Activity-Guided Isolation of Constituents of Renealmia nicolaioides with the Potential to Induce the Phase II Enzyme Quinone Reductase

Three new prenylated dihydrochalcones, (±)-nicolaioidesins A, B, and C (1−3), as well as a new natural product, 5-styrylfuran-2-carboxylic acid methyl ester (4), along with four known compounds, 2'-hydroxy-4',6'-dimethoxychalcone (5), (±)-5-hydroxy-7-methoxyflavanone (6), (±)-5-hydroxy-7,4'-dimethoxyflavanone, and panduratin A, were isolated from the roots of Renealmia nicolaioides, using a bioassay to determine the induction of quinone reductase (QR) activity with cultured Hepa lclc7 mouse hepatoma cells. Among these isolates, 5 and 6 induced QR activity, with observed concentrations to double activity (CD) values of 1.7 and 0.9 μg/mL, respectively, while the other constituents were not regarded as being active (CD >10 μg/mL). The chemical structures of 1−4 were elucidated by spectroscopic methods. A biogenetic pathway for the formation of (±)-nicolaioidins A−C (1−3) is proposed.