A new branched polyprenol, designated cupaniol, has been isolated from the methanol extract of the leaves of Cupania latifolia (Sapindaceae). The structure was determined to be (2E,6E,12E,16E)-3,7,13,17,21-pentamethyl-10-(1-methylethenyl)-2,6,12,16,20-docosapentaen-1-ol on the basis of spectral analysis and conversion to a known compound.