In this study, one new quinolizidine alkaloid, lanatine A (1), together with three other known alkaloids, 13-alpha-trans-cinnamoyloxylupanine (2), 13-alpha-hydroxylupanine (3), and (-)-multiflorine (4) were isolated from the aerial parts of Lupinus lanatus (Fabaceae). The structures of alkaloids 1-4 were elucidated by spectroscopic data analysis. The stereochemistry of 1 was determined by single crystal X-ray analysis. Bayesian statistical analysis of the Bijvoet differences suggests the absolute stereochemistry of 1. In addition, the antimicrobial potential of alkaloids 1-4 is also reported. (C) 2011 Elsevier B.V. All rights reserved.