Phytochemical Study On Two Rhododendron Genus Plants

Objective:In order to exploit the potential medical use of Rhododendron plant,this research systematically studied the chemical constituents of two species of Rhododendron,Rhododendron mariae Hance and Rhododendron annae Franch,and the anti-inflammatory activities of the isolated compounds were also studied at the cellular level.The chemotaxonomic of the isolated compounds was preliminarily discussed in order to provide a scientific basis for the development and utilization of Rhododendron plant resources.Methods:The 95% ethanol extract of the Rhododendron mariae Hance was extracted by the petroleum ether,dichloromethane and ethyl acetate,respectively.The compounds were isolated from the dichloromethane and ethyl acetate extract by means of chromatography on silica gel column,ODS column,Sephadex LH-20 column and preparative HPLC.The structures were elucidated by using ¹H-NMR,¹³C-NMR and MS analyses.The 95% ethanol extract of the Rhododendron annae Franch was eluted by macroporous resin column chromatography.Then the compounds were isolated by means of chromatography on silica gel column,ODS column,Sephadex LH-20column and preparative HPLC.The structures were elucidated by using ¹H-NMR,¹³C-NMR and MS analyses.In addition,LPS-induced RAW 264.7 cell model was used to detect the inhibitory activity of the 23 isolated compounds for the release of NO.The chemotaxonomic significance of the isolated compounds was preliminarily discussed by comparing with the species which has obtained the same components.Results:Thirteen compounds were isolated and identified from Rhododendron mariae Hance,namely:7S,8R-dihydrodehydrodiconiferyl alcohol（A1）,5-hydroxy-3’,4’,7-trimethoxyflavone（A2）,2,3,4’-trihydroxy-3’,5’-dimethoxypropiophenone（A3）,β-asarone（A4）,α-asarone（A5）,isoscopoletin（A6）,syringaldehyde（A7）,vanillic acid（A8）,smiglanin（A9）,quercetin（A10）,quercitrin（A11）,farrerol（A12）,hyperoside（A13）.Thirteen compounds were isolated and identified from Rhododendron annae Franch,namely:（-）-epicatechin（B1）,（+）-catechin（B2）,（-）-gallocatechin（B3）,procyanidin A1（B4）,3,7-dimethoxy-5,3’,4’-trihydroxyflavone（B5）,a stilbin（B6）,guaijaverin（B7）,kaempferol-3-O-ɑ-L-rhamnoside（B8）,3,5,7-trihydroxylchromone-3-O-A-L-arabinopyranoside（B9）,taxifolin-3-O-α-L-arabin opyranoside（B10）,hyperoside（B11）,quercetin（B12）,（7R,8S）-3,5’-dimet hoxy-4’,7-epoxy-8,3’-neolignane-5,9,9’-triol（B13）.RAW 264.7 cell model was induced by LPS,and five isolated compounds were detected to inhibit NO release in the model.Conclusion:Compounds A2～A9 are isolated from Rhododendron mariae Hance for the first time.Compounds A2～A5,A7 and A9 are isolated from Rhododendron genus for the first time.Compounds B1～B13 are isolated from Rhododendron annae Franch for the first time.Compounds B13 are isolated from Rhododendron genus for the first time.At the same time,the anti-inflammatory activities of the isolated compounds were studied at the cellular level,and it was concluded that compounds A2,A3,A7,A10 and A11 had a certain activity of inhibiting the release of NO in the model.Moreover,the chemotaxonomic significance of the isolated compounds was preliminarily discussed,and most Rhododendron plants contain flavonoids.Thus,we draw a conclusion that flavonoids could be the characteristic constituents of Rhododendron plants.The compound（7R,8S）-3,5’-dimethoxy-4’,7-epoxy-8,3’-neolignane-5,9,9’-triol may serve as a potential chemotaxonomic marker for distinguishing Rhododendron annae Franch from other species of the Rhododendron genus.