Chem. Pharm. Bull. 55(10) 1505—1511 (2007)

Rhodiolae Radix, have been widely used as a hemostatic, antibechic, tonic, and endermic liniment for burns and contusions in traditional Chinese medicine. Chemical and biological studies on several Rhodiola plants have been reported. For example, the methanolic extract from the roots of R. sachalinensis was reported to show inhibitory activity on prolyl endopeptidase. During the course of our serial studies on the bioactive constituents from Chinese natural medicines, we have characterized the structures of several monoterpene oligoglycosides and cyanogenic glycosides from the roots of R. quadrifida (PALL.) FISCH. et MAY and R. sacra (PRAIN ex HAMET) S. H. FU. Among the isolated constituents, monoterpene oligoglycosides, sacranosides A and B, were found to inhibit histamine release from rat exudate cells induced by an antigen–antibody reaction. As a continuing study on the bioactive constituents of Rhodiolae Radix, the methanolic extract from the roots of R. sachalinensis A. BOR. was found to show a protective effect on Dgalactosamine (D-GalN)-induced cytotoxicity in primary cultured mouse hepatocytes. From the methanolic extract, we have isolated two new monoterpene glycosides, sachalosides I and II, two new flavonol bisdesmosides, sachalosides III and IV, a new cyanogenic glycoside, sachaloside V, together with 34 known compounds. Furthermore, we examined the protective effects of principal constituents on D-GalN-induced cytotoxicity in primary cultured mouse hepatocytes. In this paper, we describe the isolation and structure elucidation of the new constituents (1—5) and the hepatoprotective effects of principal constituents from the roots of R. sachalinensis. The roots of R. sachalinensis were extracted with methanol under reflux. The methanolic extract (14.6% from the roots) was partitioned into an EtOAc–H2O mixture to furnish an EtOAc-soluble fraction (3.5%) and aqueous layer. The aqueous layer was further extracted with n-BuOH to give n-BuOH and H2O-soluble fractions (4.4% and 6.5%, respectively). As shown in Table 1, the methanolic extract and the EtOAcand n-BuOH-soluble fractions were found to show hepatoprotective effects, but the H2O-soluble fractions showed weak effect. The EtOAc-soluble fraction was subjected to normal-phase and reversed-phase column chromatographies, and finally HPLC to give 13 known compounds, geranyl b-D-glucopyranoside (6, 0.0070%), myrtenyl 10-O-b-D-glucopyranoside (9, 0.0054%), p-tyrosol (17, 0.062%), 3-phenylpropyl b-D-glucopyranoside (21, 0.052%), trans-cinnamyl alcohol (22, 0.0065%), pcoumaric acid (26, 0.017%), trans-caffeic acid (27, 0.0011%), p-hydroxyphenethyl anisate (30, 0.0003%), eriodictyol (32, 0.019%), luteolin (33, 0.0011%), kaempferol (34, 0.023%), tricin (37, 0.0069%), 1-octylb-D-glucopyranoside (38, 0.0019%). The n-BuOH-soluble fraction was also subjected to Diaion HP-20 column chromatography (H2O→MeOH) to give the waterand methanoleluted fractions (0.8% and 3.5%, respectively). The methanol-eluted fraction was subjected to normaland reversed-phase column chromatographies, and finally HPLC to give sachalosides I (1, 0.0004%), II (2, 0.0005%), III (3, 0.0003%), IV (4, 0.0004%), and V (5, 0.0007%), together with 21 known compounds, geranyl 1-O-a-L-arabinofuranosyl(1→6)-b-D-glucopyranoside (7, 0.0029%), kenposide A (8, 0.0028%), sacranoside A (10, 0.0011%), rhodiocyanoside A (11, 0.23%), lotaustralin (12, 0.0014%), hetorodendrin (13, 0.0002%), benzyl b-D-glucopyranoside (14, 0.0022%), phenylmethyl 6-O-a-L-arabinofuranosyl(1→6)-b-D-glucopyranoside (15, 0.0004%), benzylalcohol 7-O-a -L-arabinopyranosyl(1→6)-b -D-glucopyranoside (16, 0.0002%), 2-phenylethyl b-D-glucopyranoside (18, 0.0022%), salidroside (19, 0.10%), 2-(4-methoxyphenyl)ethyl b-D-glucopyranoside (20, 0.0004%), trans-cinnamyl b-D-glucopyranoside (23, 0.0046%), rosarin (24, 0.0097%), rosavin (27, 0.034%), eugenyl O-b-D-apiofuranosyl(1 →6 )-b-D-glucopyranoside (28, 0.0001%), gein (29, 0.0007%), nodakenin (31, 0.0021%), leucoside (35, 0.0028%), rhodiosin (36, 0.014%), 1-octyl-a-D-arabinofuranosyl(1→6)-b-D-glucopyranoside (39, 0.0009%). Bioactive Constituents from Chinese Natural Medicines. XXVI. Chemical Structures and Hepatoprotective Effects of Constituents from Roots of Rhodiola sachalinensis