Kaempferol

Reference standards quercetin-3-O-rutinoside (rutin), (+)-catechin, luteolin, quercetin and apigenin, kaempferol, isorhamnetin and cyanidin-3-O-glucoside were obtained from Carl Roth GmbH (Karlsruhe, Germany). Primeverin and primula acid I were purchased from Phytolab GmbH (Vestenbergsgreuth, Germany).

The compounds kaempferol, acacetin, galangin, chrysin, homoeriodictyol were obtained from Carl Roth GmbH (Karlsruhe, Germany), apigenin, nargingenin, hispidulin, scutellarein, baicalein, quercetin, wogonin, and diosmetin from Sigma-Aldrich (Vienna, Austria), herbacetin, pinocembrin, luteolin, eriodictyol, norwogonin from Extrasynthése (Genay, France) and nepetin as well as oroxylin A from Phytolab (Vestenbergsgreuth, Germany). All stock solutions were prepared in dimethylsulfoxide (DMSO; 99.7% cell culture grade, Sigma-Aldrich (Vienna, Austria).

References used for the HPLC-MS analysis were purchased from Sigma Aldrich (St. Louis, MO, USA): Chlorogenic acid, p-coumaric acid, caffeic acid, rutin, apigenin, quercetin, isoquercitrin, quercitrin, hyperoside, kaempferol, myricetol, and fisetin, Roth (Karlsruhe, Germany): Ferulic acid, sinapic acid, gentisic acid, gallic acid, patuletin, luteolin or from Dalton (Toronto, ON, Canada): cichoric acid, caftaric acid. HPLC grade solvents, analytical grade acids used for mobile phases and Folin-Ciocâlteu reagent were purchased from Merck (Darmstadt, Germany), together with sodium carbonate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate and aluminium chloride used for antioxidant assays. ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt) ≥98% purity, potassium peroxodisulfate (≥99% purity), DPPH, and Trolox (6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid; ≥97% purity) also used in antioxidant tests were purchased from Sigma Aldrich (Schnelldorf, Germany). Gallic acid monohydrate (99.5%) was purchased from Serva, (Heidelberg, Germany).