Which of the following is an alkaloid?

Options

A. Nicotine
B. Piperine
C. Quinine
D. All

Explanation

To determine which of the given options is an alkaloid, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Alkaloids**:
Alkaloids are naturally occurring organic compounds that mostly contain basic nitrogen atoms. They are often derived from plants and have significant pharmacological effects.

2. **Examine the Options**:
- **Option 1: Nicotine**: This is a well-known alkaloid found in tobacco plants. It has a nitrogen atom and exhibits basic properties.
- **Option 2: Piperine**: This compound is found in black pepper and is also classified as an alkaloid. It contains nitrogen and has basic characteristics.
- **Option 3: Quinine**: This is an alkaloid derived from the bark of the cinchona tree, known for its use in treating malaria. It also contains nitrogen and is basic in nature.

3. **Analyze the Choices**:
Since all three options (nicotine, piperine, and quinine) are alkaloids, we can conclude that they all fit the definition.

4. **Select the Correct Answer**:
Since all three options are alkaloids, the correct answer is **Option 4: All**.

### Final Answer:
The correct answer is **Option 4: All**.

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