Nematocidal alkaloids from the roots of Stemona mairei (H.Lév.)K.Krause and identification of their pharmacophoric moiety

Fifteen undescribed alkaloids are identified from Stemona mairei. All the hitherto undescribed compounds possess a pyrrolo[1,2-α]azepine core structure but differ in important structural features, which reflects their nematocidal activities. The key pharmacophore of these alkaloids lies in the aliphatic side chain of these compounds and spatial distribution of alkaloids in the roots indicate protective effects against underground herbivores.