The binding mechanisms of plasma protein to active compounds in Alismaorientale rhizomes (Alismatis Rhizoma)

Abstract

Ultrafiltration and HPLC were employed to assess binding rates between rat plasma protein and two active compounds with lipid-regulating properties (alisol B 23-acetate and alisol A 24-acetate) from Alismaorientale rhizomes (Alismatis Rhizoma), a traditional Chinese medicine. SDS–PAGE was used for the evaluation of the binding between the alisol acetates and Hb in plasma. The fluorescence spectroscopy and circular dichroism spectroscopy were also combined with molecular modeling to explore binding mechanisms between Hb and the alisol acetates under imitative physiological condition. The ultrafiltration results show that alisol B 23-acetate bound more strongly than alisol A 24-acetate to plasma protein. SDS–PAGE results may suggest that alisols bind to Hb in plasma. The spectroscopy results are consisting with the molecular modeling results, and they indicate that the differences in plasma protein binding strength between the two compounds may be related to their side chains. A folded side chain/parent ring bound more strongly to Hb than an open side chain/parent ring.