Biosynthesis and medicinal chemistry of therapeutically promising plant natural products

Abstract

Modern molecular biology, biochemical, and chemical techniques have made it possible to identify individual natural products that possess pharmacological activity from medicinal plants. While approximately 50% of all new FDA-approved small molecule therapeutics in the past 40 years were natural products or natural product analogs, challenges including limited natural resources and the difficulty of solving the total synthesis or semi-synthesis of natural products has limited our ability to harness the full diversity of chemical structures provided by nature to treat human diseases. One solution to these challenges is the elucidation of plant specialized metabolite biosynthetic pathways. Identifying and characterizing the enzymes involved in specialized metabolite biosynthesis will provide insight into the evolution of enzymes performing interesting chemistries and provide new tools for the enzymatic production of therapeutically promising natural products. The goal of this dissertation is to explore the aspects of both medicinal chemistry and the elucidation of biosynthetic pathways that can contribute to the development of novel therapeutics. First, we analyzed the structure-activity relationship of analogs of the the flavonoid icariin and identified analogs with improved potency in inhibiting human phosphodiesterase-5. We subsequently identified and characterized a novel flavonoid prenyltransferase and O-methyltransferase from the medicinal herb Epimedium sagittatum that is known to produce many bioactive prenylated and methylated flavonoids.