Identification of phenanthrene derivatives in Aerides rosea (Orchidaceae) using on-line hyphenated systems

In our continued efforts to contribute to the general knowledge about the chemical diversity of orchids, our investigations focused on the Aeridinae subtribe. After our previous phytochemical study of Vanda coerulea, which has led to the identification of stem-specific phenanthrene derivatives [1], a closely-related species, Aerides rosea Lodd. ex Lindl. & Paxton, has been explored. A dereplication strategy using an HPLC-DAD-HRMS/MS targeted method allowed the characterization of the major metabolites and in the same time avoided the isolation of four already known compounds previously isolated from V. coerulea stem extract: gigantol, imbricatin, methoxycoelonin and coelonin. The analyses of two A. rosea fractions performed by the hyphenated HPLC-DAD-MS-SPE-UV/NMR system, permitted the identification of five additional minor constituents including one phenanthropyran, two phenanthrenes and two dihydrophenanthrene derivatives. The full set of NMR data of each compound was obtained from only microgram quantities. Finally, using state-of-the art hyphenated systems, nine secondary metabolites were characterized in A. rosea stem extract. Two of them are newly described phenanthrene derivatives: 5-methoxyphenanthrene-2,3,7-triol (1) and 3-methoxy-9,10-dihydro-2,5,7-phenanthrenetriol (2), named aerosanthrene and aerosin, respectively.

Keywords: Orchids, hyphenated systems, dereplication, phenanthrene derivatives

References:

[1] Simmler C, Antheaume C, Lobstein A. (2010). Plos One 5: e13713.