Au, Ag, and Au/Ag colloidal nanoparticles coated with the J-aggregate of an anionic cyanine dye, 3,3′disulfopropyl-5,5′-dichlorothiacyanine sodium salt (TC), have been prepared for the first time. The absorption spectrum of TC-coated Au colloidal nanoparticles is not a simple sum of the contributions of colloidal gold and TC but is characterized by an evident absorption dip at the position corresponding to the J-band of TC. These spectral features are reproduced by the simulation based on the Maxwell-Garnett-type treatment of Gao et al. The alternate adsorption technique allowed us to deposit dye-coated Au/Ag composite nanoparticles at the surface of a cationic polymer, poly(diallyldimethylammonium chroride).
Avenanthramides are characteristic constituents of oat seeds. We analyzed the methanol extract of oat seeds by HPLC and detected three compounds 1, 2, and 3 eluted at retention times similar to avenanthramides. The three compounds were purified by column chromatography and HPLC. Spectroscopic analyses of 1, 2, and 3 suggested that they are amides of 4,5-dihydroxyanthranilic acid with caffeic, p-coumaric, and ferulic acids, respectively. Their identities were confirmed by comparing spectra and chromatographic behavior with compounds synthesized from 4,5-dihydroxyanthranilic acid and N-hyrdroxysuccinimide esters of hydroxycinnamic acids. LC-MS/MS analysis with multiple reaction monitoring showed that the amounts of 1, 2, and 3 were 16.5-26.9% of corresponding avenanthamides with 5-hydroxyanthranilic acid. Compounds 1, 2, and 3 showed stronger 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity than the corresponding avenanthramides with 5-hydroxyanthranilic acid, indicating the involvement of 4,5-dihydroxyanthranilic acid moiety in the scavenging of DPPH radicals.
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