Synergistic Effect of Quercetin on Antibacterial Activity of Florfenicol Against Aeromonas hydrophila In Vitro and In Vivo

Fruit Extract and Phenolic Compounds of Phyllanthus emblica Fruits as Bioactivity Enhancer of Chloramphenicol Against Bacterial Species

Phyllanthus emblica L. (syn. Emblica officinalis) fruits have been traditionally exploited to enhance the immune system and provide protection against bacterial and fungal diseases. The present study aimed to evaluate the synergistic interactions between chloramphenicol and several phenolic compounds found in P. emblica fruits against bacterial strains. The combination of P. emblica fruit extracts and its phenolic compounds demonstrated synergistic antibacterial activity when used in conjunction with chloramphenicol against both Gram-positive and Gram-negative bacteria. The combination of MICGA with ½MICChl exhibited a significant increase in bioactivity, with a 333.33-fold enhancement against B. subtilis. Similarly, the combination of MICGA with 2MICChl displayed a bioactivity enhancement of 16.02 folds against S. aureus. The co-administration of ½MICQ and ½MICChl resulted in a significant 35.71-fold increase in bioactivity against P. aeruginosa. Similarly, the combination of MIC GA and ½MICChl exhibited a remarkable 166.66-fold enhancement in bioactivity against E. coli. The combinations of 2MICFPE and ½MICChloramphenicol, as well as ½MICGA and ½MICChl demonstrated the highest bioactivity enhancement of 17.85 folds for K. pneumoniae. This study claimed that the fruit extracts of P. emblica and its phenolic compounds could be utilized to augment the effectiveness of conventional antibiotics, which have acquired resistance to bacterial infections.

Nitrogen-Containing Flavonoids-Preparation and Biological Activity

In this work, we report the application of Buchwald-Hartwig amination for the preparation of new derivatives of quercetin and luteolin. Our investigation delves into the impact of aniline moiety on antioxidant, and anti-inflammatory activity, cytotoxicity, and the ability of flavonoids to modulate drug-resistance mechanisms in bacteria. The anti-inflammatory activity disappeared after the introduction of aniline into the flavonoids and the cytotoxicity remained low. Although the ability of quercetin and luteolin to modulate bacterial resistance to antibiotics has already been published, this is the first report on the molecular mechanism of this process. Both flavonoids attenuate erythromycin resistance by suppressing the ribosomal methyltransferase encoded by the ermA gene in Staphylococcus aureus. Notably, 4-(trifluoromethyl)anilino quercetin emerged as a potent ErmA inhibitor, likely by interacting with the RNA-binding pocket of ErmA. Additionally, both 4-fluoroanilino derivatives effectively impended the staphylococcal efflux system. All the prepared derivatives exhibited superior activity in modulating gentamicin resistance in S. aureus compared to the parent compounds. Overall, the incorporation of substituted anilines into the flavonoid core significantly enhanced its ability to combat multidrug resistance in bacteria.

Pharmacokinetics of florfenicol and its metabolite florfenicol amine in the plasma, urine, and feces of fattening male donkeys following single oral administration

Florfenicol (FF) is a commonly used antibacterial agent in animals. We investigated the pharmacokinetics of FF and its metabolite florfenicol amine (FFA) in donkeys. Donkeys were administered FF (30 mg/kg bodyweight, p.o.). Pharmacokinetic parameters were calculated using a non-compartmental model. The FF (FFA) pharmacokinetics parameters were characterized by along elimination half-life (t1/2 kz) of 5.92 h (15.95 h), plasma peak concentration (Cmax) of 0.13 μg/mL (0.08 μg/mL), and the time taken to reach Cmax (Tmax) of 0.68 h (0.72 h). The area under plasma concentration-time curve and mean residence time of FF (FFA) in plasma were 1.31 μg·mL-1·h (0.47 μg·mL-1·h) and 10.37 h (18.40 h), respectively. The t1/2 kz of FF and FFA in urine was 21.93 and 40.26 h, and the maximum excretion rate was 10.56 and 4.03 μg/h reached at 25.60 and 32.20 h, respectively. The respective values in feces were 0.02 and 0.01 μg·h-1 reached at 33.40 h. The amount of FF and FFA recovered in feces was 0.52 and 0.22 μg, respectively. In conclusion, FF (FFA) is rapidly absorbed and slowly eliminated after a single oral administration to donkeys. Compared to FF, FFA was more slowly eliminated. FF (FFA) is mostly excreted through urine.

Nano-Formulating Besifloxacin and Employing Quercetin as a Synergizer to Enhance the Potency of Besifloxacin against Pathogenic Bacterial Strains: A Nano-Synergistic Approach

The present study applied a nano-synergistic approach to enhance besifloxacin's potency via nano-formulating besifloxacin on gold nanoparticles (Besi-AuNPs) and adding quercetin as a natural synergistic compound. In fact, a one-pot AuNP synthesis approach was applied for the generation of Besi-AuNPs, where besifloxacin itself acted as a reducing and capping agent. Characterization of Besi-AuNPs was performed by spectrophotometry, DLS, FTIR, and electron microscopy techniques. Moreover, antibacterial assessment of pure besifloxacin, Besi-AuNPs, and their combinations with quercetin were performed on Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. UV-spectra showed a peak of AuNPs at 526 nm, and the electron microscopy-based size was estimated to be 15 ± 3 nm. The effective MIC₅₀ concentrations of besifloxacin after loading on AuNPs were reduced by approximately 50% against the tested bacterial strains. Interestingly, adding quercetin to Besi-AuNPs further enhanced their antibacterial potency, and isobologram analysis showed synergistic potential (combination index below 1) for different quercetin and Besi-AuNP combinations. However, Besi-AuNPs and quercetin combinations were most effective against Gram-positive S. aureus in comparison to Gram-negative P. aeruginosa and E. coli. Their potent activity against S. aureus has its own clinical significance, as it is one the main causative agents of ocular infection, and besifloxacin is primarily used for treating infectious eye diseases. Thus, the outcomes of the present study could be explored further to provide better medication for eye infections caused by resistant pathogens.