Alpinia hainanensis Rhizome Extract Ameliorates Dextran Sulfate Sodium-Induced Ulcerative Colitis: Active Ingredient Investigation and Evaluation

Alpinia hainanensis is an important food spice and ethnic medicine in Southwest China. In this study, we found that the EtOAc-soluble fraction (AHE) of the A. hainanensis rhizome ethanol extract could ameliorate dextran sulfate sodium-induced ulcerative colitis (UC). To explore active constituents, five pairs of previously unreported enantiomers (1-5), together with nine known ones (6-14), were obtained. Structural characterization was achieved by comprehensive spectroscopic methods. Compounds 1 and 2 were new curcumin-butyrovanillone hybrids featuring a rare structural fragment of 2,3-dihyrofuran. The anti-inflammatory activities of isolates were evaluated, and the results indicated that compounds (-)-1, (-)-3, 6, 9, 11, and 12 significantly inhibited the nuclear factor-κB signaling pathway. These findings indicate the major active fraction of the A. hainanensis rhizome ethanol extract enriched with diarylheptanoids, flavonoids, phenolics, and their hybrid mixtures, which could be developed as a nutritional and dietary supplement for treating UC.