BackgroundIn response to the propagation of bacteria resistant to many antibiotics also called multi-drug resistant (MDR) bacteria, the discovery of new and more efficient antibacterial agents is primordial. The present study was aimed at evaluating the antibacterial activities of seven Cameroonian dietary plants (Adansonia digitata, Aframomum alboviolaceum, Aframomum polyanthum, Anonidium. mannii, Hibiscus sabdarifa, Ocimum gratissimum and Tamarindus indica).MethodsThe phytochemical screening of the studied extracts was performed using described methods whilst the liquid broth micro dilution was used for all antimicrobial assays against 27 Gram-negative bacteria.ResultsThe results of the phytochemical tests indicate that all tested extracts contained phenols and triterpenes, other classes of chemicals being selectively present. The studied extracts displayed various degrees of antibacterial activities. The extracts of A. digitata, H. sabdarifa, A. polyanthum, A. alboviolaceum and O. gratissimum showed the best spectra of activity, their inhibitory effects being recorded against 81.48%, 66.66%, 62.96%, 55.55%, and 55.55% of the 27 tested bacteria respectively. The extract of A. polyanthum was very active against E. aerogenes EA294 with the lowest recorded minimal inhibitory concentration (MIC) of 32 μg/ml.ConclusionThe results of the present work provide useful baseline information for the potential use of the studied edible plants in the fight against both sensitive and MDR phenotypes.

The morbidity and mortality caused by bacterial infections significantly increased with resistance to commonly used antibiotics. This is partially due to the activation of efflux pumps in Gram-negative bacteria. The present work designed to assess the in vitro antibacterial activities of seven Cameroonian dietary plants (Sesamum indicum, Sesamum radiatum, Cinnamomum zeylanicum, Corchous olitorius, Cyperus esculentus, Adansonia digitata, Aframomum kayserianum), against multidrug resistant (MDR) Gram-negative bacteria over expressing active efflux pumps. The standard phytochemical methods were used to detect the main classes of secondary metabolites in the extracts. The antibacterial activities of the studied extracts in the absence or presence of an efflux pump inhibitor (PAβN) were evaluated using liquid microbroth dilution method. The results obtained indicated that apart from the extract of C. esculentus, all other samples contained alkaloids, phenols and polyphenols meanwhile other classes of chemicals were selectively present. The studied extracts displayed antibacterial activities with minimal inhibitory concentrations (MICs) values ranged from 64 to 1024 μg/mL on the majority of the 27 tested microbial strains. The extract of S. indicum was active against 77.77% of the tested microorganisms whilst the lowest MIC value (64 μg/mL) was recorded with that of A. kayserianum against E. aerogenes EA294. The results of the present work provide baseline information on the possible used of the tested Cameroonian dietary plants in the treatment of bacterial infections including multi-drug resistant phenotypes.

In the current study forty eight compounds belonging to anthraquinones, naphthoquinones, benzoquinones, flavonoids (chalcones and polymethoxylated flavones) and diterpenoids (clerodanes and kauranes) were explored for their antimicrobial potential against a panel of sensitive and multi-drug resistant Gram-negative and Gram-positive bacteria. The minimal inhibitory concentration (MIC) determinations on the tested bacteria were conducted using modified rapid INT colorimetric assay. To evaluate the role of efflux pumps in the susceptibility of Gram-negative bacteria to the most active compounds, they were tested in the presence of phenylalanine arginine β-naphthylamide (PAβN) (at 30 µg/mL) against selected multidrug resistance (MDR) bacteria. The anthraquinone, emodin, naphthaquinone, plumbagin and the benzoquinone, rapanone were active against methicillin resistant Staphylococcus aureus (MRSA) strains of bacteria with MIC values ranging from 2 to 128 μg/mL. The structure activity relationships of benzoquinones against the MDR Gram-negative phenotype showed antibacterial activities increasing with increase in side chain length. In the chalcone series the presence of a hydroxyl group at C3′ together with a methoxy group and a second hydroxyl group in meta orientation in ring B of the chalcone skeleton appeared to be necessary for minimal activities against MRSA. In most cases, the optimal potential of the active compounds were not attained as they were extruded by bacterial efflux pumps. However, the presence of the PAβN significantly increased the antibacterial activities of emodin against Gram-negative MDR E. coli AG102, 100ATet; K. pneumoniae KP55 and KP63 by >4–64 g/mL. The antibacterial activities were substantially enhanced and were higher than those of the standard drug, chloramphenicol. These data clearly demonstrate that the active compounds, having the necessary pharmacophores for antibacterial activities, including some quinones and chalcones are substrates of bacterial efflux pumps and therefore should be combined to efflux pump inhibitors in the fight against MDR bacterial infections.

BackgroundMalignacies are still a major public concern worldwide and despite the intensive search for new chemotherapeutic agents, treatment still remains a challenging issue. This work was designed to assess the cytotoxicity of six selected Cameroonian medicinal plants, including Nauclea pobeguinii and its constituents 3-acetoxy-11-oxo-urs-12-ene (1), p-coumaric acid (2), citric acid trimethyl ester (3), resveratrol (4), resveratrol β-D-glucopyranoside (5) and strictosamide (6), against 8 drug-sensitive and multidrug-resistant (MDR) cancer cell lines.MethodsThe resazurin reduction assay was used to evaluate the cytotoxicity of the crude extracts and compounds, whilst column chromatography was used to isolate the constituents of Nauclea pobeguinii. Structural characterization of isolated compounds was performed using nuclear magnetic resonance (NMR) spectroscopic data.ResultsPreliminary experiments on leukemia CCRF-CEM cells at 40 μg/mL showed that the leaves and bark extracts from Tragia benthamii, Canarium schweinfurthii, Myrianthus arboreus, Dischistocalyx grandifolius and Fagara macrophylla induced more than 50 % growth of this cell line contrary to the leaves and bark extracts of N. pobeguinii. IC50 values below or around 30 μg/mL were obtained with leaves and bark extracts of N. pobeguinii towards two and five, respectively, of the 8 tested cancer cell lines. The lowest IC50 value was obtained with the bark extract of N. pobeguinii against HCT116 (p53−/−) colon cancer cells (8.70 μg/mL). Compounds 4 and 6 displayed selective activity on leukemia and carcinoma cells, whilst 1–3 were not active. IC50 values below 100 μM were recorded with compound 5 on all 9 tested cancer cell lines as well as with 4 against 7 out of 8 and 6 against 2 out of 8 cell lines.Collateral sensitivity was observed in CEM/ADR5000 leukemia cells, MDA-MB-231-BCRP breast adenocarcinoma cells (0.53-fold), HCT116 (p53+/+) cells, human U87MG.ΔEGFR glioblastome multiforme cells to the methanolic bark extract of N. pobeguinii, as well as in MDA-MB-231-BCRP cells and HCT116 (p53+/+) cells and U87MG.ΔEGFR cells (0.86-fold) to compound 5.ConclusionsThe results of this study demonstrate the cytotoxicity of six Cameroonian medicinal plants, Canarium schweinfurthii, Dischistocalyx grandifolius, Tragia benthamii, Fagara macrophylla, Myrianthus arboreus and Nauclea pobeguinii. We also demonstrated the antiproliferative potential of Nauclea pobeguinii against drug-resistant cancer cell lines. Resveratrol and its glucoside are the major cytotoxic constituents in the bark of Nauclea pobeguinii.Electronic supplementary materialThe online version of this article (doi:10.1186/s12906-015-0841-y) contains supplementary material, which is available to authorized users.

Cancer cells may rapidly acquire multidrug resistance, mainly due to the presence of adenosine triphosphate-binding cassette transporters, epidermal growth factor receptor, or mutations in the p53 tumor suppressor gene. This work was designed to assess the cytotoxicity of the methanol crude extracts and compounds from the fruits of Uapaca togoensis, namely, β-amyryl acetate (1), 11-oxo-α-amyryl acetate (2), lupeol (3), pomolic acid (4), futokadsurin B (5), arborinin (6), and 3-O-β-D-glucopyranosyl sitosterol (7) against nine drug sensitive and multidrug-resistant cancer cell lines. The resazurin reduction assay was used to evaluate the cytotoxicity of the fruits of U. togoensis and compounds, whilst the caspase-Glo assay was used to detect the activation of caspase enzymes by the fruits of U. togoensis and compound 6. Cell cycle, mitochondrial membrane potential, and levels of reactive oxygen species were all analyzed via flow cytometry. The acridone alkoid 6 and the crude extract from the fruits of U. togoensis were active on all of the nine tested cancer lines with IC50 values below 32 µM and 30 µg/mL, respectively. Compounds 2 and 5 showed selective activities and IC50 values below 99 µM or 42 µM, respectively, which were obtained towards 3/9 and 6/9 tested cancer cell lines. Compound 6 displayed IC50 values below 10 µM towards seven of the nine tested cancer cell lines. The IC50 values ranged from 3.55 µM (against CEM/ADR5000 cells) to 31.77 µM (against CCRF-CEM cells) for alkaloid 6 and from 0.20 µM (against CCRF-CEM cells) to 195.12 µM (against CEM/ADR5000 cells) for doxorubicin. The crude extract of the fruits of U. togoensis induced apoptosis in the CCRF-CEM leukemia cells, which was mediated by the disruption of the mitochondrial membrane potential. Compound 6 also strongly induced apoptosis in CCRF-CEM cells and cell cycle arrest in the G0/G1 and S phases. The crude extract from the fruits of this plant as well as aborinin are potential antiproliferative natural products that deserve further investigation to develop novel cytotoxic drugs to fight sensitive and otherwise drug-resistant phenotypes.