Immunomodulatory Potential of a Bibenzyl-dihydrophenanthrene Derivative Isolated from <i>Calanthe cardioglossa</i>

Bibenzyls and dihydrophenanthrenes exhibit promising immunomodulatory effects in various human diseases. In this study, we isolated one new dihydrophenanthrene derivative (<b>1</b>), two new bibenzyl-dihydrophenanthrene derivatives (<b>2, 3</b>) along with 12 known compounds (<b>4</b>-<b>15</b>) from the methanol extract of <i>Calanthe cardioglossa</i>. These compounds were identified by using physicochemical analyses and spectroscopic methods. The three new compounds possess enantiomeric forms, and their configurations were determined by comparing the experimental electronic circular dichroism (ECD) spectra to data from the literature. The immunomodulatory activity of the isolated compounds was assessed in THP-1 monocytes and human peripheral blood mononuclear cells (PBMCs) derived from multiple sclerosis (MS) patients. Notably, five of the isolated compounds significantly reduced the TNF-α levels in LPS-stimulated THP-1 monocytes. Furthermore, calancardin B (<b>2</b>) exhibited a significant reduction in TNF-α levels in both THP-1 monocytes and CD14⁺ monocytes from MS PBMCs.