The efficiency of cancer chemotherapy is seriously hampered by the development of resistance of neoplastic cells to cytotoxic agents. In the present investigation, the cytotoxicity of the dichloromethane-methanol (1:1) extract of Acacia sieberiana (ASL), fractions (ASLa-c) from the leaves and isolated compounds: chrysoeriol 5) and luteolin (6) was investigated. The study was extended to the assessment of the mode of induction of apoptosis by ASL. The resazurin reduction assay (RRA) was used for cytotoxicity studies. Assessments of cell cycle distribution, apoptosis, and reactive oxygen species (ROS) were performed by flow cytometry. A caspase-Glo assay was used to evaluate caspase activities. Botanicals ASL, ASLb and ASLc as well as doxorubicin displayed observable IC 50 values towards the nine tested cancer cell lines while ASLa and compounds 1-7 had selective activities. The IC 50 values ranged from 13.45 μg/mL (in CCRF-CEM leukemia cells) to 33.20 μg/mL (against MDA-MB-231-BCRP breast adenocarcinoma cells) for ASL, from 16.42 μg/mL (in CCRF-CEM cells) to 29.64 μg/mL (against MDA-MB-231-pcDNA cells) for ASLc, and from 22.94 μg/mL (in MDA-MB-231-BCRP cells) to 40.19 μg/mL (against HCT116 (p53À/À) colon adenocarcinoma cells) for ASLb (Table 1), and from 0.02 μM (against CCRF-CEM cells) to 122.96 μM (against CEM/ADR5000 cells) for doxorubicin. ASL induced apoptosis in CCRF-CEM cells, mediated by ROS production. Acacia sieberiana is a good cytotoxic plant and should be further explored to develop an anticancer phytomedicine to combat both sensitive and drug resistant phenotypes.

Background The rise of multidrug-resistant (MDR) bacteria is a real public health problem worldwide and is responsible for the increase in hospital infections. Donella welwitschii is a liana or shrub belonging to the family Sapotaceae and traditionally used to cure coughs. Objective This study was conducted with the objective to validate the medicinal properties of this plant, the aerial part was studied for its phytochemical composition using column and PTLC chromatography and exploring its antibacterial and antibiotic-modifying activity as well as those of its phytochemicals. Methods The structures of the compounds were elucidated from their physical and spectroscopic data in conjunction with literature. The antibacterial activity of the isolated metabolites was performed toward a panel of MDR Gram negative and Gram-positive bacteria. The broth micro-dilution method was used to determine antibacterial activities, efflux pump effect using the efflux pump inhibitor (EPI) (phenylalanine-arginine-ß-naphthylamide (PAβN)), as well as the modulating activity of antibiotics. Monitoring the acidification of the bacterial growth medium was used to study the effects of the samples on the bacterial proton-ATPase pumps and cellular ATP production. Results Eleven compounds were isolated including pentacyclic triterpenes, C-glucosyl benzophenones. With a MIC value < 10 μg/mL, diospyric acid (7) significantly inhibited the growth of Escherichia coli AG102, Enterobacter aerogenes ATCC13048, Klebsiella pneumoniae KP55, Providencia stuartii NEA16 and Staphylococcus aureus MRSA3. 28-hydroxy-β-amyrin (8) significantly impaired the growth of Enterobacter aerogenes EA27, Klebsiella pneumoniae ATCC11296 and Staphylococcus aureus MRSA6; and oleanolic acid (9) strongly impaired the growth of Escherichia coli AG 102, Enterobacter aerogenes EA27 and Providencia stuartii PS2636. Diospyric acid (7) and 28-hydroxy-β-amyrin (8) induced perturbation of H+-ATPase pump and inhibition of the cellular ATP production. Moreover, at MIC/2 and MIC/4, compounds 7, 8, and 9 strongly improved the antibacterial activity of norfloxacin, ciprofloxacin and doxycycline with antibiotic-modulating factors ranging between 2 and 64. Conclusion The overall results of the current work demonstrate that diospyric acid (7), 28-hydroxy-β-amyrin (8) and oleanolic acid (9) are the major bioactive constituents of Donella welwitschia towards Gram-negative bacteria expressing MDR phenotypes.

Background: In recent years, drug resistance to human pathogenic bacteria has been commonly reported from all over the world. As antimicrobial activities of most medicinal plants and antibiotics have been already explored, it is more important to make investigations on animal species mainly invertebrates which could constitute an efficient source of antimicrobial molecules. This work was aimed at contributing to the fight against microbial resistance through the study of antibacterial potential of three animal species (Helix aspersa, Bitis arietans, Aristaeomorpha foliacea) on several multidrug-resistant (MDR) Gram-negative strains overexpressing efflux pumps including Escherichia coli, Enterobacter aerogenes, Klebsiella pneumoniae, Pseudomonas aeruginosa. Methods: The microdilution technique was used to evaluate the antibacterial activities of the tested samples by determining their minimal inhibitory concentrations (MICs), as well as the effect of their combination with antibiotics. Studies on the mechanisms of action of the most active sample, dried Bitis arietans extract, was carried out using standard methods for evaluating the effects of this extract on bacterial H+-ATPases-mediated proton pumps and on bacterial growth kinetics. In this latter case, the optical density was read spectrophotometrically. Results: Zoochemical screening indicated the presence of protein constituents and alkaloids and the absence of other metabolites in all tested extracts. Dried B. arietans showed the best antibacterial activity by inhibiting the growth of 90% of studied bacterial strains with MICs ranging from 128 to 2048 μg/ml. Moreover, this extract presented a significant activity (100≤MIC≤512 µg/ml) against 35% of bacteria that are E. coli (ATCC8739, AG100ATet, MC4100), E. aerogenes EA27, K. pneumoniae ATCC11296, P. aeruginosa (PA01, PA124) and a moderate activity (512<MIC≤2048 µg/ml) against 55% of studied bacteria. It was followed by fresh B. arietans which inhibited the growth of 65% of bacteria with significant activity on three bacteria (E. coli ATCC8739, E. aerogenes ATCC13048 and K. pneumoniae ATCC11296. These two extracts showed bactericidal effects on many strains. The other extracts samples selectively exhibited an antibacterial activity against less than 40% of strains. All samples potentiated the activity of at least 56% of used antibiotics against at least 70% of studied bacterial strains. B. arietans extracts at MIC/2 and MIC/4 mostly improved the activities of more than 78% of antibiotics on at least 70% of bacteria with improvement activity factors (IAF) ranging from 2 – 128 suggesting that this animal contains bioactive compounds which could act as efflux pumps inhibitors. Bacterial growth kinetic study showed that when treated with dried B. arietans extract (the most active sample) at different concentrations MIC/2, MIC and 2xMIC, the growth of tested bacteria (E. coli ATCC8739) decreased respectively when the concentrations increased. Furthermore, this extract inhibited the H+-ATPase-mediated proton pumps of this bacterium increasing the pH values. Conclusion: Results obtained in the present work provide interesting data for the use of dried B. arietans extract and invertebrates in general in the traditional therapy for the treatment of bacterial infections involving multidrug-resistant phenotypes. Keywords: Gram-negative bacteria; multidrug resistance; efflux pumps; infectious diseases; animal species; secondary metabolites.

Background: The rapid emergence of multidrug resistant (MDR) bacteria is occurring worldwide, endangering the efficacy of antibiotics, which have transformed medicine and saved millions of lives. Antibiotic-resistant infections are already widespread in the Sub-Saharan Africa and across the globe. To extend the search for new and more efficient antimicrobial drugs from natural sources, this work has been carried out to study the phytochemical composition and the antibacterial activities of some Cameroonian dietary plants (Cocos nucifera, Glycine max and Musa sapientum) against several MDR Gram-negative strains including Escherichia coli, Enterobacter aerogenes, Providencia stuartii, Klebsiella pneumoniae, Pseudomonas aeruginosa species expressing efflux pumps. Methods: Phytochemical screening of plant extracts was performed using qualitative standard methods and the antimicrobial assays of these extracts alone and in combination with antibiotics were done using serial 96-wells microplate dilution essays. Results: Each plant extract contained at least three mean classes of secondary metabolites. Glycine max, epicarps, leaves and bark of C. nucifera as well as mesocarps of M. sapientum contained each alkaloids, polyphenols, flavonoids, and triterpenes. Moreover, steroids were also found in G. max, steroids and saponins in epicarps and saponins in bark of C. nucifera. Meanwhile epicarps from M. sapientum contained only polyphenols, flavonoids and saponins. Antibacterial assays showed that different parts of C. nucifera were more active than other extracts. Their minimal inhibitory concentrations (MICs) varied from 128 to 2048 µg/mL. The bark part presented the highest antibacterial potential inhibiting the growth of 90% of strains with significant activity (100≤MIC≤512 µg/mL) against 50% of them (three E. coli, four E. aerogenes and three K. pneumoniae). It showed bactericidal effects (MBC/MIC≤4) on 45% of the same bacterial species. It was followed by epicarps and leaves parts which exhibited an inhibitory power against 75% and 60% of bacteria with significant activity on 40% and 20% of them respectively. They also showed bactericidal effects on E. coli ATCC8739 for epicarps extract and E. coli ATCC8739 and P. stuartii NEA16 for leaves extract. Extracts from G. max were less active and those from mesocarps and epicarps of M. sapientum did not showed any activity on all studied bacteria. Bark and epicarps extracts of C. nucifera potentiated the activities of all used antibiotics against at least 70% of bacteria while leaves extract exhibited this effect improving the activities of 67% of antibiotics with improvement activity factors (IAF) ranging from 2 to 256 suggesting that they contain bioactive compounds which could be considered as efflux pumps inhibitors. Extracts from G. max, epicarps and mesocarps of M. sapientum enhanced the inhibitory potential of 56%, 34% and 23% of antibiotics respectively against at least 70% of studied bacteria. These increases of activities also characterize synergistic effects between antibiotics and bioactive compounds of plants. Conclusion: The findings of this work suggest that infections by resistant bacteria can be treated using different parts of C. nucifera as an alternative to commonly used antibiotics.

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