A new strychnine alkaloid, 16,17,19,20-tetrahydro-2,16-dehydro-18-deoxyisostrychnine (1), and fourteen known alkaloids were isolated from the leaves of Psychotria pilifera. Their structures were identified on the basis of extensive spectroscopic analysis, as well as by comparison with the reported spectroscopic data. The new alkaloid (1) exhibited potent antibacterial activity against Escherichia coli, equivalent to cefotaxime with MIC value of 0.781 μg/ml.
Keywords: 16,17,19,20–tetrahydro–2,16–dehydro–18–deoxyisostrychnine; Psychotria pilifera; Rubiaceae; antibacterial activity; indole alkaloid.