Spectroscopic studies of neutral and chemically oxidized species of B-carotene, lycopene and norbixin in CH2C12: Fluorescence from intermediate compounds

Abstract

AttachedRadical cations, dicatipns and oxidized in term ed iate species o f th re e carotenoids, nam ely, P-carotene, lycopene an d norbixin, w ere generated in CH2CI2 solutions via chem ical oxidation using anhydrous FeCl3. UV-vis, fluorescence and fluorescence-excitation spectroscopic studies, w e re perform ed ,to understan d and com pare th e natu re of in term ed iate species gen erated during th e chem ical oxidation process and subsequent degradation. The in ten se em ission observed a t 550 nm can be assigned to the S2 -* S0 (1 ' Bu -> 11 Ag) transition o f th e carotenoid m olecules. The 3 50 n m excitation during th e oxidation irocess for p-carotene, lycopene and norbixin exhibit intense fluorescence peaks a t 492 nm , 493 nm and 50 0 nm , respectively. These peaks are assigned to in term ed iate peroxy/epoxy. com pounds o f th e th ree m olecules th a t are form ed w ith m olecular oxygen p rio r to th e form ation o f oxidized short-chain stable com pounds.