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Chapter 10: Problem 38

Vitamin \(E\) is often sold as a racemic mixture of \((+)\) and (-) isomers. Use the web to find answers to these questions. a. Which is the more physiologically active isomer? b. How does the cost of the racemic mixture compare with the price of the pure, physiologically active isomer?

Short Answer

Expert verified
The (+) isomer is more physiologically active, and the racemic mixture is cheaper than the pure active isomer.

Step by step solution

01

Understanding Isomers

Vitamin E consists of several isomers, specifically (+) and (-) isomers, which differ in spatial arrangement. A racemic mixture contains equal amounts of these two isomers.
02

Identify the Active Isomer

Among the isomers of Vitamin E, the (+) or natural (R,R,R) alpha-tocopherol is known to be the most physiologically active form in the human body.
03

Comparing Costs

The racemic mixture, which contains both (+) and (-) isomers, is generally cheaper than the pure, naturally occurring (+) isomer, because synthesizing a single active isomer (such as (R,R,R) alpha-tocopherol) is more complex and costly.
04

Final Comparison

Therefore, while more cost-effective, the racemic mixture is less beneficial in terms of physiological activity compared to the pure active isomer, which is more expensive due to its enhanced efficacy and production process.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Physiologically Active Isomer
The term "physiologically active isomer" refers to the specific form of a vitamin or compound that actively functions and contributes within the body. In the case of Vitamin E, there are many isomers but only one that truly stands out. Among these, the (R,R,R)-alpha-tocopherol isomer is the one that exhibits the most beneficial effects in humans. This isomer plays a critical role in antioxidant protection and helps prevent oxidative damage in cells. Unlike other forms, this purely natural alpha-tocopherol has a unique orientation of atoms, making it most efficient in biological functions.
Racemic Mixture
A racemic mixture contains equal parts of two isomers, specifically the (+) and (-) forms. In chemistry, isomers are molecules with the same molecular formula but different three-dimensional configurations. In the case of Vitamin E, the racemic mixture is composed of both the active form (R,R,R)-alpha-tocopherol and its mirror image. However, the (-) form may not contribute as effectively to biological processes. Despite this, racemic mixtures are popular in supplements because they are often easier and more cost-effective to produce, even if they aren't as beneficial as their naturally active counterparts.
Alpha-Tocopherol
Alpha-tocopherol is a specific type of Vitamin E that is highly regarded for its antioxidant properties. While Vitamin E includes several compounds like beta, gamma, and delta-tocopherol, (R,R,R)-alpha-tocopherol is the most biologically active in the human body. This isomer helps in protecting cellular membranes by neutralizing free radicals. Moreover, it plays a crucial role in maintaining a healthy immune system, skin health, and eye function. When choosing Vitamin E supplements, it is often recommended to select those that specifically state they contain natural (R,R,R)-alpha-tocopherol for optimal benefits.
Cost Comparison of Isomers
The cost of Vitamin E supplements can heavily depend on the type of isomer present. As a general rule, racemic mixtures, which include both (+) and (-) isomers, are less expensive because they are simpler to manufacture. Extracting or synthesizing only the (R,R,R)-alpha-tocopherol isomer is more intricate and requires additional steps in lab production, translating to a higher cost. This is due to the need to not only isolate the beneficial isomer but also to ensure its stability and purity. For consumers seeking the greatest health benefits from Vitamin E, investing in pure (R,R,R)-alpha-tocopherol may offer greater physiological advantages, justifying its higher price tag.

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Most popular questions from this chapter

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