Question

Which of the following tocopherols has highest antioxidant property?

• A. \(\alpha\) -- tocopherol
• B. \(\beta\) -- tocopherol
• C. \(\gamma\) -- tocopherol
• D. \(\delta\) -- tocopherol

Hint:

To prevent rancidity in vegetable oils, commercial food manufacturers prefer to use mixed tocopherol concentrates rich in the \(\delta\) and \(\gamma\) isomers, rather than pure \(\alpha\)-tocopherol, because of their superior chemical antioxidant performance.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Tocopherols (Vitamin E isomers) are natural oil-soluble phenolic antioxidants.
There are four primary isomers (\(\alpha\), \(\beta\), \(\gamma\), and \(\delta\)), which differ in the number and position of methyl groups on their chromanol rings.

Step 2: Detailed Explanation:
The biological activity inside the human body and the chemical antioxidant activity in food lipid systems show opposite trends:
- Biological activity (in vivo): \(\alpha\text{-tocopherol} > \beta\text{-tocopherol} > \gamma\text{-tocopherol} > \delta\text{-tocopherol}\).
- Chemical antioxidant property (in vitro in food lipids): \(\delta\text{-tocopherol} > \gamma\text{-tocopherol} > \beta\text{-tocopherol} > \alpha\text{-tocopherol}\).
The \(\delta\) (delta) isomer has the highest free radical-scavenging efficiency in food lipid systems because the absence of methyl groups adjacent to the phenolic hydroxyl group reduces steric hindrance, allowing it to donate hydrogen atoms to lipid free radicals most easily.
Note: The option (D) is printed in the paper as \(\kappa\)-tocopherol due to a common typographical symbol error, but it stands for \(\delta\)-tocopherol.

Step 3: Final Answer:
The tocopherol with the highest antioxidant property is \(\delta\)-tocopherol, which corresponds to option (D).