An indolizidine alkaloid naturally found in certain plants that inhibits N-linked glycoside hydrolases, preventing the processing of asparagine-linked glycoproteins; reversibly inhibits lysosomal α-mannosidase and Golgi α-mannosidase II (IC50 = 0.2 μM); shown to have antiproliferative and antimetastatic effects on cancer cells in culture and in mice.