Screening of Some Essential Oil Constituents as Potential Inhibitors of the ATP Synthase of Escherichia coli

Insights into the potential dual-antibacterial mechanism of Kelisha capsule on Escherichia coli

Traditional Chinese medicine (TCM), AYURVEDA and Indian medicine are essential in disease prevention and treatment. Kelisha capsule (KLSC), a TCM formula listed in the Chinese Pharmacopoeia, has been clinically proven to possess potent antibacterial properties. However, the precise antimicrobial mechanism of KLSC remained unknown. This study aimed to elucidate the dual antibacterial mechanism of KLSC using network pharmacology, molecular docking, and experimental validation. By analyzing the growth curve of Escherichia coli (E. coli), it was observed that KLSC significantly inhibited its growth, showcasing a remarkable antibacterial effect. Furthermore, SEM and TEM analysis revealed that KLSC damaged the cell wall and membrane of E. coli, resulting in cytoplasmic leakage, bacterial death, and the exertion of antibacterial effects. The network pharmacology analysis revealed that KLSC exhibited an effect on E. coli ATP synthase, thereby influencing the energy metabolism process. The molecular docking outcomes provided evidence that the active compounds of KLSC could effectively bind to the ATP synthase subunit. Subsequently, experimental findings substantiated that KLSC effectively suppressed the activity of ATP synthase in E. coli and consequently decreased the ATP content. This study highlighted the dual antibacterial mechanism of KLSC, emphasizing its effects on cell structure and energy metabolism, suggesting its potential as a natural antibacterial agent for E. coli-related infections. These findings offered new insights into exploring the antibacterial mechanisms of TCM by focusing on the energy metabolism process.

Combination of Chromatographic Analysis and Chemometric Methods with Bioactivity Evaluation of the Antibacterial Properties of Helichrysum italicum Essential Oil

Helichrysum italicum (immortelle) essential oil is one of the most popular essential oils worldwide and it has many beneficial properties, including antimicrobial. However, in this plant, the chemical diversity of the essential oil is very pronounced. The aim of this work was to process the GC-MS results of four samples of H. italicum essential oil of Serbian origin by chemometric tools, and evaluate the antimicrobial activity in vitro and in silico. Overall, 47 compounds were identified, the most abundant were γ-curcumene, α-pinene, and ar-curcumene, followed by α-ylangene, neryl acetate, trans-caryophyllene, italicene, α-selinene, limonene, and italidiones. Although the four samples of H. italicum essential oil used in this study were obtained from different producers in Serbia, they belong to the type of essential oil rich in sesquiterpenes (γ-curcumene and ar-curcumene chemotype). In vitro antimicrobial potential showed that five were sensitive among ten strains of tested microorganisms: Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Saccharomyces cerevisiae, and Candida albicans. Therefore, these microorganism models were used further for in silico molecular docking through the mechanism of ATP-ase inhibitory activity. Results showed that among all compounds from H. italicum essential oil, neryl acetate has the highest predicted binding energy. Artificial neural network modeling (ANN) showed that two major compounds γ-curcumene and α-pinene, as well as minor compounds such as trans-β-ocimene, terpinolene, terpinene-4-ol, isoitalicene, italicene, cis-α-bergamotene, trans-α-bergamotene, italidiones, trans-β-farnesene, γ-selinene, β-selinene, α-selinene, and guaiol are responsible for the antimicrobial activity of H. italicum essential oil. The results of this study indicate that H. italicum essential oil samples rich in γ-curcumene, α-pinene, and ar-curcumene cultivated in Serbia (Balkan) have antimicrobial potential both in vitro and in silico. In addition, according to ANN modeling, the proportion of neryl acetate and other compounds detected in these samples has the potential to exhibit antimicrobial activity.

The performance of plant essential oils against lactic acid bacteria and adverse microorganisms in silage production

Plant essential oils have played an important role in the field of antibiotic alternatives because of their efficient bacteriostatic and fungistatic activity. As plant essential oils are widely used, their activity to improve the quality of plant silage has also been explored. This review expounds on the active ingredients of essential oils, their bacteriostatic and fungistatic activity, and mechanisms, as well as discusses the application of plant essential oils in plant silage fermentation, to provide a reference for the development and application of plant essential oils as silage additives in plant silage fermentation feed.

Montivipera bornmuelleri Venom: Inhibitory Effect on Staphylococcus epidermidis and Escherichia coli F1F0-ATPases and Cytotoxicity on HCT116 Cancer Cell Lines

In this work, we pursued the biological characterization of the venom of Montivipera bornmuelleri, a viper from the Lebanese mountains. In relation to its antibacterial potential, the inhibitory effect of this venom on the F1F0-ATPase enzymes of Gram-positive Staphylocoocus epidermidis and Gram-negative Escherichia coli bacteria was examined. In order to determine the degree of cytotoxicity of the venom on the HCT116 human colon cancer cell lines, the biological MTT proliferation and cell viability test were implemented. After validation of the enzymatic F1F0-ATPase model by the spectrophotometric method, using quercetin as the reference ligand, results revealed that M. bornmuelleri venom is able to inhibit the activity of the enzyme of these two bacteria with a concentration of the order of 100–150 µg/mL. In addition, a venom concentration of 10 µg/mL was sufficient to kill the totality of HCT116 cell lines cultivated in vitro. These data show that M. bornmuelleri venom is a mixture of diverse molecules presenting activities of interest, and is a potential source to explore in order to discover new drug candidates.

Potential Inhibitory Effect of Apis mellifera's Venom and of Its Two Main Components-Melittin and PLA2-on Escherichia coli F1F0-ATPase

Bacterial resistance has become a worrying problem for human health, especially since certain bacterial strains of Escherichia coli (E. coli) can cause very serious infections. Thus, the search for novel natural inhibitors with new bacterial targets would be crucial to overcome resistance to antibiotics. Here, we evaluate the inhibitory effects of Apis mellifera bee venom (BV-Am) and of its two main components -melittin and phospholipase A₂ (PLA₂)- on E. coli F₁F₀-ATPase enzyme, a crucial molecular target for the survival of these bacteria. Thus, we optimized a spectrophotometric method to evaluate the enzymatic activity by quantifying the released phosphate from ATP hydrolysis catalyzed by E. coli F₁F₀-ATPase. The protocol developed for inhibition assays of this enzyme was validated by two reference inhibitors, thymoquinone (IC₅₀ = 57.5 μM) and quercetin (IC₅₀ = 30 μM). Results showed that BV-Am has a dose-dependent inhibitory effect on E. coli F₁F₀-ATPase with 50% inhibition at 18.43 ± 0.92 μg/mL. Melittin inhibits this enzyme with IC₅₀ = 9.03 ± 0.27 µM, emphasizing a more inhibitory effect than the two previous reference inhibitors adopted. Likewise, PLA₂ inhibits E. coli F₁F₀-ATPase with a dose-dependent effect (50% inhibition at 2.11 ± 0.11 μg/mL) and its combination with melittin enhanced the inhibition extent of this enzyme. Crude venom and mainly melittin and PLA₂, inhibit E. coli F₁F₀-ATPase and could be considered as important candidates for combating resistant bacteria.