Twenty-six alkaloids have been identified in the root bark of Strychnos matopensis from Zaïre. They are Wieland-Gumlich aldehyde (WGA), desoxy WGA, N-formyldesoxy WGA, nor-C-fluorocurarine, N-desacetylretuline, N-desacetylisoretuline, isorosibiline, (16R)-isositsirikine, 1 1-methoxy diaboline, diaboline, matopensine, 16-methoxy isomatopensine, 16-ethoxy isomatopensine, 18-hydroxy matopensine, 18,18′-bis-hydroxy matopensine, matopensine N-oxide, strychnofuranine, bisnordihydrotoxiferine, bisnor-C-alkaloid H, bisnor-C-curarine, bisnor-C-alkaloid D, longicaudatine, longicaudatine F, longicaudatine Y, longicaudatine Z and N-oxylongicaudatine. The new compounds are N-formyldesoxy-Wieland-Gumlich aldehyde, the derivatives of matopensine, strychnofuranine and longicaudatine Z. Strychnofuranine is made up of two geissoschizal units with C-16 and C-17 being condensed into a furan ring. © 1988.