Which natural bioactive water-soluble phenolic compound is present in Fruits, vegetables, and grains with red, purple, blue, or black hues?
Anthocyanins
Understanding Natural Bioactive Phenolic Compounds
The question asks to identify a specific type of natural bioactive water-soluble phenolic compound found in fruits, vegetables, and grains, which imparts red, purple, blue, or black colors. Let's analyze the properties described and see which option fits best.
Analyzing the Key Properties
We are looking for a compound that is:
- Natural
- Bioactive
- Water-soluble
- Phenolic compound
- Present in fruits, vegetables, and grains
- Gives red, purple, blue, or black colors
Evaluating the Options
Let's consider each option based on these properties:
| Compound | Category | Solubility | Color Property | Common Sources | Fit the Description? |
|---|---|---|---|---|---|
| Coumarins | Phenolic compound (Benzopyran) | Generally not highly water-soluble (more soluble in organic solvents or hot water) | Typically colorless or pale yellow; associated with fragrance/flavor, not color | Many plants (e.g., Tonka bean, cinnamon, citrus peel) | No (Color and solubility don't match) |
| Anthocyanins | Phenolic compound (Flavonoid subclass) | Highly water-soluble | Provide red, purple, blue, black colors (pH dependent) | Berries, grapes, cherries, red cabbage, eggplant, black beans | Yes (All properties match) |
| Quercetin | Phenolic compound (Flavonoid subclass, Flavonol) | Poorly water-soluble (soluble in organic solvents) | Typically yellow pigment | Onions, apples, berries, tea | No (Solubility and color don't match) |
| Naringenin | Phenolic compound (Flavonoid subclass, Flavanone) | Poorly water-soluble (soluble in organic solvents) | Typically colorless | Citrus fruits (grapefruit, oranges) | No (Solubility and color don't match) |
Detailed Explanation of Anthocyanins
Anthocyanins are a group of water-soluble vacuolar pigments that appear red, purple, or blue depending on pH. They are the most important group of pigments in flowers and fruits. They belong to the class of compounds called flavonoids, which are a subclass of phenolic compounds. These pigments are found in the cells of many plants, particularly in the skin of fruits and vegetables with vibrant colors. They are known for their antioxidant properties and are considered bioactive compounds beneficial to health.
Examples of sources rich in anthocyanins include:
- Blueberries and Blackberries (blue/black)
- Strawberries and Cherries (red)
- Red Cabbage and Eggplant skin (purple)
- Grapes and Red Wine (red/purple)
- Black Beans (black)
Their water solubility is key to their function as pigments within the aqueous environment of plant cell vacuoles. This property, along with their distinct red, purple, blue, or black colors and their presence in the specified food sources, makes them a perfect match for the description.
Why Other Options Are Incorrect
As shown in the table:
- Coumarins are phenolic compounds but are not known for providing these specific colors and are generally less water-soluble than anthocyanins.
- Quercetin is a phenolic compound (flavonol) and is bioactive, but it is typically a yellow pigment and has poor water solubility.
- Naringenin is a phenolic compound (flavanone) and is bioactive, but it is usually colorless and has poor water solubility.
Therefore, only Anthocyanins possess all the characteristics mentioned in the question: natural, bioactive, water-soluble, phenolic, found in these foods, and responsible for red, purple, blue, or black hues.
Revision Table: Phenolic Compounds
| Class/Subclass | Key Characteristics | Examples | Color/Pigment Role |
|---|---|---|---|
| Phenolic Acids | Simple structure, aromatic ring with hydroxyl group | Gallic acid, Caffeic acid | Generally colorless |
| Flavonoids | Basic C6-C3-C6 structure (two benzene rings linked by a 3-carbon bridge) | Anthocyanins, Flavonols (Quercetin), Flavanones (Naringenin), Flavones, Isoflavones | Varies (Anthocyanins are colored pigments; others often yellow or colorless) |
| Stilbenes | C6-C2-C6 structure | Resveratrol | Generally colorless |
| Coumarins | Benzopyran structure | Coumarin | Generally colorless or pale yellow |
Additional Information on Anthocyanins
Anthocyanins are glycosides, meaning they are composed of an anthocyanidin (the aglycone or non-sugar part) and a sugar moiety attached. The sugar attachment increases their water solubility. The color of anthocyanins is highly dependent on pH. In acidic conditions, they are typically red or pink. As pH increases towards neutral, they may become purple. In alkaline conditions, they can turn blue or even green/yellow, though they are less stable at high pH. This pH sensitivity is why some plant pigments change color, for example, red cabbage juice changing color when mixed with acids or bases.
Important Questions from Classification, Nomenclature, Isomerism
Which of the following is an organic compound with the formula CH 3OC 6H 5 used as a perfume, fragrance and solvent?
Trichloromethane is better known as:
What is called arenes?
Polyatomic positive ions often have common names ending with the suffix ______.
Negative ions that consist of a single atom are named by adding the suffix ___________ to the stem of the name of the element.
