New acylglycosides from the roots of Rheum palmatum L.

Abstract

A phytochemical investigation of the EtOH extract of the roots of Rheum palmatum L. was performed, leading to the isolation of 3 new acylglycosides ( 1 – 3 ) and 19 previously reported compounds, including 4 cinnamoyl glucosides ( 4 – 7 ) and 15 anthraquinones ( 8 – 22 ). Their structures were elucidated using nuclear magnetic resonance, infrared, ultraviolet and high-resolution electrospray ionization mass spectra and X-ray diffraction data. The biological activities of compounds 2 , 4 – 9 , and 11 – 13 , including their lymphocyte activation gene 3 (LAG3)/major histocompatibility complex class II (MHC II) and LAG3/fibrinogen-like protein 1 (FGL1) binding inhibition activities, were evaluated. Among the isolates, compound 7 exhibited clear inhibitory activity against the LAG3/FGL1 interaction with an IC 50 of 7.89 μ M, meanwhile compound 6 inhibited the LAG3/MHC II interaction with an IC 50 of 6.00 μ M. • Three undescribed acylglycosides were isolated from roots of Rheum palmatum L. • The absolute configuration of 1 was confirmed by single crystal X-ray diffraction. • This is the first report of the crystal structure of a cinnamoyl glucoside. • Their activities against the interaction of LAG3 with MHC II or FGL1 were evaluated.