Molecular design of antibrowning agents

Area of Science:

• Biochemistry
• Enzymology
• Food Chemistry

Background:

• Tyrosinase is a key enzyme in melanin production, responsible for enzymatic browning in foods.
• Gallic acid and its derivatives are known for their antioxidant properties.
• Understanding structure-activity relationships is crucial for developing effective tyrosinase inhibitors.

Purpose of the Study:

• To investigate the tyrosinase inhibitory and antioxidant activities of gallic acid and its alkyl chain esters.
• To determine the effect of alkyl chain length on these activities.
• To explore the potential of gallates as antibrowning agents.

Main Methods:

• Enzyme inhibition assays using mushroom tyrosinase and L-3,4-dihydroxyphenylalanine (L-DOPA) as substrate.
• Antioxidant activity assessment using linoleic acid autoxidation and 1,1-diphenyl-2-p-picryhydrazyl (DPPH) radical scavenging assays.
• Analysis of oxidation products and correlation with alkyl chain length.

Main Results:

• All gallic acid esters inhibited tyrosinase.
• Gallic acid and short-chain esters were oxidized, producing colored products.
• Long-chain esters inhibited tyrosinase without significant oxidation, indicating a role for hydrophobic interactions.
• All esters demonstrated potent antioxidant activity, irrespective of chain length.

Conclusions:

• Alkyl chain length is critical for tyrosinase inhibition, likely due to hydrophobic interactions within the enzyme's active site.
• Long-chain gallate esters are effective antibrowning agents due to their ability to inhibit tyrosinase without undergoing oxidation.
• The antioxidant capacity of gallates is independent of their alkyl chain length.