The plant kingdom offers a rich source of structural biodiversity in the form of a variety of natural products. Our work on new bioactive compounds from medicinal plants has led to the isolation and structure elucidation of a number of exciting new pharmacophores. Bioassay-guided fractionation has recently led to the discovery of a series of new acetylcholinesterase, urease and a-glucosidase inhibitors, antioxidants and other classes of bioactive compounds, which will be presented. A theory based on hydrogen bonding on the chemical basis of memory storage in the brain is presented.