Preliminary characterization of some natural dyes

A preliminary study on the chemical structure of dyes from Rothmannia hispidia, Pterocarpus osun and Terminalia superba was made using chemical tests, UV-visible and infrared spectroscopies. R. hispidia dye was found to contain an alkyl amino group (-NHR) and carbon-carbon double bond conjugated with a carbonyl (C = O) group, and also showed maximum absorption at 595 nm in the visible region. P. osun dye contains conjugated systems, hydroxyl (-OH) and amino (NHR) groups and showed maximum absorption at 506 nm in the visible region whereas T. superba dye is made up of conjugated system, nitro (NO2) and hydroxyl (-OH) groups. It showed maximum absorption at 478 nm in the visible region. Key words: Rothmannia hispidia, Pterocarpus osun, Terminalia superba, dyes, characterization.