Botanical description, ethnomedicinal uses, phytochemistry, and pharmacological activities of genus Kniphofia and Aloe: A review

Genus Kniphofia and Aloe belong to Asphodeloideae and Alooideae subfamily of Asphodelaceae respectively. Asphodelaceae is a family of lily-related monocotyledonic flowering plants with 2 subfamilies, 16 genera and about 780 species distributed in arid and mesic regions of the temperate, subtropical and tropical zones of the old world, with the main center of diversity in southern Africa. The genus Kniphofia has about 70 species distributed in eastern and southern Africa, including the 7 species known to occur in Ethiopia, of which 5 species are endemic. Aloe is the largest genus among the Asphodelaceae family and it comprises of more than 400 species that are widely distributed in Africa, India, and other arid areas, with the major diversity in South Africa. The leaves of Kniphofia species are non-succulent, unlike the leaves of Aloe species. Aloe species are distinguished by having fleshy and cuticularized leaves usually with spiny margins. Kniphofia species have regular flowers with fused tepals while Aloe species have regular flowers with free tepals. Both Kniphofia and Aloe species have been employed in ethnopharmacology and have provided many bioactive compounds through phytochemical-pharmacological research works. They are traditionally used for treatment of various diseases by herbalists. Both genus elaborate naphthoquinone, preanthraquinone, anthraquinones and alkaloids in common. Additionally, Kniphofia elaborates benzene, naphthalene, and phloroglucinol derivatives while Aloe produces anthrones and chromones. The genus Kniphofia is rich in Knipholone type compounds while the genus Aloe is rich in anthrone-C-glycosides. Secondary metabolites isolated from the two genus have wide range of pharmacological activities such as antiplasmodial, anticancer, anti-inflammatory, antioxidant and antimicrobial activities. There is no published review article on the botanical description, traditional uses, phytochemistry, and pharmacological activities of the genus Kniphofia and only few review articles are available on the genus Aloe. In this review, an attempt is made to present pharmacological activities and secondary metabolites reported to date from genus Kniphofia and Aloe. Secondary metabolites reported from both plant genus have interesting biological activities so the authors of this review paper strongly recommend studies on toxicity of these compounds and their structural activity relationship so as to develop new pharmaceutical drug.