This research on the chemical constituents of Melodorum fruticosum Lour, flowers (Annonaceae) led to the isolation of four heptene derivatives and two flavones. The structure identification and structure elucidation of these compounds were based on the data from various spectroscopic techniques and comparison with reported data. Three novel derivatives of heptenes were assigned the chemical structures (4Z) -7-benzoyloxy-2,4-heptadiene-6-one-4-olide, (4E) -7-benzoyloxy-2,4-heptadiene-6-one-4-ohde, and (E) -7-benzoyloxy-4-hydroxy-1-methoxy-2,4-heptadiene-l, 6-dione, and were given the trivial names melodorinone-A, melodorinone-B, and tautomelodienone, respectively. The other three are the known compounds acetylmelodorinol, chrysin, and 5,7-dimethoxyflavone. Tautomelodienone was found to exhibit interesting cytotoxic activity against P388 cell line, with an IC₅₀ value of 0.60 {u1D77B}{u1D5F4}/ml
