Saponins from Vietnamese ginseng, Panax vietnamensis Ha et Grushv. Collected in central Vietnam. I.

From rhizomes and roots of Panax vietnamensis Ha et Grushv., Araliaceae, commonly known as Vietnamese Ginseng, two new acetylate saponins named vina-ginsenoside-R1 (13) and vina-ginsenoside-R2 (15) were isolated. On the basis of chemical and spectral data, 13 was formulated as monoacetyl 24(S)-pseudo-ginsenoside-F11 and 15 was proved to be monoacetyl majonside-R2. Besides the two new saponins and beta-sitosteryl-3-O-beta-D-glucopyranoside, sixteen known saponins were also isolated and identified. Dammarane saponins:ginsenoside-Rh1 and 20(R)-ginsenoside-Rh1 (1), ginsenosides-Rg1 (2), -Re (3), -Rd (6), -Rb3 (7), -Rb2 (8), -Rb1 (9), pseudo-ginsenoside-RS1 (= monoacetyl ginsenoside-Re, 4), notoginsenosides-R1 (5) and -Fa (10). Ocotillol-type saponins:pseudo-ginsenoside-RT4 (11), 24(S)-pseudo-ginsenoside-F11 (12), majonosides-R1 (16) and -R2 (14). Oleanolic acid saponins:ginsenoside-Ro (= chikusetsusaponin V, 17) and hemsloside-Ma3 (18), a saponin previously isolated from a cucurbitaceous plant, Hemsleya macrosperma C. Y. Wu. Despite having large horizontally elongated rhizomes, the underground part of this plant contains mainly dammarane saponins and a small amount of oleanolic acid saponins. In addition, the yield of ocotillol-type saponins, especially majonoside-R2, is surprisingly very high (more than 5% and ca. half of the total yield of saponin). This characteristic saponin composition has made Vietnamese Ginseng an interesting species among Panax spp.