Hierarchical Key for the LC–MSⁿ Identification of All Ten Regio- and Stereoisomers of Caffeoylglucose

Abstract

A chromatographic method was developed to separate all 10 regio- and stereoisomers of caffeoylglucose. Following chromatographic separation on reversed phase, the fragmentation behavior of all 10 regio- and stereoisomers of caffeoylglucose has been investigated using LC-MS(n). It is possible to discriminate between each of the isomers based on their characteristic fragment spectra and order of elution, including those for which commercial standards are not available. On the basis of the synthesis of authentic standards for 6-caffeoylglucose and 3-caffeoylglucose and nonselective further synthesis of suitable mixtures of isomers, it was possible to fully assign regiochemistry of all 10 isomeric compounds and stereochemistry of eight isomeric compounds. Their fragmentation pattern was rationalized based on assuming different hydrogen-bonding arrays of gas-phase ions opening distinct fragmentation pathways. An analysis of yerba maté extract showed all 10 regio- and stereoisomers of caffeoylglucose to be present in this dietary material, which could all be assigned to regioisomeric level and eight to stereoisomeric level.

Profiling hydroxycinnamic acid glycosides, iridoid glycosides, and phenylethanoid glycosides in baobab fruit pulp (Adansonia digitata)

“…The current study isolated four hydroxycinnamic acid glycosides (HAGs): 1- O -( E )-feruloyl- β -D-glucose ( 1 ) (Jaiswal & Kuhnert, 2014; Jaiswal, Matei, Glembockyte, Patras, & Kuhnert, 2014), 1- O -( E )-caffeoyl- β -D-glucose ( 2 ) (Jaiswal & Jaiswal & Kuhnert, 2014; Jaiswal, Matei, Glembockyte, Patras, & Kuhnert, 2014), 6- O -( E )-caffeoyl- β -D-glucose ( 3 ) (Jaiswal & Kuhnert, 2014; Jaiswal, Matei, Glembockyte, Patras, & Kuhnert, 2014), 6- O -( E )-caffeoyl- α -D-glucose ( 4 ) (Jaiswal & Kuhnert, 2014; Jaiswal, Matei, Glembockyte, Patras, & Kuhnert, 2014), six iridoid glycosides (IGs): (−)-specioside ( 5 ) (Sha’aban, El-Naggar, & Doskotch, 1980), verminoside ( 6 ) (Sticher & Afifi-Yazar, 1979), 6- O -( E )-feruloylcatalpol ( 7 ) (Young, Kim, Park, Chung, & Choi, 1992), 6- O - p -coumaroylajugol ( 8 ) (Nishimura, Sasaki, Morota, Chin, & Mitsuhashi, 1989), 6- O -( E )-caffeoylajugol ( 9 ) (Harinantenaina Liva, Kasai, Rakotocao, & Yamasaki, 2001), 6- O -( E )-feruloylajugol ( 10 ) (Li et al, 2011), and three phenylethanoid glycosides (PGs): martynoside ( 11 ) (Li et al, 2011; Sasaki, Nishimura, Chin, & Mitsuhashi, 1989), acteoside ( 12 ) (Li et al, 2011; Sasaki, Nishimura, Chin, & Mitsuhashi, 1989), isoacteoside ( 13 ) (Kim, Kim, Jung, Ham, & Whang, 2009) from the baobab fruit pulp (Figure 1 and Table 1). Their structures were established on the basis of spectroscopic data, particularly the 1D NMR and several 2D shift-correlated NMR pulse sequences ( 1 H- 1 H COSY, HSQC, HMBC and ROESY).…”

“…The loss of 162 mass unit indicated the existence of a hexose. Based on the MS 2 spectra and the information obtained from the literatures (Jaiswal & Kuhnert, 2014; Jaiswal, Matei, Glembockyte, Patras, & Kuhnert, 2014), the fragment ions at m / z 281, 251 and 221 were obtained through the ring fission fragmentation of the hexose (Scheme 1). Compounds 3 and 4 , which are the α / β anomers of 6-caffeoylglucose, can be distinguished from 2 based on the base peak of 3 and 4 at m / z 281 and that of 2 at m / z 179.…”

Enzymatic Browning in Sugar Beet Leaves (Beta vulgaris L.): Influence of Caffeic Acid Derivatives, Oxidative Coupling, and Coupled Oxidation

“…Compound 2 was annotated as caffeic acid O -β-hexoside, with characteristic caffeoyl fragments in MS 3 . 17 Glycosylated coumaric acids were not annotated. Trace amounts of dopamine ( 3 , 5 , 8 – 10 , 16 ) and tryptophan ( 13 ) derivatives were annotated.…”

“…16 The presence of phenolic derivatives was determined by the presence of characteristic neutral losses upon MS 2 and MS 3 fragmentation. Phenolic acid O -glycosides 17 ( 2 , Figure 2) and flavonoid O -glycosides were annotated by a neutral loss of 162 ( O -hexose). Glycosylation in phenolic acid glycosyl esters ( 6 , Figure 2) was annotated by a neutral loss of 162 ( O -hexose) 14,18 or 132 ( O -pentose) 18 and additional polyol fragment ions (− 30, – 60, – 90) 13,17 in MS 2 , originating from ring fission fragmentation within the glycosyl residue.…”

Bioactive Phenanthrene and Bibenzyl Derivatives from the Stems ofDendrobium nobile

“…These were identified as (+)-and (−)-denobilone A (1 and 2), denobilones B and C (3 and 4), 7-hydroxy-9,10-dihydro-1,4-phenanthrenedione (5), hircinol (6), 21 ephemeranthol-A (7), 23 erianthridin (8), 24 4,5-dihydroxy-2-methoxy-9,10-dihydrophenanthrene (9), 25 flavanthridin (10), 26 lusianthridin (11), 27 6,7-dihydroxy-2-methoxy-1,4-phenanthrenedione (12), 28 moscatin (13), 29 confusarin (14), 30 nudol (15), 31 lusianthrin (16), 27 3′,4-dihydroxy-3,5′-dimethoxybibenzyl (17), 32 3-hydroxy-5-methoxybibenzyl (18), 33 batatasin III (19), 34 tristin (20), 35 3,3′,5-trihydroxybibenzyl (21), 36 denthyrsinol A (22), denthyrsinol B (23), denthyrsinol C (24), denthyrsinol (25), 37 phochinenin G (26), 38 phochinenin D (27), 39 and 4,4′,7,7′-tetrahydroxy-2,2′-dimethoxy-9,9′,10,10′-tetrahydro-1,1′-phenanthrene (28). 40 Denobilone A (1/2) possesses a molecular formula of C 15 . The COSY correlations of H-6 to H-7 and H-7 to H-8, combined with the HMBC correlations from H-6 to C-5a/C-5 and H-8 to C-5a/C-8a, indicated the presence of a benzene moiety in 1 (Figure 2).…”