Bioactive Dimeric Diterpenoids from Taiwania cryptomerioides (Hayata) and Their Biological Activities

Taiwania cryptomerioides Hayata is an endangered relict plant belonging to Taxodiaceae, and it is also an endemic plant to China. The decay‐resistant of Taiwania timber can provide highly quality wood for building and furniture. Plenty of regenerative of leaves of T. cryptomerioides also has been used as a resource for the discovery of new dimeric diterpenoids. In a search for structurally diverse dimeric diterpenoids and potent bioactive isolates, ten new heterodimeric diterpenoids, taiwaniadducts K−T (1–4, 6, 8–11, and 14), along with five known ones (5, 7, 12, 13, and 15), were isolated from the leaves of T. cryptomerioides. These new compounds were defined by comprehensive spectroscopic analyses, putative biosynthetic pathways, and the values of optical. Biologically, anti‐multidrug resistance (MDR) activities of compounds were evaluated. Compounds 4 and 10 exerted a 9.18‐fold potentiation effect on bortezmib (BTZ) susceptibility at a tested concentration (20 μM) better than the positive control verapamil. The research of the leaves of T. cryptomerioides not only added the new data to the structural diversity and activities of dimeric diterpenoids but also could provide support for the medical and industrial application of the leaves of this endangered relict plant.