We currently describe a programmatic effort to discover novel natural product cancer chemopreventive agents, i.e., agents capable of preventing, inhibiting or reversing the process of carcinogenesis. Employing a panel of bioassays reflective of modulating carcinogenesis at the stages of initiation, promotion or progression, and a mouse mammary organ culture model as a secondary discriminator, promising plant extracts are identified and subjected to activity guided fractionation schemes. The isolates represent 16 major plant secondary metabolite compound classes, comprising alkaloids, aryl polysulfides, a benzenoid, diterpenoids, flavonoids, furocoumarins, lignans, a monoterpenoid, rotenoids, quinones, simaroubolides, stilbenoids, a sterol glycoside, triterpenoids, withanolides, and a xanthone. These compounds mediate a variety of biological effects that are consistent with cancer chemoprevention and thus far deguelin and resveratrol have been found active in full-term tumor inhibition studies with laboratory animals. The program is ongoing, focusing to a greater extent on dietary materials, with the long-term objective of providing nontoxic substances useful for the prevention of cancer in humans.
China has a rich tradition of natural medicines.
Among the plants employed by the general population, a large proportion is thought to contain saponins. In this review, an update is given of recent results on saponins iso-lated from Chinese medicinal plants, particularly of the Araliaceae, Compositae, Phytolaccaceae, Ranunculaceae, Rubiaceae and Leguminosae families. Details of isolation, structure determination and pharmacological testing are reported. S. Rodriguez, A. Marston, J.-L. Wolfender and K. Hostettmann . The iridoids and secoiridoids form the largest class of naturally-occurring monoterpenes.