Gold-Catalyzed Access to Isophosphinoline 2-Oxides

Gold(I)-catalyzed reactions of electron-poor alkynes are still a challenging process. A straightforward synthesis of phosphorus-based heterocycles, namely, 2-phenyl 1H-isophosphinoline 2-oxides 1, is reported. The reaction used PPh₃AuCl precatalyst in combination with triflic acid under microwave activation and afforded isophosphinoline 2-oxides 1 in moderate to quantitative yields through a fully regioselective 6-endo-dig hydroarylation cyclization, paving the way toward an effective synthesis of phosphorus heterocycles.

A new dibenzofuran derivative from the stem bark of Scyphocephalium ochocoa with anti-inflammatory and cytotoxic activities

The phytochemical investigation of the dichloromethane/methanol (1:1) extract of the stem bark of Scyphocephalium ochocoa, led to the isolation of one new dibenzofuran derivative, named scyphocephalione A (1), along with three other compounds, including epicatechin (2), gentisic acid (3) and myo-inositol (4). The structures of all the compounds were established with help of spectroscopic data including IR, UV, MS, 1 D- and 2 D-NMR, as well as by comparison with previously reported data in literature, and chemical modification. All the compounds were obtained from the genus Scyphocephalium for the first time. The anti-inflammatory activity (using chemiluminescence technique) of the crude extract and compound 1, together with NO inhibition (using ELISA), TNF-α (using ELISA) and MCF-7 cells cytotoxicity effects (using MTT assay) of compound 1 were assessed. From the results obtained, compound 1 could be considered as a promising chemotherapeutic agent for the treatment of inflammatory diseases.

Two new alkylresorcinol derivatives from the leaves of Scyphocephalium ochocoa

Two new alkylresorcinol derivatives, namely ochocinone A and ochocinone B (1, 2), as well as a known alkylresorcinol oleiferinone (3) were isolated from the methanol extract of the leaves of Scyphocephalium ochocoa. The structures of these compounds were established by detailed spectroscopic analysis and by comparison with the spectral data of related known compounds. Compounds 1–3 showed significant immunomodulatory activity and cytotoxic effect on the mammary carcinoma MCF-7 cell line.

Antidiabetic potential of two medicinal plants used in Gabonese folk medicine

BACKGROUND

Diabetes mellitus is a metabolic disorder which is rising globally in rich and developing countries. In the African region this rate is the highest, with 20 million diagnosed diabetics. Despite a noticeable progress in the treatment of diabetes mellitus by synthetic drugs, the search for new natural anti-diabetic agents is going on. Nauclea diderrichii (De Wild.) Merr. (ND) and Sarcocephalus pobeguinii Hua ex Pellegr. (SP) are used as traditional medicines in Gabon for the treatment of different diseases, especially in the case of diabetes. The aim of this study was to evaluate the antidiabetic potential of these two medicinal plants traditionally used in Gabon.

METHODS

Pharmacological (inhibitory action on α and β-glucosidases) and toxicological (effect on human T cell proliferation) studies were conducted on aqueous extracts of ND (leaves and bark) and SP (bark) collected in Gabon. All raw extracts were analyzed by HPTLC and their content in phenolic compounds was determined by using standard method. The most active extracts were submitted to preparative HPLC in order to evidence the most efficient subfractions by biological evaluation.

RESULTS

The results showed that two extracts from ND were potent α-glucosidase inhibitors, the leaf extract being more active that the bark extract: the first one was more than 60 fold more active than Acarbose, which is an oral medication used to treat type 2 diabetes; the extract from SP bark was less efficient. The HPLC subfractions of the extracts of ND leaves and SP bark were tested in the same experimental conditions. In each case, the most active subfractions still show very potent inhibitory effect on α-glucosidase (80-90% inhibition at 0.1 mg/mL). The most efficient extract, from ND leaves, was also characterized by the highest percentage of phenolic compounds, which suggests a relationship between its inhibitory potential on α-glucosidase and its content in phenolic compounds. Conversely, only a moderate inhibitory activity of the three extracts was observed on β-glucosidase.

CONCLUSION

These results clearly indicated that active compounds present in N. diderrichii and S. pobeguinii leaves or/and bark were selective and highly potent inhibitors of α-glucosidase and validate their popular use for the treatment of diabetes.

Ethnopharmacological surveys and pharmacological studies of plants used in traditional medicine in the treatment of HIV/AIDS opportunistic diseases in Gabon

ETHNOPHARMACOLOGICAL RELEVANCE

Ethnopharmacological surveys were conducted in two regions of Gabon. This led to highlighting some of the medicinal plants used by local populations in the management of HIV/AIDS opportunistic diseases. Two regions with the highest occurrence of HIV/AIDS cases were visited and ethnopharmarcological data was gathered. These regions were the Estuaire Province (Libreville and its neighborhood) and the Haut-Ogooué Province (Franceville and its neighborhood). The opportunistic diseases and symptomatic conditions considered during this study were: diarrhea, respiratory tract infections, cough, tuberculosis, abscesses, stomach ache, skin rashes, venereal diseases, typhoid fever, anemia, general tiredness, hepatitis and vomiting.

MATERIALS AND METHODS

The reported species were evaluated through three parameters: specificity, reliability and frequency. Plant parts of relevant species were harvested and extracted with an aqueous alcohol solution (ethanol/water: 1/1). The extracts obtained were submitted to phytochemical screening and in vitro microbiological assays on some clinical isolates and ATCC strains, involved in HIV/AIDS opportunistic diseases through the Agar well diffusion and Microbroth dilution methods.

RESULTS

Among the 52 species identified during this survey, Coelocaryon klainei Pierre ex Heckel (Myristicaceae), Dacryodes klaineana (Pierre) H.J. Lam (Bursecaceae), Phyllanthus diandrus Pax (Euphorbiaceae), Saccoglotys gabonensis (Baill.) Urb. (Humiriaceae) and Tetrorchidium didymostemon (Baill.) Pax & K. Hoffm. (Euphorbiaceae) were submitted to in vitro microbiological assays. Phyllanthus diandrus bark and leaves show best antibacterial activities against Pseudomonas aeruginosa and Klebsiella pneumoniae with MIC value of 0.25 respectively. Phytochemical screening revealed the presence in all the plant parts extracts of potentially bioactive molecules, including polyphenols, especially flavonoids and tannins.

CONCLUSION

It is concluded that some of these plants might be submitted to further scientific studies, including the identification and isolation of bioactive principles, that could be developed to drugs for the treatment of HIV/AIDS opportunistic diseases.

In vitro antiplasmodial activity and cytotoxicity of extracts and fractions of Vitex madiensis, medicinal plant of Gabon

Vitex madiensis Oliv. (Lamiaceae) is traditionally used to treat malaria symptoms in Haut-Ogooué, Gabon. Leaves and stem barks extracts were obtained using dichloromethane (CH(2)Cl(2)), ethyl acetate (EtOAc) and methanol (MeOH) as extraction solvents and fractionated on silica gel column. The in vitro antiplasmodial activity of CH(2)Cl(2), EtOAc and MeOH extracts and fractions was evaluated against the chloroquine-resistant FCB strain and field isolates of Plasmodium falciparum using the DELI test. The cytotoxicity of the extracts was tested on MRC-5 and THP1 cells using the tetrazolium salt MTT colorimetric assay, and the selectivity index (SI) of each extract was calculated. CH(2)Cl(2) extract, the EA1 fraction from EtOAc extract of stem barks and cyclohexane (L(cycl)), dichloromethane (L(DM)) and butanol (L(but)) fractions from MeOH/H(2)O extract of leaves exhibited the highest in vitro antiplasmodial activity on FCB strain and field isolates (IC(50) from 0.53 to 4.87 μg/ml) with high selectivity index (of 20.15-1800). These data support the use of V. madiensis in malaria treatment along with continued investigations within traditional medicines in the search of new antimalarial agents. The EA1, C(6)H(12) and CH(2)Cl(2) fractions could be selected for future investigation or/and for the treatment of malaria symptoms after standardization.

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.

Essential oil of Plectranthus tenuicaulis leaves from Gabon, source of (R),(E)-6,7-epoxyocimene. An unusual chemical composition within the genus Plectranthus

Water distilled essential oils from leaves of Plectranthus tenuicaulis (Hook. f.) J. K. Morton collected in Gabon were analyzed using GC-FID and GC-MS. The main constituent, unusual within the genus Plectranthus, was isolated and formally identified as being the (+)-(R)-enantiomer of (E)-6,7-epoxyocimene [(E)-myroxide]. This enantiomer, which represents about 75% of the essential oil, has been previously identified as a pheromone emitted by the male fruit-spotting bug Amblypelta nitida; this insect is responsible of destruction of most fruit crops in tropical and subtropical areas. The potential application of P. tenuicaulis essential oil in crop protection programs is discussed and the atypical chemical profile of the gabonese essential oil is compared with those previously reported in the genus Plectranthus (or Coleus).

Essential Oil of Plectranthus tenuicaulis Leaves from Gabon, Source of (R),(E)-6,7-Epoxyocimene. An Unusual Chemical Composition within the Genus Plectranthus

Water distilled essential oils from leaves of Plectranthus tenuicaulis (Hook. f.) J. K. Morton collected in Gabon were analyzed using GC-FID and GC-MS. The main constituent, unusual within the genus Plectranthus, was isolated and formally identified as being the (+)-( R)-enantiomer of ( E)-6,7-epoxyocimene [( E)-myroxide]. This enantiomer, which represents about 75% of the essential oil, has been previously identified as a pheromone emitted by the male fruit-spotting bug Amblypelta nitida; this insect is responsible of destruction of most fruit crops in tropical and subtropical areas. The potential application of P. tenuicaulis essential oil in crop protection programs is discussed and the atypical chemical profile of the gabonese essential oil is compared with those previously reported in the genus Plectranthus (or Coleus).

In vitro antiplasmodial activity and cytotoxicity of nine plants traditionally used in Gabon

AIM OF THE STUDY

As part of a project to identify new compounds active on malarial parasites, we tested the in vitro antiplasmodial activity of nine plants traditionally used to treat malaria symptoms in Haut-Ogooué Province, South-East Gabon.

MATERIALS AND METHODS

Dichloromethane and methanolic extracts of each plant were tested for their antiplasmodial activity on two chloroquine-resistant strains of Plasmodium falciparum (FCB and W2), based on lactate dehydrogenase activity. Cytotoxicity was assessed with the MTT test on MRC-5 human diploid embryonic lung cells.

RESULTS

The methanolic extract of Staudtia gabonensis and the dichloromethane extract of Adhatoda latibracteata showed high antiplasmodial activity (IC₅₀<1 μg/ml) and low cytotoxicity, with selectivity indexes of about 58.25 and 16.43, respectively. The methanolic extract of Monodora myristica and the dichloromethane extract of Afromomum giganteum also showed promising activity (1<IC₅₀<10 μg/ml) and low cytotoxicity, with selectivity indexes about 15.70 and 12.48, respectively. Dichloromethane extracts of Monodora myristica and Leonotis Africana showed moderate activity (10<IC₅₀<40 μg/ml), with selectivity indexes about 6.07 and 28.89, respectively. Both extracts of Culcasia lancifolia had IC₅₀ values of 10-40 μg/ml but high cytotoxicity (selectivity indexes <2.77). The methanolic extract of Dorstenia klaineana had moderate antiplasmodial activity (IC₅₀ around 17 μg/ml) but strong cytotoxicity (0.43 μg/ml), giving a selectivity index of about 0.03.

CONCLUSIONS

Most extracts of nine selected plants traditionally used to treat malaria in Gabon had interesting antiplasmodial activity in vitro. This supports continued investigations of traditional medicines in the search for new antimalarial agents. The compounds responsible for the observed antiplasmodial effects are under investigation.

Chemical composition and biological activities of Santiria trimera (Burseraceae) essential oils from Gabon

Water-distilled essential oils from leaves and bark of Santiria trimera (Oliv.) Aubrév. (Burseraceae) collected in Gabon were analyzed using capillary GC-FID and GC-MS. The leaf essential oil, which is described for the first time, was dominated by sesquiterpenes (76.5%), among which alpha-humulene (34.6%) and beta-caryophyllene (14.9%) were the major components. The bark essential oil was almost exclusively monoterpenic, with alpha-pinene (51.5%) and alpha-terpineol (16.8%) as main constituents. The antimicrobial activities of both essential oils were tested against eight Gram-positive and three Gram-negative bacteria by using agar disc diffusion and broth microdilution methods; anticandidal effect was also tested on different strains of Candida albica. The Gram-negative bacteria were the less sensitive to the leaf essential oil, which was effective against Bacillus cereus and Enterococcus faecalis. The bark essential oil was more active and, in particular, exhibited significant antimicrobial activity against Proteus mirabilis, which was resistant to the leaf oil. A weak anticandidal effect of both essential oils was observed.

Chemical Composition and Biological Activities of Santiria trimera (Burseraceae) Essential Oils from Gabon

Water-distilled essential oils from leaves and bark of Santiria trimera (Oliv.) Aubrév. (Burseraceae) collected in Gabon were analyzed using capillary GC-FID and GC-MS. The leaf essential oil, which is described for the first time, was dominated by sesquiterpenes (76.5%), among which α-humulene (34.6%) and β-caryophyllene (14.9%) were the major components. The bark essential oil was almost exclusively monoterpenic, with α-pinene (51.5%) and α-terpineol (16.8%) as main constituents. The antimicrobial activities of both essential oils were tested against eight Gram-positive and three Gram-negative bacteria by using agar disc diffusion and broth microdilution methods; anticandidal effect was also tested on different strains of Candida albica. The Gram-negative bacteria were the less sensitive to the leaf essential oil, which was effective against Bacillus cereus and Enterococcus faecalis. The bark essential oil was more active and, in particular, exhibited significant antimicrobial activity against Proteus mirabilis, which was resistant to the leaf oil. A weak anticandidal effect of both essential oils was observed.

Chemical composition and antimicrobial activity of the essential oils of leaves, roots and bark of Glossocalyx staudtii

The chemical composition of the essential oils obtained by hydrodistillation from air dried leaves, bark and roots of Glossocalyx staudtii Engl. grown in Gabon was analyzed by GC and GC-MS. The essential oil content was 0.84% (w/w), 0.28% (w/w), and 0.74% (w/w), respectively. The leaf oil was characterized by a high content of monoterpene hydrocarbons (64.8%), with beta-pinene (30.6%) and alpha-pinene (22.6%) as the major constituents. The oil obtained from the bark contained 30.5% of oxygenated monoterpenes with cryptone as the main constituent (11.5%) and 28.9% of aliphatic compounds, with 9.3% of 2-tridecanone; in the roots oil, the main component was 2-tridecanone (55.2%). The antimicrobial activity of the oils was studied by means of the agar disc diffusion and broth microdilution methods. The Gram positive bacteria were the most sensitive to the essential oils. A significant anticandidal effect of the bark essential oil was observed.

Chemical Composition and Antimicrobial Activity of the Essential Oils of Leaves, Roots and Bark of Glossocalyx staudtii

The chemical composition of the essential oils obtained by hydrodistillation from air dried leaves, bark and roots of Glossocalyx staudtii Engl. grown in Gabon was analyzed by GC and GC-MS. The essential oil content was 0.84% (w/w), 0.28% (w/w), and 0.74% (w/w), respectively. The leaf oil was characterized by a high content of monoterpene hydrocarbons (64.8%), with β-pinene (30.6%) and α-pinene (22.6%) as the major constituents. The oil obtained from the bark contained 30.5% of oxygenated monoterpenes with cryptone as the main constituent (11.5%) and 28.9% of aliphatic compounds, with 9.3% of 2-tridecanone; in the roots oil, the main component was 2-tridecanone (55.2%). The antimicrobial activity of the oils was studied by means of the agar disc diffusion and broth microdilution methods. The Gram positive bacteria were the most sensitive to the essential oils. A significant anticandidal effect of the bark essential oil was observed.

In vitro antimalarial activity of a new organometallic analog, ferrocene-chloroquine

The in vitro activities of new organometallic chloroquine analogs, based on 4-amino-quinoleine compounds bound to a molecule of ferrocene, were evaluated against chloroquine-susceptible, chloroquine-intermediate, and chloroquine-resistant, culture-adapted Plasmodium falciparum lineages by a proliferation test. One of the ferrocene analogs totally restored the activity of chloroquine against chloroquine-resistant parasites. This compound, associated with tartaric acid for better solubility, was highly effective. The role of the ferrocene in reversing chloroquine resistance is discussed, as is its potential use for human therapy.