Isolation of Food Grade Dye from Flower Petals of Butea monosperma and Determination of Marker Compounds for Its Quantitative Analysis.

ABSTRACT

Health concerns associated with synthetic dyes/colorants have fostered the use of natural coloring materials for food applications. This study has been carried out to extract a natural dye from the flower petals of Butea monosperma (family Fabaceae) under an eco-friendly and organic solvent-free approach. Hot aqueous extraction of dry B. monosperma flowers followed by lyophilization of the resulting extract furnished an orange-colored dye in ∼35% yield. Silica gel column chromatography of dye powder resulted in the isolation of three marker compounds, viz. iso-coreopsin (1), butrin (2), iso-butrin (3) which were characterized by spectral methods, e.g., ultra violet, Fourier-transform infrared spectroscopy, nuclear magnetic resonance, and high-resolution mass spectrometry. The XRD analysis of isolated compounds established an amorphous nature for compounds 1 and 2 while compound 3 showed good crystallinity. The stability of dye powder and the isolated compounds 1-3 was determined by thermogravimetric analysis which showed excellent stability up to 200 °C. In trace metal analysis, the product B. monosperma dye powder exhibited low relative abundance <4% for Hg along with negligible concentrations of Pb, As, Cd, and Na. The detection and quantification of marker compounds 1-3 in the B. monosperma flower extracted dye powder were carried out by a highly selective UPLC/PDA method of analysis.