Identification and characterization of three new flavonoids from Rhododendron dauricum.

The present study was designed to determine the major chemical constituents of the leaves of Rhododendron dauricum L. Compounds were isolated and purified by various chromatographic methods, and their structures were elucidated by physicochemical properties and spectral data. The present study identified two new C-methyl flavanones, 5, 7, 3', 5'-tetrahydroxy-6, 8-di-C-methyl flavanone (1) and 5, 4'-dihydroxy-8-C-methylflavanone-7-O-ß-D-glucopyranoside (2), and one new flavonoid glycoside, quercetin-3-O-ß-D-(6"-O-cinnamoyl)-galactoside (3), along with seven known compounds, including syzalterin (4), poriolin (5), farrerol-7-O-ß-D-glucopyranoside (6), myrciacetin (7), quercetin-3-O-ß-D-(6-p-hydroxy-benzoyl)-galactoside (8), quercetin-3-O-ß-D-(6-p-coumaroyl)-galactoside (9), and 5, 7, 3', 5'-tetrahydroxyl flavanone (10). Compounds 1-3 were determined to be new flavonoids; compounds 4-6 were isolated from this species for the first time; and compounds 7-10 were reported for the first time from this genus.

Systematic characterization and simultaneous quantification of the multiple components of Rhododendron dauricum based on high-performance liquid chromatography with quadrupole time-of-flight tandem mass spectrometry.

Rhododendron dauricum L. has been used as a traditional Chinese medicine to treat cough and asthma and relieve phlegm and bronchitis. In this study, a reliable method based on high-performance liquid chromatography with diode array detection and quadrupole time-of-flight tandem mass spectrometry was established to systematically identify and quantify the components in this herb for the first time. A total of 33 compounds were identified, including 24 flavonoids, six phenolic acids, two coumarins and one terpene. Among them, poriolin (17), farrerol-7-O-ß-d-glucopyranoside (20), and syzalterin (30) were isolated from this plant for the first time, and quercetin-3-ß-d-(6-p-hydroxy benzoyl) galactoside (19), quercetin-3-ß-d-(6-p-coumaroyl) galactoside (21), and myrciacetin (23) were identified from this genus for the first time. Fragmentation pathways of flavonoids also have been investigated by electrospray ionization mass spectrometry. Moreover, seven bioactive constituents, namely, gallic acid (1), scopoletin (6), dihydroquercetin (7), quercetin (22), kaempferol (25), 8-desmethyl farrerol (27), and farrerol (28), were simultaneously quantified. The developed method has been validated and applied to analyze ten samples of R. dauricum from Hebei Province successfully. The contents of the seven compounds have been detected and compared.