Antibacterial and antibiotic-modifying activities of three food plants (Xanthosoma mafaffa Lam., Moringa oleifera (L.) Schott and Passiflora edulis Sims) against multidrug-resistant (MDR) Gram-negative bacteria.

BACKGROUND: The 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. METHODS: Broth 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. RESULTS: The 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 ß-Naphtylamide (PAßN)], 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. CONCLUSION: The results of the present study indicate that the tested plants may be used in the treatment of bacterial infections including the multi-resistant bacteria.

Antibiotic-potentiation activities of four Cameroonian dietary plants against multidrug-resistant Gram-negative bacteria expressing efflux pumps.

BACKGROUND: The continuous spread of multidrug-resistant (MDR) bacteria, partially due to efflux pumps drastically reduced the efficacy of the antibiotic armory, increasing the frequency of therapeutic failure. The search for new compounds to potentiate the efficacy of commonly used antibiotics is therefore important. The present study was designed to evaluate the ability of the methanol extracts of four Cameroonian dietary plants (Capsicum frutescens L. var. facilulatum, Brassica oleacera L. var. italica, Brassica oleacera L. var. butyris and Basilicum polystachyon (L.) Moench.) to improve the activity of commonly used antibiotics against MDR Gram-negative bacteria expressing active efflux pumps. METHODS: The qualitative phytochemical screening of the plant extracts was performed using standard methods whilst the antibacterial activity was performed by broth micro-dilution method. RESULTS: All the studied plant extracts revealed the presence of alkaloids, phenols, flavonoids, triterpenes and sterols. The minimal inhibitory concentrations (MIC) of the studied extracts ranged from 256-1024 µg/mL. Capsicum frutescens var. facilulatum extract displayed the largest spectrum of activity (73%) against the tested bacterial strains whilst the lower MIC value (256 µg/mL) was recorded with Basilicum polystachyon against E. aerogenes ATCC 13048 and P. stuartii ATCC 29916. In the presence of PAßN, the spectrum of activity of Brassica oleacera var. italica extract against bacteria strains increased (75%). The extracts from Brassica oleacera var. butyris, Brassica oleacera var. italica, Capsicum frutescens var. facilulatum and Basilicum polystachyon showed synergistic effects (FIC ≤ 0.5) against the studied bacteria, with an average of 75.3% of the tested antibiotics. CONCLUSION: These results provide promising information for the potential use of the tested plants alone or in combination with some commonly used antibiotics in the fight against MDR Gram-negative bacteria.

Pharmacological Preconditioning Improves the Viability and Proangiogenic Paracrine Function of Hydrogel-Encapsulated Mesenchymal Stromal Cells.

The efficacy of cell therapy is limited by low retention and survival of transplanted cells in the target tissues. In this work, we hypothesize that pharmacological preconditioning with celastrol, a natural potent antioxidant, could improve the viability and functions of mesenchymal stromal cells (MSC) encapsulated within an injectable scaffold. Bone marrow MSCs from rat (rMSC) and human (hMSC) origin were preconditioned for 1 hour with celastrol 1 µM or vehicle (DMSO 0.1% v/v), then encapsulated within a chitosan-based thermosensitive hydrogel. Cell viability was compared by alamarBlue and live/dead assay. Paracrine function was studied first by quantifying the proangiogenic growth factors released, followed by assessing scratched HUVEC culture wound closure velocity and proliferation of HUVEC when cocultured with encapsulated hMSC. In vivo, the proangiogenic activity was studied by evaluating the neovessel density around the subcutaneously injected hydrogel after one week in rats. Preconditioning strongly enhanced the viability of rMSC and hMSC compared to vehicle-treated cells, with 90% and 75% survival versus 36% and 58% survival, respectively, after 7 days in complete media and 80% versus 64% survival for hMSC after 4 days in low serum media (p < 0.05). Celastrol-treated cells increased quantities of proangiogenic cytokines compared to vehicle-pretreated cells, with a significant 3.0-fold and 1.8-fold increase of VEGFa and SDF-1α, respectively (p < 0.05). The enhanced paracrine function of preconditioned MSC was demonstrated by accelerated growth and wound closure velocity of injured HUVEC monolayer (p < 0.05) in vitro. Moreover, celastrol-treated cells, but not vehicle-treated cells, led to a significant increase of neovessel density in the peri-implant region after one week in vivo compared to the control (blank hydrogel). These results suggest that combining cell pretreatment with celastrol and encapsulation in hydrogel could potentiate MSC therapy for many diseases, benefiting particularly ischemic diseases.

Antibacterial activities of the methanol extracts of Canarium schweinfurthii and four other Cameroonian dietary plants against multi-drug resistant Gram-negative bacteria.

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.