Free radical scavengers from dendrobium draconis

Phytochemical study of Dendrobium draconis Rchb.f. led to the isolation of a new phenanthrenequinone, namely 5-methoxy-7-hydroxy-9,10-dihydro-1,4-phenanthrenequinone, as well as five known compounds including hircinol, gigantol, batatasin III, 4-methoxy-9,10-dihydrophenanthrene -2,5,7-triol and tristin. The identification and structure determination of the isolated compounds were achieved by analysis of their spectroscopic data (MS, IR, UV, NMR) in comparison with previously reported data. Most of the isolated compounds showed appreciable activity against DPPH radical but weak activity against superoxide radical. 4-Methoxy-9,10-dihydrophenanthrene-2,5,7-triol, however, showed DPPH radical scavenging activity comparable to that of Trolox.