Digital image colorimetric detection of ceftazidime based on azo compound formation on a polyethyleneimine-modified cotton sponge.

A novel colorimetric platform using cotton sponges modified with polyethyleneimine (PEI) was fabricated for the detection of ceftazidime through the diazotization and coupling reaction. In this work, cotton sponges were initially prepared by freeze drying using 2 w/w% cotton fibers modified with 3-aminopropyl triethoxysilane (APTES), followed by grafting of PEI through a crosslinking reaction using epichlorohydrin (ECH). The optimal concentrations of modifying agents were 170 mM APTES for 1.

Bioactive galloyl flavans from the stems of .

Three new flavans, (2)-7--galloyl-5,3',4'-trihydroxyflavan (), (2)-7,3--digalloyl-5,4-dihydroxyflavan (), and (2)-7,4--digalloyl-5,3-dihydroxyflavan (), together with four known compounds, (2)-5,7,3',4'-tetrahydroxyflavan (), (-)-epicatechin (), (-)-syringaresinol (), and methyl gallate () have been isolated from the EtOAc extract of the stems of . Compounds and were obtained as a mixture of positional isomers. The structures of the isolated compounds were established using extensive spectroscopic data.