Where does nicotine come from?

Nicotine has two main sources: one is naturally present in certain plants, and the other is artificially synthesized in the laboratory through chemical methods.
Natural Nicotine: A Bioalkaloid from Plants
Natural nicotine is a bioalkaloid that is naturally produced by plants and is mainly found in the Solanaceae plant family.
Main source: Tobacco - The most abundant and commercially valuable source is the Nicotiana genus plants, mainly common tobacco (Nicotiana tabacum) and yellow-flowered tobacco (Nicotiana rustica). Nicotine is synthesized in the roots of tobacco plants and mainly accumulates in the leaves, accounting for 5% or even up to 9% of the dry weight of the leaves. The vast majority of the nicotine we come into contact with comes from tobacco.
Other Solanaceae plants: Nicotine is also present in common vegetables and fruits such as chili peppers, tomatoes, potatoes, and eggplants. However, the content is extremely low, usually ranging from 3 to 100 μg/kg, which is much lower than that in tobacco. Daily consumption will not have any impact on the human body.
Synthetic Nicotine: A Laboratory Product
Synthetic Nicotine is a substance entirely synthesized in the laboratory using chemical raw materials. Its chemical composition is almost the same as that of natural nicotine. Natural nicotine is mainly left-handed nicotine (S-nicotine), while the early synthetic versions were usually a mixture of left-handed and right-handed components in equal parts. However, high-purity left-handed nicotine can now also be synthesized.
In recent years, due to regulatory and other factors, some e-cigarette manufacturers have begun to use synthetic nicotine in their products.
Summary
Source Essence Primary Characteristics
Natural Nicotine Natural alkaloid produced by plants Extracted mainly from tobacco, and also present in small amounts in vegetables and fruits of the Solanaceae family.
Synthetic Nicotine Chemical substance artificially synthesized in the laboratory Has a similar chemical structure to natural nicotine, and is mainly used in some new types of tobacco products.
Regardless of whether nicotine is obtained through natural extraction or chemical synthesis, its addictive properties and other characteristics are the same.