Chemical constituents of Dendrobium nobile Lindl. and their inhibitory activity on the collagen production in NIH 3T3 cells.

Dendrobium nobile Lindl. is a major source of "Shi-Hu" listed in the 'Chinese Pharmacopoeia'. D. nobile has been cultivated in large areas. A comprehensive investigation of the chemical constituents of D. nobile is pivotal for production, exploitation, and quality control. A detailed examination on the chemical components led to the identification of 81 compounds, including 23 undescribed ones. The undescribed compounds consist of 16 sesquiterpenoids (1-14, 16, and 17), one alkaloid (15), one phenanthrene (18), and five bibenzyls (19-23). Compound 1 is a structurally unique sesquiterpenoid, which is possibly biosynthesized from a copacamphane-type sesquiterpene. Compounds 16 and 17 are the first muurolane-type sesquiterpenoids with demethylation of C-15. Compounds 14, 19, and 59 significantly inhibited the collagen formation in TGF-β induced NIH 3T3 cells, with IC50 values of 5.83, 7.48, and 7.43 μM, respectively, suggesting their potential to inhibit pulmonary fibrosis.