Diarylheptanoid-flavanone adducts from Alpinia officinarum and their neuroprotective activities

Guided by the characteristic highly π-conjugated system of HPLC-UV experiments, four pairs of enantiomeric diarylheptanoid-flavanone adducts, officinoids A–D (1–4), were isolated from the rhizomes of medicinal plant Alpinia officinarum. Their structures with absolute configurations were fully characterized through a combination of extensive spectroscopic analysis, single-crystal X-ray diffraction, and density functional theory quantum chemical calculation. These isolated compounds represent a new class of diarylheptanoid-flavanone adducts with an unprecedented C-11–C-8′(C-6′) and C-9–O–C-7′ connection mode. Notably, compounds 3 and 4 contain an unusual ketal motif in the dihydropyrano[2,3-f]chromone or dihydropyrano[3,2-g]chromone skeleton. In the bioactivity assays, compound 2 exhibited significant neuroprotective effects against neuronal injury induced by oxygen-glucose deprivation and re‑oxygenation (OGD/R) in SH-SY5Y cells.