Cured leaves of plants of the family Solanaceae, genus Nicotiiana; the species N. tabacum is the most important domestic source. Curing consists of drying and long aging. The leaves are dehydrated by hanging in warm air to terminal moisture content of 20–30%, during which time starches reduce to sugars, the chlorophyll is discharged, and the color darkens. The product is then aged from one to five years to remove unpleasant odor; cigar tobacco is “fermented” with water, with resulting hydrolysis, deamination, and decarboxylation. Aging fermentation and oxidizers improve taste, aroma, and smoking qualities. Humectants and flavoring agents are added to some cigarette blends.Scores of chemical compounds have been identified in unburned tobacco. Basically it is cellulose. The cured product contains acids (citric, oxalic, formic), alkaloids (nicotine, anabasine, myosmine), and carbohydrates (lignin, pentosans, starch, sucrose), as well as tannin, ammonia, glutamine, and micro amounts of zinc, iodine, copper, manganese, and polonium-210. See Cigarette Tar; Smoke.A nicotine-free tobacco substitute, TM “Cytrel,” has been developed. See “Cytrel” [Celanese].