Which of the following is a solid alkaloid?

• A. Coniine
• B. Berberine
• C. Nicotine
• D. None of the above

Answer: (B)

Alkaloids are nitrogen-containing compounds produced by plants that behave as bases. The physical state at room temperature helps distinguish them here. Berberine is a well-known isoquinoline alkaloid that forms yellow crystalline solids, so it fits the description of a solid alkaloid. In contrast, coniine and nicotine are typically encountered as liquids at room temperature due to their molecular structure, so they don’t match the “solid” criterion. Thus berberine is the solid alkaloid in the list.