A new triterpenoid saponin, se-saponin A, was isolated from the aerial parts of Clerodendrum serratum var. amplexifolium Moldenke. Its structure was determined by spectral and chemical methods. Only one triterpenoid saponin has been isolated from Clerodendrum genus before. Se-saponin A is the second instance. A new triterpenoid saponin, se-saponin A, was isolated from the aerial parts of Clerodendrum serratum var. Amplexifolium Moldenke. Its structure was determined by spectral and chemical methods. Only one triterpenoid saponin has been isolated from Clerodendrum genus before. Se-saponin A is the second instance.