Isolation and identification of anti-inflammatory diterpenoids from the post-distillation arils of Torreya grandis

Torreya grandis arils (TGAs), historically underutilized due to processing limitations, have gained value through the efficient extraction of essential oils. However, the post-distillation residue from this process remains rich in non-volatile bioactive compounds. In the present study, the post-distillation TGAs were systematically investigated and led to the identification of 32 diterpenoids, including twenty-three abietane-type 1-23, two pimarane-type 24-25, and seven labdane-type diterpenoids 26-32. Compounds 1-5 were elucidated to possess previously undescribed structures by extensive spectroscopic methods and quantum chemical calculations of NMR coupled with DP4+ probability analysis. Compounds 7, 8, 14, 19, 20, 23, 25, 29, 30, and 31 were obtained for the first time from the genus Torreya. In an in vitro bioassay, compounds 2, 3, 6, 7, 8, 10, 12, 26, 27, and 30 exhibited significant suppression of interleukin-6 (IL-6) and interleukin-1β (IL-1β) gene expression in LPS-induced RAW 264.7 macrophages, demonstrating anti-inflammatory potential.