Many plants produce very attractive flowers, leaves and fruits. Colour pigments that are derived from nature are believed to be environmentally friendly because of their non-toxic, non-carcinogenic and biodegradable nature. In this project, colour pigment from ethanol extract of Sorghum bicolour was investigated using three different spectroscopic techniques (UV-Vis, FT-IR and GC/MS). The effects of dyeing parameters; temperature, pH and the presence of mordant on dyeing quality of the extract were also examined. UV-VIS absorption spectra indicates a λmax peak at 535 nm, value associated to delphinidin dyes under bathochromic shift. Structural characterization by FT-IR revealed presence of C=O, OH and C=C of aromatic. Twelve phytochemicals were identified through GC/MS study.The extract showed colour change from brown to red between pH ranges of 3 to 12. The best dyeing quality was achieved at 30°C with alum pre-treated cloth at neutral pH. Presence of delphinidin dye in S. bicolour extract was confirmed from spectroscopy and chemical analysis results; however, further feasibility study has to be carried out on S. bicolour before it can be applied as dye in industry.

 

Key words: Sorghum bicolour, spectroscopy, natural dye, delphinidin.