Medicinal Foodstuffs. XXXIV. Structures of New Prenylchalcones and Prenylflavanones with TNF-α and Aminopeptidase N Inhibitory Activities from Boesenbergia rotunda

Abstract

The methanolic extract from the rhizomes of Boesenbergia rotunda (Zingiberaceae) was found to show inhibitory effect on tumor necrosis factor-α (TNF-α)-induced cytotoxicity in L929 cells (IC₅₀=6.1 μg/ml). By bioassay-guided separation, four new prenylcalcones, (+)-krachaizin A (1a), (−)-krachaizin A (1b), (+)-krachaizin B (2a), and (−)-krachaizin B (2b), and four new prenylflavanones, rotundaflavones Ia (3a), Ib (3b), IIa (4a), and IIb (4b), were isolated together with 18 known constituents (5a—7b and 8—19). The structures of eight new compounds were elucidated on the basis of physicochemical evidence. Among them, (+)-krachaizin B (2a), (−)-krachaizin B (2b), (+)-4-hydroxypanduratin A (6a), (−)-4-hydroxypanduratin A (6b), (+)-isopanduratin A (7a), (−)-isopanduratin A (7b), alpinetin (10), cardamonin (14), and 2,6-dihydroxy-4-methoxydihydrochalcone (15) significantly inhibited TNF-α-induced cytotoxicity in L929 cells at 10 μM. In addition, 2a, 2b, (+)-panduratins A (5a), (−)-panduratin A (5b), 6a, 7b, and geranyl-2,4-dihydroxy-6-phenylbenzoate (17) were found to show strong inhibitory effects on aminopeptidase N activity.