Identification of a Novel Retinoid X Receptor Agonist from <i>Boenninghausenia albiflora</i> var. <i>japonica</i>

Retinoid X receptors (RXRs) are nuclear receptors involved in various crucial biological processes, such as gene regulation, metabolism, and cell differentiation. They predominantly function as heterodimers with other nuclear receptors and modulate gene expression in response to ligand binding. Additionally, they act as therapeutic targets for different conditions, such as cancer and metabolic disorders. Although synthetic RXR agonists, such as bexarotene, are used in clinical settings, they exert adverse side effects. In this study, to explore insights into potential natural RXR agonists as alternatives to existing drugs, we isolated 14 coumarins, including 1 new compound from Boenninghausenia albiflora var. japonica (Rutaceae). Among them, daphnoretin methyl ether (14), a known biscoumarin, was found to exhibit subtype-nonspecific RXR agonist activity.