Studies On Chemical Constituents From Rhododendron Principis

Rhododendron principis Bur. et Franch. (Ericacea), is an evergreen small tree. They distribute from south to south-east Tibet especially. Most of them lived at the edge of dark coniferous forest and among bushes at the hight of 3600-4500 meters on mountains. However, Studies on chemistry and biological activities about R. principis have never been reported.We studied the chemical constituents of R. principis to provide theoretical support for the further development and protection of the unique plant in Tibet. In our study,21 chemical constituents have been isolated and identified and eight of them are new. We get nine diterpenoids, seven of which are new. Including a new kalmane type diterpenoid, rhodopricipin VII (7). It is the forth example of kalmane type diterpenoid found so far. And six new grayanane type diterpenoids, rhodoprincipin I-VI (1-6). They are all comparatively new in structure:Rhodopricipin I-III (1-3) are compounds with H-1β, which is different from the common H-la. Rhodopricipin IV (4) is the first grayanane diterpenoid with H-9a. Rhodopricipin V and VI are isomers, both of which present epoxides between C-6 and C-10 and 5α-OH for the first time. The structures of rhodopricipin I (1), rhodopricipin IV (4) and rhodopricipin V(5) are identified by X-ray diffraction respectively. The series of new diterpenoids greatly riched the chemical diversity of the family of grayanane type diterpenoids.Otherwise, a series of known compounds have been isolated and identified. including two lignans:one is new,9-acetyl-isolariciresinol-9’-O-P-D-xyloside (10), the other is its glycone,9-acetyl-isolariciresinol (11); two known phenolics: rhododendrin (12) and its glycone, rhododendrol (13); two apocarotenoids, tectoionols A (14) and megastigm-5-en-3,9-diol (15); four known flavanoids: quercetin (16), keamferol (17),3’,4’,5,7-tetrahydroxy-3-methoyflavone (18), (2R,3R)-(+)-taxifolin (19); and two known stilbene:resveratrol (20), cis-3,4’, 5-trihydroxystilbene (21).In the end, a review on the progress in chemistry and biological activities of Rhododendron is presented.