A biomimetic strategy was employed in the development of oxoanion-selective ionophores containing the guanidinium functional group. These ionophores mimic the selective interaction observed between arginine residues of proteins and oxoanions. In previous work, it was demonstrated that a structurally rigid guanidinium ionophore exhibited excellent hydrogen sulfite selectivity (Anal. Chem. 1994, 66, 3188-3192). Herein, we describe guanidinium-containing ionophores that are selective for the oxoanion salicylate. The ability to rationally design anion-selective electrodes through this biomimetic strategy, and to both alter selectivity and improve response characteristics through structural changes to the ionophore, has been demonstrated. (1)H-NMR complexation and modeling studies were used to examine and correlate the selectivity observed with the structure of the guanidinium compounds.

A B S T R A C T Present study was conducted to develop a new optimized MicrowaveAssisted Extraction (MAE) method for Tinospora cordifolia in order to improve the efficiency and yield of chief bioactive compounds. Stems of the Tinospora cordifolia were subjected for extraction using MAE technique using three variable factors (extraction time, irradiation power and solvent concentration) optimized through central composite design. Berberine which was used, as marker was estimated in prepared extract by High Performance Thin Layer Chromatography (HPTLC) and compared with extracts prepared by conventional techniques like maceration and soxhlation. The results revealed that MAE of Tinospora cordifolia at 60% irradiation power, 80% ethanol concentration and at 3 min extraction time produced highest extract yield (91.3% better yield than maceration and 25.7% than soxhlation) as well as berberine content (492.8% better than maceration and 59.6% than soxhlation) as compared to extracts prepared with conventional techniques. Efficiency of the MAE method was considerably better than the conventional procedures, especially in terms of shortening extraction time (3 min as compared to 3 h for soxhlation and 7 days fort maceration), reduction of solvent used and energy consumption. The optimized microwave extraction method can provide a valuable extraction alternative of Tinospora cordifolia stem at industrial scale.

An environmentally benign solvent free synthesis of various spiro-1,4-dihydropyridines (1,4-DHPs) incorporating 2-oxindole/piperidines is performed in 5-8 min with reasonable purity in 80-90% yield under microwave irradiation using montmorillonite KSF as an inorganic solid support. The reaction is found to be general with respect to various cyclic carbonyl compounds, e.g. cyclohexanone, substituted indole-2,3-dione, and piperidinone derivatives. In our study, these compounds were also found effective against dermatophytes and other fungal organisms. Our results suggest that novel spiro derivatives can be used for the treatment of dermatophytosis or ringworm infections.

Oxazine derivatives can be prepared with yield upto 98% within a few minutes by an efficient and novel one pot microwave-assisted three-component reaction from 1-naphthol, various anilines and formalin using montmorillonite as the catalyst. The procedure is very simple, efficient and environmentally friendly as it does not use any toxic auxiliary or solvent. The key advantages of this process are high yields, shorter reaction times, and easy work-up and non -chromatographic method has been used for the purification of products.