Caffeic

Acetonitrile (hypergrade for LC–MS), formic acid (for LC–MS) and methanol (an-alytical grade) were purchased from Merck (Merck, Bulgaria). The reference standards used for compound identification were obtained from Extrasynthese (Genay, France) for gallic, protocatechuic, p-coumaric, m-coumaric, o-coumaric, vanillic, and salicylic acid, as well as luteolin 7-O-rutinoside, luteolin 7-O-glucoside, isorhamnetin 3-O-glucoside, apigenin 7-O-glucoside, and luteolin. Neochlorogenic, chlorogenic, caffeic, 3,4-dicaffeoylquinic, 3,5-dicaffeylquinic and 1,5-dicaffeoylquinic acids were supplied from Phytolab (Vesten-bergsgreuth, Bavaria, Germany).

Acetonitrile (hypergrade for LC–MS), formic acid (for LC-MS), and methanol (analytical grade) were purchased from Chromasolv (Bulgaria). The authentic standards gallic, vanillic, protocatechuic, gentisic, salicylic, p-coumaric, rutin, isoquercitrin, luteolin 7-O-rutinoside, luteolin 7-O-glucoside, isorhamnetin 3-O-glucoside, apigenin 7-O-glucoside, luteolin, quercetin, apigenin, and chrysoeriol were obtained from Extrasynthese (Genay, France). Rosmarinic, caffeic, ferulic, chlorogenic, neochlorogenic, 3,4-dicaffeoylquinic, 3,5-dicaffeoylquinic, 1,5-dicaffeoylquinic, and 4,5-dicaffeoylquinic acid were supplied from Phytolab (Vestenbergsgreuth, Germany). Sonchuside A and 8-acetyl-15β-D -glucopyranosyllactucin were previously isolated and identified by Zidorn et al., 2005 [8 (link)].

Acetonitrile (hypergrade for LC–MS), formic acid (for LC–MS), and methanol (analytical grade) were purchased from Chromasolv (Sofia, Bulgaria). The reference standards used for compound identification were obtained from Extrasynthese (Genay, France) for protocatechuic, gentisic acids, and apigenin. Chlorogenic, caffeic, rosmarinic, cichoric acid, pectolinarigenin, and scutellarein were supplied from Phytolab (Vesten-bergsgreuth, Bavaria, Germany).