In-Silico molecular screening of natural compounds as a potential therapeutic inhibitor for Methicillin-resistant Staphylococcus aureus inhibition.

Methicillin-resistant Staphylococcus aureus (MRSA) is a life-threatening superbug causing infectious diseases such as pneumonia, endocarditis, osteomyelitis, etc. Conventional antibiotics are ineffective against MRSA infections due to their resistance mechanism against the antibiotics. The Penicillin Binding Protein (PBP2a) inhibits the activity of antibiotics by hydrolyzing the ß-lactam ring. Thus, alternate treatment methods are needed for the treatment of MRSA infections. Natural bioactive compounds exhibit good inhibition efficiency against MRSA infections by hindering its enzymatic mechanism, efflux pump system, etc. The present work deals with identifying potential and non-toxic natural bioactive compounds (ligands) through molecular docking studies through StarDrop software. Various natural bioactive compounds which are effective against MRSA infections were docked with the protein (6VVA). The ligands having good binding energy values and pharmacokinetic and drug-likeness properties have been illustrated as potential ligands for treating MRSA infections. From this exploration, Luteolin, Kaempferol, Chlorogenic acid, Sinigrin, Zingiberene, 1-Methyl-4-(6-methylhepta-1,5-dien-2-yl)cyclohex-1-ene, and Curcumin have found with good binding energies of -8.6 kcal/mol, -8.4 kcal/mol, -8.2 kcal/mol, -7.5 kcal/mol, -7.4 kcal/mol, -7.3 kcal/mol, and -7.2 kcal/mol, respectively.

Discovery of an Orally Available Diazabicyclooctane Inhibitor (ETX0282) of Class A, C, and D Serine ß-Lactamases.

Multidrug resistant Gram-negative bacterial infections are an increasing public health threat due to rapidly rising resistance toward ß-lactam antibiotics. The hydrolytic enzymes called ß-lactamases are responsible for a large proportion of the resistance phenotype. ß-Lactamase inhibitors (BLIs) can be administered in combination with ß-lactam antibiotics to negate the action of the ß-lactamases, thereby restoring activity of the ß-lactam. Newly developed BLIs offer some advantage over older BLIs in terms of enzymatic spectrum but are limited to the intravenous route of administration. Reported here is a novel, orally bioavailable diazabicyclooctane (DBO) ß-lactamase inhibitor. This new DBO, ETX1317, contains an endocyclic carbon-carbon double bond and a fluoroacetate activating group and exhibits broad spectrum activity against class A, C, and D serine ß-lactamases. The ester prodrug of ETX1317, ETX0282, is orally bioavailable and, in combination with cefpodoxime proxetil, is currently in development as an oral therapy for multidrug resistant and carbapenem-resistant Enterobacterales infections.

Anti-Helicobacter pylori Activity of Isocoumarin Paepalantine: Morphological and Molecular Docking Analysis.

The Helicobacterpylori bacterium is one of the main causes of chronic gastritis, peptic ulcers, and even gastric cancer. It affects an average of half of the world population. Its difficult eradication depends upon multi-drug therapy. Since its classification as a group 1 carcinogenic by International Agency for Research on Cancer (IARC), the importance of H. pylori eradication has obtained a novel meaning. There is considerable interest in alternative therapies for the eradication of H. pylori using compounds from a wide range of natural products. In the present study, we investigated the antibacterial property of the isocoumarin paepalantine against H. pylori and it exhibited significant anti-H. pylori activity at a minimum inhibitory concentration (MIC) of 128 µg/mL and at a minimum bactericidal concentration (MBC) of 256 µg/mL. The scanning electron microscopy (SEM) revealed significant morphological changes of the bacterial cell as a response to a sub-MIC of paepalantine, suggesting a penicillin-binding protein (PBP) inhibition. Computational studies were carried out in order to study binding modes for paepalantine in PBP binding sites, exploring the active and allosteric sites. The data from the present study indicates that paepalantine exhibits significant anti-H. pylori activity, most likely by inhibiting membrane protein synthesis.

[Virtual screening and antibacterial activity of lead compounds targeting to penicillin-binding protein 3 (PBP3) of Pseudomonas aeruginosa].

OBJECTIVE: This study was carried out to obtain lead compounds targeting penicillin-binding protein 3 (PBP3) of Pseudomonas aeruginosa by virtual screening. METHODS: UCSF dock 6.5 was used for the virtual screening from a database containing 1.04 million small molecules. Hit compounds with simple structures were synthesized and then evaluated for their antibacterial activities. RESULTS: Grid score was used for the first round of screening, and 60000 small molecules whose scores lower than -30 kcal/mol were screened out from the database. These molecules were subjected to the second round of screening using amber score. Approximately 200 hit compounds with scores lower than -20 kcal/mol were analyzed and 4 of them were selected as lead compounds and then synthesized. The minimal inhibition concentrations (MICs) of the lead compounds were between 175-275 µg/mL, which were lower than that of Sulfadiazine (500 µg/mL) significantly. Meanwhile, these compounds were effective for both Gram-negative and Gram-positive bacteria. CONCLUSION: The lead compounds had potential to become new antibacterial agents for conquering the drug resistance of P. aeruginosa.

Bioactivity Studies of ß-Lactam Derived Polycyclic Fused Pyrroli-Dine/Pyrrolizidine Derivatives in Dentistry: In Vitro, In Vivo and In Silico Studies.

The antibacterial activity of ß-lactam derived polycyclic fused pyrrolidine/pyrrolizidine derivatives synthesized by 1, 3-dipolar cycloaddition reaction was evaluated against microbes involved in dental infection. Fifteen compounds were screened; among them compound 3 showed efficient antibacterial activity in an ex vivo dentinal tubule model and in vivo mice infectious model. In silico docking studies showed greater affinity to penicillin binding protein. Cell damage was observed under Scanning Electron Microscopy (SEM) which was further proved by Confocal Laser Scanning Microscope (CLSM) and quantified using Flow Cytometry by PI up-take. Compound 3 treated E. faecalis showed ROS generation and loss of membrane integrity was quantified by flow cytometry. Compound 3 was also found to be active against resistant E. faecalis strains isolated from failed root canal treatment cases. Further, compound 3 was found to be hemocompatible, not cytotoxic to normal mammalian NIH 3T3 cells and non mutagenic. It was concluded that ß-lactam compound 3 exhibited promising antibacterial activity against E. faecalis involved in root canal infections and the mechanism of action was deciphered. The results of this research can be further implicated in the development of potent antibacterial medicaments with applications in dentistry.

Molecular docking and inhibition studies on the interactions of Bacopa monnieri's potent phytochemicals against pathogenic Staphylococcus aureus.

BACKGROUND: Bacopa monnieri Linn. (Plantaginaceae), a well-known medicinal plant, is widely used in traditional medicine system. It has long been used in gastrointestinal discomfort, skin diseases, epilepsy and analgesia. This research investigated the in vitro antimicrobial activity of Bacopa monnieri leaf extract against Staphylococcus aureus and the interaction of possible compounds involved in this antimicrobial action. METHODS: Non-edible plant parts were extracted with ethanol and evaporated in vacuo to obtain the crude extract. A zone of inhibition studies and the minimum inhibitory concentration (MIC) of plant extracts were evaluated against clinical isolates by the microbroth dilution method. Docking study was performed to analyze and identify the interactions of possible antimicrobial compounds of Bacopa monnieri in the active site of penicillin binding protein and DNA gyrase through GOLD 4.12 software. RESULTS: A zone of inhibition studies showed significant (p < 0.05) inhibition capacity of different concentrations of Bacopa monnieri's extract against Staphylococcus aureus. The extract also displayed very remarkable minimum inhibitory concentrations (≥16 µg/ml) which was significant compared to that (≥75 µg/ml) of the reference antibiotic against the experimental strain Staphylococcus aureus. Docking studies recommended that luteolin, an existing phytochemical of Bacopa monnieri, has the highest fitness score and more specificity towards the DNA gyrase binding site rather than penicillin binding protein. CONCLUSIONS: Bacopa monnieri extract and its compound luteolin have a significant antimicrobial activity against Staphylococcus aureus. Molecular binding interaction of an in silico data demonstrated that luteolin has more specificity towards the DNA gyrase binding site and could be a potent antimicrobial compound.