3 o cis p coumaroyl tormentic acid

Triterpenoids isolated from E. japonica leaves for biological activities were obtained as follow: Ursolic acid (1) was obtained from Wako Pure Chemical Industries (Osaka, Japan); Oleanolic acid (2) was from Cayman Chemicals (Ann Arbor, MI, USA); Uvaol (3) was obtained from Extrasynthese (Genay Cedex, France); Betulinic acid (4) was obtained from Focus Biomolecules (Plymouth Meeting, PA, USA); Maslinic acid (7) was obtained from Cayman Chemicals; Pomolic acid (10) was obtained from Quality Phytochemicals (East Brunswick, NJ, USA); Corosolic acid (8), 3-epicorosolic acid (9), tormentic acid (11), euscaphic acid (12), 3-oxours-12-en-28-oic acid (13), 6β,19-dihydroxyurs-12-en-3-oxo-28-oic acid (14), hyptadienic acid (16), 3-O-trans-p-coumaroyl tormentic acid (17) and 3-O-cis-p-coumaroyl tormentic acid (18) were obtained from Chemfaces (Wuhan, China). Methyl maslinate (5), methyl corosolate (6) and 2α, 19α-dihydroxy-3-oxo-12-ursen-28-oic acid (15) were previously isolated from E. japonica leaves. The purity of all tested compounds was above 95% as verified by analytical high-performance liquid chromatography (HPLC).

Silica gel 60A (35–75 microns) (ANALTECH, Newark, DE, USA) was used for column chromatography. Thin layer chromatography (TLC) was performed on a Kieselgel 60 F₂₅₄ plate (MERK, Darmstadt, Germany). The TLC plates were developed with a chloroform–methanol solution (20:1) and visualized using a Spectroline UV lamp (Westbury, NY, USA). Tissue culture plates, including six-well and 24-well ultralow attachment cluster plates, were obtained from Corning. Cell viability was measured using a CellTiter 96^® Aqueous One Solution cell proliferation assay kit (Promega, WI, USA). An ALDEFLUOR™ Kit was purchased from STEMCELL Technologies Inc (Vancouver, BC, Canada). 3-O-trans-p-Coumaroyltormentic acid and 3-O-cis-p-coumaroyltormentic acid were obtained from ChemFaces (Wuhan, Hubei, China). All other chemicals were obtained from Sigma-Aldrich Co (St. Louis, MO, USA).