Recent updates on guar gum derivatives in colon specific drug delivery.

Colon specific delivery of therapeutics have gained much attention of pharmaceutical researchers in the recent past. Colonic specific targeting of drugs is used not only for facilitating absorption of protein or peptide drugs, but also localization of therapeutic agents in colon to treat several colonic disorders. Among various biopolymers, guar gum (GG) exhibits pH dependent swelling, which allows colon specific release of drug. GG also shows microbial degradation in the colonic environment which makes it a suitable excipient for developing colon specific drug delivery systems. The uncontrolled swelling and hydration of GG can be controlled by structural modification or by grafting with another polymeric moiety. Several graft copolymerized guar gum derivatives are investigated for colon targeting of drugs. The efficacy of various guar gum derivatives are evaluated for colon specific delivery of drugs. The reviewed literature evidenced the potentiality of guar gum in localizing drugs in the colonic environment. This review focuses on the synthesis of several guar gum derivatives and their application in developing various colon specific drug delivery systems including matrix tablets, coated formulations, nano or microparticulate delivery systems and hydrogels.

Selective turn-on fluorescence sensing of Fe2+ in real water samples by chalcones.

The design of fluorescence sensor for selective detection of Fe2+ is very important as it is part of different biochemical redox system related to a number of diseases. In many occasion sensors are unable to distinguish Fe2+ from Fe3+ ions. In the present work, we report simple chalcone type sensors for sensing Fe2+ ions in semi aqueous system. The receptors R1 and R2 have showed excellent sensing properties at pH 7 in CH3OH-H2O (1:1, v/v) solvent system. The fluorescence emission intensity of the complexes between hosts and Fe2+ is least affected by the other competitive metal ions leading to the formation of very tight host-guest complex. The LOD for the R1 and R2 for Fe2+ are 1.91 µM and 3.54 µM respectively, which is quite low in compared to the many other reported sensors. The practical applicability of these sensors is determined by the detection of Fe2+ in real water samples. So chalcones would be cost effective PET inhibited fluorescence sensor for Fe2+.

HFIP-promoted halo-carbocyclizations of N- and O-tethered arene-alkene substrates to access all halo (X = Br, I, Cl)-functionalized tetrahydroquinoline and chroman cores.

A new method for the stereoselective metal-, additive- and oxidant-free Friedel-Crafts-type halo-carbocyclization of N- and O-tethered arene-olefin substrates is reported, involving reaction with a suitable electrophilic halogenating reagent (NXS/DCDMH) in hexafluoroisopropanol. All halo (X = Br, I, Cl)-functionalized tetrahydroquinolines and chromans were obtained in excellent yields and with high levels of diastereocontrol (dr = >99 : 1), and these products were successfully transformed into synthetically useful compounds such as dihydroquinolines and partial or full azahelicene compounds.