Synthesis and Biological Evaluation of (−) and (+)-Spiroleucettadine and Analogues

A second-generation enantiospecific synthesis of spiroleucettadine is described. The original reported antibacterial activity was not observed when the experiment was repeated on the synthetic samples; however, significant anti-proliferative activity was uncovered for both enantiomers of spiroleucettadine. Comparison of the optical rotational data and ORD-CD spectra of both enantiomers and the reported spectrum from the natural source have not provided a definitive answer regarding the absolute stereochemistry of naturally occurring spiroleucettadine. Efforts then focussed on alteration at the C-4 and C-5 positions of the slightly more active (−)-spiroleucettadine. Ten analogues were synthesised, with three analogues found to possess similar anti-proliferative profiles to spiroleucettadine against the H522 lung cancer cell line.     

Dehydration of 1,4-dioxane by pervaporation using crosslinked calcium alginate-chitosan blend membranes

Summary  Sodium alginate (SA) and chitosan (CS) blended membranes were crosslinked with maleic anhydride (MA) for the separation of 1,4-dioxane/water mixtures at 30 °C by pervaporation (PV). The membranes were characterized by Fourier transform infrared (FTIR) analysis and Ion Exchange Capacity (IEC) to verify the crosslinking. Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) pattern were used to observe the thermal degradation and crystalline nature of the membrane respectively. The membrane performance was studied by calculating flux, selectivity, and pervaporation separation index. Sorption studies were carried out to evaluate the extent of interaction and degree of swelling of the membranes in pure liquids as well as in binary mixtures. The effects of experimental parameters such as feed composition, membrane thickness, and permeate pressure on separation performance of the crosslinked membranes were determined. The experimental result suggested that the membrane has a good potential for breaking the aqueous azeotrope 1,4-dioxane.     

Removal of hexavalent chromium from wastewater using a new composite chitosan biosorbent

A new composite chitosan biosorbent was prepared by coating chitosan, a glucosamine biopolymer, onto ceramic alumina. The composite bioadsorbent was characterized by high-temperature pyrolysis, porosimetry, scanning electron microscopy, and X-ray photoelectron spectroscopy. Batch isothermal equilibrium and continuous column adsorption experiments were conducted at 25 degrees C to evaluate the biosorbent for the removal of hexavalent chromium from synthetic as well as field samples obtained from chrome plating facilities. The effect of pH, sulfate, and chloride ion on adsorption was also investigated. The biosorbent loaded with Cr(VI) was regenerated using 0.1 M sodium hydroxide solution. A comparison of the results of the present investigation with those reported in the literature showed that chitosan coated on alumina exhibits greater adsorption capacity for chromium(VI). Further, experimental equilibrium data were fitted to Langmuir and Freundlich adsorption isotherms, and values of the parameters of the isotherms are reported. The ultimate capacity obtained from the Langmuir model is 153.85 mg/g chitosan.     

Antibiofilm and quorum sensing inhibitory potential of Cuminum cyminum and its secondary metabolite methyl eugenol against Gram negative bacterial pathogens

Quorum sensing inhibitory (QSI) activity of common South Indian spices and vegetables were evaluated using the bacterial model Chromobacterium violaceum. Among the 22 samples tested the QSI compound present in the methanolic extract of Cuminum cyminum at 2 mg/ml inhibited violacein production in C. violaceum. Further, the outcome of the present investigation reveals that C. cyminum extract strongly interferes with acyl homoserine lactone (AHL) regulated physiological functions coupled with biofilm formation such as flagellar motility and exopolysaccharides (EPS) production. It promotes the loosening of biofilm architecture and powerfully inhibits in vitro biofilm formation in Pseudomonas aeruginosa PAO1, Proteus mirabilis and Serratia marcescens at sub-MIC levels. The result of molecular docking analysis attributes the QSI activity exhibited by C. cyminum to methyl eugenol (ME). The ability of ME to interfere with quorum sensing (QS) systems of various Gram-negative bacterial pathogens comprising diverse AHL molecules was also assessed and ME was found to reduce the AHL dependent production of violacein, bioluminescence and biofilm formation.