Five new compounds from Dendrobium crystallinum.

Five new compounds, dencryol A (1), dencryol B (2), crystalltone (3), crystallinin (4), and 3-hydroxy-2-methoxy-5,6-dimethylbenzoic acid (5), together with six known compounds, dendronobilin B (6), syringic acid (7), apigenin (8), isoviolanthin (9), 6'''-glucosyl-vitexin (10), and palmarumycin JC2 (11), have been isolated from the stems of Dendrobium crystallinum, of which compounds 9-11 were isolated from the genus Dendrobium for the first time, and all the other compounds were first obtained from this plant. Their structures were established on the basis of spectroscopic analysis and literature data.