Minor alkaloids found in Strychnos nux vomica L.; naturally occurring in two chemically distinct forms, α and β. Isolation from mother liquor of commercial strychnine extraction: K. Warnat, Helv. Chim. Acta 14, 997 (1931). Isolation and characterization from S. nux vomica L.: G. B. Marini-Bettolo et al., J. Assoc. Off. Anal. Chem. 51, 185 (1968). Structure of α- and β-colubrine: S. P. Findlay, J. Am. Chem. Soc. 73, 3008 (1951); of β-colubrine: P. Rosenmund, Ber. 95, 2639 (1962); of α-colubrine: J. M. Culver, M. Sainsbury, J. Chem. Res. Synop. 1987, 304. Synthesis from strychnine: P. Rosenmund, H. Franke, Ber. 97, 1677 (1964). Determn by GLC: N. G. Bisset, P. Fouché, J. Chromatogr. 37, 172 (1968); by HPLC: G. M. Iskander et al., J. Liq. Chromatogr. 5, 1481 (1982). Chiroptical properties of β-colubrine: J. W. Snow, T. M. Hooker, Jr., Can. J. Chem. 56, 1222 (1978).