Antifungal activity of silver nanoparticles prepared using Aloe vera extract against Candida albicans.

Background and Aim: Resistance to antifungal agents is a serious public health concern that has not been investigated enough because most studies on antimicrobials are dedicated to antibacterial resistance. This study aimed to synthesize silver nanoparticles (AgNPs) using Aloe vera extract, and to assess its antifungal activity against Candida albicans. Materials and Methods: Silver nanoparticles were synthesized by reducing Ag nitrate with aqueous A. vera extracts. Physicochemical properties of synthesized AgNPs were determined by ultraviolet-visible spectrophotometry, photon cross-correlation spectroscopy, energy-dispersive X-ray fluorescence spectrometry, X-ray diffraction analysis, and Fourier-transform infrared spectroscopy. An antifungal investigation was performed against four clinical C. albicans (C1, C2, C3, and C4) and a reference strain, C. albicans ATCC 10321. Results: Cubic AgNPs with a mean X50 hydrodynamic diameter of 80.31 ± 10.03 nm were successfully synthesized. These AgNPs exhibited maximum absorbance at 429.83 nm, and X-ray fluorescence (XRF) confirmed the presence of Ag in AgNPs solution by a characteristic peak in the spectrum at the Ag Kα line of 22.105 keV. Infrared spectra for AgNPs and A. vera extract indicated that the compounds present in the extract play an essential role in the coating/capping of synthesized AgNPs. Different concentrations (200, 100, 50, 25, 10, and 5 µg/mL) of AgNPs were tested. The antifungal activity was shown to be dose-dependent with inhibition zones ranging from 10 mm to 22 mm against C. albicans ATCC 10231, 0 mm to 15 mm against C1, 0 mm to 16 mm against C2 and C3, and 0 mm to 14 mm for C4. Minimum inhibitory concentration ranged from 16 µg/mL to 32 µg/mL against clinical C. albicans (C1, C2, C3, and C4) and was 4 µg/mL against C. albicans ATCC 10231. Conclusion: This study showed the ability of A. vera to serve as an efficient reducing agent for the biogenic synthesis of AgNPs with excellent antifungal activity.

Antimicrobial and Antibiotic-Resistance Reversal Activity of Some Medicinal Plants from Cameroon against Selected Resistant and Non-Resistant Uropathogenic Bacteria.

BACKGROUND AND AIM: Antibiotics' resistance is the leading cause of complications in the treatment of urinary tract infections. This study aimed to screen the antimicrobial potential of 8 plants from Cameroon against multi-resistant uropathogenic (MRU) bacteria and to investigate their antibioresistance reversal properties. METHOD: Bioactive compounds were extracted from leaves of Leucanthemum vulgare, Cymbopogon citratus, Moringa oleifera and Vernonia amygdalina; barks of Cinchona officinalis and Enantia chlorantha barks and seeds of Garcinia lucida and leaves and seeds of Azadirachta indica using water and ethanol as solvents. The extracts were tested against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 6538 and Candida albicans 10231 using the well diffusion and the broth microdilution methods. The antibiotic-resistance reversal activity was assessed against selected MRU bacteria. The phytochemical composition and the elemental composition of the most active extracts were assessed respectively using HPLC-MS/MS and X-ray fluorescence (XRF) spectrometry. RESULTS: Among the most active plants, in decreasing order of antimicrobial activity we found ethanolic (EE) and aqueous extracts (AE) of E. chloranta bark (ECB), EE of L. vulgare leaves and G. lucida seeds. The best synergies between common antibiotics and extracts were found with EE-ECB which well-modulated kanamycin nitrofurantoin and ampicillin. All the compounds identified in EE-ECB were alkaloids and the major constituents were palmatine (51.63%), columbamine+7,8-dihydro-8-hydroxypalmatine (19.21%), jatrorrhizine (11.02%) and pseudocolumbamine (6.33%). Among the minerals found in EE-ECB (S, Si, Cl, K, Ca, Mn, Fe, Zn and Br), Br, Fe and Cl were the most abundant with mean fluorescence intensities of 4.6529, 3.4854 and 2.5942 cps/uA respectively. CONCLUSIONS: The ethanol extract of the bark of E. chlorantha has remarkable, broad-spectrum antimicrobial and contains several palmatine derivatives.

In vitro antimicrobial activity, antibioresistance reversal properties, and toxicity screen of ethanolic extracts of Heracleum mantegazzianum Sommier and Levier (giant hogweed), Centaurea jacea L. (brown knapweed), and Chenopodium album L. (Pigweed): Three invasive plants.

Background: Plants, including invasive ones, can play a significant role in the fight against antibiotic resistance and the search for new antimicrobials. Aims: The present study aimed at assessing the antimicrobial activity, antibioresistance reversal properties, and toxicity of four samples from invasive plants, namely, Heracleum mantegazzianum (leaves and flowers), Chenopodium album (leaves), and Centaurea jacea (flowers). Methods: The extraction of active compounds was done with ethanol (80%, v/v) and the extraction yields were calculated. Antimicrobial activity was studied using the agar-well diffusion method against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 6538, and Candida albicans ATCC 10231. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) were determined using the mircodilution method. The antibioresistance reversal properties were assessed using the checkerboard method and the toxicity of the extracts was studied using the larval form of the Greater Wax Moth (Galleria mellonella). Results: The mass yields were 11.9, 15.0, 18.2, and 21.5, respectively, for C. jacea flower (CJF), H. mantegazzianum flower (HMF), H. mantegazzianum leaf (HML), and C. album leaf (CAL). The highest inhibition diameters (ID) were found with HMF, CAL, CJF, and HML against S. aureus with 26.6, 21.6, 21.0, and 20.0 mm, respectively. Only CJF and HMF were active against E. coli with respective ID of 15.3 and 19.0 mm. Except HMF (ID = 13.6 ± 2.0 mm), no other extract was active against C. albicans. Moreover, HMF exhibited the lowest MIC (0.5 mg/ml) and the lowest MBC (1 and 4 mg/ml) against both S. aureus and E. coli. Regarding the synergy test, an additional effect [0.5 ≤ fractional inhibitory concentration (FIC) ≤ 1] was found in almost all the combinations antibiotics + extracts excepted for HMF + (Kanamycin or Ampicillin) against S. aureus and CJF + Ampicillin against E. coli where we found synergy effect (FIC ≤0.5). The median lethal doses (LD50s) of HMF, HML, CAL, and CJF were 20.2, 0.58, 13.2, and 4.0 mg/ml, respectively. Conclusion: Only the ethanolic extract of HMFs showed noteworthy broad spectrum antimicrobial activity.