Studies On The Chemical Constituents Of The Polar Fraction Of Gynostemma Longipes

The traditional Chinese medicine,Herba Gynostemma,is the whole plant from the genus Gynostemma in the family Cucurbitaceae,which has lots of pharmacological activities including regulating blood lipid,hypoglycemic,antitumor,antioxidant,improving immunity effects.Its original species include Gynostemma pentaphyllum（Thunb.）Makino and G.longipes C.Y.Wu and so on.According to the literature,the main components of G.pentaphyllum are dammarane triterpenoid saponins,some of which are same as ginsenosides from ginseng.Therefore,Herba Gynostemma is known as"Southern ginseng"or"Second ginseng".The total saponins of G.longipes were analyzed by UPLC-QTOF/MS and showed that a lot of unidentified components in the large polar part of the total saponins of G.longipes.In the study,the large polar part of G.longipes were systematically separated and purified based on LC-MS analysis of the total saponins of G.longipes.Twenty compounds were isolated by several kinds of column chromatograms on D101 resin,MCI,silica gel,C18,and preparative HPLC.Their structures were elucidated by physicochemical and spectral analyses,including 18 new compounds and 2 known compounds.The structure of 18 new compounds were determined as（20S,24R）-3β,21,25-trihydroxy-20,24-epoxydrammar-19-oxo-3-O-{[α-L-rhamnopyranosyl（1→2）][β-D-xylopyranosyl（1→3）]-α-L-arabinpyranosyl-21-O-β-D-glucopyra noside（1）,（20S,24S）-3β,21,25-trihydroxy-20,24-epoxydrammar-19-oxo-3-O-{[α-L-rhamnopyranosyl（1→2）][β-D-xylopyranosyl（1→3）]-α-L-arabinp yranosyl}-21-O-β-D-glucopyranosie（2）,（20S,24R）-3β,21,25-trihydroxy-20,24-epoxydrammar-3-O-{[α-L-rhamnopyranosyl（1→2）][β-D-xylopyran osyl（1→3）]-α-L-glucopyranosyl}-21-O-β-D-glucopyranoside（3）,（20R,24R）-3β,21,25-trihydroxy-20,24-epoxydrammar-3-O-{[α-L-rhamnopyranosyl（1→2）][β-D-xylopyranosyl（1→3）]-α-L-glucopyranosyl}-21-O-β-D-glucopy ranoside（4）,（20R,21R,23R,24R）-3β,20,21,23-terahydroxy-19-oxo-21,24-cyclodrammar-25-ene-3-O-[α-L-rhamnopyranosyl（1→2）][β-D-glucopyran osyl（1→3）]-α-L-arabinopyranside（6）,（20R,21R23R,24R）-3β,19,20,21,23-pentahydroxy-21,24-cyclodrammar-25-ene-3-O-[α-L-rhamnopyranosyl（1→2）][β-D-xylopyranosyl（1→3）]-α-L-glucopyranside（7）,（20R,21R,23R,24R）-3β,19,20,21,23-pentahydroxy-21,24-cyclodramma-25-ene-3-O-[α-L-rhamnopyranosyl（1→2）][β-D-xylopyranosyl（1→3）]-α-L-arabinopyranside（8）,（20S,21S,23S,24S）-3β,20,21,23-tetrahydroxy-19-oxo-21,24-cyclodam mar-25-ene-3-O-[α-L-rhamnopyranosyl（1→2）][β-D-xylopyranosyl（1→3）]-α-L-arabinopyranoside（9）,（20S,21S,23S,24S）-3β,20,21,23,25-pentahydr oxy-19-oxo-21,24-cyclodammar-3-O-[α-L-rhamnopyranosyl（1→2）][β-D-xylopyranosyl（1→3）]-α-L-arabinopyranoside（10）,（20S,21R,23R,24R）-3β,20,21,23,25-pentahydroxy-19-oxo-21,24-cyclodammar-3-O-[α-L-rhamno pyranosyl（1→2）][β-D-xylopyranosyl（1→3）]-α-L-arabinopyranoside（11）,（20S,21S,24S）-3β,20,21,25-tetrahydroxy-20,24-cyclodammar-3-O-{[α-L-rhamnopyranosyl（1→2）][β-D-xylopyranosyl（1→3）]}-α-L-glucopyranosyl-25-O-β-D-glucopyranoside（12）,（20S,21R,23R）-3β,20,21-trihydroxy-24-ene-epoxydrammar-3-O-{[α-L-rhamnopyranosyl（1→2）]-[β-D-xylopyranos yl（1→3）]-β-D-glucopyranosyl}-21-O-β-D-glucopyranosyl（1→6）-β-D-gluc opyranoside（13）,（20ξ,21ξ,23ξ,24ξ）-3β,21,23-trihydroxy-19-oxo-21,24-cy cly-20,25-epoxydrammar-3-O-[α-L-rhamnopyranosyl（1→2）][β-D-xylopyr anosyl（1→3）]-α-L-arabinopyranoside（15）,（20S,23ξ,24ξ）-3β,20,21,23,24-pentahydroxy-3-O-[α-L-rhamnopyranosyl（1→2）][β-D-xylopyranosyl（1→3）]-α-L-arabinopyranoside（16）,（20S）-3β,20,21-trihydroxydammar-19-oxo-24-ene-3-O-{[α-L-rhamnopyranosyl（1→2）]-[β-D-xylopyranosyl（1→3）]-α-L-arabinopyranosyl}-21-O-β-D-glucopyranosyl（1→6）-β-D-glucopyranosid e（17）,（20S）-3β,19,20,21-terahydroxydammar-24-ene-3-O-{[α-L-rhamnop yranosl（1→2）][β-D-xylopyranosyl（1→3）]-α-L-arabinopyranosyl}-21-O-[β-D-glucopyranosyl（1→6）]-β-D-glucopyranoside（18）,（20S）-3β,20,21-trihy droxydammar-24-ene-19-oxo-3-O-[α-L-rhamnopyranosyl-（1→2）][β-D-xyl opyranosyl（1→3）]-α-L-arabinopyranosyl-21-O-α-L-rhamnopyranosyl-（1→6）-β-D-glucopyranoside（19）,（20S）-3β,20,21-trihydroxydammar-24-ene-3-O-{[α-L-rhamnopyranosyl（1→2）][β-D-glucopyranosyl（1→3）]-β-D-gluc opyranosyl}-21-O-[β-D-glucopyranosyl（1→6）]-β-D-glucopyranoside（20）.Simultaneously,the lipid-lowering activities of the above compounds were studied in vitro.Compound 15 and 17 can significantly reduce the content of cholesterol on SMMC-7721 cells（human hepatoma cells）.In this study,the 20 compounds isolated from the large polar part of G.longipes are all damarane triterpenoid saponins,and they have the following structural features.Triterpenoid saponins which C-20 to C-25are straight chains,△^24（25）position contains double bonds;C-21 and C-24are connected into a ring;C-20 and C-24 re connected into a ring containing oxygen,and C-21 is connected with a monosaccharide group.Some compounds have an aldehyde group or a hydroxymethyl group at C-19.All compounds are linked to a trisaccharide at C-3,and some compounds are linked to a disaccharide at C-21 in addition to a trisaccharide at C-3,which type of compound were rarely reported in the previous studies of G.longipes.Meanwhile,the vitro cell experiment was performed,and two monomer compounds showed the significant reduction of the content of cholesterol in cells,and lay a foundation for the comprehensive development and utilization of Herba Gynostemma.