Novel Anthracene and Carbazole Based Aggregation Induced Enhanced Emission Active Schiff Base as a Selective Sensor for Cu2+ ions.

In present work our group has synthesized two novel Schiff-bases, Di-Carbazole based Schiff-base (DB-1) and Di-Anthracene based Schiff-base (DB-2) using condensation reaction and characterized thorough different spectroscopic techniques such as mass spectrometry, IR spectroscopy, 1H and 13C NMR spectroscopy. Furthermore, the AIE(Aggregation induced emission) studies were done using water-THF mixture. As compared to pure THF, the DB-2 showed a 17.8-fold increase in fluorescence intensity with a bathochromic shift of 64 nm in 80% water: THF mixture. For DB-1increase was seen at 70% water-THF combination. The analysis of the dynamic light scattering (DLS) further supported this excellent AIEE (Aggregation induced enhanced emission) characteristic. Furthermore, the spectrofluorometric techniques were used to examine the capacity of both Schiff bases to detect the heavy metals. It was discovered that only DB-1, with a detection limit of 2.4 × 10-8 M, was selective for the Cu2+ ion, whereas DB-2 had no sensing capability for metal ions. The Job's plot was used to determine the stoichiometry ratio of the DB-1 with Cu2+ to further examine the process. It was discovered that the ratio was 1:1 (DB-1:Cu2+). Additionally, the association constant of DB-1 for Cu2+ was 5.1 × 1011 M-1, demonstrating the excellent binding affinity of DB-1 for the Cu2+ ion.

Natural Pigments-Based Two-Component White Light Emitting Systems.

In this paper, a new class of two component white light emitting systems viz, JaB (java plum + beetroot) {I}, and CaB (carrot + beetroot) {II} were developed through resonance energy transfer (RET) phenomenon by using a fruit (java plum) and two vegetable (carrot and beetroot) extracts. In these white light emitting systems, java plum and carrot are the donors while beetroot is the acceptor. The primary fluorescent pigments present in the natural extracts (i.e., anthocyanin in java plum, ß-carotene in carrot, and betanin in beetroot) were responsible for the white light emission. The CIE (Commission Internationale d'Eclairage) coordinates for I and II were {0.32, 0.34} and {0.33, 0.33}, respectively, in solution phase. Interestingly, the white light emission (WLE) was also achieved in agar-agar gel medium. In gel medium, the CIE values were {0.31, 0.34} and {0.33, 0.32} for I and II, respectively. The donor-acceptor distance (r) for I and II were found to be 0.5 and 0.4 nm, respectively. Furthermore, the rate of energy transfer was also quantified with the values of 2.78 × 109 s-1 for JaB (I) and 1.02 × 108 s-1 for CaB (II) systems. The mechanistic investigation of the two white light systems was further supported by DFT studies.

Assessment of different carrier materials for the preparation of microbial formulations to enhance the shelf life and its efficacy on the growth of spinach (Spinacia oleracea L.).

The current study was undertaken to determine the ability of different carrier materials for sustaining the viability of microbial consortium during storage. Different bioformulations consisting of carrier material and microbial consortium were prepared and examined for viability and stability for one year stored at 4 °C and ambient temperature. Total 8 bio-formulations were prepared consisting five economically viable carriers (gluten, talc, charcoal, bentonite, broth medium) and a microbial consortium. In present study, maximum enhanced shelf-life of consortium based on colony forming unit count were recorded for talc + gluten based (B4) bioformulation (9.03 log10 cfu/g) over other bio-formulations stored for 360 days. Furthermore, the pot experiments was conducted to evaluate the efficacy of B4 formulation on growth of spinach in comparison with recommended dose of chemical fertilizer, uninoculated and no amendment control. The results depicted that B4 formulation increased biomass (176-666%), leaf area (33-123%), chlorophyll content (131-789%) and protein content (68.4-94.4%) of spinach over controls. Further B4 application significantly increased the nutrients like available nitrogen (131-475%), phosphorus (75-178%) and potassium (31-191%) of pot soil along with noteworthy improvement in root colonization as evident from scanning electron microscope analysis in comparison to controls at 60 days after sowing. Therefore, exploiting B4 formulation can serve as the environmentally sound approach to enhance the productivity, biomass and nutritional value of spinach. Thus, Plant growth promoting microbes-based formulation can be the novel paradigm to improve the soil health and eventually the crop productivity in economical and sustainable manner.

Red-Emitting AIEE-Active Rhodamine-Based Ionic Liquid for the Ultrasensitive and Selective Detection of Mercury Ions.

A highly fluorescent, red-emitting rhodamine-based imidazolium ionic liquid (RhB-IL) was synthesized, and its structure was extensively verified using various spectroscopic techniques. The novel molecule showed exceptional selectivity toward Hg2+ ions over other competitive metal ions. Additionally, inspired by the solution results, a paper-based device was fabricated by embedding RhB-IL on paper strips and tested for the on-site detection of Hg2+ ions using a portable UV light source. Significantly, the device displayed excellent PL sensing behavior toward Hg2+ with a detection limit of 0.21 nM. In addition, RhB-IL showed the phenomena of aggregation-induced enhanced emission. In fact, when compared to the pure THF solution of RhB-IL, a remarkable 7.7-fold increase in PL intensity was seen for the 90% water fraction. Evidently, this is the first report of a paper-based Hg2+ detection system that uses a red fluorescent ionic liquid.

Bile acid-based receptors and their applications in recognition.

Ion recognition has attracted great attention in the past decades because of its important role in biology, medicine, environment, and chemistry. The combination of rigidity, curved structure and amphiphilic nature makes bile acids a host system for ion recognition. In addition, the availability of hydroxyl groups in bile acids can be used for further derivatization to develop various ion recognition receptors. The detection of ions is revealed by the binding constant ka value, log approach, and UV-visible or 1H NMR titration, while visual detection is determined by gel-phase transition, colorimetric and fluorescent probes. In this review, we have discussed the bile acid-based receptors and their ion-recognition capability. These bile acid-based systems have the potential for the development of anion transport for biological activity.

An improved procedure for the synthesis of dehydroamino acids and dehydropeptides from the carbonate derivatives of serine and threonine using tetrabutylammonium fluoride.

Dehydroamino acids are important precursors for the synthesis of a number of unnatural amino acids and are structural components in many biologically active peptide derivatives. However, efficient synthetic procedures for their production in large amounts and without side reactions are limited. We report here an improved procedure for the synthesis of dehydroalanine and dehydroamino butyric acid from the carbonate derivatives of serine and threonine using TBAF. The antiselective E(2) elimination of the carbonate derivatives of serine and threonine using TBAF is milder and more efficient than other available procedures. The elimination reaction is completed in less than 10 min with various carbonate derivatives studied and the methodology is very efficient for the synthesis of dehydroamino acids and dehydropeptides. The procedure thus provides an easy access to key synthetic precursors and can be used to introduce interesting structural elements to designed peptides.

Updates in bile acid-bioactive molecule conjugates and their applications.

Bile acid conjugates are emerging as important chemical resources due to their low cost and wide availability of bile acids, making them privileged molecules in drug carrier systems and building blocks for derivatization and chiral template introduction into bioactive molecules. In recent years, bile acids as scaffolds in supramolecular, medicinal, and material chemistry attracted prime focus of researchers as an area of research to be followed with passion. Due to peculiar physicochemical and biological properties, bile acid exhibited various applications in biomedical and pharmaceutical fields. In this review, the bile acid conjugations with different bioactive compounds have been discussed to understand their influence on the bioavailability of bioactive compounds.

Development and characterization of lysine based tripeptide analogues as inhibitors of Sir2 activity.

Sirtuins are NAD(+) dependent deacetylases that modulate various essential cellular functions. Development of peptide based inhibitors of Sir2s would prove useful both as pharmaceutical agents and as effectors by which downstream cellular alterations can be monitored. Click chemistry that utilizes Huisgen's 1,3-dipolar cycloaddition permits attachment of novel modifications onto the side chain of lysine. Herein, we report the synthesis of peptide analogues prepared using click reactions on Nepsilon-propargyloxycarbonyl protected lysine residues and their characterization as inhibitors of Plasmodiumfalciparum Sir2 activity. The peptide based inhibitors exhibited parabolic competitive inhibition with respect to acetylated-peptide substrate and parabolic non-competitive inhibition with NAD(+) supporting the formation of EI(2) and E.NAD(+).I(2) complexes. Cross-competition inhibition analysis with the non-competitive inhibitor nicotinamide (NAM) ruled out the possibility of the NAM-binding site being the second inhibitor binding site, suggesting the presence of a unique alternate pocket accommodating the inhibitor. One of these compounds was also found to be a potent inhibitor of the intraerythrocytic growth of P.falciparum with 50% inhibitory concentration in the micromolar range.

Efficient Approach for the Tritylation of Alcohols Using Recyclable Lewis Acid-Based Ionic Liquid (EMIM·AlCl4).

A new efficient approach has been reported for the tritylation of primary alcohols over secondary alcohols using triphenyl methyl alcohol and 4-monomethoxyl trityl alcohols in the presence of imidazolium-based ionic liquid 1-ethyl-3-methylimidazolium tetrachloroaluminate as catalyst. At room temperature, 5 mol % of catalyst in dichloromethane and acetonitrile solvent has been shown to be excellent for the tritylation of benzyl alcohol and various other alcohols The method was compatible with Fmoc/acetyl protecting group of amino and tert-butyldiphenylsilyl ether protecting group of alcohol. Moreover, the catalyst was reused for three to four catalytic cycles with little loss of catalytic activity. Excellent yields, reusability, chemoselectivity, and easy workup are advantages of this protocol.

A strategy for selective N-acylation of purine and pyrimidine bases of deoxy and ribo nucleosides.

A novel cost effective N-acylation procedure for exocyclic amino function of ribonucleosides (adenosine/guanosine/cytidine) and deoxynucleosides (adenosine/guanosine/cytidine) has been developed. In the present method the acids used for acylation were activated by preparing their corresponding p-nitrophenyl esters. These esters couple with - NH(2) group in presence of dicyclohexylcarbodiimide as coupling agent and catalysts viz. DMAP, HOBT & HOSu to give the--CO-NH- bond; a well-established strategy in peptide synthesis. To minimise the contamination of DCU, different combinations of activated ester and nucleosides has been used. The use of catalysts viz. DMAP, HOBt & HOSu enhanced the yields. HOSu was found to give best results.

Design, development and synthesis of mixed bioconjugates of piperic acid-glycine, curcumin-glycine/alanine and curcumin-glycine-piperic acid and their antibacterial and antifungal properties.

In the present communication different curcumin bioconjugates viz. 4,4'-di-O-glycinoyl-curcumin, 4,4'-di-O-d-alaninoyl-curcumin, 4,4'-di-O-(glycinoyl-di-N-piperoyl)-curcumin, 4,4'-di-O-piperoyl curcumin, curcumin-4,4'-di-O-beta-d-glucopyranoside, 4,4'-di-O-acetyl-curcumin along with piperoyl glycine, have been synthesised and characterised by spectra UV, (1)H NMR and elemental analysis. All the covalent bonds used are biodegradable. This makes these derivatives as potent prodrugs, which can get hydrolysed at the target sites. These bioconjugates were tested in vitro against different bacteria and fungi. The 4,4'-di-O-(glycinoyl-di-N-piperoyl)-curcumin and 4,4'-di-O-acetyl-curcumin are more effective than Cefepime, an antibacterial drug available in market, at the same concentration. The 4,4'-di-O-(glycinoyl-di-N-piperoyl)-curcumin and 4,4'-di-O-piperoyl curcumin had antifungal activity in vitro almost comparable with fluconazole, the most popular antifungal drug. The enhanced activity of these bioconjugates vis-a-vis the parent molecule that is curcumin may be due to improved cellular uptake or reduced metabolism of these bioconjugates resulting in building up of enough concentration inside the infected cells. It opens a new era for exploring suitably designed curcumin bioconjugates as potential antibacterial/antifungal drugs.