Aloin is a bitter, yellow-coloured anthraquinone glycoside found in the latex or sap of Aloe. It exists as two stereoisomers Aloin A (barbaloin) and Aloin B (isobarbaloin). It has laxative effects and was formerly one ingredient of some over-the-counter laxatives. Its use for this purpose was banned by the FDA in 2003. It is used in small quantities as a bitter flavouring.
Aloe vera latex and juice have a range of uses. The juice does not contain a significant amount of aloin and so can be used as a digestive healer. The gel released by breaking open a leaf is often used to soothe burns to the skin including sunburn, and it is widely used in cosmetics.