Antibacterial phytocomplexes and compounds from Psychotria sycophylla (Rubiaceae) against drug-resistant bacteria

HPLC-ESI-QTOF-MS profiling of antibacterial bioactive solvent fractions of Senna alata (L.) roxb (Fabaceae) leaves, and in silico prediction of pharmacokinetic, drug-likeness, and toxicity of major phyto-components

ETHNOPHARMACOLOGICAL RELEVANCE

Medicinal plants are a rich source of new antibacterial leads. One such plant is Senna alata (L.) Roxb (Fabaceae), a valuable medicinal tree known in folk medicine for its effectiveness in treating various ailments such as ringworms, wounds, diabetes, skin diseases, hypertension, malaria, mycosis, and bacterial diseases.

AIM OF THE STUDY

This study assesses the antibacterial and antibiotic-resistance reversal properties of S. alata leaf extracts against 32 multi-drug resistant (MDR) clinically relevant bacterial strains and clinical isolates.

MATERIALS AND METHODS

The hydromethanol extract (70%) was obtained through ultrasound-assisted extraction, followed by partitioning with solvents of increasing polarity, specifically petroleum ether (PE), ethyl acetate (EA), n-butanol (n-BuOH), and water, to isolate different fractions. Antibacterial and combination tests were conducted using the broth microdilution method. Subsequently, high-resolution HPLC-ESI-QTOF-MS analysis was performed to profile the bioactive secondary metabolites in the most active fractions. In addition, the pharmacokinetic (PK) properties, drug-likeness, and medicinal chemistry of the key phytoconstituents were predicted in silico using SwissADME. Moreover, we utilized the ProTox-II web server to predict the toxicity profile of the potential drug candidates.

RESULTS

The herbal fractions, except for the water fraction, showed remarkable antibacterial activity, with MICs ranging from 16 to 1024 μg/mL. The ethyl acetate (SA-EA) and n-butanol (SA-n-BuOH) fractions were the most potent, with the overall most significant effects recorded with SA-EA (with MIC <100 μg/mL on 31 out of the 32 MDR studied strains). Additionally, SA-EA enhanced the efficacy of antibiotics, leading to up to a 64-fold reduction in MICs (of chloramphenicol, imipenem, ciprofloxacin, cefepime, and doxycycline) in combination. A total of 27 and 36 compounds were tentatively identified from SA-EA and SA-n-BuOH, respectively, with the majority being phenolic compounds known for their antibacterial properties. Furthermore, 17 phytochemicals were reported for the first time in S. alata fractions. Seven metabolites, including phloretin, 7,4'-dihydroxyflavone, isorhamnetin, apigenin, genistein, naringenin, and lactarorufin B, emerged as potential drug candidates that satisfy most of the drug candidacy criteria and PK profile amongst which apigenin, genistein, and naringenin depicted the best safety profile.

CONCLUSION

The positive outcomes observed in the antibacterial activity assays, coupled with the presence of bioactive metabolites and emerging drug leads in these fractions, underscore the importance of selecting S. alata for the discovery and development of new antibacterial agents targeting MDR phenotypes.

Study of the Antioxidant and Antibacterial Effects of Genipa americana L. Against Food Pathogens

This study presents the chemical profile of the ethanolic extract of Genipa americana L. stem bark and the evaluation of its antibacterial and antioxidant activities. The chemical prospecting consisted of a qualitative analysis and quantification by HPLC-DAD. An antibacterial evaluation was performed using broth microdilution to determine the MIC, while gentamicin and amikacin were used to modify the antimicrobials. The antioxidant tests included the DPPH• method, ABTS•+ radical cation capture, Fe2+ chelation, Fe3+ reduction, and oxidative degradation of deoxyribose. Phytochemical tests identified its flavonoid and alkaloid classes, and an HPLC analysis allowed for caffeic acid quantification in the extract. The results of this study showed satisfactory MICs for E. coli and K. pneumoniae, 256 µg/mL; S. flexneri and P. vulgaris, 512 µg/mL; and S. typhimurium, ≥ 1024 µg/mL. Furthermore, there was a modifying effect on the bacterial strains, except for S. enterica. The antioxidant tests using the DPPH• method showed an IC50 of 298.1 µg.mL-1, with the highest percentage of ABTS•+ radical cation capture occurring at a concentration of 500 µg/mL; regarding Fe2+, chelating activity was not present, and for Fe3+ reduction, the best concentrations were 10 µg/mL and 25 µg/mL. The data obtained can be used to turn G. americana into a viable species as an agent for antibacterial and antioxidant functionalities in foods.

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

Background and Aim

Antibiotic resistance, especially in Gram-negative bacteria, is a major public health risk affecting all industries requiring the use of antibiotics, including agriculture and animal breeding. This study aimed to use papaya extracts to synthesize silver nanoparticles (AgNPs) and evaluate their antimicrobial activity against various Gram-negative bacteria.

Materials and Methods

Silver nanoparticles were synthesized from the aqueous extracts of papaya seed, root, and bark, with AgNO3 used as a reducing agent. The phytofabricated AgNPs were analyzed by ultraviolet-visible absorbance, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy, and photon cross-correlation spectroscopy (PCCS). The disc-diffusion method was used to perform antibacterial analysis, and the minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations were determined. We also investigated the antibiofilm activity of AgNPs and attempted to elucidate the potential mechanism of action on Escherichia coli ATCC 25922.

Results

Phytofabrication of AgNPs was successful with papaya root (PR-AgNPs) and papaya seed (PS-AgNPs), but not with papaya bark. Silver nanoparticles using papaya root and PS-AgNPs were both cubic and showed maximum absorbances of 2.6 and 0.3 AUs at 411.6 and 416.8 nm wavelengths and average hydrodynamic diameters X50 of 59.46 ± 7.03 and 66.57 ± 8.89 nm, respectively. The Ag in both AgNPs was confirmed by X-ray fluorescence by a distinctive peak in the spectrum at the silver Kα line of 22.105 keV. Both AgNPs exhibited broad-spectrum antimicrobial and antibiofilm activity against all Gram-negative bacteria, and PR-AgNPs were slightly better than AgNPs-PS. The MIC ranged from 16 μg/mL-128 μg/mL and 16 μg/mL-64 μg/mL, respectively, for PS-AgNPs and PR-AgNPs. The elucidation of the mechanism of action revealed interference with E. coli ATCC 25922 growth kinetics and inhibition of H+-ATPase proton pumps.

Conclusion

Papaya seed and root extracts were efficient reducing agents for the biogenic synthesis of AgNPs, with noteworthy antibacterial and antibiofilm activities. Future studies should be conducted to identify the phytochemicals and the mechanism involved in AgNPs synthesis.