A new phenanthrenequinone from Dendrobium draconis

Abstract

A number of Dendrobium species (Orchidaceae) have been used as health foods. In Thailand, the tea prepared from the stems of Dendrobium draconis Rchb.f. (Orchidaceae) has been used as a blood tonic. Our phytochemical investigation of this plant led to the isolation of a new compound namely 5-methoxy-7-hydroxy-9,10-dihydro-1,4-phenanthrenequinone (1), along with four known stilbenoids including hircinol (2), gigantol (3), batatasin III (4), and 7-methoxy-9,10-dihydrophenanthrene-2,4,5-triol (5). The structures of these compounds were determined through extensive spectroscopic studies, including ¹H and ¹³C NMR, DEPT, COSY, NOESY, HMQC, HMBC, ESI-MS, and HR-ESI-MS experiments. In the DPPH-free radical assay, these stilbene derivatives showed appreciable antioxidant activity.

Keywords:

• Dendrobium draconis
• phenanthrenequinone
• NMR
• free radical scavenging

Acknowledgements

This work was supported by the National Research University Project of CHE and the Ratchadaphiseksomphot Endowment Fund (FW1016A). M.A. is grateful to the Chulalongkorn University Graduate School for a research scholarship, and the Research Instrument Center of the Faculty of Pharmaceutical Sciences for research facilities. We thank Prof. T. Phadungcharoen for the plant identification.