Oleanolic

We purchased commercial lyophilizates of oleanolic, maslinic, and ursolic acids (references 42515, 68594, and 89797, respectively; Sigma-Aldrich, Barcelona, Spain), and suspended them in dimethyl sulfoxide to obtain three solutions of triterpenic acids: one with oleanolic acid (100%) (T1), one with maslinic acid (100%) (T2), and one with ursolic acid (100%) (T3).

Methanol (99.9% purity), ethanol (99.9% purity), ammonium acetate (99.9% purity), and acetic acid (99.9% purity) were purchased from Merck (Darmstadt, Germany) and used without further purification. Standard polyphenolic compounds: rosmarinic acid, caftaric acid, gentisic acid, chlorogenic acid, caffeic acid, p-coumaric acid, ferulic acid and sinapic acid, hyperoside, isoquercitrin, rutin, myricetin, fisetin, quercitrin, quercetol, luteolin, kaempferol, and apigenin, were purchased from Sigma-Aldrich (Germany). Standard pentacyclic triterpenic compounds: ursolic, oleanolic, and betulinic acid, were also purchased from Sigma-Aldrich (Germany). For the preparation of sample solutions, ultrapure deionized water was provided by a MiliQ system Milli-Q® Integral Water Purification System (Merck Milipore, Darmstadt, Germany).

β-Sitosterol, α-amyrin, β-amyrin, oleanolic- and usrosolic acid were purchased from Sigma-Aldrich (St-Louis, MO, USA). 24-Methylencycloartanol was previously isolated from the latex of E. palustris (Krstić et al. 2016 (link)).