6-methoxy gossypol and 6,6'-dimethoxy gossypol were isolated from cottonseeds. Bioactivities of these two gossypol derivatives and gossypol were investigated regarding their antioxidant activities, DNA damage prevention ability, anti-cancer, and anti-trypanosomal activities. Both methoxy compounds had nearly equivalent bioactivities, but gossypol showed greater bioactivities than either methoxy derivative on free radical scavenging activity, reducing power, and DNA damage prevention ability. Gossypol and its methoxy derivatives inhibited growth of three cancer cell lines, i.e., SiHa (cervical cancer), MCF-7 (breast cancer) and Caco-2 (colon cancer) cells, in a dose dependent manner. These three compounds also significantly inhibited growth of trypanosome T. brucei, the cause of African Sleeping Sickness, which affects thousands in western and central Africa.