Chemical constituents from Dendrobium densiflorum

5-[2'-(3-Hydroxy-5-methoxyphenyl)-ethyl]-1,3-benzodioxole and 7-hydroxy-2-methoxy-1,4-phenanthrenedione, along with 16 known compounds were identified from the stems of Dendrobium densifiorum Lindl. ex Wall. (Orchidaceae). The structure of a previously reported compound dendroflorin obtained from the plant was revised on the basis of spectroscopic analysis. Among the identified compounds, five were found to exhibit anti-platelet aggregation activity in vitro. (C) 2001 Elsevier Science Ltd. All rights reserved.