Identification and Determination of Betacyanins in Fruit Extracts of Melocactus Species

Abstract

Betacyanin pigments were studied in edible fruits of four Melocactus species, M. violaceus Pfeiff., M. bahiensis (Britton & Rose) Luetzelb, M. amoenus (Hoffm.) Pfeiff., and M. curvispinus Pfeiff., by means of chromatographic and mass spectrometric techniques. The main pigment constituent, melocactin, endogenously present in the Melocactus species, was identified as betanidin 5- O -β-sophoroside betacyanin, previously known as “bougainvillein-r-I”. The highest total concentration of betacyanins was found in fruits of M. amoenus (∼0.08 mg/g). Except for melocactin being the most abundant betacyanin (34.8–38.8%) in the analyzed species, a presence of its malonylated derivative, mammillarinin (15.2–19.9%), as well as more hydrophobic feruloyled and sinapoyled melocactins was confirmed by additional co-chromatographic experiments with authentic reference betacyanins. The acyl migration isomers of the malonylated betacyanins as well as a presence of 5′′- O - E -sinapoyl-2′- O -apiosyl-betanin (2.3–3.0%) found frequently in light-stressed cacti was also acknowledged.

Structural Studies on Diverse Betacyanin Classes in Matured Pigment-Rich Fruits of Basella alba L. and Basella alba L. var. ‘Rubra’ (Malabar Spinach)

“…In the group of polar betacyanins identified in the fruits of B. alba and var. ‘Rubra’ by LC-DAD-MS and co-elution experiments with the known references [ 7 , 26 , 28 , 29 , 30 , 31 , 32 ], except for the known mono- and bi-glucosylated betacyanins 1 , 4, 5 and 7 as well as their isoforms 1 ’, 4 ’, 5 ’ and 7 ’ ( Table 1 ), novel pigments 2 / 2 ’, 3 / 3 ’ and 6 / 6 ’ were detected, which were not co-eluted with the reference betacyanins.…”

“…The molecular mass and the fragmentation pattern suggested a presence of a dihexosyl (713 − 389 = 2 × 162) of betanidin. The observed low absorption maxima λ max 536–537 nm suggested the 5- O -substitution pattern with a sugar system in betanidin, similarly to melocactin [ 7 , 28 ]. During the high-resolution mass spectrometric experiments on compounds 2 and 6 in the Orbitrap system, the molecular masses were obtained at m / z 713.2030 and 713.2033, respectively (C 30 H 37 N 2 O 18 , calculated m / z 713.2036), which together with the detected fragmentation ions ( Table 2 ) confirmed the elemental composition of 2 and 6 .…”

“…Unexpectedly, compound 3 with [M+H] + ions at m / z 551 appeared as a hexosyl (551 − 389 = 162) of betanidin during the low-resolution mass spectrometric analysis, which together with the observed higher absorption maximum λ max 539 nm ( Table 1 ) tentatively suggested a presence of a betanidin 6- O -substitution system. The 2 nm difference in λ max is always observed between betanins and gomphrenins acylated with aliphatic acids [ 7 , 28 , 31 ]. The obtained protonated molecular mass for 3 during the HRMS experiments corresponding to the ion at m / z 551.1505 (C 24 H 27 N 2 O 13 , calculated m / z 551.1508) and for its fragment ion ( Table 2 ) at m / z 389.0973 (C 18 H 17 N 2 O 8 , calculated m / z 389.0979) confirmed a presence of a novel isomeric betacyanin to the well-known betanin 4 and gomphrenin 7 .…”

“…The position of 6- O -glucosylation in 8a – 8c / 8a ’– 8c ’ might be suggested by a bathochromic shift of their obtained absorption maxima λ max (537 nm), similar to the shift from 535 nm for betanin to 537 nm for gomphrenin in the applied chromatographic eluent [ 34 ]. This is the always-observed difference between betanins and gomphrenins acylated with aliphatic acids [ 7 , 28 , 31 , 34 ].…”

“…The not fully explored properties and unexplored possibilities of using plants rich in betalains [ 26 , 27 , 28 ], as well as the presence of unknown compounds in the profiles of extracts from individual plants, make this topic very demanding for the development of science and trends in functional food and nutraceuticals.…”