Abstract:To understand the chemical constituents and antibacterial activities of Trigonostemon heterophyllus, six compounds, including five diterpenoids and one lignan, were isolated and purified by silica gel column chromate- graphy, gel column chromatography and high performance liquid chromatography. Based on spectroscopic data, their structures were identified as trigonochinene E (1), neoboutomannin (2), 6,9-O-dedimethyl trigonostemone (3), stelltian B (4), 3,4-secosonderianol (5), biondinin A (6). The inhibitory activity and MIC values of compounds against a Gram-negative bacterium, Escherichia coli, and a Gram-positive bacterium, Pneumococcus, were detected by Oxford Cup method and double dilution method. Compounds 1, 2, 3 and 5 had inhibitory effects on Escherichia coli with MIC values of 9.375, 18.75, 18.75 and 18.75 μg/mL, respectively. Compounds 2, 3, 4, and 6 were isolated from T. heterophyllus for the first time, and compound 4 was isolated from Trigonostemon genus for the first time. Except compound 4, all the other compounds had certain antibacterial activity, and compounds 1, 2 and 3 had stronger inhibitory effect on Escherichia coli than Kanamycin sulfate positive control.