Phytochemical study on Sabina przewalskii, a Tibetan medicinal plant.

摘要

Sabina przewalskii, a Tibetan medicinal plant, belongs to the Cupressaceae family. The present study focused on the chemical composition of S. przewalskii, with the objective of discovering new chemical entities.; Air-dried twigs and leaves of S. przewalskii were extracted with aqueous ethanol. The crude extract was combined with celite and eluted with hexane, chloroform, ethyl acetate and methanol, successively. Repeated chromatographic separations of these fractions led to the isolation of 32 compounds, each of which was subjected to spectroscopic analysis, including optical rotation, UV, IR, 1D and 2D NMR, MS, X-ray crystallography, etc.; Among the isolated compounds, eighteen of them fall into two major chemical classes. They are six alkanols, i.e., 8,21-octacosanediol ( 1), icariside H₁ (24), cinnamyl alcohol O-α-L-arabinofuranosyl (1→6) β-D-glucopyranoside (25), 1,3-hexanediol 1-O-β-D-glucopyranoside (26), 1-hydroxyhexan-3-one β-D-glucopyranoside (27 ) and 3′,4′,5′ -trimethoxy-cinnamyl alcohol (29) were identified. Twelve terpenoids were obtained; they include a monoterpene, i.e., 2-etheno-2,6-dimethyl-3H, 4H-oxepin-7-one (14), a sequiterpenoid, i.e., β-cedrol ( 2), a diterpene possessing primarane skeleton, i.e., isopimarol ( 8), two abietane-type diterpenes, i.e., totarol (5) and sugiol (7), and seven labdane-type diterpenes, i.e., 13-oxo-14,15-dinorlabd-8(17)-en-19-oic acid (10), cupressic acid (11), 3α-acetoisocupressic acid (12), 3α-acetoxy-14(R,S), 15-dihydroxy-labd-8(17),13(16)-dien-19-oic acid (13), 3α-hydroxy-13-oxo-14,15-dinor-8(17)-labden-19-oic acid (15), 14,15-dihydroxy-8(17),13(16)-labdadien-19-oic acid (16) and 3α-hydroxyisocupressic acid (17). In addition, the following fourteen compounds were purified during the course of study: two sterols, i.e., β-sitosterol (9) and daucosterol (4); three isopropylphenols, i.e., junipediol A 8-glucoside (20), junipediol B 8-glucoside ( 22) and juniperdiol A (28); four coumarins, i.e., ekersenin (3), 3-methoxypereflorin (6), skimmin (21) and umbelliferone (32); two lignans, i.e., (7R,8S)-erythro-3′,4,7,9,9′-pentahydroxy-3-methoxy-8,4 ′-oxyneolignan (30) and 2,3-threo-dihydro-7-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-3-(O-α-L-rhamnopyranosylmethyl)-5-benzofuranpropanol (31); two flavonoids, i.e., cupressflavone ( 18) and quercitrin (19); an aromatic glycoside, i.e., 1-[2-(O-β-D-glucopyranosylmethyl)-6-methoxyphenyl]-ethanone ( 23). Among the 32 compounds isolated, seven were proven to be new natural products; they are 8,21-octacosanediol (1), 2-etheno-2,6-dimethyl-3H, 4H-oxepin-7-one (14), 3α-hydroxyisocupressic acid ( 17), 1-[2-(O-β-D-glucopyranosylmethyl)-6-methoxyphenyl]-ethanone (23), cinnamyl alcohol O-α-L-arabinofuranosyl (1→6) β-D-glucopyranoside (25), 1,3-hexanediol 1-O-β-D-glucopyranoside (26) and 1-hydroxyhexan-3-one β-D-glucopyranoside (27). (Abstract shortened by UMI.)