Bioinspired green synthesis of ZnO nanoparticles by marine-derived Streptomyces plicatus and its multifaceted biomedicinal properties

The present study explores the bioinspired green synthesis of zinc oxide nanoparticles (ZnONPs) using marine Streptomyces plicatus and its potent antibacterial, antibiofilm activity against dental caries forming Streptococcus mutans MTCC and S. mutans clinical isolate (CI), cytotoxicity against oral KB cancer cells, hemolysis against blood erythrocytes and artemia toxicity. The bioinspired ZnONPs showed a distinctive absorption peak at 375 nm in UV-Vis spectra, the FT-IR spectra divulged the active functional groups, and XRD confirmed the crystalline nature of the nanoparticles with an average grain size of 41.76 nm. SEM analysis evidenced hexagonal morphology, and EDX spectra affirmed the presence of zinc. The ZnONPs exerted higher antagonistic activity against S. mutans MTCC (Inhibitory zone: 19 mm; MIC: 75 μg/ml) than S. mutans CI (Inhibitory zone: 17 mm; MIC: 100 μg/ml). Results of biofilm inhibitory activity showed a concentration-dependent reduction with S. mutans MTCC (15 %-95 %) more sensitive than S. mutans CI (13 %-89 %). The 50 % biofilm inhibitory concentration (BIC50) of ZnONPs against S. mutans MTCC was considerably lower (71.76 μg/ml) than S. mutans CI (78.13 μg/ml). Confocal Laser Scanning Microscopic visuals clearly implied that ZnONPs effectively distorted the biofilm architecture of both S. mutans MTCC and S. mutans CI. This was further bolstered by a remarkable rise in protein leakage (19 %-85 %; 15 %-77 %) and a fall in exopolysaccharide production (34 mg-7 mg; 49 mg-12 mg). MTT cytotoxicity of ZnONPs recorded an IC50 value of 22.06 μg/ml against KB cells. Acridine orange/ethidium bromide staining showed an increasing incidence of apoptosis in KB cells. Brine shrimp cytotoxicity using Artemia salina larvae recorded an LC50 value of 78.41 μg/ml. Hemolysis assay substantiated the biocompatibility of the ZnONPs. This study underscores the multifaceted application of bioinspired ZnONPs in dentistry.

Exploring the potential of biologically active phenolic acids from marine natural products as anticancer agents targeting the epidermal growth factor receptor

The epidermal growth factor receptor (EGFR) dimerizes upon ligand bindings to the extracellular domain that initiates the downstream signaling cascades and activates intracellular kinase domain. Thus, activation of autophosphorylation through kinase domain results in metastasis, cell proliferation, and angiogenesis. The main objective of this research is to discover more promising anti-cancer lead compound against EGRF from the phenolic acids of marine natural products using in-silico approaches. Phenolic compounds reported from marine sources are reviewed from previous literatures. Furthermore, molecular docking was carried out using the online tool CB-Dock. The molecules with good docking and binding energies scores were subjected to ADME, toxicity and drug-likeness analysis. Subsequently, molecules from the docking experiments were also evaluated using the acute toxicity and MD simulation studies. Fourteen phenolic compounds from the reported literatures were reviewed based on the findings, isolation, characterized and applications. Molecular docking studies proved that the phenolic acids have good binding fitting by forming hydrogen bonds with amino acid residues at the binding site of EGFR. Chlorogenic acid, Chicoric acid and Rosmarinic acid showed the best binding energies score and forming hydrogen bonds with amino acid residues compare to the reference drug Erlotinib. Among these compounds, Rosmarinic acid showed the good pharmacokinetics profiles as well as acute toxicity profile. The MD simulation study further revealed that the lead complex is stable and could be future drug to treat the cancer disease. Furthermore, in a wet lab environment, both in-vitro and in-vivo testing will be employed to validate the existing computational results.Communicated by Ramaswamy H. Sarma.

Inhibitory activity of marine sponge metabolites on SARS-CoV-2 RNA dependent polymerase: virtual screening and molecular dynamics simulation

Marine species are known as rich sources of metabolites involved mainly in the pharmaceutical industry. This study aimed to evaluate the effect of biologically active compounds in the marine sponge on the SARS-CoV-2 RNA-dependent-RNA polymerase protein (RdRp) using the in-silico method. A total of 51 marine compounds were checked for their possible interaction with SARS-CoV-2 RdRp using Maestro interface for molecular docking, molecular dynamic (MD) simulation, and MM/GBSA method to estimate compounds binding affinities. Among the 51 compounds screened in this study, two (mycalamide A, and nakinadine B) exhibited the lowest docking energy and best interaction. Among these compounds, mycalamide A was identified as a potent inhibitor of SARS-CoV-2 RdRp that showed the best and stable interaction during molecular dynamic simulation, with residues (Asp760 and Asp761) found in the catalytic domain of RdRp. The analysis through MM/GBSA for molecular dynamic simulation results revealed binding energy -59.7 ± 7.18 for Mycalamide A and -56 ± 10.55 for Nakinadine B. These results elucidate the possible use of mycalamide A for treating coronavirus disease.Communicated by Ramaswamy H. Sarma.

Endophytic Fungi and Secondary Metabolites of Rehmannia Glutinosa Based on Traditional Chinese Medicine Fingerprints

Research on the active components of medicinal plants has always been the focus of research, and research on the active components of medicinal plant endophytic fungi and their secondary metabolites has also attracted widespread attention. Endophytic fungi of medicinal plants are widely distributed and are ubiquitous in various biological groups in nature. Rehmannia glutinosa contains a variety of active ingredients, which are regarded as the top grade of Chinese medicinal materials. It is of certain significance to study endophytic fungi and their metabolites of Rehmannia glutinosa. In this paper, endophytic fungi and their secondary metabolites of Rehmannia glutinosa were studied using fingerprint technology, which initially understands the diversity of endophytic fungi in Rehmannia glutinosa. In this paper, the roots and leaves of Rehmannia glutinosa were used as experimental materials. The fungi were cultured in the medium, the fungi were isolated and purified by the tissue block method, the fungal growth of Rehmannia glutinosa in different parts was determined, and the types of endophytic fungi were identified by microscopic identification and fingerprinting. The isolated strains were tested for biological activity using oryza oryzae spores, and highly active strains were screened. Fermentation products of endophytic fungi were separated and purified by chromatography, and the structure of the compounds was identified by nuclear magnetic resonance spectroscopy. Through the above studies, the population structure of endophytic fungi of Rehmannia glutinosa was determined, 3 highly active strains were found, and the structures of 7 endophytic fungi metabolites were identified, of which 3 were newly discovered compounds.

Secondary Metabolites of Purpureocilliumlilacinum

Fungi can synthesize a wealth of secondary metabolites, which are widely used in the exploration of lead compounds of pharmaceutical or agricultural importance. Beauveria, Metarhizium, and Cordyceps are the most extensively studied fungi in which a large number of biologically active metabolites have been identified. However, relatively little attention has been paid to Purpureocillium lilacinum. P. lilacinum are soil-habituated fungi that are widely distributed in nature and are very important biocontrol fungi in agriculture, providing good biological control of plant parasitic nematodes and having a significant effect on Aphidoidea, Tetranychus cinnbarinus, and Aleyrodidae. At the same time, it produces secondary metabolites with various biological activities such as anticancer, antimicrobial, and insecticidal. This review attempts to provide a comprehensive overview of the secondary metabolites of P. lilacinum, with emphasis on the chemical diversity and biological activity of these secondary metabolites and the biosynthetic pathways, and gives new insight into the secondary metabolites of medical and entomogenous fungi, which is expected to provide a reference for the development of medicine and agrochemicals in the future.

Antimicrobial resistance in biofilms: Exploring marine actinobacteria as a potential source of antibiotics and biofilm inhibitors

Antimicrobial resistance (AMR) is one of the serious global public health threats that require immediate action. With the emergence of new resistance mechanisms in infection-causing microorganisms such as bacteria, fungi, and viruses, AMR threatens the effective prevention and treatment of diseases caused by them. This has resulted in prolonged illness, disability, and death. It has been predicted that AMR will lead to over ten million deaths by 2050. The rapid spread of multidrug-resistant bacteria is also causing old antibiotics to become ineffective. Among the diverse factors contributing to AMR, intrinsic biofilm development has been highlighted as an essential contributing facet. Moreover, biofilm-derived antibiotic tolerance leads to serious recurrent chronic infections. Therefore, the discovery of novel bioactive molecules is a potential solution that can help combat AMR. To achieve this, sustained mining of novel antimicrobial leads from actinobacteria, particularly marine actinobacteria, can be a promising strategy. Given their vast diversity and different habitats, the extraordinary capacity of actinobacteria can be tapped to synthesize new antibiotics or bioactive molecules for biofilm inhibition. Advanced screening strategies and novel approaches in the field of modern biochemical and molecular biology can be used to detect such new compounds. In view of this, the present review focuses on understanding some of the recent strategies to inhibit biofilm formation and explores the potential role of marine actinobacteria as sources of novel antibiotics and biofilm inhibitor molecules.

Antioxidative and α-glucosidase inhibitory constituents of Polyscias guilfoylei: experimental and computational assessments

Searching for bioactive agents from medicinal plants, eleven constituents were isolated from Polyscias guilfoylei stem for the first time, including a nucleoside uracil (1), two sterols β-sitosterol (2) and daucosterol (3), a saponin androseptoside A (4), two lignans (+)-pinoresinol (5) and (+)-syringaresinol (6), four phenolic acids protocatechuic acid (7), methyl protocatechuate (8), caffeic acid (9), and 5-O-caffeoylquinic acid (10), and a flavonoid quercitrin (11). Metabolites 1, 4, and 6-11 have never been observed in genus Polyscias before. Phenolic compounds 7 and 9 possessed the respective IC₅₀ values of 21.33 and 13.88 µg/mL in DPPH (2,2-diphenyl-1-picrylhydrazyl) antioxidative assay, as compared with that of the positive control resveratrol (IC₅₀ = 13.21 µg/mL). From density functional theory (DFT) calculated approach, the DPPH free radical scavenging capacity of two compounds 7 and 9 can be explained by the role of OH groups at carbons C-3 and C-4. Antioxidative actions of these two potential agents are followed HAT (H atom transfer) mechanism by OH bond disruption in gas, but SPLET (sequential proton loss electron transfer) mechanism in solvents water and methanol. Compared to 4-OH group, 3-OH group showed better bond disruption enthalpies and better kinetic energies since it reacted with HOO^• and DPPH radicals. Sterols 2-3 and flavonoid 11 induced the IC₅₀ values of < 2.0 µg/mL better than the positive control acarbose (IC₅₀ = 184.0 µg/mL) in α-glucosidase inhibitory assay. Their interactions with human intestinal C- and N-terminal domains of α-glucosidase were explored using molecular docking study. The obtained results proved that compounds 2, 3, and 11 bind relatively stronger with the C-terminal domain than to the N-terminal domain through pivotal residues in the binding site and could be hypothesized as mixed inhibitors.

Streptomyces dysideae sp. nov., isolated from a marine Mediterranean sponge Dysidea tupha

A Gram-stain-positive bacterium, strain RV15^T, forming an extensively branched substrate mycelium and aerial hyphae that differentiate into spiral chains of spores, was isolated from a marine sponge Dysidea tupha collected from Rovinj (Croatia). Comparison of 16S rRNA gene sequences showed that strain RV15^T is a member of the genus Streptomyces with highest sequence similarity to the type strains of Streptomyces caeruleatus (98.8 %), Streptomyces cyaneochromogenes (98.6 %) and Streptomyces shaanxiensis (98.5 %). Sequence similarities to all other Streptomyces types strains were below 98.5 %. The multilocus sequence analysis-based evolutionary distance, the average nucleotide identity value and the genome-to-genome distance of strain RV15^T and the type strain of S. caeruleatus were clearly below the species cut-off values. Strain RV15^T exhibited a quinone system composed of the major menaquinones MK-9(H₄), MK-9(H₆) and MK-9(H₂), typical for the genus Streptomyces. The polar lipid profile of strain RV15^T consisted of the predominant compounds diphosphatidylglycerol and phosphatidylethanolamine, moderate amounts of phosphatidylinositol, phosphatidylinositol mannoside, an unidentified lipid and an unidentified phospholipid. Major polyamines were spermine and spermidine. The diagnostic diaminoacid of the peptidoglycan was meso-diaminopimelic acid. The major fatty acids were iso C_16 : 0, anteiso C_17 : 1 ω9c and anteiso C_17 : 0. The results of physiological and biochemical tests allowed further phenotypic differentiation of strain RV15^T from its most-related species and hence clearly merits species status. We propose the name Streptomyces dysideae sp. nov. with the type strain RV15^T (=DSM 42110^T=LMG 27702^T).