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Antibiotic resistance is becoming a pivotal concern for public health that has accelerated the search for new antimicrobial molecules from nature. Numbers of human pathogens have inevitably evolved to become resistant to various currently available drugs causing considerable mortality and morbidity worldwide. It is apparent that novel antibiotics are urgently warranted to combat these life-threatening pathogens. In recent years, there have been an increasing number of studies to discover new bioactive compounds from plant origin with the hope to control antibiotic-resistant bacteria. This review attempts to focus and record the plant-derived compounds and plant extracts against multi-drug-resistant (MDR) pathogens including methicillin-resistant Staphylococcus aureus (MRSA), MDR- Mycobacterium tuberculosis and malarial parasites Plasmodium spp. reported between 2005 and 2015. During this period, a total of 110 purified compounds and 60 plant extracts were obtained from 112 different plants. The plants reviewed in this study belong to 70 different families reported from 36 countries around the world. The present review also discusses the drug resistance in bacteria and emphasizes the urge for new drugs.

The objective of the present work was to improve the biological activity of Padina gymnospora. In the current study, silver chloride nanoparticles have been synthesized using the aqueous extract of Padina gymnospora and further characterized by ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, x-ray powder diffraction, scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy and atomic force microscope. Further, the hemolytic activity and eco-toxicity of silver chloride nanoparticles analyzed. The synthesized silver chloride nanoparticles were found to be mono-dispersed and spherical with an average size of 11.5-32.86 nm. The particles showed an anticancer effect in a dose-dependent manner against breast cancer cell line (MCF-7 cell lines) (IC50 = 31.37 g ml−1). In addition, it showed the larvicidal activity against Aedes aegypti at a lower dose (3.92 g ml−1) than that of the aqueous extract (13.01 g ml−1). Nanoparticles also exhibited greater antimicrobial activity for both bacterial and fungal pathogens. The synthesized silver chloride nanoparticles showed a maximum zone of inhibition, i.e., 31 mm for Candida albicans followed and 27 mm for vancomycin resistance Enterococcus faecalis.The results suggest the possible use of synthesized silver nanoparticles with P. gymnospora as therapeutic agent for breast cancer, dengue vector control and as antimicrobial agent.

Anthranilic acid (AA) holds significant importance in the chemical industry. It serves as a crucial building block for the amino acid tryptophan by manipulating the tryptophan biosynthesis pathway, it is possible to increase the production of anthranilic acid. In this study, we utilized metabolic engineering approaches to produce anthranilic acid from the halophilic bacterium Virgibacillus salarius MML1918. The halophilic bacteria were grown in an optimized production medium, and mass production of secondary metabolites was made in ATCC medium 1097 Proteose peptone—for halophilic bacteria and subjected to column chromatography followed by sub-column chromatography the single band for the purified compound was confirmed. Further, various spectral analyses were made for the partially purified compounds, and fluorescence microscopy for fungal cell observation was performed. The purified compound was confirmed by single crystal X-ray diffraction (XRD) analysis, and it was identified as 2-amino benzoic acid. The Fourier transform infrared Spectroscopy (FT-IR) spectrum and nuclear magnetic resonance (NMR) spectrum also confirm the structural characteristic of 2-amino benzoic acid. The UV–Vis absorption spectrum of AA shows the maximum absorption at 337.86 nm. The emission spectrum of 2-amino benzoic acid showed the maximum emission at 453 nm. The bio-imaging application of 2-amino benzoic acid was examined with fungal mycelium of Rhizoctonia solani . It was effectively bound and emitted the blue color at the concentration of 200 and 300 µg/mL. The halophilic bacterium ( V. salarius ), may have unique metabolic pathways and requirements compared to non-halophilic organisms, to produce AA effectively. This could have implications for industrial biotechnology, particularly in manufacturing environments where high salt concentrations are present and also it can be used as bio-imaging agent.

Imidazo[1,2- a ]pyridine derivatives have excellent potential for chelation with transition metal ions. Two new imidazo[1,2- a ]pyridine-8-carboxylates were synthesized and characterized by 1 H NMR, 13 C NMR, HRMS, and single crystal-XRD techniques. Methyl carboxylate (probe 1 ) turns on fluorescence upon coordination with Zn 2+ , while sodium carboxylate (probe 2 ) turns off its fluorescence upon coordination with Co 2+ or Cu 2+ ions present in aqueous acetonitrile medium. 13 C NMR study revealed that the change in metal ion specific binding was due to the involvement of carboxylate anion in complex formation with Co 2+ or Cu 2+ ions. The carboxylate anion at 8-position also enhanced the sensitivity of detection of probe 2 by an order of magnitude (detection limits: 3.804 × 10 –7  M, probe 1 /Zn 2+ ; 0.420 × 10 –7  M, probe 2 /Co 2+ and 0.304 × 10 –7  M, probe 2/ Cu 2+ ). The detection limits of probes 1 and 2 comply well with the World Health Organization (WHO) and US Environmental Protection Agency (US-EPA) guidelines for detection of heavy metal ions present in drinking water and ground water. Both the probes form a 1:1 complex with Zn 2+ , Co 2+ or Cu 2+ , and the stoichiometry was verified by Job plot and ESI-mass analysis. The sensing mechanism is explained using 13 C NMR experiments, ESI-mass analytical data and theoretical DFT calculations. The suitability of probes 1 and 2 for on-site detection and quantitative determination of Zn 2+ , Co 2+ and Cu 2+ ions present in biological, environmental and industrial samples is demonstrated. In addition, both 1 and 2 are used for detection of intracellular contamination of Zn 2+ , Co 2+ or Cu 2+ ions in onion epidermal cells. Graphical Abstract

Imidazoles are a category of azole antifungals that encompass compounds such as ketoconazole, miconazole, esomeprazole, and clotrimazole. In contrast, the triazoles group, which includes fluconazole, voriconazole, and itraconazole, also plays a significant role. The rise of antibiotic resistance in fungal pathogens has evolved into a substantial global public health concern. In this study, two newly synthesized imidazo[1,2-a]pyridine derivative (Probe I and Probe II) molecules were investigated for its antimicrobial potency against of a panel of bacterial (Gram-positive and Gram-negative bacteria) and fungal pathogens. Among the different types of pathogens, we found that Probe II showed excellent antifungal activity against fungal pathogens, based on the preliminary screening the potent molecule further investigated against multidrug-resistance Candida sp. (n = 10) and compared with commercial molecules. In addition, in-silico molecular docking, its dynamics, absorption, distribution, metabolism, excretion and toxicity (ADMET) were analyzed. In this study, the small molecule (Probe II) displayed potent activity only against the Candida spp. including several multidrug-resistant Candida spp. Probe II exhibited minimum inhibitory concentration ranges from 4 to 16 µg/mL and minimum fungicidal concentration in the range 4‒32 µg/mL as the lowest concentration enough to eliminate the Candida spp. The selected molecules inhibit the formation of yeast to mold as well as ergosterol formation by the computational simulation against Sterol 14-alpha demethylase (CYP51) and inhibition of ergosterol biosynthesis by in-vitro model show that the Probe II completely inhibits the formation of ergosterol in yeast cells at 2× MIC. The ADMET analysis Probe II could be moderately toxic to the human being, though the in-vitro toxicity studies will help to understand the real-time toxic level. The novel compound Probe II, which was synthesized during the study, shows promise for development into a new generation of drug treatments aimed at addressing the emerging drug resistance in Candida sp.

Imidazo[1,2-a]pyridine derivatives have excellent potential for chelation with transition metal ions. Two new imidazo[1,2-a]pyridine-8-carboxylates were synthesized and characterized by 1H NMR, 13C NMR, HRMS, and single crystal-XRD techniques. Methyl carboxylate (probe 1) turns on fluorescence upon coordination with Zn2+, while sodium carboxylate (probe 2) turns off its fluorescence upon coordination with Co2+ or Cu2+ ions present in aqueous acetonitrile medium. 13C NMR study revealed that the change in metal ion specific binding was due to the involvement of carboxylate anion in complex formation with Co2+ or Cu2+ ions. The carboxylate anion at 8-position also enhanced the sensitivity of detection of probe 2 by an order of magnitude (detection limits: 3.804 × 10-7 M, probe 1/Zn2+; 0.420 × 10-7 M, probe 2/Co2+ and 0.304 × 10-7 M, probe 2/Cu2+). The detection limits of probes 1 and 2 comply well with the World Health Organization (WHO) and US Environmental Protection Agency (US-EPA) guidelines for detection of heavy metal ions present in drinking water and ground water. Both the probes form a 1:1 complex with Zn2+, Co2+ or Cu2+, and the stoichiometry was verified by Job plot and ESI-mass analysis. The sensing mechanism is explained using 13C NMR experiments, ESI-mass analytical data and theoretical DFT calculations. The suitability of probes 1 and 2 for on-site detection and quantitative determination of Zn2+, Co2+ and Cu2+ ions present in biological, environmental and industrial samples is demonstrated. In addition, both 1 and 2 are used for detection of intracellular contamination of Zn2+, Co2+ or Cu2+ ions in onion epidermal cells.Imidazo[1,2-a]pyridine derivatives have excellent potential for chelation with transition metal ions. Two new imidazo[1,2-a]pyridine-8-carboxylates were synthesized and characterized by 1H NMR, 13C NMR, HRMS, and single crystal-XRD techniques. Methyl carboxylate (probe 1) turns on fluorescence upon coordination with Zn2+, while sodium carboxylate (probe 2) turns off its fluorescence upon coordination with Co2+ or Cu2+ ions present in aqueous acetonitrile medium. 13C NMR study revealed that the change in metal ion specific binding was due to the involvement of carboxylate anion in complex formation with Co2+ or Cu2+ ions. The carboxylate anion at 8-position also enhanced the sensitivity of detection of probe 2 by an order of magnitude (detection limits: 3.804 × 10-7 M, probe 1/Zn2+; 0.420 × 10-7 M, probe 2/Co2+ and 0.304 × 10-7 M, probe 2/Cu2+). The detection limits of probes 1 and 2 comply well with the World Health Organization (WHO) and US Environmental Protection Agency (US-EPA) guidelines for detection of heavy metal ions present in drinking water and ground water. Both the probes form a 1:1 complex with Zn2+, Co2+ or Cu2+, and the stoichiometry was verified by Job plot and ESI-mass analysis. The sensing mechanism is explained using 13C NMR experiments, ESI-mass analytical data and theoretical DFT calculations. The suitability of probes 1 and 2 for on-site detection and quantitative determination of Zn2+, Co2+ and Cu2+ ions present in biological, environmental and industrial samples is demonstrated. In addition, both 1 and 2 are used for detection of intracellular contamination of Zn2+, Co2+ or Cu2+ ions in onion epidermal cells.

A total of 288 marine samples were collected from different locations of the Bay of Bengal starting from Pulicat lake to Kanyakumari, and 208 isolates of marine actinomycetes were isolated using starch casein agar medium. The growth pattern, mycelial coloration, production of exopolysaccharides and diffusible pigment and abundance of Streptomyces spp. were documented. Among marine actinomycetes, Streptomyces spp. were present in large proportion (88%). Among 208 marine actinomycetes, 111 isolates exhibited antimicrobial activity against human pathogens, and 151 showed antifungal activity against two plant pathogens. Among 208 isolates, 183, 157, 116, 72 and 68 isolates produced lipase, caseinase, gelatinase, cellulase and amylase, respectively. The results of diversity, antimicrobial activity and enzymes production have increased the scope of finding industrially important marine actinomycetes from the Bay of Bengal and these organisms could be vital sources for the discovery of industrially useful molecules/enzymes.

Fluorescence spectroscopy was examined as a potential technique for identification and classification of bacterial pathogens. Colonies of Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella typhi, and Klebsiella pneumoniae on agar plates were measured directly using a laboratory spectrofluorimeter coupled with optical fiber. Steady state fluorescence spectra were collected following excitation at 280 nm (tryptophan) and 380 nm (NADH). Results showed that fluorescence lifetime decays of tryptophan at 280 nm excitation from the four organisms were best described with triexponential fit and it reveals the existence of different protein conformation. The emission spectroscopy of the four bacteria at 380 nm excitation (NADH) provided better classification (100% of original grouped cases correctly classified and 98.1% of cross-validated grouped cases correctly classified) than that of 280 nm excitation (tryptophan). Our results demonstrated that optical fiber-based fluorescence identification and classification of bacteria is rapid, easy to perform, and of low cost compared to standard methods.

Since ancient times, medicinal plants have been widely used against dreadful pathogens due to their ability to kill microbes. Also, the limitations of the present treatment methods have led the researchers to explore for new formulations with aspects of better wound healing and control of infections. In the present study antimicrobial, antioxidant and cytotoxicity properties of a polyherbal formulation prepared from the barks of three medicinal plants for treating wound infection were investigated. The polyherbal formulation was tested for broad spectrum antimicrobial activity against gram-positive bacteria Methicillin-Resistant Staphylococcus aureus (MRSA) and gram-negative bacteria such as Pseudomonas aeruginosa, Escherichia coli, Salmonella typhi and antifungal activity against Fluconazole resistant Candida albicans . The result reveals that the polyherbal formulation exhibited antimicrobial activity against antibiotic resistant gram-positive MRSA and C. albicans and moderate against gram-negative P. aeruginosa, E. coli and S. typhi. The antioxidant activities like 1,1′-diphenyl-2-picrylhydrazyl and hydrogen peroxide scavenging ability of the formulation was compared with standard ascorbic acid. The higher antioxidant activity was found mostly due to the presence of higher amount of phenols and flavonoids. The phenol was found to be 48.63 ± 0.35 mg/g and flavonoids was 29.52 ± 1.13 mg/g. The polyherbal formulation helps in the proliferation of fibroblast cells without affecting the viability. The above result reveals that the formulation has good antimicrobial and antioxidant activity without affecting the viability of the cell.

Totally 191 different marine actinomycetes were isolated from 256 different marine samples collected from the Bay of Bengal and its associated Pulicat lake and Pichavaram mangrove, India. Among them, 157 produced caseinase, 113 produced gelatinase and 108 produced both the protease enzymes. An isolate coded as MML1614 was selected for further study as it exhibited high proteolytic activity. The MML1614 was identified as Streptomyces fungicidicus based on polyphasic taxonomical approach including 16S rRNA sequence analysis. The culture conditions were standardized for the growth and protease production in S. fungicidicus MML1614. The protease was isolated from a 6-day-old culture filtrate of S. fungicidicus MML1614 and partially purified up to 4.5-fold. The protease was optimally active at pH 9 and 40 °C and it was stable up to pH 11 and 60 °C. PMSF and NaCl inhibited the enzyme activity up to 22 and 11%, respectively. The partially purified protease removed the blood stain more effectively when combined with different detergents than the detergents alone.