Integrated strategy by combining preparative HSCCC with HPLC-UV-QDa for efficient isolation of specific...

Salicin derivatives, the most abundant secondary metabolites in Salix tetrasperma Roxb, interfere with the purification of the trace triterpenoids in the plant, which are characterized by minimal or no UV absorption. Herein, a modified isolation approach, integrating preparative high-speed countercurrent chromatography with preparative HPLC with UV/vis and ACQUITY QDa detectors, was applied to remove salicin derivatives and purify the minor triterpenoids of S. tetrasperma. Application of the strategy led to a successful isolation of 11 new and highly oxidized friedelane-type triterpenoids, salixtetrones A‒K (1‒11), and one rare 29-nor-friedelane-type triterpenoid salixtetrone L (12) from the ethyl acetate extract of S. tetrasperma barks. This is, to the best of our knowledge, the first report on the friedelane-type triterpenoids from species of Salix L. The structures of all compounds were elucidated mainly by conventional spectroscopic and spectrometric data analyses, coupled with single-crystal X-ray diffraction. Compounds 1 and 8 showed moderate antiproliferative activity against the A549 cell line.