Purity of commercial morin products and their spectrophotometric characterisation

Reagents of commercially available morin contain considerable levels of impurities. Recrystallisation after silica-gel column chromatography yielded morin dihydrate with a purity of 99%. 1H NMR spectrometry indicated that the purity of commercial morin ranged from 30 to 62%. Glycosylated, oxidised and polymerised morin derivatives are the major impurities. Consistent absorption maxima can be obtained when acidified methanol is used as the solvent. Extinction coefficients of 1.59 × 104 M-1 cm-1 at 354 nm and 0.51 M-1 cm-1 at 490 nm are obtained for the purified morin reagent. It is recommended that the absorption maximum at 354 nm should be used for determination of morin concentration and that the absorption at 490 nm can be used as an index for the presence of impurities.