Extraction of antioxidant pigments from dye sorghum leaf sheaths

Extraction of antioxidant biocolorant pigments from leaf sheaths of dye sorghum was optimized. Effects of temperature and ethanol concentration of the extraction solvent on the concentrations of the 3-deoxyanthocyanidins, total phenolics and total anthocyanins, and the colour parameters of the biocolorant extract were evaluated using the response surface methodology. Extraction parameters affected the extraction rate of the biocolorant pigments and the colour characteristics of the extract. Maximum pigment yields were obtained at 50 °C and an ethanol concentration of the solvent of 51 mL 100 mL-1. Addition of HCl (1 mL 100 mL-1) to the solvent significantly improved the extractability of the biocolorant pigments. The crude extract from the leaf sheaths showed high antioxidant capacity with a total antioxidant capacity of 1026 mg of Trolox equivalent (TE) g-1 of DM. --------------------------------------------------------------------------------