Dendrowardols A and B, two new sesquiterpenoids from Dendrobium wardianum Warner

Two structurally unique sesquiterpenoids, dendrowardols A (1) and B (2), both possessing an unprecedented 5/7/4 tricyclic ring system, together with a known biogenetically related sesquiterpenoid, 10β,12,14-trihydroxy alloaromadendrane (3), were isolated from the stems of Dendrobium wardianum Warner. The structures of 1 and 2 were established on the basis of spectroscopic data. The absolute configuration of 1 and the relative configuration of 2 were determined by single-crystal X-ray diffraction crystallography. The hypothetical biosynthetic pathways of 1 and 2 were postulated. The effect on the proliferation of human lens epithelial cells (HLECs) induced by d-galactose of compound 2 was evaluated by an MTT assay.