[Studies on the chemical constituents of rutaceous plants. LXVII. The chemical constituents of Toddalia asiatica (L.) Lam. (T. aculeata Pers). Examination of coumarins using supercritical fluid and soxhlet extraction. Is toddalolactone a genuine natural coumarin?].

It is well known that toddalolactone (1) is a main component of Toddalia asiatica (L.) Lam. (T. aculeata Pers.) (Rutaceae). However, supercritical fluid (SCF) extraction of the plant by using CO2 showed that a main component of the extract was not 1, but aculeatin (2), a coumarin having an epoxy ring on the side chain. The same result was obtained from Soxhlet extraction by using aprotic solvents. On the other hand, Soxhlet extraction by using methanol yielded 13, corresponding to a methanol adduct of 2, as an additional component, which was able to be also produced in 50.2% yield only by heating pure 2 in methanol, indicating that the epoxy ring in 2 can be easily attacked by a weak nucleophile like methanol. These facts strongly suggested that 1, corresponding to the hydrate of 2, was an artefact derived from 2 during extraction. SCF extraction under various conditions was examined in detail by quantitative analyses of 1 and 2 by high performance liquid chromatography and the optimum condition extracting the both components was found to be at 40 degrees C and at 300 kg/cm2. The condition was applied to the plant treated with aqueous sodium hydrogen carbonate in order to remove any acidic substances and 1 was still detected in the extract. Thus, it is conclude that 1 should be a genuine natural coumarin but that previous isolation of 1 as a main component resulted in an isolation of an artefact derived from 2. SCF extraction was suggested to be a useful extraction method.