Abstract:Six sesquiterpene lactones were isolated from the whole plant of Wedelia trilobata (Compositae). On the basis of spectral data, the structures of these constituents were identified as trilobolide-6-O-isobutyrate (1), 1β-acetoxy - 4α, 9α-dihydroxy - 6β- isobutyroxyprostatolide (2), 1β, 9α- diacetoxy- 4α- hydroxy - 6β- isobuty-roxyprostatolide (3a), 1β, 9α-diacetoxy- 4α-hydroxy- 6β-methacryloxyprostatolide (3b), 1β, 4α-di hydroxy - 9α-tigloyloxy-6β-methylpropanoylprostatolide (4a), and 9α-angeloyloxy-1β，4α-dihydroxy-6β-methylpropanoyl-prostatolide(4b)．All compounds except 1 and 3a were isolated from this plant for the first time．Compounds 1，2，a mixture of 3a and 3b， and a mixture of 4a and 4b exhibited potent growth inhibitory effect on the seedlings of radish，cabbage，and tomato in seed germination and seedling growth inhibition test．The mixture of 4a and 4b showed toxicity to brine shrimp in lethality test.