Sutherlandia frutescens (L.) R. Br (Fabaceae) is a multipurpose medicinal plant with diverse biological activities, and has been widely used for the treatment of cancer, AIDS, diabetes, and infectious diseases in southern Africa. The primary goal of this study was to investigate the chemical constituents of S. frutescens and develop an analytical method to analyze this plant and the dietary supplements derived from this plant. The dissertation is composed of six chapters. Chapter 1 introduces the general background of S. frutescens, including traditional uses and chemical and biological studies on the plant. Chapter 2 describes the phytochemical studies that have led to the identification of eight new cycloartane-type triterpene glycosides, sutherlandiosides A-H, and four new flavonol glycosides, sutherlandins A-D. The structures of these compounds were established by a combination of chemical methods and extensive spectroscopic analyses and X-ray crystallography. Several cycloartane glycosides possess unique carbon skeletons. Chapter 3 describes an improved method for determination of the absolute configuration of monosaccharides, which is based on structure elucidation of sutherlandins. Chapter 4 summarizes the results of the biological activities of the isolated compounds from S. frutescens. The major compound sutherlandioside B in the plant shosome antiviral activities against EBV and Tacaribe virus. Chapter 5 presents a newly established HPLC-based analytical method for standardization of the herbal products using the isolated new compounds. Chapter 6 provides concluding remarks for the study of S. frutescens. A brief description of future studies is proposed
