8β-triacetoxy-9β-benzoyloxy-6β-cinnamoyloxy-4β-hydroxy-dihydro-β-agarofuran), salaterpene C (3) (1α,2β-diacetoxy-6β,9β-dibenzoyloxy-4β-hydroxy-dihydro-β-agarofuran) and salaterpene D (4) (2β-acetoxy-1α,6β-dibenzoyloxy-4β-hydroxy-9β-nicotinoyloxy-dihydro-β-agarofuran) together with two known compounds (5 and 6). The structures of the compounds were established by means of NMR spectroscopy. Compounds 1-4 and 6 were tested in vitro for their antiplasmodial activity against Plasmodium falciparum chloroquine-resistant strain W2. All the tested compounds exhibited a moderate potency with IC50 below 2.7 μM.

Chemical constituents from Glyphaea brevis and Monodora myristica: chemotaxonomic significance

A chemical investigation of the Glyphaea brevis leaves and of the Monodora myristica fruits led to the identification of thirteen compounds, seven linear long-chain aliphatic compounds, 1, 2, 4, 6, and 9-11, three steroids, 3a, 3b, and 7, two triterpenes, 5a and 5b, and one polyol, 8. The compounds 2 and 8, previously mentioned in the literature, are here characterized by their complete (1)H- and (13)C-NMR assignments. This is the first report of a full NMR assignment for linear fatty acid esters of aliphatic primary alcohols and for meso-erythritol. Compound 5b and 8 were isolated for the first time from plant extracts of the Tiliaceae family, and compounds 9-11 from the Annonaceae plant family. Our results constitute the basis for further chemotaxonomic studies on the two species.

Ceramide, cerebroside and triterpenoid saponin from the bark of aerial roots of Ficus elastica (Moraceae)

Three compounds, ficusamide (1), ficusoside (2) and elasticoside (3), were isolated from the bark of aerial roots of Ficus elastica (Moraceae), together with nine known compounds, including four triterpenes, three steroids and two aliphatic linear alcohols. The chemical structures of the three compounds were established by extensive 1D and 2D NMR spectroscopy, mass spectrometry and by comparison with published data. The growth inhibitory effect of the crude extract and isolated compounds was evaluated against several microorganisms and fungi. The cytotoxicity against human cancer cell lines was also assessed. Ficusamide (1) displayed a moderate in vitro growth inhibitory activity against the human A549 lung cancer cell line and a strong activity against Staphylococcus saprophyticus, while elasticoside (3) showed a potent activity on Enterococcus faecalis.

Obscurine: A New Cyclostachine Acid Derivative from Beilschmiedia obscura

From the methylene chloride extract of the stem bark of Beilschmiedia obscura, a new cyclostachine derivative, obscurine (1), has been isolated, together with six known compounds. The structure of compound 1 was established by spectroscopic methods, including 1- and 2-dimensional NMR techniques.

Obscurine: a new cyclostachine acid derivative from Beilschmiedia obscura

From the methylene chloride extract of the stem bark of Beilschmiedia obscura, a new cyclostachine derivative, obscurine (1), has been isolated, together with six known compounds. The structure of compound 1 was established by spectroscopic methods, including 1- and 2-dimensional NMR techniques.

Isoflavone dimers and other bioactive constituents from the figs of Ficus mucuso

Phytochemical investigation of the figs of Ficus mucuso led to the isolation of three new isoflavone dimer derivatives, mucusisoflavones A-C (1-3), together with 16 known compounds. Some of the isolates were tested in vitro for their inhibitory properties toward β-glucuronidase and Plasmodium falciparum enoyl-ACP reductase (PfENR) enzymes. Compound 1 (IC₅₀) 0.68 μM) showed inhibitory activity on β-glucuronidase enzyme, while 3 (IC₅₀) 7.69 μM) exhibited a weak inhibitory activity against P. falciparum enoyl-ACP reductase (PfENR).

Potent antiplasmodial extracts from Cameroonian Annonaceae

AIM OF THE STUDY

In a search for new antimalarial leads, we have carried out a preliminary ethnopharmacological study with the aim of evaluating the in vitro antiplasmodial activity of extracts from thirteen Annonaceae species growing in Cameroon, and of assessing the acute toxicity of promising fractions in Swiss albino mice.

MATERIALS AND METHODS

Plants were selected on the basis of an ethnobotanical survey carried out in four sites in centre and south regions of Cameroon (Yaoundé neighbourhoods, Kon-Yambetta, Ngobayang and Mbalmayo) on Annonaceae plants locally used to treat malaria and related symptoms. The choice of the sites was mainly based on environmental factors enabling mosquito breeding, cosmopolitan areas regrouping people from different cultural origins, areas with limited access to health centers, and areas with people relying exclusively on traditional medical practices. Collected materials were extracted by maceration in 95% ethanol. The crude extract was partitioned using organic solvents and the fractions afforded were evaluated for antiplasmodial activity in culture against the W2 strain of Plasmodium falciparum. Promising fractions (methanol fractions) were assessed for their acute toxicity in Swiss albino mice.

RESULTS

From the results achieved, 37 (31.3%) out of 118 extracts tested exhibited antiplasmodial activity, with IC(50) values ranging from 1.07 μg/ml to 9.03 μg/ml. Of the active extracts, 29 (78.4%) were methanol fractions, 21 (72.4%) of which inhibited the parasites with IC(50)<5 μg/ml. The promising fractions proved to be safe through oral administration in mice.

CONCLUSIONS

The activities and toxicity profiles of methanol fractions indicate that they deserve to be further investigated in detail for antimalarial lead discovery.

Antiplasmodial constituents from the fruit pericarp of Pentadesma butyracea

Bioassay-guided fractionation of the fruit pericarp of Pentadesma butyracea, using the antiplasmodial test, led to the isolation of a new xanthone, named pentadexanthone (1), together with six known compounds: cratoxylone (2), α-mangostin (3), 1,3,5-trihydroxy-2-methoxyxanthone (4), garcinone E (5), (-)-epicathechin (6), and lupeol (7). The structure of 1 was elucidated by spectroscopic data analysis. An antiplasmodial assay was performed with the isolates, in which compounds 1- 3 and 5 exhibited potent activity in vitro against Plasmodium falciparum chloroquine-resistant strain W2, with IC₅₀ values below 3 µM.

Antiprotozoal activities of some constituents of Markhamia tomentosa (Bignoniaceae)

Phytochemical investigation of an ethyl-acetate extract of the stem bark of Markhamia tomentosa (Bignoniaceae), which had good antimalarial activity in vitro, resulted in the isolation of eight known compounds: 2-acetylnaphtho[2,3-b]furan-4,9-dione (1), 2-acetyl-6-methoxynaphtho[2,3-b]furan-4,9-dione (2), oleanolic acid (3), pomolic acid (4), 3-acetylpomolic acid (5), tormentic acid (6), beta-sitosterol (7) and beta-sitosterol-3-O-beta-D-glucopyranoside (8). The structures of these compounds were established by spectroscopic methods. Each of compounds 1, 2, 4 and 5 was evaluated in vitro for its antiprotozoal activities against the ring stages of two chloroquine-resistant strains of Plasmodium falciparum (K1 and W2), the amastigotes of Leishmania donovani, and the bloodstream trypomastigotes of Trypanosoma brucei rhodesiense (the species responsible for human malaria, visceral leishmaniasis and African trypanosomiasis, respectively). Although compounds 1 and 2 exhibited potent antiprotozoal activities, they also showed high toxicity against a mammalian (L-6) cell line.

In vitro antimicrobial activity of extracts and compounds of some selected medicinal plants from Cameroon

AIM OF THE STUDY

Seven extracts and eight compounds from four selected Cameroonian medicinal plants, Solanecio mannii Hook f. (Asteraceae), Monodora myristica Dunal (Annonaceae), Albizia gummifera (J.F. Gmel) C.A. Smith (Fabaceae/Mimosoideae) and Glyphaea brevis (Spreng) Monachino (Tiliaceae), traditionally used for the treatment of hepatitis, parasites and other infectious diseases, were tested in vitro for their antimicrobial activity against Gram-positive (5 species) and Gram-negative (4 species) bacteria species and pathogenic yeasts (2 Candida species), to establish whether or not they have antimicrobial activity and to validate scientifically their use in traditional medicine.

MATERIALS AND METHODS

The agar disc diffusion and the microbroth dilution methods were used to determine the zone of inhibition between the edge of the filter paper and the edge of the inhibition area (IZ) and the minimal inhibitory concentration (MIC) respectively.

RESULTS

The most active extracts against Candida albicans and Candida krusei were respectively the cyclohexane extract from the fruits of Monodora myristica and the ethyl acetate extract from the stem bark of Albizia gummifera (MIC=6.3 microg/ml for both extracts). The lowest MIC value (1.6 microg/ml) for purified compounds was obtained on Candida albicans with a mixture of linear aliphatic primary alcohols (n-C24H50O to n-C30H62O), with n-hexacosanol (1b) as major compound and mixture of fatty acid esters of diunsaturated linear 1,2-diols (6).

CONCLUSION

These results afford ground informations for the potential use of the crude extracts of these species as well as of some of the isolated compounds in bacterial and fungal infections.

Two new antimicrobial dimeric compounds: febrifuquinone, a vismione-anthraquinone coupled pigment and adamabianthrone, from two Psorospermum species

Febrifuquinone (1), a new vismione-anthraquinone coupled pigment and a new bianthrone named adamabianthrone (2), were isolated respectively, from the roots of Psorospermum febrifugum and from the bark of Psorospermum adamauense along with eight known compounds including: two bianthrones [(bianthrone A(1) (3) and bianthrone A(2b)], one vismione [(vismione D (4)], one anthrone (3-geranyloxyemodin anthrone) and four anthraquinones [(1,8-dihydroxy-3-isoprenyloxy-6-methylanthraquinone, emodin (5), 3-geranyloxy-1,8-dihydroxy-6-methylanthraquinone and 2-geranyl-1,8-dihydroxy-6-methylanthraquinone]. Their structures were determined using modern spectroscopic methods including one and two dimensional-NMR techniques as well as MS. Compounds 1 and 2 showed significant antimicrobial activities against a wide range of bacteria and fungi.

Bioactive constituents of the stem bark of Beilschmiedia zenkeri

Phytochemical investigation of the stem bark of Beilschmiedia zenkeri led to the isolation of four new methoxylated flavonoid derivatives, (2S,4R)-5,6,7-trimethoxyflavan-4-ol (1), (2S,4R)-4,5,6,7-tetramethoxyflavan (2), beilschmieflavonoid A (3), and beilschmieflavonoid B (4), together with seven known compounds. The structures of 1-4 were established by spectroscopic methods, and their relative configurations confirmed by X-ray crystallographic and CD analysis. The isolated compounds were evaluated in vitro for their antibacterial activity against three strains of bacteria, Pseudomonas agarici, Bacillus subtilis, and Streptococcus minor, and for their antiplasmodial activity against Plasmodium falciparum, chloroquine-resistant strain W2.

Antiplasmodial activity of extracts from seven medicinal plants used in malaria treatment in Cameroon

AIM OF THE STUDY

In a search for new plant-derived biologically active compounds against malaria parasites, we have carried out an ethnopharmacological study to evaluate the susceptibility of cultured Plasmodium falciparum to extracts and fractions from seven Cameroonian medicinal plants used in malaria treatment. We have also explored the inhibition of the Plasmodium falciparum cysteine protease Falcipain-2.

MATERIALS AND METHODS

Plant materials were extracted by maceration in organic solvents, and subsequently partitioned or fractionated to afford test fractions. The susceptibility of erythrocytes and the W2 strain of Plasmodium falciparum to plant extracts was evaluated in culture. In addition, the ability of annonaceous extracts to inhibit recombinant cysteine protease Falcipain-2 was also assessed.

RESULTS AND DISCUSSION

The extracts showed no toxicity against erythrocytes. The majority of plant extracts were highly active against Plasmodium falciparumin vitro, with IC(50) values lower than 5 microg/ml. Annonaceous extracts (acetogenin-rich fractions and interface precipitates) exhibited the highest potency. Some of these extracts exhibited modest inhibition of Falcipain-2.

CONCLUSION

These results support continued investigation of components of traditional medicines as potential new antimalarial agents.

Cytotoxic and antiplasmodial xanthones from Pentadesma butyracea

Four new xanthones, butyraxanthones A-D (1-4), were isolated from the stem bark of Pentadesma butyracea, together with six known xanthones (5-10) and a triterpenoid (lupeol). The structures of 1-4 were established by spectroscopic methods. Compounds 1-10 were tested in vitro for antiplasmodial activity against a Plasmodium falciparum chloroquine-resistant strain and for cytotoxicity against a human breast cancer cell line (MCF-7). Nearly all of these xanthones exhibited good antiplasmodial activity, and some of them also demonstrated potent cytotoxicity.

Spathoside, a cerebroside and other antibacterial constituents of the stem bark of Spathodea campanulata

Spathoside, a new cerebroside was isolated from the stem bark of Spathodea campanulata, besides known compounds (n-alkanes, linear aliphatic alcohols, sitosterol and their esters, beta-sitosterol-3-O-beta-D-glucopyranoside, oleanolic acid, pomolic acid, p-hydroxybenzoic acid and phenylethanol esters). The structures of the isolated compounds were established by spectroscopic studies. The antibacterial activity of the isolated compounds against a wide range of microorganisms was examined. They inhibited significantly the growth of some gram-positive and -negative bacteria.

Bioactive aristolactams from Piper umbellatum

Four alkaloids named piperumbellactams A-D (1-4) were isolated from branches of Piper umbellatum together with known N-hydroxyaristolam II (5), N-p-coumaroyl tyramine (6), 4-nerolidylcatechol (7), N-trans-feruloyltyramine, E-3-(3,4-dihydroxyphenyl)-N-2-[4-hydroxyphenylethyl]-2-propenamide, beta-amyrin, friedelin, apigenin 8-C-neohesperidoside, acacetin 6-C-beta-d-glucopyranoside, beta-sitosterol, its 3-O-beta-d-glucopyranoside and its 3-O-beta-d-[6'-dodecanoyl]-glucopyranoside. Glycosidase inhibition, antioxidant and antifungal activities of these compounds were evaluated. Compounds 1-3 showed moderate alpha-glucosidase enzyme inhibition with IC50 values 98.07+/-0.44, 43.80+/-0.56 and 29.64+/-0.46, respectively. In DPPH radical scavenging assay, compounds 2, 3 and 6 showed potent inhibitory activity while compounds 4, 5 and 7 showed potent antifungal activity.

Anthraquinones from the fruits of Vismia laurentii

Phytochemical study of the fruits of Vismia laurentii resulted in the isolation of five structurally related compounds. Three of them are constituents, namely, laurentiquinone A (1) (methyl 1,6,8-trihydroxy-3-methyl-7-(3-methylbut-2-enyl)-9,10-dioxo-9,10-dihydroanthracene-2-carboxylate), laurentiquinone B (2) (methyl 5,7-dihydroxy-2,2,9-trimethyl-6,11-dioxo-6,11-dihydro-2H-anthra[2,3-b]pyran-8-carboxylate) and laurentiquinone C (3) (methyl 9-(ethanoyloxymethyl)-5,7-dihydroxy-2,2-dimethyl-6,11-dioxo-6,11-dihydro-2H-anthra[2,3-b]pyran-8-carboxylate) and two are known compounds, emodin (4) and isoxanthorin (5). Their structures were elucidated by spectroscopic means. Crude extracts of hexane and EtOAc showed anti-plasmodial activity against the W2 strain of Plasmodium falciparum.

Anthraquinones from the stem bark of Stereospermum zenkeri with antimicrobial activity

Two anthraquinones, zenkequinones A and B were isolated from the stem bark of Stereospermum zenkeri together with known sterequinone-F, p-coumaric acid, sitosterol-3-O-beta-D-glucopyranoside and 3beta-hydroxyolean-12-en-28-O-beta-D-glucopyranoside. Their structures were established by spectroscopic methods. The antimicrobial activity of the isolated compounds was evaluated against six multiresistant strains of pathogens. Zenkequinone B showed the best antibacterial activity (MIC 9.50 microg/ml) against gram-negative Pseudomonas aeruginosa.

In vitro antiprotozoal activities and cytotoxicity of some selected Cameroonian medicinal plants

Eight extracts from seven selected Cameroonian medicinal plants, traditionally used to treat malaria and other protozoal diseases, were tested in vitro for their antiprotozoal activities against Plasmodium falciparum K1 chloroquine-resistant strain, Leishmania donovani, Trypanosoma cruzi and Trypanosoma brucei rhodesiense, protozoa responsible for malaria, visceral leishmaniasis, Chagas disease and African trypanosomiasis, respectively. The most active extract against Plasmodium falciparum K1 strain and Trypanosoma brucei rhodesiense was the methanolic extract of Albizia zygia (Fabaceae) stem bark with IC(50) values of 1.0 microg/ml and 0.2 microg/ml, respectively. Five extracts showed IC(50) values below 5mug/ml against Leishmania donovani, with the methanolic seed extract of Harungana madagascarensis showing the highest activity, but only the methanolic extract of Albizia zygia showed activity against Trypanosoma cruzi. Cytotoxicity and selectivity indexes were estimated for the most active extracts. The best ratio of cytotoxicity to antiplasmodial activity (SI(a)=14) was established for the methanolic leaf extract of Symphonia globulifera (Clusiaceae), while the methanolic stem bark extract of Albizia zygia showed the best ratio of cytotoxicity to antitrypanosomal activity (SI(b)=22.5).

Anti-plasmodial Activity of Some Constituents of the Root Bark of Harungana madagascariensis LAM. (Hypericaceae)

Bazouanthrone (1), a new anthrone derivative, has been isolated from the root bark of Harungana madagascariensis, together with known compounds, feruginin A (2), harunganin (3), harunganol A (4), harunganol B (5), friedelan-3-one (6) and betulinic acid (7). The structure of the compound (1) was assigned as 3,5,8,9-tetrahydroxy-2,4,4-tri-(3,3-dimethylallyl)-6-methyl-1-(4H)-anthracenone, by means of spectroscopic analysis. The anti-plasmodial activity of the isolated compounds was evaluated in culture against W2 strain of Plasmodium falciparum. All the compounds were found to be active against the Plasmodium parasites with bazouanthrone (1) showing particular potency (IC50=1.80 microM).