Background Cancer cells rapidly acquire resistance leading to treatment failures. In the present study, we have evaluated the cytotoxicity of 17 methanol extracts from 11 Cameroonian medicinal plants against the sensitive leukemia CCRF–CEM cells and the best ones were further tested on a panel of 8 other human cancer cell lines, including various MDR phenotypes as well as against the normal AML12 hepatocytes.MethodsThe cytotoxicity of the extracts was determined using a resazurin reduction assay meanwhile flow cytometry was used to measure cell cycle, apoptosis, mitochondrial membrane potential (MMP), and reactive oxygen species.ResultsIn an initial screening using leukemia CCRF–CEM cells, ten extracts from five plants namely Alchornea floribunda, Annona muricata, Euphorbia prostata, Pachypodanthium staudtii and Passiflora edulis displayed IC50 values below 20 µg/mL. They were further tested in 8 other cell lines as well as in normal AML12 hepatocytes. All selected extracts were active against leukemia CEM/ADR5000 cells with IC50 value below 40 µg/mL. IC50 values ranging from 10.13 µg/mL (towards CEM/ADR5000 cells) to 72.01 µg/mL [towards resistant colon carcinoma HCT116 (p53−/−) cells] for Pachypodanthium staudtii roots and from 0.11 µg/mL (towards CCRF–CEM cells) to 108 µg/mL (towards P-glycoprotein-over-expressing CEM/ADR5000 cells) for doxorubicin were obtained in the eight other cancer cell lines studied. Extracts from Annona muricata leaves (AML) and seeds (AMS), and Passiflora edulis fruit (PEF) had IC50 values below 1 µg/mL against CCRF–CEM cells and below 10 µg/mL against its MDR subline CEM/ADR5000 cells. AML, AMS and PEF induced MMP-loss-mediated apoptosis in CCRF–CEM cells.ConclusionsResults of the present study suggest that some of the tested plants namely Alchornea floribunda, Annona muricata, Euphorbia prostata, Pachypodanthium staudtii and Passiflora edulis represent a source of anticancer drugs. Annona muricata and Passiflora edulis are good cytotoxic plants that could be exploited to develop phytomedicine to fight mostly hematological cancers including MDR phenotypes.

BackgroundThe present study was designed to investigate the antibacterial activities of the methanol extract of three edible plants, namely Xanthosoma mafaffa, Moringa oleifera and Passiflora edulis and their synergistic effects with some commonly used antibiotics against MDR Gram-negative bacteria expressing active efflux pumps.MethodsBroth microdilution method was used to determine the minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) of the extracts, as well as those of antibiotics in association with the extracts.ResultsThe phytochemical test indicate that all tested crude extracts contained polyphenols, triterpenes and steroids whilst other phytochemical classes were selectively distributed. Extracts showed antibacterial activities with minimum inhibitory concentrations ranging from 128-1024 μg/mL on the majority of the 19 tested Gram-negative bacterial strains. Extract from the pericarp of P. edulis inhibited the growth of 89.5 % of the 19 tested bacterial strains, the lowest minimal inhibitory concentration (MIC) value of 128 μg/mL being recorded against Escherichia coli AG100 strain. In the presence of Phenylalanine-Arginine β-Naphtylamide (PAβN)], an efflux pump inhibitor (EPI), the activity of the extract from X. mafaffa increased on 40 % of tested strains. In combination with antibiotics, extracts of X. mafaffa, M. oleifera and pericarp of P. edulis showed synergistic effects with some antibiotics against more than 75 % of the tested bacteria.ConclusionThe results of the present study indicate that the tested plants may be used in the treatment of bacterial infections including the multi-resistant bacteria.

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.

BackgroundNutmeg is the seed kernel inside the fruit of Myristica fragrans Houtt. (Myristicaceae). It possesses various pharmacological activities but is used in Cameroon only for its flavor in making cakes. The present study thus aimed to investigate the in vitro antibacterial activity and antibiotic modifying activities of crude seed kernel methanol extract (MFS), fractions (MFSa-e) as well as 3′,4′,7-trihydroxyflavone from Myristica fragrans against a panel of multi-drug resistant (MDR) Gram-negative bacteria.MethodsThe modified rapid p-iodonitrotetrazolium chloride (INT) colorimetric assay was used to determine the Minimal Inhibitory Concentration (MIC) and Minimal Bactericidal Concentration (MBC) on the tested bacteria, as well as those of antibiotics in association with the extract and/or isolated compound. Column chromatography was used for the fractionation and purification of the seed kernel extract whilst the chemical structures of compounds were determined using spectroscopic techniques.ResultsPhytochemical investigations lead to the isolation of 3′,4′,7-trihydroxyflavone from the fraction MFSb. The crude extract showed antibacterial activity with MICs ranging from 32 to 1024 μg/mL on the majority of the 29 tested Gram-negative bacterial strains. Fraction MFSb inhibited the growth of 100% (29/29) of the tested bacterial strains, as well as the compound 3′,4′,7-trihydroxyflavone (12/12) with a MIC values ranging from 32 to 1024 μg/mL, and 4 to 128 μg/mL respectively. The lowest MIC value (4 μg/mL) was recorded with 3′,4′,7-trihydroxyflavone against Providencia stuartii ATCC299645 as well as the best MBC value (16 μg/mL) against the same strain. In the presence of Phenylalanine-Arginine-β-Naphthylamide (PAßN), an efflux pumps inhibitor, the activity of the extract increased on 73.33% (11/15) meanwhile that of 3′,4′,7-trihydroxyflavone increased on 100% tested bacteria. The compound 3′,4′,7-trihydroxyflavone potentiated the activity of antibiotics in the majority of the tested bacterial strains.ConclusionThe results of the present work provide additional information on the use of nutmeg and it major antibacterial component, 3′,4′,7-trihydroxyflavone, as a potential drug in the treatment of bacterial infections including multidrug resistant phenotypes.Electronic supplementary materialThe online version of this article (10.1186/s12906-018-2084-1) contains supplementary material, which is available to authorized users.

Bacterial infections are among the major cause of morbidity and mortality worldwide. The present study was designed to evaluate the in vitro antibacterial activities of the methanol extracts of five Cameroonian edible plants namely Colocasia esculenta, Triumfetta pentandra, Hibiscus esculentus, Canarium schweinfurthii and Annona muricata against a panel of 19 multidrug resistant Gram-negative bacterial strains. The liquid broth microdilution was used to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of the extracts. The preliminary phytochemical screening of the extracts was conducted according to the standard phytochemical methods. Results showed that all extracts contained compounds belonging to the classes of polyphenols, triterpenes and steroids, other classes of chemicals being selectively distributed. Canarium schweinfurthii extract showed the best activity with MIC values ranging from 64 to 1024 μg/mL against 89.5% of the 19 tested bacteria strains. MIC values below or equal to 1024 μg/mL were also recorded with Triumfetta pentandra, Annona muricata, Colocasia esculenta and Hibiscus esculentus extracts respectively against 15/19 (78.9%), 11/19 (57.9%), 10/19 (52.6%) and 10/19 (52.6%) tested bacteria. Extract from C. schweinfurthii displayed the lowest MIC value (64 μg/mL) against Escherichia coli AG100ATet. Finally, the results of this work provide baseline information for the use of C. esculenta, T. pentandra, H. esculentus, C. schweinfurthii and A. muricata in the treatment of bacterial infections including multidrug resistant phenotypes.