Four new diarylheptanoids and two new terpenoids from the fruits of Alpinia oxyphylla and their anti-inflammatory activities

Four previously unreported diarylheptanoids (1a/1b−2a/2b), one undescribed sesquiterpenoid (8), one new diterpenoid (12), and twelve known analogs were isolated from the fruits of Alpinia oxyphylla. The structural elucidation of these compounds was achieved through a comprehensive analysis of spectroscopic data, single-crystal X-ray diffraction, electronic circular dichroism (ECD), and modified Mosher’s method. Enantiomeric mixtures (1a/1b, 2a/2b, 3a/3b, 4a/4b, and 5a/5b) were separated on a chiral column using acetonitrile-water mixtures as eluents. Among them, compounds 3a/3b and 4a/4b were isolated as optically pure enantiomers in the initial chiral separation. Furthermore, most of the isolates were evaluated for their inhibitory effects against the production of nitric oxide (NO) and interleukin-6 (IL-6) in lipopolysaccharide (LPS)-induced RAW264.7 macrophages. Interestingly, 2 and 4 showed significant inhibitory activities against NO production with IC₅₀ values of 33.65 and 9.88 μmol·L⁻¹ (hydrocortisone: IC₅₀ 34.26 μmol·L⁻¹), respectively. Additionally, they also partially reduced the secretion of IL-6.