Abstract: In this study,four coumarins were extracted from Melilotus officinalis (Linn.) Pall.The optimal extraction conditions were established through the optimization of particle size of M.officinalis, ratio of material to liquid,ethanol concentration,extraction temperature and extraction time by single factor and orthogonal experiments.In addition,the antibacterial activity of the coumarin extract was investigated.Using the optimized extraction conditions,721.92 mg of psoralen,425.88 mg of coumarin,165.73 mg of imepratorin and 182.49 mg of isoimperatorin were extracted from per kilogram of crude M.officinalis. The crude extract was applied for further purification.Finally,613.63 mg of psoralen,362.00 mg of coumarin,140.87 mg of imepratorin and 155.12 mg of isoimperatorin were obtained from per kilogram of crude M.officinalis. The 10-fold and 50-fold diluted coumarin solution showed inhibitory effect on bacteria.

Key words: Melilotus officinalis (Linn.) Pall, coumarin, extraction technology, antibacterial