Synthesis, PASS-Predication and in Vitro Antimicrobial Activity of Benzyl 4-O-benzoyl-α-l-rhamnopyranoside Derivatives

Assessment of antidiabetic activity of three Phenylspirodrimanes from fungus Stachybotrys chartarum MUT 3308 by ADME, QSAR, molecular docking and molecular dynamics simulation studies against protein tyrosine phosphatase 1B (PTP1B)

Phenylspirodrimanes (PSD) are the sesquiterpene quinone type meroterpenoids found in nature. PSDs are found to exhibit inhibitory activity against immunocomplex diseases, and tyrosine kinase receptors. Three of the different PSDs C1, C2, and C3 that have been reported to be isolated from the sponge-associated fungus Stachybotrys chartarum MUT 3308 are selected for studying their possible inhibitory effect against type 2 diabetes mellitus. Mechanistically, blocking protein tyrosine phosphatase 1B (PTP1B) helps to reduce the insulin resistance induction caused by the high expression of PTP1B. The QSAR, ADME, toxicity (T) study was carried out to predict the pharmacokinetic properties and the biological activities of the PSDs. PASS prediction web tool was used to find and select the target proteins 1NNY, and 2HNP. According to the molecular docking simulations, C1 and C2 showed better binding affinity of -8.5 kcal/mol, and -8.1 kcal/mol respectively against 1NNY compared to the control ligand. RMSD, RMSF, Rg, and SASA analysis revealed that both C1, and C2 showed better stability, minor conformational changes, and minor fluctuation upon binding to PTP1B. Protein contact analysis was carried out to validate the residues that are in contact with the ligands according to molecular docking studies. Overall, C1, and C2 could be proposed as novel natural hits to be developed and small modifications of these PSDs could result in inducing the binding affinity significantly, although experimental validation is required for further evaluation of the work.Communicated by Ramaswamy H. Sarma.

Rhamnopyranoside-Based Fatty Acid Esters as Antimicrobials: Synthesis, Spectral Characterization, PASS, Antimicrobial, and Molecular Docking Studies

The most widely used and accessible monosaccharides have a number of stereogenic centers that have been hydroxylated and are challenging to chemically separate. As a result, the task of regioselective derivatization of such structures is particularly difficult. Considering this fact and to get novel rhamnopyranoside-based esters, DMAP-catalyzed di-O-stearoylation of methyl α-l-rhamnopyranoside (3) produced a mixture of 2,3-di-O- (4) and 3,4-di-O-stearates (5) (ratio 2:3) indicating the reactivity of the hydroxylated stereogenic centers of rhamnopyranoside as 3-OH > 4-OH > 2-OH. To get novel biologically active rhamnose esters, di-O-stearates 4 and 5 were converted into six 4-O- and 2-O-esters 6-11, which were fully characterized by FT-IR, ¹H, and ¹³C NMR spectral techniques. In vitro antimicrobial assays revealed that fully esterified rhamnopyranosides 6-11 with maximum lipophilic character showed better antifungal susceptibility than antibacterial activity. These experimental findings are similar to the results found from PASS analysis data. Furthermore, the pentanoyl derivative of 2,3-di-O-stearate (compound 6) showed better antifungal functionality against F. equiseti and A. flavus, which were found to be better than standard antibiotics. To validate the better antifungal results, molecular docking of the rhamnose esters 4-11 was performed with lanosterol 14α-demethylase (PDB ID: 3LD6), including the standard antifungal antibiotics ketoconazole and fluconazole. In this instance, the binding affinities of 10 (-7.6 kcal/mol), 9 (-7.5 kcal/mol), and 7 (-6.9 kcal/mol) were better and comparable to fluconazole (-7.3 kcal/mol), indicating the likelihood of their use as non-azole type antifungal drugs in the future.

Novel Galactopyranoside Esters: Synthesis, Mechanism, In Vitro Antimicrobial Evaluation and Molecular Docking Studies

One-step direct unimolar valeroylation of methyl α-D-galactopyranoside (MDG) mainly furnished the corresponding 6-O-valeroate. However, DMAP catalyzed a similar reaction that produced 2,6-di-O-valeroate and 6-O-valeroate, with the reactivity sequence as 6-OH > 2-OH > 3-OH,4-OH. To obtain novel antimicrobial agents, 6-O- and 2,6-di-O-valeroate were converted into several 2,3,4-tri-O- and 3,4-di-O-acyl esters, respectively, with other acylating agents in good yields. The PASS activity spectra along with in vitro antimicrobial evaluation clearly indicated that these MDG esters had better antifungal activities than antibacterial agents. To rationalize higher antifungal potentiality, molecular docking was conducted with sterol 14α-demethylase (PDB ID: 4UYL, Aspergillus fumigatus), which clearly supported the in vitro antifungal results. In particular, MDG ester 7−12 showed higher binding energy than the antifungal drug, fluconazole. Additionally, these compounds were found to have more promising binding energy with the SARS-CoV-2 main protease (6LU7) than tetracycline, fluconazole, and native inhibitor N3. Detailed investigation of Ki values, absorption, distribution, metabolism, excretion, and toxicity (ADMET), and the drug-likeness profile indicated that most of these compounds satisfy the drug-likeness evaluation, bioavailability, and safety tests, and hence, these synthetic novel MDG esters could be new antifungal and antiviral drugs.

In vitro antimicrobial, physicochemical, pharmacokinetics and molecular docking studies of benzoyl uridine esters against SARS-CoV-2 main protease

Different esters were found potential against microorganisms, and could be a better choice to solve the multidrug resistant (MDR) pathogenic global issue due to their improved biological and pharmacokinetic properties. In this view, several 4-t-butylbenzoyl uridine esters 4-15 with different aliphatic and aromatic groups were synthesized for antimicrobial, physicochemical and biological studies. In vitro antimicrobial tests against nine bacteria and three fungi along with prediction of activity spectra for substances (PASS) indicated promising antifungal functionality of these uridine esters compared to the antibacterial activities. In support of this observation their cytotoxicity and molecular docking studies have been performed against lanosterol 14α-demethylase (CYP51A1) and Aspergillus flavus (1R51). Significant binding affinities were observed against SARS-CoV-2 main protease (7BQY) considering hydroxychloroquine (HCQ) as standard. ADMET predictions were investigated to evaluate their absorption, metabolism and toxic properties. Most of the uridine esters showed better results than that of the HCQ. Overall, the present study might be useful for the development of uridine-based novel MDR antimicrobial and COVID-19 drugs.

DFT Based Comparative Studies of Some Glucofuranose and Glucopyranoside Esters and Ethers

Carbohydrate-based molecular scaffolding received significant interest due to its impact on the drug discovery and development in synthetic carbohydrate chemistry during the last couple of decades. In this respect, four glucose compounds in the furanose and pyranose forms with ester and ether functionality were selected for their structural, thermodynamic and chemical reactivity studies. PASS predication indicated that the glucose in the six-membered pyranose form was more prone to biological properties compared to their five-membered furanose form. Also, in the pyranose form acetate ester (3) had more potentiality than the ethyl ether (4). The HOMO-LUMO energy gaps were almost similar for both monosubstituted furanose and pyranose glucose indicating their almost similar reactivities. It was also inferred that these 6-O-substituted compounds followed Lipinski’s rule with the acceptable range of ADMET levels, and hence, safe from lethal proarrhythmic risks. Hopefully, these results can be used in the near future for their probable pharmaceutical use without any remarkable toxicity.

Efficient Synthetic Technique, PASS Predication, and ADMET Studies of Acylated n-Octyl Glucopyranosides

Direct dimolar pentanoylation of octyl β-D-glucopyranoside (OBG) in pyridine-chloroform solvent system furnished the corresponding 3,6-di-O-pentanoate in improved yield. The pentanoate was further converted into three 2,4-di-O-acyl esters to get novel octyl glucopyranosides. To explore medicinal probability of OBG-based esters all the synthesized compounds were subjected for in silico PASS (prediction of activity spectra for substances) predication and ADMET (absorption, distribution, metabolism, excretion, and toxicity) studies. Both the studies indicated that OBG derived carbohydrate fatty acid (CFA) esters are potential alternative for multidrug resistant (MDR) pathogens, especially for fungal infections.

Green Synthesis of Silver Nanoparticles Using the Lotus lalambensis Aqueous Leaf Extract and Their Anti-Candidal Activity against Oral Candidiasis

Oral candidiasis is widely spread in both humans and animals, which is caused mainly by Candida albicans. In this study, we aimed to biosynthesize silver nanoparticles (AgNPs) for the first time using the Lotus lalambensis Schweinf leaf extract (L-AgNPs) and investigated their anti-candidal potency alone or in combination with the leaf extract of L. lalambensis (L-AgNPs/LL) against C. albicans. The biosynthesized L-AgNPs were characterized by imaging (transmission electron microscopy, TEM), UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The results of the disk diffusion method showed the potent synergistic anti-candidal activity of L-AgNPs/LL (24 mm inhibition zone). L-AgNPs/LL completely inhibited the morphogenesis of C. albicans and suppressed the adhesion and the formation of the biofilm of C. albicans by 82.5 and 78.7%, respectively. Further, L-AgNPs/LL inhibited the production of antioxidant enzymes of C. albicans by 80%. SEM and TEM revealed deteriorations in the cell wall ultrastructure in L-AgNPs/LL-treated C. albicans. Interestingly, L-AgNPs/LL showed less than 5% cytotoxicity when examined with either the primary bone marrow derived mesenchymal stem cell (BMSCs) or MCF-7 cell line at MIC values of L-AgNPs/LL. In conclusion, we identified L-AgNPs/LL as a potential biosynthesized-based drug for oral candidiasis in humans and animals.

Synthesis, PASS Predication, Antimicrobial, DFT, and ADMET Studies of Some Novel Mannopyranoside Esters

Due to the biodegradability and drug-likeness properties sugar esters (SEs) are getting especial attention to the synthetic and bioorganic chemists. In this context, we have synthesized several 6-O-pentanoyl mannopyranoside esters (5-9) with alkanoyl and sylfonyl chains reasonably in good yields. Both the prediction of activity spectra for substances (PASS) and in vitro tests indicated that these mannopyranoside esters possess better potentiality against fungal pathogens than the bacterial organisms. These SEs were also optimized with quantum chemical density functional theory (DFT), and various thermodynamic properties like frontier molecular orbital, and molecular electrostatic potential (MEP) were calculated and discussed. Absorption, distribution, metabolism, excretion, and toxicity (ADMET) calculations indicated that these SEs can pass through blood brain barrier and less toxic. Drug-likeness results indicated good conditions for alkanoyl esters rather than sulfonyl esters despite their promising antifungal results. All the in vitro and in silico results indicated that the combination of pentanoyl (C5) and lauroyl (C12) chains in mannopyranoside framework, as in 9, might be a potential candidate for novel antifungal agent.

Novel mannopyranoside esters as sterol 14α-demethylase inhibitors: Synthesis, PASS predication, molecular docking, and pharmacokinetic studies

Direct unimolar one-step valeroylation of methyl α-d-mannopyranoside (MDM) furnished mainly 6-O-valeroate. However, similar reaction catalyzed by DMAP resulted 3,6-di-O-valeroate (21%) and 6-O-valeroate (47%) indicating reactivity sequence as 6-OH>3-OH>2-OH,4-OH. To get potential antimicrobial agents, 6-O-valeroate was converted into four 2,3,4-di-O-acyl esters, and 3,6-di-O-valeroate was converted into 2,4-di-O-acetate. Direct tetra-O-valeroylation of MDM gave a mixture of 2,3,4,6-tetra-O-valeroate and 2,3,6-tri-O-valeroate indicating that the C2-OH is more reactive than the equatorial C4-OH. The activity spectra analysis along with in vitro antimicrobial evaluation clearly indicated that these novel MDM esters had better antifungal activities over antibacterial agents. In this connection, molecular docking indicated that these MDM esters acted as competitive inhibitors of sterol 14α-demethylase (CYP51), an essential enzyme for clinical target to cure several infectious diseases. Furthermore, pharmacokinetic studies revealed that these MDM esters may be worth considering as potent candidates for oral and topical administration. Structure activity relationship (SAR) affirmed that saturated valeric chain (C5) in combination with caprylic (C8) chains was more promising CYP51 inhibitor over conventional antifungal antibiotics.

Synthesis, PASS predication, in vitro antimicrobial evaluation and pharmacokinetic study of novel n-octyl glucopyranoside esters

Octyl β-d-glucopyranoside (OBG), prepared from d-glucose and octan-1-ol employing MW method, was subjected to direct dimolar valeroylation in pyridine at room temperature (25 °C) with valeroyl chloride. This mainly furnished the corresponding 3,6-di-O-valeroate in 57% yield indicating the regioselectivity at C-6 and C-3 positions. For structural elucidation and to get newer glucopyranosides of potential antimicrobial 3,6-di-O-valeroate was further converted into four novel 2,4-di-O-acyl esters reasonably in good yields. Per-O-acetate and per-O-benzoate of OBG were also prepared for SAR study. PASS predication and in vitro antimicrobial studies established them as better antifungal agent than that of antibacterial. SAR study along with AdmetSAR and SwissADME suggested that incorporation of alkanoyl and aromatic ester groups on octyl glucopyranoside core increase antimicrobial potentiality in very low concentration (10 μgmL^-1). Molecular docking revealed that novel 2,4-di-O-tosyl ester and 2,3,4,6-tetra-O-benzoyl ester may act as competitive inhibitors of lanosterol 14-alpha demethylase.

Photodynamic inactivation as an emergent strategy against foodborne pathogenic bacteria in planktonic and sessile states

Foodborne microbial diseases are still considered a growing public health problem worldwide despite the global continuous efforts to ensure food safety. The traditional chemical and thermal-based procedures applied for microbial growth control in the food industry can change the food matrix and lead to antimicrobial resistance. Moreover, currently applied disinfectants have limited efficiency against biofilms. Therefore, antimicrobial photodynamic therapy (aPDT) has become a novel alternative for controlling foodborne pathogenic bacteria in both planktonic and sessile states. The use of aPDT in the food sector is attractive as it is less likely to cause antimicrobial resistance and it does not promote undesirable nutritional and sensory changes in the food matrix. In this review, aspects on the antimicrobial photodynamic technology applied against foodborne pathogenic bacteria and studied in recent years are presented. The application of photodynamic inactivation as an antibiofilm strategy is also reviewed.

Complete Genome Sequence of Streptomyces sp. TN58, a Producer of Acyl Alpha-l-Rhamnopyranosides

Streptomyces sp. TN58, isolated from a Tunisian soil sample, produces several natural products, including acyl alpha-l-rhamnopyranosides. It possesses a 7.6-Mb linear chromosome. This is, to our knowledge, the first genome sequence of a microorganism known to produce acyl alpha-l-rhamnopyranosides, and it will be helpful to study the biosynthesis of these specialized metabolites.