Nicotiana tabacum: From a Beneficial Plant to Harmful Products-A Comprehensive Review of Smokeless Tobacco and Its Adverse Health Effects.

Nicotiana tabacum is a cash crop that originated in America and was introduced to the world by Christopher Colombus. It is now cultivated in many countries with major producers including China, the USA, India, and Brazil. The plant was widely used by the indigenous people of America for different reasons (spiritual, hallucination, and medical). The medicinal usage of the plant was confirmed by many phytochemical and pharmacological studies on different parts of the plant. The plant essentially contains alkaloids (nicotine is the major component) and phenolic compounds such as flavonoids, tannins, and many phenolic acids. Glycosides and terpenes are also present in N. tabacum. These components are responsible for many pharmacological effects. Besides the therapeutic usage of the plant, the leaves of the plant served as a hallucination agent; they were either smoked or chewed. Nowadays tobacco products are universally used. Smokeless tobacco products are numerous and diversified; they can be handmade or manufactured. Unlike the plant, smokeless tobacco products are harmful to health. Many products exist around the world with different compositions and names, such as paan, zarda, toombak, khaini, naswar, loose leaf, moist snuff, snus, and shammah. These products have been confirmed to cause many serious pathological conditions. In addition to being addictive, they can lead to various types of cancer especially oral cancer, hypertension, cardiovascular diseases, fertility issues, and fetal damage when consumed by pregnant women. They also increase the risk of thrombosis and so on. While the harmful effects of some products have been scientifically proven, others (e.g., chemma) have not. This highlights the importance of scientific investigation to confirm their potential risks.