Cloning and functional characterization of the Na+/H+ antiporter (NHX1) gene promoter from an extreme halophyte Salicornia brachiata.

Salinity is one of the major abiotic stresses which affect plant growth and productivity by imposing dual stress, ionic and osmotic stress, on plants. Halophytes which are adapted to complete their life cycle in saline soil keep the transcript expression of stress-responsive genes constitutively higher in the optimum growth environments, which can be further increased by several folds under stress conditions. The transcript expression of SbNHX1 gene, cloned from a leafless succulent halophyte Salicornia brachiata, was up-regulated under salinity stress, but its transcriptional regulation has not been studied so far. In the present study, a 1727 bp putative promoter (upstream to translation start site) of the SbNHX1 gene was cloned using a genome walking method. The bioinformatics analysis identified important stress-responsive cis-regulatory motifs, GT1, MBS, LTR and ARE, in addition to two leaf-specific enhancer motifs. The GUS expression analysis of stable transgenic tobacco plants, transformed with a transcriptional fusion of GUS with the full SbNHX1 promoter (NP1) or any of its five deletion fragments (NP2 to NP6), showed that the deletion of two enhancer motifs resulted in the sudden decrease in GUS expression in leaves but not in the stem or root tissues. In contrast, under salinity stress, the higher induction of GUS expression observed in NP1 and NP2 was correlated by the presence of salt-inducible GT1- and MBS-motifs which is distributed only in NP1 and NP2 deletion promoter fragments. Finally, we concluded that the SbNHX1 promoter has a 624 bp (-1727 to -1103 bp) regulatory region which contains the two leaf-specific enhancer motifs and salinity stress-inducible GT-1 and MBS motifs. We suggest the SbNHX1 gene promoter and fragments as a candidate alternative promoter/s for crop engineering for better stress tolerance, which can be amended according to the desired level of expression needed.

A novel synthesis of 2-arylbenzimidazoles in molecular sieves-MeOH system and their antitubercular activity.

Arylbenzimidazoles have been synthesized as antimycobacterial agents. An efficient synthesis has been developed for 2-arylbenzimidazoles from o-phenylenediamines and aromatic aldehydes in molecular sieves-methanol system. The methodology is straightforward to get 2-arylbenzimidazoles (3a-3z) in excellent yields with high chemoselectivity over 2-aryl-1-benzylbenzimidazoles (4a-4z). All these benzimidazole analogues were evaluated against M. tuberculosis in BACTEC radiometric assay. The compounds 4y and 4z exhibited potential antitubercular activity against M. tuberculosis H37RV, MIC at 16 µM and 24 µM respectively. The best compound of the series i.e. compound 4y was well tolerated by Swiss-albino mice in acute oral toxicity. Compound 4y possessing a diarylbenzimidazole core, can further be optimized for better activity.

Synthesis of combretastatin A4 analogues on steroidal framework and their anti-breast cancer activity.

Combretastatin A4 analogues were synthesized on steroidal framework from gallic acid with a possibility of anti-breast cancer agents. Twenty two analogues were synthesized and evaluated for cytotoxicity against human breast cancer cell lines (MCF-7 & MDA-MB 231). The best analogue 22 showed potent antitubulin effect. Docking experiments also supported strong binding affinity of 22 to microtubule polymerase. In cell cycle analysis, 22 induced apoptosis in MCF-7 cells significantly. It was found to be non-toxic up to 300 mg/kg dose in Swiss albino mice in acute oral toxicity. This article is part of a Special Issue entitled "Synthesis and biological testing of steroid derivatives as inhibitors".

An efficient and novel approach for the synthesis of substituted N-aryl lactams.

A quick, efficient, one-pot method for the synthesis of substituted N-aryl lactams through the reaction of various kinds of corresponding substituted arenes with a variety of ω-azido alkanoic acid chlorides using a Lewis acid (i.e. EtAlCl(2)) at room temperature, through the in situ involvement of a Friedel-Crafts reaction followed by intramolecular Schimdt rearrangement was developed, and afforded good to excellent yields.

Gallic acid based steroidal phenstatin analogues for selective targeting of breast cancer cells through inhibiting tubulin polymerization.

Phenstatin analogues were synthesized on steroidal framework, for selective targeting of breast cancer cells. These analogues were evaluated for anticancer efficacy against breast cancer cell lines. Analogues 12 and 19 exhibited significant anticancer activity against MCF-7, hormone dependent breast cancer cell line. While analogues 10-14 exhibited significant anticancer activity against MDA-MB-231, hormone independent breast cancer cell line. Compound 10 showed significant oestrogen antagonistic activities with low agonistic activity in in vivo rat model. These analogues also retain tubulin polymerization inhibition activity. The most active analogue 10 was found to be non-toxic in Swiss albino mice up to 300 mg/kg dose. Gallic acid based phenstatin analogues may further be optimized as selective anti-breast cancer agents.