Identification and characterization of two new derivatives of chlorogenic acids in Arnica (Arnica montana L.) flowers by high-performance liquid chromatography/tandem mass spectrometry.

Arnica montana is a medicinally important plant due to its broad health effects, and it is used in Ayurvedic, Homeopathic, Unani, and folk medicines. We have used LC-MS(n) (n = 2-5) to detect and characterize in Arnica flowers 11 quantitatively minor fumaric and methoxyoxalic acid-containing chlorogenic acids, nine of them not previously reported in nature. These comprise 1,5-dicaffeoyl-3-methoxyoxaloylquinic acid, 1,3-dicaffeoyl-4-methoxyoxaloylquinic acid, 3,5-dicaffeoyl-4-methoxyoxaloylquinic acid, and 1-methoxyoxaloyl-4,5-dicaffeoylquinic acid (M(r) 602); 3-caffeoyl-4-feruloyl-5-methoxyoxaloylquinic acid and 3-feruloyl-4-methoxyoxaloyl-5-caffeoylquinic acid (M(r) 616); 1,5-dicaffeoyl-4-fumaroyl and 1,5-dicaffeoyl-3-fumaroylquinic acid (M(r) 614); 3,5-dicaffeoyl-1,4-dimethoxyoxaloylquinic acid (M(r) 688); and 1-methoxyoxaloyl-3,4,5-tricaffeoylquinic acid and 1,3,4-tricaffeoyl-5-methoxyoxaloylquinic acid (M(r) 764). All of the structures have been assigned on the basis of LC-MS(n) patterns of fragmentation, relative hydrophobicity, and analogy of fragmentation patterns if compared to caffeoylquinic acids. This is the first time when fumaric acid-containing chlorogenic acids are reported in nature.