The cis-isomer and trans-isomers of the plant-derived compound gnetin H are shown have anticancer properties, anti-inflammatory properties, and low toxicity. Therapeutic and prophylactic compositions that contain cis-gnetin H, trans-gnetin H, an derivatives thereof, as well as methods of making and using said compositions, are provided. cis-gnetin H and/or trans-gnetin H can be used in purified form or as a plant extract.