An epimeric mixture of the limonoid photogedunin, isolated from the heartwood of C. ciliolata, as well as its R-and S-acetate derivative were evaluated for phytotoxicity in mono-and dicotyledoneous plants. A mixture of epimeric photogedunin 1 and 2, a mixture of epimeric photogedunin acetate,(R)-photogedunin acetate 3, and (S)-photogedunin acetate 4 inhibited seed germination, seedling growth, and root and hypocotyl/coleoptyle growth in all species assayed. The concentration of phytochemicals required for 50% inhibition