Which one is derived from the aminoacid tryptophan

Options

A. Melanin
B. Melatonin
C. Insulin
D. Thyroxine

Answer

To determine which substance is derived from the amino acid tryptophan, we can analyze the options provided:

1. **Melanin**: This pigment is derived from the amino acid tyrosine, not tryptophan. Melanin is responsible for the color of skin, hair, and eyes.

2. **Melatonin**: This is a hormone that is indeed derived from the amino acid tryptophan. It is primarily produced in the pineal gland and is involved in regulating sleep-wake cycles.

3. **Insulin**: This hormone is derived from a precursor molecule called proinsulin, which is not derived from tryptophan. Insulin is crucial for regulating blood sugar levels.

4. **Thyroxin**: This hormone, produced by the thyroid gland, is derived from tyrosine and iodine, not tryptophan.

Based on this analysis, the only substance derived from the amino acid tryptophan is **melatonin**.

### Step-by-Step Solution:
1. **Identify the options**: List the substances provided in the question.
2. **Analyze each option**:
- **Melanin**: Derived from tyrosine.
- **Melatonin**: Derived from tryptophan.
- **Insulin**: Derived from proinsulin (not tryptophan).
- **Thyroxin**: Derived from tyrosine and iodine.
3. **Determine the correct answer**: Since melatonin is the only substance derived from tryptophan, it is the correct answer.

### Final Answer:
**Melatonin** is derived from the amino acid tryptophan.