Fourier transform infrared spectroscopic analysis of the polymethoxylated flavone content of orange oil residues.

Preliminary studies have shown that orange peel polymethoxylated flavones (PMFs) exhibit beneficial biological properties in animals. These properties have increased the demands for these compounds as candidate nutraceuticals and specialty food ingredients. Orange oil residues are a likely commercial source of the PMFs, and a rapid, solvent-free method for the analysis of the PMFs in orange oil residues has been developed based on Fourier transform infrared (FTIR) spectroscopy. The intensities of the FTIR vibrations of the phenyl ring nu(C=C) stretch at 1515 cm(-1) of the PMFs can be used, relative to the intensity of the carbonyl stretch at 1733 cm(-1) of the non-PMF orange oil residue components, to measure PMF content. Excellent correlations for the ratios of the intensities of these vibrations and the total PMF content were observed irrespective of the source, viscosity, and presence of particulate material. The detection limit by this method is approximately 0.1% PMF.