The correct answer is option 4, Saccharin. Saccharin is an artificial sweetener that is not derived from plants. It is synthesized chemically and does not come from any plant source.

Option 1, Caffeine, is a plant product found naturally in coffee beans, tea leaves, and cacao plants. It acts as a stimulant.

Option 2, Piperine, is a compound found in black pepper. It gives pepper its characteristic taste and has various health benefits.

Option 3, Nicotine, is a natural product found in tobacco plants. It is highly addictive and is primarily responsible for the addictive properties of cigarettes.

Therefore, all options except option 4 are plant products.