Polar fractions of the methanolic extracts of the stem- and root-barks of Schumanniophyton magnificum (Rubiaceae) reduced the effects of cobra venom cardiotoxin in the chick biventer cervicis nerve-muscle preparation in vitro. No activity was observed against a curaremimetic neurotoxin from cobra venom. Further fractionation of the extracts showed that the activity was not due to alkaloidal components, but the active substances could not be identified or isolated.