Studies On Chemical Constituents Of Tibetan Rhododendron Lepidotum Wall. Ex G. Don

Rhododendron lepidotum Wall. ex G. Don (Ericaceae) is a low shrub, grows in western Sichuan, northwestern Yunnan, southern and southeastern Tibet in China, also distributes in Nepal, Bhutan, Sikkim and northeastern Burma. It has been used to treat headache, fever, cough, cold, tonsillitis, and also kill bugs. It’s the first time to study the chemical constituents of Tibetan Rhododendron lepidotum systematically, which provides a scientific basis for fully developing and utilizing this plant.The volatile oils in the aerial parts of Rhododendron Lepidotum Wall. ex G. Don were extracted by water steam distillation (0.2817%) and its constituents were identified by GC-MS method. A total of64chromatographic peaks were separated and60components were identified, occupying98.70%of total amount. The compounds types including terpenes, aromatic compounds, heterocycle compounds, alcohols, and aliphatic hydrocarbons ect. The main compounds are α-pinene(18.30%), limonene(14.85%), naphthalene(11.78%), β-pin-ene(8.81%), γ-terpinene(5.54%), trans-caryophyllene(4.57%), nerolidol (3.19%), m-cym-ene(2.99%), caryophyllene oxide(2.37%), β-myrcene(2.03%) etc.The chemical constituents were isolated and purified by various chromatographic techniques, and their structures were identified based on analyses of spectroscopic data and physico-chemical evidences.20compounds were isolated and18of them were identified as: hopenol-B (1),2-(4-hydroxyphenyl)-ethyl triacontanoate (2), ursolic acid (3), avicularin (5), quercetin (6), myricetin (7), hyperoside (8),(+)-taxifolin-3-O-a-L-arabinopyranoside (9), lupeol (10), confluentin (11), myricetin-3’-O-β-D-xyloside (12),(＋)-taxifolin-3-O-β-D-glucopyranoside (13),2,6-dimethoxy-4-hydroxyphenyl-1-O-β-D-glucopyranoside (15),(-)-2-hydroxy-5-(2-hydroxyethyl)phenyl-O-β-D-glucopyranoside (16),(-)-isolariciresinol (17),2,4,6-trihydroxacetophenone-3,5-di-C-β-D-glucoside (18), isofraxoside (19), lyoniside (20). The structure types including triterpene, flavonoid, lignanoid, acetophenone and other phenols. Compound18was an unusual natural product, compounds1,2,15-19were firstly reported occurrence in Rhododendron spp., as well as all the other compounds were isolated from this plant for the first time.