Identification of Diterpenoids From Icacina Oliviformis

Icacina oliviformis (Poir.) J. Raynal (Icacinaceae) is an indigenous plant commonly found in west and central Africa. It has been traditionally used as a source of starch especially during the famine periods. Medicinally the plant is considered a panacea; there is long history of the leaves or roots being used by local herbalists for the treatment of a variety of common diseases such as fever and malaria. Despite the extensive use of Icacina oliviformis by the local tribes, most of early studies on the plant were focused on its nutritional properties, and biological evaluations were all conducted with extracts rather than pure compounds isolated from the plant. Only limited research has been done on its chemical constituents, leading to the identification of several diterpenes and sterol glycosides. In this first systematic phytochemical study of diterpenes in Icacina oliviformis. A total of eleven secondary metabolites were isolated and identified, including three new structures, viz., icacinlactone M, icacinlactone H 2-O-β-D-glucopyranoside, and icacinlactone N 3-O-β-D-glucopyranoside. Among the known structures, icacinlactone A, icacinlactone B, icacinlatone H, 12-hydroxyicacinlatone A, 14α-methoxyhumirianthol, annonalide and acrenol (isolated as an acetone adduct), were reported from I. oliviformis for the first time, whereas icacinol has been found in this plant in other studies. This is also the first report of pimarane glycosides in genus Icacina. Icacinol, 14α-methoxyhumirianthol and annonalide displayed moderate cytotoxic activity in a panel of human cancer cell lines. These phytochemical and biological findings have expanded our knowledge of this under-studied medicinal plant species.