rolizidine alkaloids in Parsonsia laevigata ALSTON and phenanthroindolizidine alkaloids in Tylophora tanakae

Asclepiadaceous plants, we have described that the pyrrolizidine alkaloids in Parsonsia laevigata ALSTON and phenanthroindolizidine alkaloids in Tylophora tanakae MAXIM. act as an oviposition-activating substance for Danaid butterflies, Idea leuconoe and Ideopsis similis, respectively. Since Parantica sita lays eggs on the leaves of Marsdenia tomentosa MORREN et DECAISNE and cyclitols such as conduritol A, conduritol F and their glucosides in this plant are involved in host-recognition, we have investigated polar compounds, including cyclitols, in other Asclepiadaceous plants. This paper deals with the isolation of conduritol F and its glucosides, along with a megastigmane glucoside and a monoterpenoid glucoside from Cynanchum liukiuense WARB., which is known as a host-plant for Salatura genutia CRAMER, one of the Danaid butterflies in the Ryukyu district. We also describe the comparison of conduritol F and its glucosides from T. tanakae, A. curassavica L. and A. fruticosa L. The leaves of C. liukiuense, collected in the Yaeyama Islands, were homogenized with MeOH, and the MeOH extract was partitioned with CHCl3 and then n-BuOH. The water layer was fractionated on a charcoal column and eluted with H2O, 5—50% EtOH, and MeOH. Each fraction was then purified on a silica gel column and subjected to HPLC to afford five substances (1—5). Substance 1, obtained from the H2O effluent, was identified as conduritol F (L-leuchanthemitol). Substance 2 was obtained from the 10—20% EtOH effluent, and has the molecular formula, C12H20O9, based on high resolution (HR)-FAB-MS. In addition to the signals due to a b-glucopyranosyl moiety (dC 105.4 and dH 4.81, J58 Hz), signals due to conduritol F were observed in the Hand CNMR spectra, suggesting 2 to be a conduritol F glucoside (Table 1). Upon acid hydrolysis of 2, the glucose was confirmed to be in the D-form by GC analysis of the thiazolidine derivative. Based on the deshielding of C-3 (18.9 ppm) and the shielding of C-2 (21.4 ppm) and C-4 (20.5 ppm), in comparison with the signals for 1, 2 was determined to be 3O-b-D-glucopyranosyl-conduritol F. Substance 3 was accompanied by 2 and isolated finally by HPLC. HR-FAB-MS of 3 suggested that it has the same molecular formula as 2, C12H20O9. The NMR spectra showed a similar pattern to 2, except for the deshielding of C-4 (19.1 ppm) and the shielding of C-3 (21.4 ppm) and C-5 (21.4 ppm) in the C-NMR spectrum. Therefore, the linkage of glucose was assigned to be at C-4–OH. In the same way as for 2, glucose was confirmed to be in the D-form, and 3 was determined to be 4-O-b-D-glucopyranosyl-conduritol F. 1090 Notes Chem. Pharm. Bull. 48(7) 1090—1092 (2000) Vol. 48, No. 7