Tabernaecorymine A, an 18-normonoterpenoid indole alkaloid with conjugated (E)-3-aminoacrylaldehyde fragment was obtained from the stem bark of Tabernaemontana corymbosa. Its structure was elucidated by extensive spectroscopic data analyses, and further verified by ACD/structure elucidator, electronic circular dichroism (ECD) analyses and density functional theory (DFT) chemical shift predictions. The compound exhibited significant antibacterial bioactivity against Streptococcus dysgalactiae with an MIC value of 3.12 μg/mL, which is better than the plant drug berberine. © 2022