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Natural intoxication of livestock by the ingestion of Ipomoea carnea (Convolvulaceae) sometimes occurs in tropical regions of the world. Polyhydroxylated alkaloids were isolated from the leaves, flowers, and seeds of the poisonous plant and characterized. Chromatographic separation of the leaf extract resulted in the isolation of swainsonine (1), 2-epi-lentiginosine (2), calystegines B₁ (3), B₂ (4), B₃ (5), and C₁ (6), and N-methyl-trans-4-hydroxy-l-proline (7). The contents of 1 in the fresh leaves and flowers were 0.0029 and 0.0028%, respectively, whereas the contents of 1, 3, and 4 in the seeds were ∼10 times higher than those in the leaves and flowers. Alkaloids 3, 4, and 6 showed a potent inhibitory activity toward rat lysosomal β-glucosidase, with IC₅₀ values of 2.1, 0.75, and 0.84 μM, respectively, and alkaloid 5 was a moderate inhibitor of α- and β-mannosidases. Although alkaloid 1 is known as a powerful …