An efficient method for high-purity anthocyanin isomers isolation from wild blueberries and their radical scavenging activity

Abstract

An efficient process for the purification of anthocyanin monomeric isomers from wild blueberries of Lake Saint-Jean region (Quebec, Canada) was developed and easy scalable at industrial purpose. The blueberries were soaked in acidified ethanol, filtered, and the filtrate was cleaned by solid phase extraction using silica gel C-18 and DSC-SCX cation-exchange resin. Anthocyanin-enriched elutes (87 wt.%) were successfully fractionated by preparative liquid chromatography. The major anthocyanins mono-galactoside, -glucoside and -arabinoside isomers of delphinidin, cyanidin, petunidin, peonidin and malvidin were isolated with a purity up to 100% according to their LC-MS and (1)H NMR spectra. The oxygen radical absorbance capacity (ORAC) of the obtained pure anthocyanins was evaluated. Delphinidin-3-galactoside has the highest capacity (13.062 ± 2.729 μmol TE/μmol), and malvidin-3-glucoside the lowest (0.851 ± 0.032 μmol TE/μmol). A mechanistic pathway preview is suggested for the anthocyanins scavenging free radical activity by hydrogen transfer.

Keywords: AAPH (2,2’-azobis[2-methylpropionamidine] dihydrochloride) (2-[(1-amino-1-imino-2-methylpropan-2-yl)diazenyl]-2methylpropanimidamide] dihydrochloride) PubChem CID: 76344); Anthocyanins; Ascorbic acid ((2R)-2-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxy-2H-furan-5-one) (PubChem CID: 54670067); Blueberries; Cyanidin-3,5-di-glucoside chloride (2-(3,4-dihydroxyphenyl)-3-(|A-d-glucopyranosyloxy)-7-hydroxychromenium-5-yl A-d-glucopyranoside chloride) (PubChem CID: 164999); Cyanidin-3-glucoside (kuromanin) ((2S,3R,4S,5S,6R)-2-[2-(3,4-dihydroxyphenyl)-5,7-dihydroxychromenylium-3-yl]oxy-6-(hydroxymethyl)oxane-3,4,5-triol) (PubChem CID: 441667); Delphinidin-3-glucoside (myrtillin) ((2S,3R,4S,5S,6R)-2-[5,7-dihydroxy-2-(3,4,5trihydroxyphenyl)chromenylium-3-yl] oxy-6-(hydroxymethyl)oxane-3,4,5-triol;chloride) (PubChem CID: 165558); Dibasic potassium phosphate (dipotassium;hydrogen phosphate) (PubChem CID: 24450); Fluorescein sodium salt (disodium;2-(3-oxido-6-oxoxanthen-9-yl) benzoate) (PubChem CID: 10608); Formic acid (PubChem CID: 284); Malvidin-3,5-di-glucoside chloride (2-(4-hydroxy-3,5-dimethoxyphenyl)chromenylium-3,5,7-triol;chloride) (PubChem CID: 69512); Malvidin-3-glucoside (oenin) chloride (2-[5,7-dihydroxy-2-(4-hydroxy-3,5-dimethoxyphenyl)chromenylium-3-yl]oxy-6-(hydroxymethyl)oxane-3,4,5-triol;chloride) (PubChem CID: 12313693); Methanol (PubChem CID: 887); Monobasic potassium phosphate (potassium;dihydrogen phosphate) (PubChem CID: 516951); ORAC; Potassium hydroxide (potassium;hydroxide) (PubChem CID: 14797); Preparative-HPLC; Silica (dioxosilane) (PubChem CID:24261); Trolox (6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid) (PubChem CID:40634); Vaccinium angustifolium Aiton and Vaccinium myrtilloides Michaux.