Characterization and thermal isomerization of (all-E)-lycopene.

Area of Science:

• Carotenoid Chemistry
• Natural Product Purification
• Spectroscopy

Background:

• Lycopene, a potent antioxidant found in tomatoes, exists in various isomeric forms.
• Efficient purification of the all-trans (all-E) isomer is crucial for its study and application.
• Understanding lycopene's physical and chemical properties, including its behavior in different solvents, is important.

Purpose of the Study:

• To develop an improved method for purifying large amounts of (all-E)-lycopene from tomato paste.
• To characterize the purified (all-E)-lycopene using various analytical techniques.
• To investigate the solvent-dependent spectral properties and stability of (all-E)-lycopene.

Main Methods:

• Purification of (all-E)-lycopene from tomato paste using an improved method involving acetone washing.
• Characterization by differential scanning calorimetry (DSC) for melting point determination.
• Spectroscopic analysis including UV-Vis absorption and one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy.

Main Results:

• Achieved a yield of at least 30% for pure (all-E)-lycopene.
• Determined the melting point of (all-E)-lycopene to be 176.35 °C via DSC.
• Observed bathochromic and hypochromic shifts in UV-Vis spectra dependent on solvent polarizability, and confirmed the structure using comprehensive NMR techniques.

Conclusions:

• The developed purification method is effective for obtaining high yields of pure (all-E)-lycopene.
• The study provides detailed structural and spectral characterization of (all-E)-lycopene.
• Lycopene's spectral shifts are influenced by solvent polarizability, and its stability varies in different organic solvents.