A new group of indole alkaloids, the secamines, has been isolated from Rhazya stricta Decaisne and R. orientalis A. DC. R. stricta leaf bases were fractionated mainly by countercurrent distribution, and crude secamine concentrates further fractionated by reverse-phase buffer partition chromatography, giving five fairly symmetrical eluent bands: two tetrahydrosecamines (T.H. Sec.) C₄₁H₅₁N₄O₄ (0.016% of dry wt. of leaves), two dihydrosecamines (D.H.Sec.) C₄₂H₅₄N₄O₄ (0.015%), and secamine C₄₂H₅₈N₄O₄ (0.004%). None of these materials has yet crystallised, nor has any of the salts tried. Each of these fractions is quite homogeneous with respect to mass spectra and behaviour on t.l.c., the complexity of the n.m.r. spectra in the aliphatic CH regions however suggests mixtures of stereoisomers or conformers, or both. Although the structural work has been carried out on these stereochemically probably nonhomogeneous bases, it allows the assignment of two possible structures in which the stereochemistry is not defined; secamine itself is defined by either (I) or (II); in T.H.Sec. both C-15-C-20 and C-15'-C-20' double bonds are saturated and in D.H.Sec. only one. Main evidence includes T.H.Sec. being hydrolysed (aq. NaOH) and decarboxylated (6M-HCl/100°C/20 hr.) to an oxygen-free base didemethoxycarbonyl-T.H.Sec. C₃₂H₃₆N₄ (~20% yield), deuteriation studies (D₂O-DCl leading to C₃₂H₃₁D₅N₄), mass spectral fragment analysis (base peak at m/e 126, C₉H₁₀N), Hofmann degradation (secamine dimethiodide yields 3-ethyl-1,2,5,6-tetrahydro-N-methylpyridine, T.H.Sec. yields 3-ethyl-N-methylpiperidine, D.H.Sec. yields a mixture), MeO⁻-MeOD at 100°C introducing only one D, presence of one indolic SH group (mass spectrum increase by one mass unit with D₂O), and reductive decarbomethoxylation of T.H.Sec. to C₃₂H₃₈N₄ confirmed by ozonolysis/hydrolysis to adipic and glutaric acids (2:1) and synthesis. The secamines are of considerable biogenetic interest, for they are the first indole alkaloids to contain the unit (XI), which may well represent a key stage in the interconversion of strychnos, aspidosperma, and iboga-type bases. U.V., i.r., n.m.r., unit mass spectra, high resolution mass measurements on parent peaks and main fragments determined on the alkaloids and the degradation products were all in accordance with the proposed structures. Satisfactory elemental analyses were obtained for synthetic compounds.