Bioactivity and chemical characterisation of Lophostemon suaveolens – an endemic Australian Aboriginal traditional medicinal plant

Lophostemon suaveolens is a relatively unexplored endemic medicinal plant of Australia. Extracts of fresh leaves of L. suaveolens obtained from sequential extraction with n-hexane and dichloromethane exhibited antibacterial activity in the disc diffusion and MTT microdilution assays against Streptococcus pyogenes and methicillin sensitive and resistant strains of Staphylococcus aureus (minimum bactericidal concentration < 63 μg/mL). The dichloromethane extract and chromatographic fractions therein inhibited nitric oxide in RAW264.7 murine macrophages (IC₅₀ 3.7–11.6 μg/mL) and also PGE₂ in 3T3 murine fibroblasts (IC₅₀ 2.8–19.7 μg/mL). The crude n-hexane, dichloromethane and water extracts of the leaves and chromatographic fractions from the dichloromethane extract also showed modest antioxidant activity in the ORAC assay. GC–MS analysis of the n-hexane fraction showed the presence of the antibacterial compounds aromadendrene, spathulenol, β-caryophyllene, α-humulene and α-pinene and the anti-inflammatory compounds β-caryophyllene and spathulenol. Fractionation of the dichloromethane extract led to the isolation of eucalyptin and the known anti-inflammatory compound betulinic acid.     

A facile approach towards synthesis,characterization, single crystal structure,and DFT study of 5-bromosalicylalcohol

5-Bromosalicylalcohol was prepared by the interaction of NaBH₄ and 5-bromosalicylaldehyde. The use of sodium borohydride makes the reaction easy, facile, economic and does not require any toxic catalyst. The compound is characterized by FTIR, ¹H NMR, ¹³C NMR, TEM and ESI-mass spectra. Crystal structure is determined by single crystal X-ray analysis. Quantum mechanical calculations of geometries, energies and thermodynamic parameters are carried out using density functional theory (DFT/B3LYP) method with 6-311G(d,p) basis set. The optimized geometrical parameters obtained by B3LYP method show good agreement with experimental data.     

CuI–Zn(OAc)2 catalyzed C(sp2)–H activation for the synthesis of pyridocoumarins through an uncommon CuI–CuIII switching mechanism: A fast,solvent-free,combo-catalytic,ball milling approach

CuI–Zn(OAc)₂ catalyzed, a fast, solvent-free synthetic protocol has been developed for the oxidative C–C and C–N coupling via C(sp²)–H activation. In this work, an aldehyde, terminal alkyne and 3-aminocoumarin were coupled together to form pyridocoumarin framework through a greener ball milling process under very mild condition. In contrast to the frequently used imine-alkyne cyclization reactions, this uncommon mild Cu^I–Cu^III switching combo-catalysis is expected to proceed through the formation of a flexible propargylic amine intermediate, which leads to a rapid C(sp²)–H activation for cyclization involving transient Cu^III species. The in-situ formation of transient Cu^III species was confirmed through ultraviolet–visible spectroscopy (UV–Vis), electrospray ionization mass spectrometry (ESI-MS), and X-ray photoelectron spectroscopy (XPS) analyses of the reaction mixture.     

Synthesis of organic sulfobetaine‐based polymer gel electrolyte for dye‐sensitized solar cell application

We have synthesized eco‐friendly, economic, and equally efficient polysulfobetaine‐based gel electrolyte to the alternative of liquid electrolyte in the fabrication of dye‐sensitized solar cells (DSSCs) for the first time. This nitrogen‐rich and highly conductive polysulfobetaine was synthesized by an easy and facile method without the use of any catalyst and explored for its DSSC application. The synthesized polymer gel electrolyte exhibited good ionic conductivity about 6.8 × 10^?3 Scm^?1 at ambient temperatures. DSSCs were fabricated based on this polysulfobetaine gel electrolyte and studied for their performance based on photovoltaic parameters. The DSSC photovoltaic results were appreciable and are Voc = 0.82 V, Jsc = 11.49 mA/cm², FF = 66%, and PCE = 6.26% at 1 sun intensity. These values are slightly lower than conventional liquid electrolyte‐based DSSC shown as Voc = 0.78 V, Jsc = 12.90 mA/cm², FF = 69%, and PCE = 7.07%, both at 100 mWcm^?2. Conductivity and photovoltaic parameters of the device reveals that as prepared polysulfobetaine‐based polymer gel electrolyte may be useful in the fabrication of DSSC and other electrochemical devices. Copyright © 2017 John Wiley & Sons, Ltd.     

UV radiation induced graft copolymerization of allyl acetate onto poly(ethylene terephthalate) (PET) films for fuel cell membranes

Ultraviolet（UV）-induced graft copolymerization of allyl acetate（AA） monomer onto polyethylene terephthalate) （PET） films and the subsequent sulfonation on the monomer units in the grafting chain using chlorosulfonic acid（ClSO₃H） were carried out to prepare proton exchange membranes（PEMs） for fuel cells.A maximum grafting value of 12.8%was found for 35 vol%allyl acetate after 3 h radiation time.Optimum concentration of C1SO₃H was selected for the sulfonation reaction to be 0.05 mol/L based on the degree of sulfonation and the tensile strength studies of the membrane.The degree of sulfonation increased as the sulfonation reaction temperature and sulfonation time were increasing.The radiation grafting and the sulfonation have been confirmed by titrimetric and gravimetric analyses as well as FTIR spectroscopy.The maximum ion exchange capacity（IEC） of 0.04125 mmol g^-1 was found at 12.1%degree of sulfonation and the maximum proton conductivity was found to be 0.035 S cm^-1 at 30℃and a relative humidity of 60%.The various physical and chemical properties of the PEMs such as water uptake,mechanical strength,thermal durability and oxidative stability were also studied.To investigate the suitability of the prepared membrane for fuel cell applications,its properties were compared with those of Nafion 117.     

Antimicrobial, antileishmanial and cytotoxic compounds from Piper chaba

The petroleum ether and chloroform extracts of the root of Piper chaba showed antimicrobial, antileishmanial and cytotoxic activities. Further bioactivity-guided fractionation led to the isolation of Bornyl piperate (1), piperlonguminine (2) and piperine (3). This is the first report of isolation of compounds (1) and (2) from P. chaba. It was observed that the isolated compounds (1 and 2) showed potent antifungal activity when compared with standard drug Nystatin, and significant cytotoxic activity with the IC?? values of 0.76 and 0.83?μg?mL?1, respectively. These compounds were also found to have weak antibacterial and antileishmanial activities. This is the first report about the antileishmanial activity of Piper isolates.     

Investigating the Ultrafast Dynamics and Long-Term Photostability of an Isomer Pair,Usujirene and Palythene,from the Mycosporine-like Amino Acid Family

Mycosporine-like amino acids are a prevalent form of photoprotection in micro- and macro-organisms. Using a combination of natural product extraction/purification and femtosecond transient absorption spectroscopy, we studied the relaxation pathway for a common mycosporine-like amino acid pair, usujirene and its geometric isomer palythene, in the first few nanoseconds following photoexcitation. Our studies show that the electronic excited state lifetimes of these molecules persist for only a few hundred femtoseconds before the excited state population is funneled through an energetically accessible conical intersection with subsequent vibrational energy transfer to the solvent. We found that a minor portion of the isomer pair did not recover to their original state within 3 ns after photoexcitation. We investigated the long-term photostability using continuous irradiation at a single wavelength and with a solar simulator to mimic a more real-life environment; high levels of photostability were observed in both experiments. Finally, we employed computational methods to elucidate the photochemical and photophysical properties of usujirene and palythene as well as to reconcile the photoprotective mechanism.     

TsOH-SiO2 as an efficient and eco-friendly catalyst for Knoevenagel condensation

Tosic acid on silica gel (TsOH-SiO₂) was synthesized and characterized using microscopic and spectroscopic techniques such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and FT-IR spectroscopy. Thermal behaviour of the catalyst was investigated by differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis. TsOH-SiO₂ showed excellent catalytic activity for the Knoevenagel condensation and was recyclable for six cycles.