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A different approach to the molecular recognition events consists in synthesis and conjugating silver nanoparticles with flavonoid quercetagetin isolated from T. erecta. In this article we are reporting rapid and feasible procedure for the synthesis of querecetagetin stabilized silver nanoparticle (Qt AgNPs). These nanoparticles were characterized by UV–vis spectroscopy, FTIR, and AFM techniques. The average size of the querecetagetin coated silver nanoparticles was found to be in the range from 25 to 45 nm and are highly robust. Querecetagetin coated silver nanoparticle selectively recognize amoxicillin producing a bathochromic shift along with color change from yellow to reddish. The detection limit was calculated using standard deviation of blank and slope of regression line and was found to be 4.46 μM with a correlation factor R2 equal to 0.993. The binding stoichiometry between Qt AgNPs and amoxicillin was found to be 1:2 (Qt AgNPs: amoxicillin) as revealed by Job‘s plot. The Qt AgNPs interact selectively with amoxicillin in human blood plasma and tap water sample showing that the ingredients of tap water and blood plasma are inert towards the interaction of Qt AgNPs with amoxicillin.Photophysical events were examined using UV–vis, FTIR spectroscopy and, AFM techniques.

A new click generated triazole based chemosensor 5 was designed and synthesized, that exhibits excellent selectivity for Fe +3 ion over a wide range of tested metal ions e.g. NH 4 + , Li + , Na + , K + , Cu + , Ag + , Ca +2 , Ni +2 , Co +2 , Cd +2 , Mg +2 , Cu +2 , Zn +2 , Pb +2 , Hg +2 , In +3 , La +3 and Y +3 in an aqueous medium without any remarkable interference. With Fe +3 , the sensor 5 showed enhancement in absorption intensity at wavelength of 262 nm. The sensor forms a host-guest complex in 1:1 stoichiometry with the detection limit down to 3.21 μM. The interaction was also confirmed by FT-IR, 1 H NMR and FAB showing the Sensor 5 –Fe +3 adduct at 495. Further, the sensor was successfully utilized to detect Fe +3 in human blood plasma and laboratory tap water as well.

Synthesis, characterization and molecular recognition properties of fluorene based supramolecular cleft 1 is reported. The cleft molecule 1 was prepared in a single-step with good yield (85% yield), by linking Fluorene with 1-ethyl piperazine. The cleft molecule 1 was carefully characterized using various spectroscopic techniques such as NMR and mass spectrometry. The supramolecular interaction of cleft 1 with amoxicillin, 6APA, aspirin, captopril, cefotaxime, ceftriaxone, cefuroxime, diclofenac, penicillin, and cephradine was evaluated by fluorescent spectroscopy. The molecular recognition studies showed that amoxicillin selectively binds with cleft 1 in the presence of other drugs. The analytical method developed for the supramolecular interaction of molecular cleft 1 and amoxicillin was validated at varying pH, concentration and temperature during recognition process. Job's plots indicated that the stochiometry of the interactions between the cleft 1 and the amoxicillin was 1:1.

Three biologically active new Schiff bases, 2-[(3-hydroxybenzylidene)amino]phenol 5 , 2-[(4-hydroxybenzylidene)amino]phenol 6 and 4-[(2-hydroxyphenylimino)methyl]benzene-1,3-diol 7 , were synthesized by the reaction of 2-aminophenol 1 with three different hydroxyl-benzaldehydes 2 – 4 . They were characterized by spectroscopic analysis (IR, 1 H NMR, EI-MS) along with elemental analyses. The products were biological screened out for antioxidant, lipoxygenase inhibition, antibacterial and urease inhibition activities. The compounds 5 and 6 showed potent while 7 showed moderate antioxidant activity. Compound 6 showed potent whereas 5 and 7 showed significant lipoxygenase inhibition activity. All the target compounds showed excellent activities against Staphylococcus intermedius , Bacillus subtilis , Staphylococcus aureus, Escherichia coli and Salmonella typhi bacteria. All the compounds showed non-significant activity against urease enzyme.

Antioxidant and anticholinesterase activities of twelve flavonoids i.e. santin ( 1 ), penduletin ( 2 ), viscosine ( 3 ), 6,7-dimethylkaempferol ( 4 ), kaempferol-​3-​methylether ( 5 ), 3,4′-dimethoxy-5,7-dihydroxyflavone ( 6 ), 5,7,4′-trihydroxy-3′-(3-hydroxymethylbutyl)-3,6-dimethoxyflavone ( 7 ), 5,7-dihydroxy-3′-(2-hydroxy-3-methyl-3-butenyl)-3,6,4′-trimethoxy-flavone ( 8 ), 5,7-dihydroxy-3′-(3-hydroxy-methylbutyl)-3,6,4′-trimethoxyflavone ( 9 ), 5,7-dihydroxy-3′-(4′′-acetoxy-3′′-methylbutyl)-3,6,4′-trimethoxy flavone ( 10 ), aromadendrin, (2S,3S) 3,4′,5,7-tetrahydroxyflavanone ( 11 ), and pinocembrin ( 12 ), together with monohydrated crystal ( 1A ) of 1 and anhydrous crystal ( 3A ) of 3 – isolated from Dodonaea viscosa – were studied. The results are given as 50% inhibition concentrations (IC 50 ). Their structure–activity relationships are discussed for both activities. Flavonoids 3 and 10 showed higher antioxidant activity in all tests. 3 Also showed moderate acetylcholinesterase (IC 50 : 182.97 ± 1.25 μM) and significant butyrylcholinesterase (IC 50 : 47.07 ± 0.54 μM) inhibitory activities. Compounds 2 (IC 50 : 55.78 ± 1.01 μM) and 3A (IC 50 : 58.72 ± 1.02 μM) were also moderate anticholinesterase agents against butyrylcholinesterase enzyme. Monohydrate crystal ( 1A ) showed better antioxidant and anticholinesterase activities than its amorphous form ( 1) . In contrast, the amorphous 3 exhibited better activity than the anhydrous crystal ( 3A ). In hydrous crystal, the water molecule might be responsible for better activity. These natural flavonoids can be used as pharmaceuticals and/or preservatives in respective industries.

A ligand L has been synthesized by the condensation of 4-chlorobenzaldehyde and 2-amino-5-chlorobenzophenone. The complexes 1–5 of Pb+2, Ni+2, Co+2, Cu+2 and Cd+2 with ligand were prepared. The newly synthesized ligand L and its complexes 1–5 were characterized on the basis of elemental analyses, molar conductance, 1H NMR, IR and MS spectral data. The ligand was also characterized by X-ray crystallography. By electronic spectra and magnetic moment data, the square planar geometry for complex 1 and the octahedral geometry for complexes 2–5 were proposed. The conductivity data suggests non-electrolytic nature of the complexes 1–5. The complexes have higher antibacterial activity than the parent ligand L.

New dimeric and a trimeric coumarin glucosides namely Daphneretusin A (1) Daphneretusin B (2) along with three known oligomers (3-5) were obtained as a result of bioassay guided fractionation of Daphne retusa Hemsl. Fractions (n-hexane, CHCl3, AcOEt, CH3OH and water) exhibited potent radical scavenging activity in relevant non-physiological bioassays. The structures of isolated compounds were elucidated by UV, IR, EIMS, FAB-MS, 1D, and 2D NMR spectroscopic analysis.

A new methylene-bridged bisflavonoid, methylenebissantin (1), and nine known compounds, including flavonoids (2–5), diterpenoids (6 and 7), and phenol derivatives (8–10) were isolated from the aerial parts of Dodonaea viscosa Jacq. The structure elucidation was based on spectroscopic data analyses. The isolated compounds were evaluated for the inhibition of Plasmodium falciparum enoyl-ACP reductase (PfENR). Methylenebissantin (1) exhibited a moderate inhibition (IC50 91.13 μM) against PfENR.