Antibacterial activities of the methanol extracts of Albizia adianthifolia, Alchornea laxiflora, Laportea ovalifolia and three other Cameroonian plants against multi-drug resistant Gram-negative bacteria

Cytotoxicity, acute and sub-chronic toxicities of the leaves of Bauhinia thonningii (Schumach.) Milne-Redh. (Caesalpiniaceae)

BACKGROUND

Bauhinia thonningii is a plant traditionally used against many human diseases such as gastric ulcers, fever, inflammations, coughs, dysentery, diarrhea, and malaria. In the present investigation, the cytotoxicity of methanol extract of Bauhinia thonningii leaves (BTL), fractions and the isolated phytoconstituents was determined in a panel of 9 human cancer cell lines including drug sensitive and multidrug-resistant (MDR) phenotypes. The acute and sub-chronic oral toxicity of BTL was investigated as well.

METHODS

Compounds were isolated using chromatographic techniques while their chemical structures were determined using spectroscopic methods. The resazurin reduction assay (RRA) was used to evaluate the cytotoxicity of samples, propidium iodide (PI) for apoptosis, 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide (JC-1) staining for mitochondrial membrane potential (MMP) analysis, 2´,7´-dichlorodihydrofluoresceine diacetate (H2DCFH-DA) staining for the quantification of reactive oxygen species (ROS), whereas Caspase Glo assays were combined by means of flow cytometry. Furthermore, the toxicological investigations were performed as recommended by the Organization for Economic Cooperation and Development (OECD).

RESULTS

The botanicals as well as 6-C-methylquercetin-3,7-dimethyl ether (2), quercetin-3-O-L-rhamnopyranoside (5), quercetin-3-O-β-glucopyranoside (6), 6,8-C-dimethylkaempferol 3,7-dimethyl ether (7), and 6,8-C-dimethylkaempferol-3-methyl ether (8) had promising cytotoxic effects in the 9 tested cancer cell lines. The IC50 values below 20 µg/mL (botanicals) or 10 µM (compounds) on at least 1/9 tested cancer cell lines were considered. The best cytotoxic effects with IC50 values below 5 µM were achieved with compounds 7 against CEM/ADR5000 leukemia cells (2.86 µM) and MDA-MB-231-pcDNA breast adenocarcinoma cells (1.93 µM) as well as 8 against CCRF-CEM leukemia cells (3.03 µM), CEM/ADR5000 cells (2.42 µM), MDA-MB-231-pcDNA (2.34 µM), and HCT116 p53-/- cells (3.41 µM). BTL and compound 8 induced apoptotic cell death in CCRF-CEM cells through caspase activation, alteration of MMP, and increased ROS production. BTL did not cause any adverse effects in rats after a single administration at 5000 mg/kg or a repeated dose of 250 mg/kg body weight (b. w.).

CONCLUSION

Bauhinia thonningii and its constituents are sources of cytotoxic drugs that deserve more in-depth studies to develop novel antiproliferative phytomedicine to fight cancer including resistant phenotypes.

Appraising the therapeutical potentials of Alchornea laxiflora (Benth.) Pax & K. Hoffm., an underexplored medicinal herb: A systematic review

Ethnopharmacological relevance: Alchornea laxiflora (Benth.) Pax & K. Hoffm. (Euphorbiaceae) is an important traditional medicinal plant grown in tropical Africa. The stem, leaves, and root have been widely used in the folk medicine systems in Nigeria, Cameroon, South Africa, and Ghana to treat various ailments, including inflammatory, infectious, and central nervous system disorders, such as anxiety and epilepsy. Material and methods: The scientific name of the plant was validated using the "The Plant List," "Kew Royal Botanic Gardens," and Tropicos Nomenclatural databases. The literature search on A. laxiflora was performed using electronic search engines and databases such as Google scholar, ScienceDirect, PubMed, AJOL, Scopus, and Mendeley. Results: To the best of our knowledge, no specific and detailed review has been reported on A. laxiflora. Consequently, this review provides an up-to-date systematic presentation on ethnobotany, phytoconstituents, pharmacological activities, and toxicity profiles of A. laxiflora. Phytochemical investigations disclosed the presence of important compounds, such as alkaloids, flavonoids, phenolics, terpenoids, and fatty acids. Furthermore, various pharmacological activities and traditional uses reported for this botanical drug were discussed comprehensively. Conclusion: This systemic review presents the current status and perspectives of A. laxiflora as a potential therapeutic modality that would assist future researchers in exploring this African botanical drug as a source of novel drug candidates for varied diseases.

An Evaluation of the Antibacterial Activity of Pterocarpus tinctorius Bark Extract against Enteric Bacteria That Cause Gastroenteritis

Enteric bacteria are the leading cause of bacterial gastroenteritis worldwide, particularly in low-income countries. The bark decoction of Pterocarpus tinctorius (Fabaceae) has traditionally been used to treat bacterial gastroenteritis. However, studies reporting the antibacterial activity of Pterocarpus tinctorius are rare. Therefore, this study aimed to evaluate the antibacterial activity of stem bark extract of Pterocarpus tinctorius against Escherichia coli, Salmonella typhi, and Shigella dysenteriae. The powdered bark extract was successively extracted with methanol using the cold continuous maceration method, followed by partitioning the crude methanolic extract to obtain methanolic, hexane, and chloroform subextracts. Three fractions were isolated from the methanolic subextract using ordinary normal phase column chromatography. The antibacterial activity of the extracts and fractions was performed using the agar well diffusion method. The minimum inhibitory concentration (MIC) was determined using the agar well diffusion method. While, minimum bactericidal concentration (MBC) was obtained by the subculturing method. The methanolic subextract was the only extract that showed antibacterial activity against the tested bacteria, and its activity was highest on Shigella dysenteriae followed by Salmonella typhi and was least active on Escherichia coli, with mean inhibition zones of 14.3 ± 0.2, 13.7 ± 0.3, and 12.2 ± 0.1 at 200 mg/mL, respectively. Chloroform subextract showed antibacterial activity only on Shigella dysenteriae, while hexane subextract did not show antibacterial activity against all bacteria tested at 100 mg/mL and 200 mg/mL. Among the three subfractions of methanolic subextract, only one subfraction was active and had both mean minimum inhibitory concentration and a minimum bactericidal concentration against Escherichia coli at 1.25 mg/mL, Salmonella typhi at 1.25 mg/mL, and Shigella dysenteriae at 0.6 mg/mL. The findings of this study support the use of Pterocarpus tinctorius in traditional medicine. Therefore, purification and structural elucidation studies are highly recommended.

Chemical profiling, in vitro antimicrobial and antioxidant activities of pomegranate, orange and banana peel-extracts against pathogenic microorganisms

Background

The use of natural preservatives became of great interest; good examples of these natural preservation agents are plant peels. The use of plant peels has dual benefits; first is their antimicrobial activity against food-borne pathogens, while the second is minimizing agro-industrial wastes.

Results

The evaluation of the antimicrobial potential of both methanolic and ethanolic extracts of three fruit peels (orange, pomegranate, and banana), against 4 Gram-positive (G⁺), 3 Gram-negative bacteria (G⁻), and 2 fungal strains revealed that both pomegranate peel extracts exhibited significantly higher inhibitory effect on all tested G⁺ bacteria. Methanolic extract of pomegranate peel gave higher activity than the ethanolic one against G⁺ and G⁻ bacteria except for S. typhimurium. Against A. flavus and A. niger, both pomegranate and orange extracts showed activity ranging between 65 and 100% more than the positive control. The ethanolic extracts of all tested peels showed a considerable capacity of antioxidant compounds compared to the methanolic extracts. The highest antioxidant capacity was found for ethanolic and methanolic extracts of pomegranate, 66.870 and 56.262 mg/ml, respectively. Generally, the concentration of total phenolic compounds was higher than that of total flavonoids followed by tannins. The highest readings of all tested constituents were reported for pomegranate extracts followed by orange and then banana. The total phenolic content, total flavonoids, and tannins were proportional to antioxidant values. GC-MS of pomegranate peel extracts identified 23 compounds in the methanolic extract versus 31 compounds in the ethanolic one. These components were identified based on their retention times and mass spectral fragmentation pattern. 5-hydroxymethylfufural (HMF) represented the major component in both methanolic and ethanolic extracts with peak area percentage of 65.78% and 48.43%, respectively.

Conclusions

The results showed negative effect of methanolic and ethanolic extracts of pomegranate on G⁺ and G⁻ bacteria and two fungal pathogenic strains. The phytochemical analysis regarded these results to the high content of phenols, flavonoids, and tannins. GC-MS chromatogram identified many compounds known to be effective as antioxidants and antibacterial and antifungal agents. These indications show that pomegranate peel may be a superior natural food-preserver, but further studies about the suitable formulation, dosage, and possible side-effects are still needed.

In vitro antimicrobial activity of Millettia laurentii De Wild and Lophira alata Banks ex C. F. Gaertn on selected foodborne pathogens associated to gastroenteritis

This study aimed at evaluating the antimicrobial potential of aqueous, ethanolic and methanolic extracts of two Cameroonian plants against selected foodborne pathogens. Bioactive compounds were extracted from Millettia laurentii De Wild seeds and Lophira alata Banks ex. C. F. Gaertn leaves using distilled water, ethanol and methanol as solvents. The extracts were tested against Escherichia coli O157, Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, Proteus mirabilis, Moraxella morganii, Salmonella enteritidis, Klebsiella pneumoniae and Listeria monocytogenes using the microdilution method. The results showed that distilled water extracted a more important mass of phytochemical compounds (18.0-24.60%) compared to ethanol (4.80-5.0%) and methanol (4.20-4.60%). All the extracts exhibited significant antimicrobial activity with MIC values ranging from 5 to 20 μg/mL for M. laurentii seeds extracts and from 1.0 to 20 μg/mL for L. alata leaves extracts. The different plant extracts were ten times less active than gentamicin. The most active extracts were obtained using ethanol as solvent and K. pneumoniae was the most resistant pathogen to all extracts (MBC>20 μg/mL). M. laurentii extracts were bactericidal against L. monocytogenes and P. mirabilis while the reference antibiotic (gentamicin) was bacteriostatic against these pathogens. The results obtained from this study suggest the studied local plant materials as a source of antimicrobial compounds which can be valorized in the medical field as substitute of antibiotics for which many microorganisms have nowadays developed resistance mechanisms. Further studies need to be performed in order to characterize and identify these antimicrobial active molecules.

A New Potential Source of Anti-pathogenic Bacterial Substances from Zamioculcas zamiifolia (Lodd.) Engl. Extracts

BACKGROUND AND OBJECTIVE

The increase of antibiotic-resistant bacteria is a problem for global health that needs to find new antibiotic drugs. The plant is the potential source of antibiotic substances that important to solve the antibiotic-resistant bacteria. This study was aimed to evaluate the antibacterial activity of Zamioculcas zamiifolia stem extracts against nine human pathogenic bacteria.

MATERIALS AND METHODS

Z. zamiifolia stems were extracted with five extraction solvents. The screening of antibacterial activity of stem extract was measured using agar disc diffusion assay. The Minimal Inhibition Concentration (MIC) and Minimal Bactericidal Concentration (MBC) values of extracts were determined using the broth microdilution assay and colorimetric assay.

RESULTS

The results indicated that the lowest MIC value of 0.09 mg mL-1 against Staphylococcus aureus TISTR 1466 was obtained from hexane extraction. The lowest MBCs value of 1.56 mg mL-1 against Bacillus cereus TISTR 2373, Listeria spp. and Escherichia coli TISTR 527 were obtained from ethanol and methanol extractions.

CONCLUSION

The ethanolic and methanolic stem extracts of Z. zamiifolia demonstrated the highest anti-human pathogenic bacterial activity. This is the first report to demonstrate the high potential of antibacterial substance from Z. zamiifolia stem extracts, which can be developed further as a natural drug for treating bacterial infectious diseases.

Anti-bacterial activity of chitosan loaded plant essential oil against multi drug resistant K. pneumoniae

The development of antibiotic resistant in K. pneumoniae is an emerging thread worldwide due to the poor antimicrobial drugs. To overcome this issue, researchers are focused on plant material and their essential oils to fight against multi drug resistant bacteria. In this context, the current study was concentrated in medicinal plant of guva leaves and their essential oils to combat multi drug resistant bacterial infections. The essential oils were successfully screened and confirmed by HRLC-MS analysis. The anti-bacterial ability of the compounds were loaded into the chitosan nanoparticles and proved by FT-IR analysis. In addition, the chitosan loaded essential oils morphology was compared with chitosan alone in SEM analysis and suggested that the material was loaded successfully. Further, the anti-bacterial ability of the chitosan loaded essential oils were primarily confirmed by agar well diffusion method. At the 100 µg/mL of lowest concentration of chitosan loaded essential oils, the multi-drug resistant K. pneumoniae was inhibited with 96% and confirmed by minimum inhibition concentration experiment. Hence, all the experiments were proved that the essential oils were successfully loaded into the chitosan nanoparticles, and it has more anti-bacterial activity against multi-drug resistant K. pneumoniae.

The ethnopharmacology, phytochemistry, pharmacology and toxicology of genus Albizia: A review

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Albizia (Leguminosae) comprises about 150 species and some species have been used for the treatment of rheumatism, stomachache, cough, diarrhea, and wounds in traditional and local medicine. The aim of the review: This review article documents and critically assesses the current status of the traditional uses, phytochemistry, pharmacology, and toxicology of the Albizia species.

MATERIALS AND METHODS

All provided literatures on the Albizia species were searched using the electronic databases (e.g. Web of Science, Elsevier, Springer, PubMed, ACS, CNKI, Google Scholar, and Baidu Scholar), books, and theses with keywords of 'Albizia' and 'Albizzia'.

RESULTS

Albizia species have been used for melancholia, insomnia, wounds, fever, abscesses, diabetes, headache, stomachache, diarrhea, cough, rheumatism, snake bite, malaria, and parasitic infection in traditional and local medicine. These plants mainly contain triterpenoid saponins, flavonoids, lignanoids, alkaloids, phenolic glycosides, etc. Albizia species have been demonstrated to possess various pharmacological activities. Among them, the antidiabetic, anti-inflammatory, antifertility, antianxiety, antidepressant, and anti-fever properties are consistent with the traditional and local applications of the Albizia species.

CONCLUSIONS

The traditional and local uses of Albizia species have been partially demonstrated by the pharmacological investigation. However, some traditional applications have not been assessed scientifically due to incomplete methodologies and ambiguous findings. Moreover, no clinical evidences support the health benefits of these plants. The systematic and comprehensive preclinical studies and clinical trials are still required to verify the pharmacological activities, clinical efficacy, and safety of Albizia species.

Antimicrobial and Light-Enhanced Antimicrobial Activities, Cytotoxicity and Chemical Variability of All Tunisian Eryngium Species

This study was performed on all Eryngium species growing in Tunisia in order to evaluate their intra and interspecies variabilities and to investigate their biological activities. These species are used in traditional medicine, and literature about the phytochemical investigations of most of them is scarce. Antimicrobial and light-enhanced activities were tested against multiresistant microorganisms and extended spectrum beta-lactamase producing bacteria (ESBL). All studied species showed antimicrobial effect with several MIC values lower than 70 μg/ml. Tested Eryngium species have proven to be a promising source of photoactive compounds, while light-enhanced activity offers an alternative for the inactivation of pathogenic microorganisms which is currently subjected to a great interest. This is the first report of this activity in genus Eryngium. A significant improvement of antimicrobial activity with UV irradiation was observed, mainly for E. dichotomum, E. ilicifolium and E. triquetrum. Cytotoxicity, studied for the first time for the most species, was evaluated against cancer (J774) and non-cancer (WI38) human cell lines. Chemical composition of volatile compounds presented in the most active crude extracts (petroleum ether extracts) of the aerial parts was investigated using GC/MS analysis and was submitted to statistical analyses. It revealed their high content of bioactive phytochemicals, particularly oxygenated sesquiterpenes like spathulenol, ledol and α-bisabolol but also hydrocarbon sesquiterpenes such as β-bisabolene and copaene, as well as polyacetylene derivatives such as falcarinol. Statistical analyses permitted to evaluate the interrelations between all Tunisian Eryngium species.

Review: Southern African medicinal plants used as blood purifiers

ETHNOPHARMALOGICAL RELEVANCE

Blood purification practices, also referred to as blood cleansing or detoxification, is an ancient concept which is widespread amongst African traditional medicine, but for which no modern scientific basis exists. There prevails considerable ambiguity in defining what a blood purifier is.

AIM OF THE STUDY

The purpose of this review is to firstly define what a blood purifier is in the context of African traditional medicine and compare to other cultural and westernized interpretations. Thereafter, this study identifies traditionally used medicinal plants used as blood purifiers in southern Africa and correlates these species to scientific studies, which may support evidence for these "blood purifying plant species".

MATERIALS AND METHODS

Ethnobotanical books and review articles were used to identify medicinal plants used for blood purification. Databases such as Scopus, ScienceDirect, PubMed and Google Scholar were used to source scientific articles. An evaluation was made to try correlate traditional use to scientific value of the plant species.

RESULTS

One hundred and fifty nine plant species have been documented as traditional remedies for blood purification. Most of the plant species have some pharmacological activity, however, very little link to the traditional use for blood purification. There has been some justification of the link between blood purification and the use as an antimicrobial and this has been explored in many of the plant species identified as blood purifiers. Other pharmacological studies specifically pertaining to the blood require further attention.

CONCLUSION

Irrespective of the ambiguity of interpretation, medicinal plants used to "cleanse the blood", play an important holistic role in traditional medicine and this review with recommendations for further study provides some value of exploring this theme in the future.

Antibacterial and antibiotic-modifying activities of fractions and compounds from Albizia adianthifolia against MDR Gram-negative enteric bacteria

Background

Albizia adianthifolia (Schum.) is medicinally used in Cameroon to manage bronchitis and skin diseases. Our previous study documented the antibacterial potential of its roots’ methanol extract. In this study, methanol roots extract was subjected to chromatography techniques and fractions (AARa and AARb), sub-fractions (AARa1–4, AARb1–2 and AARb11–14) together with isolated phytochemicals were assessed for their antimicrobial as well as their antibiotic-potentiating effects towards Gram-negative multidrug resistant (MDR) bacteria.

Methods

The antibacterial activities of the samples (determination of Minimal Inhibitory « MIC » and Minimal Bactericidal Concentration « MBC ») were determined by the modified rapid p-iodonitrotetrazolium chloride (INT) colorimetric assay, as well as those of antibiotics in association with the compounds. Column chromatography was applied to isolate phytochemicals from roots extract and their chemical structures were determined using spectroscopic techniques.

Results

The phytochemicals isolated were stearic acid (1), a mixture (1:1) of stigmasterol and β-sitosterol (2 +  3), β-sitosterol 3-O-β-_D-glucopyranoside (4), palmatin (5), homomangiferin (6) and mangiferin (7). Fraction AARa exhibited selective inhibitory effects whilst all tested bacteria were inhibited by AARb in MIC ranges of 8 to 1024 μg/mL. Sub-fractions AARb1–2 had MIC values between 8 μg/mL and 1024 μg/mL on all tested bacteria. Phytochemicals 4, 2 +  3 and 7 inhibited the growth of 54.54% (6/11), 45.45% (5/11) and 27.27% (3/11) tested bacterial strains, respectively. When tested with an efflux pumps inhibitor (Phenylalanine-Arginine-β-Naphthylamide or PAβN), the inhibitory effects of compounds 2 + 3 and 4 increased towards all the tested bacteria. In association with erythromycin (ERY), streptomycin (STR) and tetracycline (TET), compounds 2 + 3 and 4 had the most significant synergistic activity on the seven selected bacteria.

Conclusion

The present study provides information on the possible use of Albizia adianthifolia and its constituents in the control of Gram-negative infections including MDR phenotypes.

Electronic supplementary material

The online version of this article (10.1186/s12906-019-2537-1) contains supplementary material, which is available to authorized users.

Isolation of Helicobacter pylori from Gastric Biopsy of Dyspeptic Patients in Ghana and In Vitro Preliminary Assessment of the Effect of Dissotis rotundifolia Extract on Its Growth

Helicobacter pylori (H. pylori) is a gram-negative bacterium that colonizes the human stomach. Infection with this microaerophilic bacterium causes gastric and duodenal ulcer. This study sought to isolate H. pylori, from gastric biopsy samples of dyspeptic patients in Ghana using a 2,3,5-triphenyltetrazolium chloride (TTC) dye incorporated medium method. This TTC dye method was further used in an antimicrobial susceptibility assay involving Dissotis rotundifolia extract (DRE). H. pylori were successfully isolated from gastric biopsy of dyspeptic patients. Pure cultures of H. pylori in 2,3,5-triphenyltetrazolium chloride (TTC) dye incorporated medium were seen as sparkling colonies. Isolates, identified as H. pylori, were gram-negative and urease, catalase, and oxidase positive and showed characteristic morphology as spiral-shaped bacteria under the microscope. The organisms were found to be susceptible to cephalothin and resistant to nalidixic acid. Above all, the observation that H. pylori grew only at 37°C and not 25°C or 42°C affirms that the bacterium is neither Helicobacter cinaedi nor Helicobacter fenneliae. The anti-H. pylori study depicts a statistically lower zone of inhibition for DRE compared to standard drugs [amoxicillin and clarithromycin] (p<0.05), whereas metronidazole showed no zone of inhibition. This study reports the first successful isolation and culturing of H. pylori in Ghana using TTC dye. It also shows that DRE possess an in vitro anti-H. pylori activity and that DRE has some therapeutic potential against H. pylori infection.

Albizia Adianthifolia: Botany, Medicinal Uses, Phytochemistry, and Pharmacological Properties

The bark, leaves, and roots of Albizia adianthifolia are highly sought after in tropical Africa as herbal medicines. Therefore, the aim of this study was to review the botany, medicinal uses, phytochemistry, and pharmacological properties of A. adianthifolia so as to provide baseline data required for evaluating the therapeutic potential of the species. Information on the botanical profile, medicinal uses, phytochemistry, and pharmacological properties of A. adianthifolia was undertaken using databases such as ScienceDirect, SciFinder, Pubmed, Google Scholar, Medline, SCOPUS, EThOS, ProQuest, OATD, and Open-thesis. Preelectronic literature search of conference papers, scientific articles, books, book chapters, dissertations, and theses was carried out at the University library. Literature search revealed that A. adianthifolia is used as purgative and herbal medicine for diabetes, eye problems, gastrointestinal problems, haemorrhoids, headache, neurodegenerative disorders, reproductive problems in women, respiratory problems, wounds and pain, skin diseases, sexually transmitted infections, and ethnoveterinary medicine. Phytochemical compounds identified from the species include apocarotenoids, chalcone, dipeptide, elliptosides, essential oils, fatty acids, flavonoids, histamine, imidazolyl carboxylic acid, prosapogenins, steroids, triterpene saponins, and triterpenoids. Pharmacological studies revealed that A. adianthifolia extracts and compounds have acetylcholinesterase enzyme inhibitory, anthelmintic, antiamoebic, antibacterial, antimycobacterial, anti-sexually transmitted infections, antifungal, anti-inflammatory, antioxidant, anxiolytic, and antidepressant, cognitive-enhancing, haemolytic, hypoglycemic and antihyperglycemic, immunomodulatory, and cytotoxicity activities. Detailed studies on the pharmacokinetics, in vivo, and clinical research involving compounds isolated from A. adianthifolia and extracts of the species are required.

Syzygium jambos Displayed Antibacterial and Antibiotic-Modulating Activities against Resistant Phenotypes

The present study was designed to evaluate the antibacterial activities of methanol extracts of bark and leaves of Syzygium jambos, as well as their synergistic effects with selected antibiotics against drug-resistant Gram-positive and Gram-negative bacteria. The crude extracts were subjected to qualitative phytochemical screening; broth microdilution method was used for antibacterial assays. Phytochemical studies indicate that leaves and bark extracts contained polyphenols, anthraquinones, tannins, and steroids. Extract of the leaves was active against all the 26 strains of Staphylococcus aureus and all the 21 strains of Gram-negative bacteria tested, within the minimum inhibitory concentration (MIC) range of 32–512 μg/mL. The lowest MIC value of 32 μg/mL was obtained with extract of the leaves against Staphylococcus aureus MRSA9 strain. In Gram-negative bacteria, the lowest MIC value of 64 μg/mL was also obtained against Enterobacter aerogenes EA294 and Klebsiella pneumoniae K24 strains. Against S. aureus strains, antibiotic-modulating activity of extracts at MIC/2 towards more than 70% of the tested strains was obtained when leaves and bark extracts were tested in association with chloramphenicol (CHL). This was also the case when leaves extract was combined with CHL, kanamycin (KAN), tetracycline (TET), and erythromycin (ERY) and when bark extract was combined with ciprofloxacin (CIP), TET, and ERY against Gram-negative bacteria. In conclusion, this study demonstrated that Syzygium jambos has antibacterial and antibiotic-modulating activities.

Antimicrobial and antibiofilm activities of nanoemulsions containing Eucalyptus globulus oil against Pseudomonas aeruginosa and Candida spp

Candida species are the main responsible microorganisms for causing fungal infections worldwide, and Candida albicans is most frequently associated with infectious processes. Pseudomonas aeruginosa is a gram-negative bacterium commonly found in immunocompromised patients. The infection persistence caused by these microorganisms is often related to antimicrobial resistance and biofilm formation. In this context, the objective of the present study was to prepare and characterize nanoemulsions containing Eucalyptus globulus oil and to verify its antimicrobial and antibiofilm activities against P. aeruginosa and Candida spp. The nanoemulsions had a size of approximately 76 nm, a polydispersity index of 0.22, a zeta potential of - 9,42 mV and a pH of approximately 5.0. The E. globulus oil was characterized by gas chromatography, being possible to observe its main components, such as 1-8-Cineol (75.8%), p- Cymene (7.5%), α-Pinene (7.4%) and Limonene (6.4%). The antimicrobial activity of the nanoemulsion was determined from the macrodilution tests and the cell viability curve, where the minimum fungicidal concentration of 0.7 mg/mL for C. albicans and 1.4 mg/mL for C. tropicalis and C. glabrata were obtained. However, the nanoemulsions did not present antimicrobial activity against P. aeruginosa, since it contains only 5% of the oil, being ineffective for this microorganism. The nanoencapsulated oil action against the formed biofilm was evaluated by atomic force microscopy and calcofluor staining, and the nanoemulsion was more efficient for two of the three Candida species when compared to free oil.

Antibacterial activity of six medicinal Cameroonian plants against Gram-positive and Gram-negative multidrug resistant phenotypes

Background

Infectious diseases due to multidrug-resistant bacteria are one of the causes of treatment failures contributing to an increase in mortality and/or morbidity. In this study, we evaluated the antibacterial potential of different parts of six medicinal plants namely Alstonia boonei, Ageratum conyzoides, Croton macrostachys, Cassia obtusifolia, Catharanthus roseus and Paullinia pinnata against a panel of 36 multi-drug resistant (MDR) Gram-negative and Gram-positive bacteria.

Methods

Minimum Inhibitory Concentration (MIC) and Minimal Bactericidal Concentration (MBC) of the methanol extracts from different parts of the plants were determined using broth microdilution method; standard phytochemical methods were used for phytochemical screening.

Results

Several phytochemical classes such as polyphenols, sterols, triterpenes, alkaloids, flavonoids and saponins were identified in the plant extracts. MIC values obtained ranged from 64 to 1024 μg/mL. Leaves extract of Catharanthus roseus (86.11 %), Croton macrostachys (83.33 %) and Paullinia pinnata (80.55 %) displayed the best antibacterial spectra. The lowest MIC value of 64 μg/mL was obtained with the Paullinia pinnata stems extract and Cassia obtusifolia extract against the strain of Staphylococcus aureus MRSA8. Results also showed that the tested samples generally displayed bacteriostatic effects with MBC values obtained in only 3.35 % of the cases where plant extracts were active.

Conclusion

The results obtained at the end of this study demonstrate for the first time the antibacterial activity of the studied medicinal plants against MDR bacteria. The tested plants could be a reservoir of molecules to fight against MDR bacterial infections.

Cytotoxicity of methanol extracts of 10 Cameroonian medicinal plants towards multi-factorial drug-resistant cancer cell lines

Background

Cancer chemotherapy is still hampered by clinical failures due to multi-drug resistance (MDR) of tumor cells. In the present study, we have investigated the cytotoxicity of 20 methanol extracts from 10 medicinal plants against the sensitive leukemia CCRF-CEM cells. The most cytotoxic extracts were then further tested on a panel of 8 human cancer cell lines, including various MDR phenotypes.

Methods

The cytotoxicity of the 20 methanol extracts from 10 Cameroonian medicinal plants 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 (ROS).

Results

In the preliminary assay using CCRF-CEM cells, 12 extracts from five plants displayed IC₅₀ values below 80 μg/mL, namely Albizia adianthifolia, Alchornea cordifolia, Alchornea laxiflora, Pennisetum purpureum, and Spathodea campanulata. the four best extracts were from two plants: Albizia adianthifolia roots (AAR) and bark (AAB) as well as Alchornea cordifolia leaves (ACL) and bark (ACB) had respective IC₅₀ values of 0.98 μg/mL, 1.45 μg/mL, 8.02 μg/mL and 12.57 μg/mL in CCRF-CEM cells. They were further tested in 8 other cell lines as well as in normal AML12 hepatocytes. IC₅₀ values ranging from 2.71 μg/mL (towards glioblastoma U87MG.ΔEGFR cells) to 10.30 μg/mL (towards breast adenocarcinoma MDA-MB-231-BCRP cells) for AAB, from 3.43 μg/mL (towards U87MG cells) to 10.77 μg/mL (towards colon carcinoma HCT116 (p53^−/−) cells) for AAR and from 0.11 μg/mL (towards CCRF-CEM cells) to 108 μg/mL (towards leukemia CEM/ADR5000 cells) for doxorubicin (as control drug) were obtained. ACL and ACB extracts displayed selective activities. AAR and ACL extracts induced apoptosis in CCRF-CEM cells, through caspases activation and loss of MMP, while apoptotic cell death was mediated by MMP diruption and increase ROS production for ACL.

Conclusion

Some of the tested plants namely Albizia adianthifolia, Alchornea cordifolia, Alchornea laxiflora, Pennisetum purpureum, Spathodea campanulata represent a potential source of novel anticancer drugs. Especially, Albizia adianthifolia and Alchornea cordifolia revealed considerable cytotoxic activities that could be exploited to develop phytomedicines to fight cancers including MDR phenotypes.