Aloes are a large genus of plants, about 450 species, from sub-Saharan Africa, Madagascar and parts of Arabia. A few species have been widely adopted as medicinal plants since ancient times while many of the others, often of limited distribution, are used locally in folk medicine. Many, but not all, are of succulent habit and typically inhabit warm or tropical semi-arid regions where they are often widespread. On the other hand, the distribution of several species is extremely limited with a few living in desert or wet mountain regions. The hope for investigating biological activity of the many aloe compounds is vast.