A Pharmacokinetic–Pharmacodynamic Study of Protosappanoside D, a Component Derived from Biancaea decapetala Extracts, for Its Anti-Inflammatory Effects

<i>Biancaea decapetala</i> (Roth) O. Deg. (Fabaceae), traditionally used by the Hmong people to treat rheumatoid arthritis (RA), has not been extensively studied for the correlation between its anti-inflammatory activity and its active components. Protosappanoside D (PTD), a new component, has been isolated for the first time from the extract of <i>Biancaea decapetala</i>. This study focused on the anti-arthritic and anti-inflammatory effects of <i>Biancaea decapetala</i> extracts (BDE) and PTD, along with their pharmacokinetic-pharmacodynamic (PK-PD) analysis. In the adjuvant-induced arthritis (AA) rat model, HE staining and cytokine assays showed that BDE alleviated joint damage and reduced inflammatory cytokines, similar to the positive control. In the LPS-induced inflammatory cell model, both BDE and PTD demonstrated anti-inflammatory effects by inhibiting the secretion of inflammatory factors. A PK-PD analysis of BDE in AA rats and inflammatory cells, as well as an analysis of PTD as a monomer, was conducted. The results indicated that PTD had different regulatory effects on cytokines like TNF-<i>α</i>, with a certain lag and sustained effects. These findings suggest the potential of BDE and PTD as treatments for rheumatoid arthritis, though further in vivo studies and clinical trials are needed.