Tocotrienols comprise one of the two groups of molecules belonging to the vitamin E family, the other group being the tocopherols. Tocotrienols and tocopherols are sometimes collectively called tocols. Just as there are four natural tocopherols, alpha-, beta-, gamma- and delta-tocopherol, there are also four natural tocotrienols, alpha-, beta-, gamma- and delta-tocotrienol. The tocotrienols differ from the tocopherols in the chemical nature of the side chain or tail. Tocopherols have a saturated phytyl side chain, whereas tocotrienols have an unsaturated isoprenoid or farnesyl side chain possessing three double bonds. The major source of tocotrienols are plant oils, and the richest sources are palm oil, rice bran oil, palm kernel oil and coconut oil. Tocotrienols are also found in such cereal grains as oat, barley and rye. Vegetable oils, such as those from canola, cottonseed, olive, peanut, safflower, soybean and sunflower, contain little to no tocotrienols. However, those oils do contain tocopherols. Corn oil has small amounts of tocotrienols. All of the natural tocotrienols are fat-soluble, water-insoluble oils.