Optimization of Ethanolic Extraction of Enantia chloranta Bark, Phytochemical Composition, Green Synthesis of Silver Nanoparticles, and Antimicrobial Activity

Abstract

In this study, using the Box–Behnken model, we optimized the ethanolic extraction of phytochemicals from Enantia chloranta bark for the first time, assessed the composition with HPLC-MS/MS, performed the green synthesis of silver nanoparticles (AgNPs) and characterized them with UV-Vis spectrophotometry, photon cross-correlation spectroscopy, energy-dispersive X-ray fluorescence spectrometry, and Fourier transform infrared spectroscopy. The antibacterial and antibiotic-resistance reversal properties of optimized extract (O-ECB) and AgNPs were assessed on various microorganisms (15 Gram−, 7 Gram+, and 2 fungi) using the well diffusion method and microbroth dilution assay. The mechanism of action was investigated on growth kinetic and proton pumps of Escherichia coli. The in vivo antimicrobial activity and toxicity were assessed on Galleria mellonella larvae. The optimal mass yield (14.3%) related to the highest antibacterial activity (31 mm vs. S. aureus ATCC 6538) was obtained with the following operating conditions: % EtOH—100%; ratio m/v—20 g/mL; and extraction time—6 h. All the compounds identified in O-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 O-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, 3.485,4, and 2.5942 cps/uA, respectively. The synthesized AgNPs revealed a strong absorption plasmon band between 430 and 450 nm and an average hydrodynamic diameter ×50 of 59.74 nm, and the presence of Ag was confirmed by a characteristic peak in the spectrum at the silver Kα line of 22.105 keV. Both O-ECB and AgNPs displayed noteworthy and broad-spectrum antimicrobial activities against 20/24 and 24/24 studied microorganisms, respectively, with recorded minimal inhibitory concentrations (MICs) ranging from 8 to ≥ 1024 µg/mL and 2 to 64 µg/mL. O-ECB and AgNPs showed antibiofilm properties and significantly enhanced the efficacy of conventional antibiotics against selected multidrug-resistant bacteria, and the mechanistic investigations revealed their interference with bacterial growth kinetic and the inhibition of H+-ATPase proton pumps. LD50s were 40 mg/mL and 0.6 mg/mL for O-ECB and AgNPs, respectively. In conclusion, the current study provides a strong experimental baseline to consider Enantia chlorantha bark and their green synthetized AgNPs as potent antimicrobial compounds in this era of antimicrobial resistance.

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

“…Recently, interest in metallic nanostructures and nanocomplexes has increased considerably. Panáček et al [1] reported that the strong bactericidal activity of silver (Ag) nanoparticles (AgNPs) against both Gram-positive and Gram-negative bacteria, including multiresistant strains, makes them a potential antifungal agent [8]. The synthesis of AgNPs is performed in physical ways (evaporation-condensation and laser ablation) [9] or by chemical reduction using inorganic and organic reducing agents, such as poly (ethylene glycol), sodium borohydride, N-dimethylformamide, hydrazine, and surfactant template approach [10,11].…”

“…The synthesis of AgNPs is performed in physical ways (evaporation-condensation and laser ablation) [9] or by chemical reduction using inorganic and organic reducing agents, such as poly (ethylene glycol), sodium borohydride, N-dimethylformamide, hydrazine, and surfactant template approach [10,11]. Although these synthesis routes are effective, they cause toxicity, and more reliable methods need to be developed [8,9]. More eco-friendly methods, such as green routes using microorganisms, enzymes, and plant extracts, are increasingly suggested to replace chemical methods [10,[12][13][14][15][16].…”

Antimicrobial activity of phytofabricated silver nanoparticles using Carica papaya L. against Gram-negative bacteria

“…Antibiotic resistance is the ability of bacteria to resist antimicrobials to which they are susceptible [1][2][3]. This phenomenon is particularly observed in Gram-negative bacteria because of their ability to easily accumulate resistance genes and the presence of efflux pumps in their membranes, which are used to expel antimicrobials from the cells.…”

“…This phenomenon is particularly observed in Gram-negative bacteria because of their ability to easily accumulate resistance genes and the presence of efflux pumps in their membranes, which are used to expel antimicrobials from the cells. This capability makes these bacteria unresponsive or resistant to various types of antibiotics [3][4][5].…”

“…In general, antibiotic resistance has prompted a major mobilization in pursuing new antimicrobial compounds and alternative treatments [2]. Several matrices with physiological potentials, such as probiotics [6,7], medicinal plants [8][9][10], antimicrobial peptides [11,12], phages [13,14], and various nanoparticles (NPs) [3,15,16], are regularly suggested as the most credible alternatives to common antibiotics. In recent years, there has also been a considerable increase in research to study the antibacterial activity of metallic nanostructures and nanocomplexes, with silver NPs (AgNPs) being among the most investigated [3,[15][16][17].…”